Breed, heterosis, and recombination effects for lactation curves in Brazilian cattle

The objective of this study was to estimate the breed, heterosis, and recombination effects on different components of the lactation curve of Girolando cattle. The dataset used consisted of 12,121 purebred cows of Holstein (H) and Gyr (G) breeds, and six H×G crossbred cows (Girolando). The model used presents random effects of herd and cow, regression coefficient associated with linear effect of proportion of H breed, regression coefficient associated with the linear effect of heterosis between H and G breeds, regression coefficient associated with the linear effect of recombination between H and G breeds, and random effect of residual. Dijkstra's (DJ), Nelder's (ND), Wilmink's (WL), and Wood's (WD) models were tested to fit production records of these different genetic groups. These models were then tested according to evaluation criteria of quality of fit (AIC, BIC, and RMSE), and the two best models (WD and WL) were chosen for estimation of 305-day milk yield (MY305), peak yield, time to peak, and persistency of milk yield. The breed effect was significant for all traits and components of the lactation curve. The heterosis effect was significant for all traits, and was more significant for MY305 (945.62±79.17 kg). Peak yield was the component of lactation curve that presented the most significant heterosis effect, partially explaining the heterosis effect (12 to 21%) found for MY305. The recombination effect was positive only for lactation period and time to peak of lactation in Girolando cows.

Influence of caprine arthritis encephalitis on milk production and quality along the lactation curve in primiparous dairy goats / Influência da artrite encefalite caprina na produção e qualidade do leite ao longo da curva de lactação em cabras leiteiras primíparas

The aim of this study was to examine the influence of caprine arthritis encephalitis (CAE) on the production of milk and its components (protein, fat and total solids) along the lactation curve of primiparous goats. The study was developed using a database from the years 2014 to 2018. Sixty-one animals were subjected to the serological test for CAE, whose result indicated that 42 were seropositive and 19 seronegative, and milk production and quality data were compiled. To adjust the curve for production of milk, fat, protein and total solids during lactation, the following nonlinear model developed by Wood (1967) was used: Y = atb e-ct, where Y represents the observations of milk, fat, protein or total solid production at time t; a is the parameter associated with the initial production; b is the parameter associated with the rate of rise in production until the peak; c is the parameter associated with the rate of decline of the lactation curve; and t is the representative time of the day in milk. The parameters were compared by the confidence interval considering 95% probability. Peak production was calculated using the following formula: a(b/c)b e-b. There was no statistical difference (p > 0.05) between seropositive and seronegative primiparous goats for initial production and the rates of rise and decline of the parameters of milk, fat, protein and total solid production. However, at their peak, these variables were 26, 27, 23 and 23% higher, respectively, in the seronegative goats than in their seropositive counter parts. In conclusion, CAE does not affect milk production or the production of fat, protein and total solids along the lactation curve, but seropositive goats produce less milk and respective components at the peak of the lactation curve than seronegative goats.

Objetivou-se avaliar a influência da artrite encefalite caprina (CAE) sobre a produção leiteira e seus constituintes (proteína, gordura e sólidos totais) ao longo da curva de lactação de cabras primíparas. O estudo foi realizado a partir do banco de dados dos anos de 2014 a 2018. Foram utilizados um total de 61 animais, todos submetidos ao teste de sorologia para CAE, sendo 42 cabras soropositivas e 19soronegativas, e os dados foram compilados de produção e qualidade do leite. Para o ajuste da curva para a produção de leite, gordura, proteína e sólidos totais ao longo da lactação foi utilizado o modelo não linear de Wood (1967): Y = atb e-ct, no qual: Y representa as observações de produção de leite, gordura, proteína ou sólidos totais no tempo t, a é o parâmetro associado à produção inicial, b é o parâmetro associado à taxa de ascensão da produção até o pico, c é o parâmetro associado à taxa declínio da curva de lactação e t é o tempo representativo do dia em lactação. Os parâmetros foram comparados pelo intervalo de confiança considerando 95% de probabilidade. A produção no pico foi calculada pela fórmula: a(b/c)b e-b. Não houve diferença estatística (p > 0,05) entre cabras primíparas soropositivas e soronegativas para a produção inicial, taxa de ascensão e taxa de declínio dos parâmetros para a produção de leite, de gordura, de proteína e de sólidos totais. Porém a produção no pico das variáveis em cabras soronegativas foi de26%, 27%, 23% e 23%, respectivamente, mais altas que em soropositivas. Conclui-se que a CAE não afeta a produção leiteira, bem como a produção de gordura, proteína e sólidos totais ao longo da curva de lactação, entretanto cabras soropositivas têm menor produção de leite e de seus componentes no pico da curva de lactação em relação às soronegativas.

Influence of caprine arthritis encephalitis on milk production and quality along the lactation curve in primiparous dairy goats / Influência da artrite encefalite caprina na produção e qualidade do leite ao longo da curva de lactação em cabras leiteiras primíparas

The aim of this study was to examine the influence of caprine arthritis encephalitis (CAE) on the production of milk and its components (protein, fat and total solids) along the lactation curve of primiparous goats. The study was developed using a database from the years 2014 to 2018. Sixty-one animals were subjected to the serological test for CAE, whose result indicated that 42 were seropositive and 19 seronegative, and milk production and quality data were compiled. To adjust the curve for production of milk, fat, protein and total solids during lactation, the following nonlinear model developed by Wood (1967) was used: Y = atb e-ct, where Y represents the observations of milk, fat, protein or total solid production at time t; a is the parameter associated with the initial production; b is the parameter associated with the rate of rise in production until the peak; c is the parameter associated with the rate of decline of the lactation curve; and t is the representative time of the day in milk. The parameters were compared by the confidence interval considering 95% probability. Peak production was calculated using the following formula: a(b/c)b e-b. There was no statistical difference (p > 0.05) between seropositive and seronegative primiparous goats for initial production and the rates of rise and decline of the parameters of milk, fat, protein and total solid production. However, at their peak, these variables were 26, 27, 23 and 23% higher, respectively, in the seronegative goats than in their seropositive counter parts. In conclusion, CAE does not affect milk production or the production of fat, protein and total solids along the lactation curve, but seropositive goats produce less milk and respective components at the peak of the lactation curve than seronegative goats.(AU)

Objetivou-se avaliar a influência da artrite encefalite caprina (CAE) sobre a produção leiteira e seus constituintes (proteína, gordura e sólidos totais) ao longo da curva de lactação de cabras primíparas. O estudo foi realizado a partir do banco de dados dos anos de 2014 a 2018. Foram utilizados um total de 61 animais, todos submetidos ao teste de sorologia para CAE, sendo 42 cabras soropositivas e 19soronegativas, e os dados foram compilados de produção e qualidade do leite. Para o ajuste da curva para a produção de leite, gordura, proteína e sólidos totais ao longo da lactação foi utilizado o modelo não linear de Wood (1967): Y = atb e-ct, no qual: Y representa as observações de produção de leite, gordura, proteína ou sólidos totais no tempo t, a é o parâmetro associado à produção inicial, b é o parâmetro associado à taxa de ascensão da produção até o pico, c é o parâmetro associado à taxa declínio da curva de lactação e t é o tempo representativo do dia em lactação. Os parâmetros foram comparados pelo intervalo de confiança considerando 95% de probabilidade. A produção no pico foi calculada pela fórmula: a(b/c)b e-b. Não houve diferença estatística (p > 0,05) entre cabras primíparas soropositivas e soronegativas para a produção inicial, taxa de ascensão e taxa de declínio dos parâmetros para a produção de leite, de gordura, de proteína e de sólidos totais. Porém a produção no pico das variáveis em cabras soronegativas foi de26%, 27%, 23% e 23%, respectivamente, mais altas que em soropositivas. Conclui-se que a CAE não afeta a produção leiteira, bem como a produção de gordura, proteína e sólidos totais ao longo da curva de lactação, entretanto cabras soropositivas têm menor produção de leite e de seus componentes no pico da curva de lactação em relação às soronegativas.(AU)

Health evaluation of donkeys: parasite control methods and a model for challenge infections / Avaliação sanitária de jumentos: métodos de controle parasitário e um modelo para o desafio das infecções

Donkeys, mules, and asses are domestic animals of worldwide distribution, found in all regions of Brazil. Although more health data is needed from these species, some sectors of today's society are exploring alternatives to use these animals for milk production and the use of donkeys in social events and onotherapy. Donkeys (Equus asinus) are used in many everyday activities, but the animals need better welfare conditions. Although it is well known that endoparasite infections (i.e. cyathostomins, Strongylus spp., Parascaris sp.) can harm the clinical condition of the animals, there are limited clinical and laboratory supporting data, including registered therapeutic drugs for their control. The objective of the present work was to review the existing literature about parasite infections of donkeys, including their clinical implications, and the drug efficacy test to help practitioners improve their health management programs. To assist with that, we have developed a questionnaire to identify the risk factors of donkey farming, which is presented here in English and in Portuguese. Lastly, the present article also includes an original simulation using the susceptible-infected-recovered (SIR) model with low, moderate, and severe scenarios to help visualize the risk of parasite infections. The SIR model was based on the disease condition of donkeys in Brazil, using transient interaction levels from 0.0015 to 0.0025, infectivity levels from 0.10 to 0.40, and distinct recovery rates (R) from 0.01 to 0.08. As milk production is an expanding new activity worldwide, we want to emphasize that the first comprehensive studies must take into account differences in animal age, breed, and body condition score, local climate, pasture quality, day of sampling, and the period of lactation within the lactation curve to measure the health condition of donkeys. (AU)

Jumentos, mulas e burros são animais domésticos de distribuição mundial, encontrados em todas as regiões do Brasil. Muito embora exista uma grande necessidade de produzir mais dados sobre estas espécies, atualmente alguns setores estão buscando alternativas de exploração para estes animais, como a produção de leite e o uso deles em atividades sociais e onoterapia. Jumentos (Equus asinus) participam de várias atividades sociais, porém os animais necessitam de melhores condições de manejo e bem-estar. Embora as endoparasitoses (ex. ciatostomíneos, Strongylus spp., Parascaris sp.) possam causar grave condição clínica para estes animais, dados clínicos e laboratoriais são escassos, incluindo a falta de produtos específicos para seu controle. O objetivo do presente trabalho foi revisar a literatura existente sobre infecções parasitárias em jumentos, incluindo as implicações clínicas e os testes de eficácia de drogas, visando auxiliar os profissionais e os seus programas de manejo sanitário.(AU)

Health evaluation of donkeys: parasite control methods and a model for challenge infections / Avaliação sanitária de jumentos: métodos de controle parasitário e um modelo para o desafio das infecções

Donkeys, mules, and asses are domestic animals of worldwide distribution, found in all regions of Brazil. Although more health data is needed from these species, some sectors of today's society are exploring alternatives to use these animals for milk production and the use of donkeys in social events and onotherapy. Donkeys (Equus asinus) are used in many everyday activities, but the animals need better welfare conditions. Although it is well known that endoparasite infections (i.e. cyathostomins, Strongylus spp., Parascaris sp.) can harm the clinical condition of the animals, there are limited clinical and laboratory supporting data, including registered therapeutic drugs for their control. The objective of the present work was to review the existing literature about parasite infections of donkeys, including their clinical implications, and the drug efficacy test to help practitioners improve their health management programs. To assist with that, we have developed a questionnaire to identify the risk factors of donkey farming, which is presented here in English and in Portuguese. Lastly, the present article also includes an original simulation using the susceptible-infected-recovered (SIR) model with low, moderate, and severe scenarios to help visualize the risk of parasite infections. The SIR model was based on the disease condition of donkeys in Brazil, using transient interaction levels from 0.0015 to 0.0025, infectivity levels from 0.10 to 0.40, and distinct recovery rates (R) from 0.01 to 0.08. As milk production is an expanding new activity worldwide, we want to emphasize that the first comprehensive studies must take into account differences in animal age, breed, and body condition score, local climate, pasture quality, day of sampling, and the period of lactation within the lactation curve to measure the health condition of donkeys.(AU)

Jumentos, mulas e burros são animais domésticos de distribuição mundial, encontrados em todas as regiões do Brasil. Muito embora exista uma grande necessidade de produzir mais dados sobre estas espécies, atualmente alguns setores estão buscando alternativas de exploração para estes animais, como a produção de leite e o uso deles em atividades sociais e onoterapia. Jumentos (Equus asinus) participam de várias atividades sociais, porém os animais necessitam de melhores condições de manejo e bem-estar. Embora as endoparasitoses (ex. ciatostomíneos, Strongylus spp., Parascaris sp.) possam causar grave condição clínica para estes animais, dados clínicos e laboratoriais são escassos, incluindo a falta de produtos específicos para seu controle. O objetivo do presente trabalho foi revisar a literatura existente sobre infecções parasitárias em jumentos, incluindo as implicações clínicas e os testes de eficácia de drogas, visando auxiliar os profissionais e os seus programas de manejo sanitário.(AU)

The geometry of the lactation curve based on Wood's equation: a two-step prediction

Lactation records from cows of the southwestern Paraná state, Brazil, form the dataset of this study. We applied the information-theoretic approach to evaluate the ability of the nonlinear Wood, Brody, Dijkstra, and Gamma functions to fit to these data by employing a two-step technique based on nonlinear mixed-effects models and generalized linear mixed-effects models. Wood's equation was fitted with the combination of a first-order autoregressive correlation structure and a variance function to account for heteroscedasticity. This version was the best choice to mimic lactation records. Some geometric attributes of Wood's model were deduced, mainly the ascending specific rate from parturition to peak milk yield and the descending specific rate as a measure of the lactation persistence of the milk yield at peak production. Breed and parity order of the cows were assumed as fixed effects to obtain a reliable model fitting process. Regardless of breed, first-order parity cows had greater persistency than their older counterparts, and the greater the ascending rate of milk yield from the parturition to the peak, the sharper the decrease in milk yield post-peak; therefore, the rates (absolute values) of ascending and descending phases correlated positively. Nonetheless, the actual estimated values of the descending phase rates are negative. Wood's equation was flexible enough to mimic either concave- and convex-shaped lactation profiles. The correlations between both peak milk yield and random estimates for ß with total milk yield per lactation were positive. However, peak milk yield might not be the only variable used for ranking cows; the total milk yield integrates all information of the lactation profile through the estimated parameters of Wood's equation.(AU)

Productive and reproductive performance of Holstein cows in agreste, Pernambuco, from 2007 to 2017 / Desempenho produtivo e reprodutivo de vacas Holandesas no agreste de Pernambuco, no período de 2007 a 2017

The aim of this study was to assess the productive and reproductive performance of Holstein cows grown in the Agreste region of Pernambuco. Dairy records were collected from three farms located in the Agreste region of the state of Pernambuco each month between 2007 and 2017. According to the National Institute of Meteorology the average annual temperature during the collection period was 24.21 ºC, mean annual rainfall was 551.7 mm and mean annual relative humidity was 75.92%. A total of 42,677 data points concerning milk production, milk components and somatic cell score (SCS), as well as other zootechnical information regarding reproductive management, are analyzed herein. In order to assess cow productive performance, lactation curve estimates were performed according to calving order by applying the Wood model, while milk production, milk components and SCS were analyzed according to calving order and farm, season, calving year and the interaction between calving order and season. Regarding reproductive evaluations, farm effects on indices such as age at first calving (IPP), calving interval (IP) and service period (PS) were evaluated. Data were processed using analysis of variance SAS PROC GLM commands, while PROC NLIN commands were used to estimate the curves. Significant (p < 0.05) farm, calving order, season, calving year and interaction effects on production values, milk composition and SCS were noted. Higher amounts of certain milk components (lactose, total solids and non-fat solids) were observed in primiparous cows. Multiparous cows were the most productive in relation to the amount of milk produced milk (34.15 kg/milk/day) and, consequently, presented the highest SCS (4.48). The Wood model showed a good fit of lactation curve characterized by an ascending phase until peaking and a descending phase following the peak. Regarding the assessed reproductive indices, a significant effect...(AU)

Objetivou-se com este trabalho avaliar o desempenho produtivo e reprodutivo de vacas holandesas criadas no Agreste de Pernambuco. Foram analisados registros de controle leiteiro obtidos em três fazendas localizadas na região Agreste do estado de Pernambuco, realizados mensalmente entre os anos de 2007 e 2017. As características climáticas, de acordo com o Instituto Nacional de Meteorologia, para o período de coleta foram: temperatura média anual de 24,21ºC; precipitação média anual de 551,7 mm e umidade relativa média anual de 75,92%. Um total de 42.677 informações sobre produção de leite, componentes do leite e escore de células somáticas (ECS) e outras informações de controle zootécnico referente ao manejo reprodutivo foram analisados neste estudo. Para avaliar o desempenho produtivo das vacas, foram feitas estimativas das curvas de lactação em função da ordem de parto utilizando o modelo de Wood e a produção de leite, componentes do leite e ECS foram analisados em função da ordem de parto e quanto aos efeitos de fazenda, estação do ano e ano de parto e a interação ordem de parto e estação do ano. Para avaliação reprodutiva, foi avaliado o efeito da fazenda sobre os índices como idade ao primeiro parto (IPP), intervalo de parto (IP) e período de serviço (PS). Os dados foram processados usando os comandos do SAS, PROC GLM para análise de variância e PROC NLIN para estimativa das curvas. Houve efeito significativo (p < 0,05) de fazenda, ordem de parto, estação do ano, ano de parto e da interação analisada, sobre os valores de produção, composição do leite e ECS. Os maiores teores de alguns componentes (lactose, sólidos totais e sólidos não gordurosos) do leite foram observados nas primíparas. As vacas multíparas foram as mais produtivas em relação à quantidade de leite produzido diariamente (34,15 kg/leite/dia) e consequentemente, apresentaram maior ECS (4,48). O modelo de Wood apresentou bom ajuste aos dados...(AU)

Practicability of somatic cell count and electrical conductivity as subclinical mastitis diagnostic tests in camels (Camelus dromedarius)

Critical gaps exist in our understanding of the diagnostic reliability of subclinical mastitis tests in dromedary camels. Using a retrospective longitudinal cross-sectional approach, 191 lactating camels were randomly sampled from 47 camel herds to investigate at first the practicability of somatic cell count (SCC) and electrical conductivity (EC) tests as subclinical mastitis tests in camels through their validations by California mastitis test (CMT) score, and then through the subsequent employments of those objective means in assessing certain potential risk markers predisposing camels to this disease. Results indicate the reliability and validity of SCC test, in contrast to EC test, in distinguishing subclinical mastitic udders in camels, as demonstrated by the strong interrelationships ( r = 0.83 vs 0.12; R 2 = 0.80 vs 0.02), excellent agreement beyond chance (kappa coefficient = 0.76 vs 0.09) between SCC test and CMT scores, as well as by the high sensitivity of SCC test [Area Under Curve (AUC) = 0.94 vs 0.48] in distinguishing mastitic udders compared to the EC test. Based on the SCC test, the calculated overall prevalence rate for subclinical mastitis was 35 %, and the breed, parity, and lactation period were the only risk markers predisposing camels to subclinical mastitis. Collectively, it can be concluded that the objective SCC test possesses considerable diagnostic merit for early detection of subclinical mastitis in camels, while the EC test was non-satisfactory and non-diagnostic. Accordingly, it seems logical to base herd management decisions on SCC readings using the cut-off Log10SCC value of 5.67 (or SCC = 472.50 × 03 cells mL–1).

Practicability of somatic cell count and electrical conductivity as subclinical mastitis diagnostic tests in camels (Camelus dromedarius)

Critical gaps exist in our understanding of the diagnostic reliability of subclinical mastitis tests in dromedary camels. Using a retrospective longitudinal cross-sectional approach, 191 lactating camels were randomly sampled from 47 camel herds to investigate at first the practicability of somatic cell count (SCC) and electrical conductivity (EC) tests as subclinical mastitis tests in camels through their validations by California mastitis test (CMT) score, and then through the subsequent employments of those objective means in assessing certain potential risk markers predisposing camels to this disease. Results indicate the reliability and validity of SCC test, in contrast to EC test, in distinguishing subclinical mastitic udders in camels, as demonstrated by the strong interrelationships ( r = 0.83 vs 0.12; R 2 = 0.80 vs 0.02), excellent agreement beyond chance (kappa coefficient = 0.76 vs 0.09) between SCC test and CMT scores, as well as by the high sensitivity of SCC test [Area Under Curve (AUC) = 0.94 vs 0.48] in distinguishing mastitic udders compared to the EC test. Based on the SCC test, the calculated overall prevalence rate for subclinical mastitis was 35 %, and the breed, parity, and lactation period were the only risk markers predisposing camels to subclinical mastitis. Collectively, it can be concluded that the objective SCC test possesses considerable diagnostic merit for early detection of subclinical mastitis in camels, while the EC test was non-satisfactory and non-diagnostic. Accordingly, it seems logical to base herd management decisions on SCC readings using the cut-off Log10SCC value of 5.67 (or SCC = 472.50 × 03 cells mL–1).(AU)

Estimativas de parâmetros genéticos e de ambiente para medidas repetidas de produção leiteira em caprinos / Estimates of genetic and environmental parameters for repeated measures of milk production in goats

Objetivou-se com este estudo comparar funções matemáticas no ajuste da curva de lactação média e individual de caprinos e estimar parâmetros genéticos e ambientais para medidas repetidas de produção de leite. Foram utilizadas 183 lactações, sendo 121 de cabras Saanen e 62 de cabras Alpinas, de animais pertencentes ao Laboratório de Caprinocultura e Ovinocultura da UFPB/CCHSA. O controle leiteiro foi realizado em intervalos de sete dias. O ajuste foi feito para curva média utilizando-se seis funções matemáticas: polinomial inversa, linear hiperbólica, gama incompleta, quadrática logarítmica, linear e quadrática, sendo ajustada por processos interativos, através de regressão não linear. Os critérios utilizados para verificar a qualidade do ajuste para cada função foram: coeficiente de determinação ajustado (R2a), percentuais de desvio entre as produções totais observadas e estimadas, percentuais de curvas típicas, desvio médio absoluto e quadrado médio dos resíduos. Verificou-se que qualquer um dos modelos testados pode ser utilizado para estimativas da curva média, porém, para o estudo das curvas individuais, o modelo Gama Incompleto deve ser preferido por apresentar melhores estimativas dos componentes da curva de lactação.

The objective of this study was to compare mathematical functions in adjusting the mean and individual lactation curve of goats and to estimate genetic and environmental parameters for repeated measures of milk production. 183 lactations were used, 121 of Saanen goats and 62 of Alpine goats, of animals belonging to the Laboratory of goat and Sheep of UFPB/CCHSA. The milk control was performed at intervals of seven days. The adjustment was made to the mean curve using six mathematical functions: inverse polynomial, linear hyperbolic, incomplete gamma, quadratic logarithmic, linear and quadratic, and adjusted by interactive processes through non-linear regression. The criteria used to verify the fit quality for each function were adjusted coefficient of determination (R2a), percentages of deviation between observed and estimated total yields, percentages of typical curves, mean absolute deviation and mean square of residues. It was verified that any of the models tested can be used for mean curve estimates, but for the study of the individual curves, the incomplete gamma model should be preferred because it presents better estimates of the components of the lactation curve.

Estimativas de parâmetros genéticos e de ambiente para medidas repetidas de produção leiteira em caprinos / Estimates of genetic and environmental parameters for repeated measures of milk production in goats

Objetivou-se com este estudo comparar funções matemáticas no ajuste da curva de lactação média e individual de caprinos e estimar parâmetros genéticos e ambientais para medidas repetidas de produção de leite. Foram utilizadas 183 lactações, sendo 121 de cabras Saanen e 62 de cabras Alpinas, de animais pertencentes ao Laboratório de Caprinocultura e Ovinocultura da UFPB/CCHSA. O controle leiteiro foi realizado em intervalos de sete dias. O ajuste foi feito para curva média utilizando-se seis funções matemáticas: polinomial inversa, linear hiperbólica, gama incompleta, quadrática logarítmica, linear e quadrática, sendo ajustada por processos interativos, através de regressão não linear. Os critérios utilizados para verificar a qualidade do ajuste para cada função foram: coeficiente de determinação ajustado (R2a), percentuais de desvio entre as produções totais observadas e estimadas, percentuais de curvas típicas, desvio médio absoluto e quadrado médio dos resíduos. Verificou-se que qualquer um dos modelos testados pode ser utilizado para estimativas da curva média, porém, para o estudo das curvas individuais, o modelo Gama Incompleto deve ser preferido por apresentar melhores estimativas dos componentes da curva de lactação.(AU)

The objective of this study was to compare mathematical functions in adjusting the mean and individual lactation curve of goats and to estimate genetic and environmental parameters for repeated measures of milk production. 183 lactations were used, 121 of Saanen goats and 62 of Alpine goats, of animals belonging to the Laboratory of goat and Sheep of UFPB/CCHSA. The milk control was performed at intervals of seven days. The adjustment was made to the mean curve using six mathematical functions: inverse polynomial, linear hyperbolic, incomplete gamma, quadratic logarithmic, linear and quadratic, and adjusted by interactive processes through non-linear regression. The criteria used to verify the fit quality for each function were adjusted coefficient of determination (R2a), percentages of deviation between observed and estimated total yields, percentages of typical curves, mean absolute deviation and mean square of residues. It was verified that any of the models tested can be used for mean curve estimates, but for the study of the individual curves, the incomplete gamma model should be preferred because it presents better estimates of the components of the lactation curve.(AU)

Association between gestation length and lactation performance, lactation curve, calf birth weight and dystocia in Holstein dairy cows in Iran

In this study, 252,798 lactations on 108,077 cows in 433 herds were used to determine the association between gestation length (GL) and lactation performance, lactation curve, calf birth weight and dystocia in Holstein dairy cows in Iran. The GL averaged 278.1 ± 5.41 d, was categorized as short (SGL; at 1 SD below the population mean), average (AGL; the population mean ± 1 SD), or long (LGL; at least 1 SD above the population mean). Factors including parity, calf gender and calving season were associated with the GL. Primiparous cows with SGL had less lactation performance than those with longer GL; however, there was no difference between those with AGL and LGL. Multiparous cows with longer GL always had more partial and 305-d lactation performance. Primiparous cows with SGL produced less milk at the beginning of lactation and at the peak than those with AGL or LGL; inverse trends were found for lactation persistency, upward and downward slopes of the lactation curve. Within multiparous, a direct relationship was found between GL and the peak yield, where cows with longer GL always produced more milk at the peak. Multiparous cows with SGL produced less milk at the beginning of lactation, reached their peaks later, had higher lactation persistency and showed a lower upward slope of lactation curve than those with AGL or LGL. There was a direct relationship between GL and calf birth weight, where cows with longer GL had calves with more weight at the birth. Within primiparous, cows with SGL had the lowest and those with LGL had the highest rate of dystocia. However, multiparous cows with AGL had a lower rate of dystocia than those with SGL or LGL. Although there was a direct relationship between GL and lactation performance, intermediate GL seems optimal when considering dystocia.(AU)

Association between gestation length and lactation performance, lactation curve, calf birth weight and dystocia in Holstein dairy cows in Iran

In this study, 252,798 lactations on 108,077 cows in 433 herds were used to determine the association between gestation length (GL) and lactation performance, lactation curve, calf birth weight and dystocia in Holstein dairy cows in Iran. The GL averaged 278.1 ± 5.41 d, was categorized as short (SGL; at 1 SD below the population mean), average (AGL; the population mean ± 1 SD), or long (LGL; at least 1 SD above the population mean). Factors including parity, calf gender and calving season were associated with the GL. Primiparous cows with SGL had less lactation performance than those with longer GL; however, there was no difference between those with AGL and LGL. Multiparous cows with longer GL always had more partial and 305-d lactation performance. Primiparous cows with SGL produced less milk at the beginning of lactation and at the peak than those with AGL or LGL; inverse trends were found for lactation persistency, upward and downward slopes of the lactation curve. Within multiparous, a direct relationship was found between GL and the peak yield, where cows with longer GL always produced more milk at the peak. Multiparous cows with SGL produced less milk at the beginning of lactation, reached their peaks later, had higher lactation persistency and showed a lower upward slope of lactation curve than those with AGL or LGL. There was a direct relationship between GL and calf birth weight, where cows with longer GL had calves with more weight at the birth. Within primiparous, cows with SGL had the lowest and those with LGL had the highest rate of dystocia. However, multiparous cows with AGL had a lower rate of dystocia than those with SGL or LGL. Although there was a direct relationship between GL and lactation performance, intermediate GL seems optimal when considering dystocia.

Glucose and insulin curve in pregnant mares and its relationship with clinical and biometric features of newborn foals

ABSTRACT: The aim of the present study was to describe the dynamics of glucose and insulin curves in pregnant mares, and to evaluate the curves according to body condition score, identifying the presence of insulin resistance and correlating these values with the weight, height and clinical changes of the neonates. For this, pregnant mares were evaluated and then grouped according to body condition score during the gestation length until lactation. GrM corresponds to mares with moderate body score (BCS 5-6); GrOv were mares with overweight body score (BCS 7) and GrOb were obese mares (BCS 8-9). A two-step oral sugar test (OST) was used to determine the data. Cortisol analysis was performed with 300-320 days of gestation, at foaling and after parturition. For evaluation of the neonate, a general clinical examination and, weight and height measurements were performed. The results showed hyperglycemia in response to OST with normal insulin values at foaling with a subsequent fall in both values at lactation disregarding group division. Baseline glucose was decreased in GrM compared to GrOv and GrOb with 70-100 days of gestation and with 130-160 days of gestation. With 270-300 days of gestation and post-partum GrOb had increased baseline glucose than GrM. After OST, glucose at foaling day in GrOb presented increased values than GrM. Baseline insulin values did not differ between groups. Post OST insulin levels were higher in GrOb than GrM and GrOv at parturition. No difference in cortisol between moments was identified. GrOb and GrOv maintained increased concentrations after foaling while GrM had a decrease. No correlation was found between maternal glucose and insulin values with foal weight and height, however, a lower ratio between neonatal weight and mares weight in GrOb and GrOv was identified in relation to the GrM. At foaling, mares presented glucose dysregulation, with obese and overweight mares presenting a greater response to OST.

RESUMO: O objetivo do presente estudo foi descrever a dinâmica das curvas de glicose e insulina em éguas gestantes e avaliar as curvas de acordo com o escore de condição corporal, identificando a presença de resistência insulínica e correlacionando esses valores com o peso, altura e alterações clínicas dos neonatos. Para isso, as éguas prenhes foram avaliadas em conjunto e agrupadas de acordo com o escore de condição corporal durante a gestação até o pós-parto. GrM pertenciam éguas com escore corporal moderado (EC 5-6); GrOv, grupo de éguas com escore corporal acima do peso (EC 7) e GrOb, grupo de éguas obesas (EC 8-9). O teste de glicose oral em duas etapas (OST) foi usado para determinar os dados. A análise do cortisol também foi realizada nos 300-320 dias de gestação, no dia do parto e após o parto. Para avaliação do neonato, foram realizados exame clínico geral e medidas de peso e altura. Os resultados mostraram hiperglicemia em resposta ao OST com valores normais de insulina no momento parto, com uma queda subsequente em ambas as variáveis na lactação, desconsiderando a divisão do grupo. A glicemia basal diminuiu no GrM em comparação com GrOv e GrOb com 70-100 dias de gestação e com 130-160 dias de gestação. Com 270-300 dias de gestação e no pós-parto, o GrOb apresentou aumento na glicemia basal em relação ao GrM. Após OST, a glicose no dia do parto no GrOb apresentou valores aumentados em relação ao GrM. Os valores basais de insulina não diferiram entre os grupos. Após OST níveis de insulina foram maiores no GrOb do que GrM e GrOv no momento do parto. Não houve diferença nos valores de cortisol entre os momentos. O GrOb e GrOv mantiveram cortisol aumentado após o parto enquanto o GrM diminuiu. Não foi encontrada correlação entre os valores de glicemia e insulina materna com o peso e a altura do potro, entretanto, foi identificada uma relação menor entre o peso neonatal e o peso da égua no GrOb e GrOv em relação ao GrM. No parto, as éguas apresentaram desregulação da glicose, sendo que as éguas obesas e com sobrepeso apresentaram uma resposta maior ao OST.

Frequency of microorganisms isolated at different stages of lactation and milk production loss associated with somatic cell count and to mastitis-causing pathogens / Frequência de microrganismos isolados em diferentes fases da lactação e perda de produção de leite associada à contagem de células somáticas e aos patógenos causadores de mastite

The aim of this study was to evaluate the frequency of isolation of agents causing subclinical mastitis in a herd and to estimate production losses associated with SCC> 200,000cells/mL. Three 7-day interval microbiological cultures were performed in all lactating animals from the same farm that was evaluated from June to July. To evaluate the negative and positive isolation frequencies between the lactation phases, a Chi-square test was performed. Simple linear regressions were performed to evaluate the lactation curve of animals grouped by pathogens isolated from negative cows in the microbiological culture and with SCC <200,000cells/mL. To estimate the production losses between the groups, regression coefficients were used. Results found in this experiment were: Culture-negative cows with SCC ≥ 200,000cells/mL, cows testing positive in milk culture, with SCC <200,000cells/mL and cows testing positive in milk culture, with SCC ≥ 200,000cells/mL. Milk production was -3.5; -0.5 and -4.27kg, respectively, when compared to culture-negative cows with SCC <200,000cells/mL. Cows infected with yeast cells, Coagulase-negative staphylococci (CNS), Staphylococcus aureus and environmental streptococci produced -3.42; -0.5; -0.168 and -2.5kg of milk when compared to culture-negative cows with SCC <200,000cells/mL. SCC indicates an inflammatory reaction in the mammary gland and it is directly associated with milk production losses and with presence of microorganisms in the mammary gland.(AU)

O objetivo deste estudo foi avaliar a frequência de isolamento de agentes causadores de mastite subclínica em um rebanho e estimar as perdas de produção associadas com CCS>200.000 cél./mL. Três cultivos microbiológicos intervalados por sete dias foram realizados em todos os animais em lactação da propriedade avaliada, no período de junho a julho. Para avaliar as frequências de isolamento negativo e positivo entre as fases da lactação, foi realizado um teste de qui-quadrado. Foram realizadas regressões lineares simples para avaliar a curva de lactação dos animais agrupados por patógenos isolados em relação a vacas negativas na cultura microbiológica e com CCS < 200.000 cél./mL. Os coeficientes das regressões foram utilizados para estimar as perdas de produção entre os grupos. Vacas com resultado negativo na microbiologia, mas com CCS ≥ 200.000 cél./mL, positivas na microbiologia com CCS < 200.000 cél./mL e positivas com CCS ≥ 200.000 cél./mL, produziram por dia, respectivamente, -3,5; -0,5 e -4,27kg de leite em relação às vacas negativas com CCS < 200.000 cél./mL. Vacas infectadas com células leveduriformes, Staphylococcus coagulase negativa, Staphylococcus aureus e Streptococcus ambientais produziram, respectivamente, -3,42; -0,5; -0,168 e -2,5kg de leite, comparadas a vacas negativas com CCS < 200.000 cél./mL. A CCS, indicativa de reação inflamatória, encontra-se diretamente associada às perdas de produção de leite, assim como a presença do microrganismo na glândula mamária.(AU)

Frequency of microorganisms isolated at different stages of lactation and milk production loss associated with somatic cell count and to mastitis-causing pathogens / Frequência de microrganismos isolados em diferentes fases da lactação e perda de produção de leite associada à contagem de células somáticas e aos patógenos causadores de mastite

The aim of this study was to evaluate the frequency of isolation of agents causing subclinical mastitis in a herd and to estimate production losses associated with SCC> 200,000cells/mL. Three 7-day interval microbiological cultures were performed in all lactating animals from the same farm that was evaluated from June to July. To evaluate the negative and positive isolation frequencies between the lactation phases, a Chi-square test was performed. Simple linear regressions were performed to evaluate the lactation curve of animals grouped by pathogens isolated from negative cows in the microbiological culture and with SCC <200,000cells/mL. To estimate the production losses between the groups, regression coefficients were used. Results found in this experiment were: Culture-negative cows with SCC ≥ 200,000cells/mL, cows testing positive in milk culture, with SCC <200,000cells/mL and cows testing positive in milk culture, with SCC ≥ 200,000cells/mL. Milk production was -3.5; -0.5 and -4.27kg, respectively, when compared to culture-negative cows with SCC <200,000cells/mL. Cows infected with yeast cells, Coagulase-negative staphylococci (CNS), Staphylococcus aureus and environmental streptococci produced -3.42; -0.5; -0.168 and -2.5kg of milk when compared to culture-negative cows with SCC <200,000cells/mL. SCC indicates an inflammatory reaction in the mammary gland and it is directly associated with milk production losses and with presence of microorganisms in the mammary gland.(AU)

O objetivo deste estudo foi avaliar a frequência de isolamento de agentes causadores de mastite subclínica em um rebanho e estimar as perdas de produção associadas com CCS>200.000 cél./mL. Três cultivos microbiológicos intervalados por sete dias foram realizados em todos os animais em lactação da propriedade avaliada, no período de junho a julho. Para avaliar as frequências de isolamento negativo e positivo entre as fases da lactação, foi realizado um teste de qui-quadrado. Foram realizadas regressões lineares simples para avaliar a curva de lactação dos animais agrupados por patógenos isolados em relação a vacas negativas na cultura microbiológica e com CCS < 200.000 cél./mL. Os coeficientes das regressões foram utilizados para estimar as perdas de produção entre os grupos. Vacas com resultado negativo na microbiologia, mas com CCS ≥ 200.000 cél./mL, positivas na microbiologia com CCS < 200.000 cél./mL e positivas com CCS ≥ 200.000 cél./mL, produziram por dia, respectivamente, -3,5; -0,5 e -4,27kg de leite em relação às vacas negativas com CCS < 200.000 cél./mL. Vacas infectadas com células leveduriformes, Staphylococcus coagulase negativa, Staphylococcus aureus e Streptococcus ambientais produziram, respectivamente, -3,42; -0,5; -0,168 e -2,5kg de leite, comparadas a vacas negativas com CCS < 200.000 cél./mL. A CCS, indicativa de reação inflamatória, encontra-se diretamente associada às perdas de produção de leite, assim como a presença do microrganismo na glândula mamária.(AU)

Glucose and insulin curve in pregnant mares and its relationship with clinical and biometric features of newborn foals / Curvas de glicose e insulina em éguas gestantes e sua relação com as características clínicas e biométricas dos neonatos

The aim of the present study was to describe the dynamics of glucose and insulin curves in pregnant mares, and to evaluate the curves according to body condition score, identifying the presence of insulin resistance and correlating these values ​​with the weight, height and clinical changes of the neonates. For this, pregnant mares were evaluated and then grouped according to body condition score during the gestation length until lactation. GrM corresponds to mares with moderate body score (BCS 5-6); GrOv were mares with overweight body score (BCS 7) and GrOb were obese mares (BCS 8-9). A two-step oral sugar test (OST) was used to determine the data. Cortisol analysis was performed with 300-320 days of gestation, at foaling and after parturition. For evaluation of the neonate, a general clinical examination and, weight and height measurements were performed. The results showed hyperglycemia in response to OST with normal insulin values at foaling with a subsequent fall in both values at lactation disregarding group division. Baseline glucose was decreased in GrM compared to GrOv and GrOb with 70-100 days of gestation and with 130-160 days of gestation. With 270-300 days of gestation and post-partum GrOb had increased baseline glucose than GrM. After OST, glucose at foaling day in GrOb presented increased values than GrM. Baseline insulin values did not differ between groups. Post OST insulin levels were higher in GrOb than GrM and GrOv at parturition. No difference in cortisol between moments was identified. GrOb and GrOv maintained increased concentrations after foaling while GrM had a decrease. No correlation was found between maternal glucose and insulin values with foal weight and height, however, a lower ratio between neonatal weight and mare's weight in GrOb and GrOv was identified in relation to the GrM. At foaling, mares presented glucose dysregulation, with obese and overweight mares presenting a greater response to OST.(AU)

O objetivo do presente estudo foi descrever a dinâmica das curvas de glicose e insulina em éguas gestantes e avaliar as curvas de acordo com o escore de condição corporal, identificando a presença de resistência insulínica e correlacionando esses valores com o peso, altura e alterações clínicas dos neonatos. Para isso, as éguas prenhes foram avaliadas em conjunto e agrupadas de acordo com o escore de condição corporal durante a gestação até o pós-parto. GrM pertenciam éguas com escore corporal moderado (EC 5-6); GrOv, grupo de éguas com escore corporal acima do peso (EC 7) e GrOb, grupo de éguas obesas (EC 8-9). O teste de glicose oral em duas etapas (OST) foi usado para determinar os dados. A análise do cortisol também foi realizada nos 300-320 dias de gestação, no dia do parto e após o parto. Para avaliação do neonato, foram realizados exame clínico geral e medidas de peso e altura. Os resultados mostraram hiperglicemia em resposta ao OST com valores normais de insulina no momento parto, com uma queda subsequente em ambas as variáveis na lactação, desconsiderando a divisão do grupo. A glicemia basal diminuiu no GrM em comparação com GrOv e GrOb com 70-100 dias de gestação e com 130-160 dias de gestação. Com 270-300 dias de gestação e no pós-parto, o GrOb apresentou aumento na glicemia basal em relação ao GrM. Após OST, a glicose no dia do parto no GrOb apresentou valores aumentados em relação ao GrM. Os valores basais de insulina não diferiram entre os grupos. Após OST níveis de insulina foram maiores no GrOb do que GrM e GrOv no momento do parto. Não houve diferença nos valores de cortisol entre os momentos. O GrOb e GrOv mantiveram cortisol aumentado após o parto enquanto o GrM diminuiu. Não foi encontrada correlação entre os valores de glicemia e insulina materna com o peso e a altura do potro, entretanto, foi identificada uma relação menor entre o peso neonatal e o peso da égua no GrOb e GrOv em relação ao GrM. No parto, as éguas apresentaram desregulação da glicose, sendo que as éguas obesas e com sobrepeso apresentaram uma resposta maior ao OST.(AU)

Glucose and insulin curve in pregnant mares and its relationship with clinical and biometric features of newborn foals / Curvas de glicose e insulina em éguas gestantes e sua relação com as características clínicas e biométricas dos neonatos

The aim of the present study was to describe the dynamics of glucose and insulin curves in pregnant mares, and to evaluate the curves according to body condition score, identifying the presence of insulin resistance and correlating these values ​​with the weight, height and clinical changes of the neonates. For this, pregnant mares were evaluated and then grouped according to body condition score during the gestation length until lactation. GrM corresponds to mares with moderate body score (BCS 5-6); GrOv were mares with overweight body score (BCS 7) and GrOb were obese mares (BCS 8-9). A two-step oral sugar test (OST) was used to determine the data. Cortisol analysis was performed with 300-320 days of gestation, at foaling and after parturition. For evaluation of the neonate, a general clinical examination and, weight and height measurements were performed. The results showed hyperglycemia in response to OST with normal insulin values at foaling with a subsequent fall in both values at lactation disregarding group division. Baseline glucose was decreased in GrM compared to GrOv and GrOb with 70-100 days of gestation and with 130-160 days of gestation. With 270-300 days of gestation and post-partum GrOb had increased baseline glucose than GrM. After OST, glucose at foaling day in GrOb presented increased values than GrM. Baseline insulin values did not differ between groups. Post OST insulin levels were higher in GrOb than GrM and GrOv at parturition. No difference in cortisol between moments was identified. GrOb and GrOv maintained increased concentrations after foaling while GrM had a decrease. No correlation was found between maternal glucose and insulin values with foal weight and height, however, a lower ratio between neonatal weight and mare's weight in GrOb and GrOv was identified in relation to the GrM. At foaling, mares presented glucose dysregulation, with obese and overweight mares presenting a greater response to OST.(AU)

O objetivo do presente estudo foi descrever a dinâmica das curvas de glicose e insulina em éguas gestantes e avaliar as curvas de acordo com o escore de condição corporal, identificando a presença de resistência insulínica e correlacionando esses valores com o peso, altura e alterações clínicas dos neonatos. Para isso, as éguas prenhes foram avaliadas em conjunto e agrupadas de acordo com o escore de condição corporal durante a gestação até o pós-parto. GrM pertenciam éguas com escore corporal moderado (EC 5-6); GrOv, grupo de éguas com escore corporal acima do peso (EC 7) e GrOb, grupo de éguas obesas (EC 8-9). O teste de glicose oral em duas etapas (OST) foi usado para determinar os dados. A análise do cortisol também foi realizada nos 300-320 dias de gestação, no dia do parto e após o parto. Para avaliação do neonato, foram realizados exame clínico geral e medidas de peso e altura. Os resultados mostraram hiperglicemia em resposta ao OST com valores normais de insulina no momento parto, com uma queda subsequente em ambas as variáveis na lactação, desconsiderando a divisão do grupo. A glicemia basal diminuiu no GrM em comparação com GrOv e GrOb com 70-100 dias de gestação e com 130-160 dias de gestação. Com 270-300 dias de gestação e no pós-parto, o GrOb apresentou aumento na glicemia basal em relação ao GrM. Após OST, a glicose no dia do parto no GrOb apresentou valores aumentados em relação ao GrM. Os valores basais de insulina não diferiram entre os grupos. Após OST níveis de insulina foram maiores no GrOb do que GrM e GrOv no momento do parto. Não houve diferença nos valores de cortisol entre os momentos. O GrOb e GrOv mantiveram cortisol aumentado após o parto enquanto o GrM diminuiu. Não foi encontrada correlação entre os valores de glicemia e insulina materna com o peso e a altura do potro, entretanto, foi identificada uma relação menor entre o peso neonatal e o peso da égua no GrOb e GrOv em relação ao GrM. No parto, as éguas apresentaram desregulação da glicose, sendo que as éguas obesas e com sobrepeso apresentaram uma resposta maior ao OST.(AU)

Appropriate mathematical models to describe the lactation curves of milk production traits of Iranian Holstein dairy cattle / Modelos Matemáticos apropriados para descrever as curvas de lactação dos traços de produção de leite do gado leiteiro Holstein Iraniano

The objective of this study was to compare the goodness of fit of lactation curve models; Wood, Wilmink, Linear Splines (SPL), Cubic Splines (SPC), Quadratic Splines (SPQ), Cobby and Le Du, Ali Schaeffer and Legendre Polynomial (LEG), in random regression model (RRM) for milk production traits of Iranian Holstein dairy cattle. For this purpose the records obtained from Test-day (TD) regarding milk (928513), fat (788577) and protein (653317) yields related to their first parity were used. These data collected from the years of 2003 to 2011 by the Karaj breeding center of Iran. The genetic parameters were estimated using REML method using WOMBAT software. Based on obtained results, RRM with SPL6 (6,6), SPC6 (6,6) and LEG (3,5) for milk yield, SPL6 (6,6), SPQ6 (6,6), LEG (3,5) for fat yield and SPL5 (5,5), SPQ4 (4,4) and LEG (3,4) for protein yield, were selected as better model to describe the lactation curves. The estimated heritabilities by best models were lower in the beginning lactation than other during lactation. The genetic trend of milk yields was showed an increasing during the 10 past years, which indicated Iranian Holstein dairy cattle population genetically was improved for milk yields.(AU)

O objetivo deste estudo foi comparar a qualidade de ajustes dos modelos da curva de lactação, Wood Wilmink, Spline Linear (SPL), Spline Cúbico (SPC), Spline Quadrático (SPQ), Cobby e Le Du, Ali Schaeffer e os Polinômios de Legendre (LEG), em um modelo de regressão aleatória (RRM) para as características da produção de leite do gado Holstein iraniano. Para este propósito os registros obtidos no teste, foram referentes ao leite (928513), gordura (788577) e proteína (653317) e os rendimentos relacionados as suas primeiras paridades foram usadas. Estas informações foram coletadas durante 2003 até 2011 por Kraj em um centro de criação no Iran. Os parâmetros genéticos foram estimulados usando o método REML WOMBAT. Baseado nos resultados obtidos, RRM com SPL6 (6.6), SPC6 (6,6) e LEG (3,5) por produção de leite, foram selecionados os melhores modelos para descrever as curvas de lactação. A hereditariedade estimada por esses melhores modelos foi menor no início da lactação do que durante outra lactação. A tendência genética da produção de leite mostrou um aumento ao longo de 10 anos, na qual indicou o melhoramento genético do gado Holstein Iraniano no que diz respeito à produção de leite.(AU)

Appropriate mathematical models to describe the lactation curves of milk production traits of Iranian Holstein dairy cattle / Modelos Matemáticos apropriados para descrever as curvas de lactação dos traços de produção de leite do gado leiteiro Holstein Iraniano

The objective of this study was to compare the goodness of fit of lactation curve models; Wood, Wilmink, Linear Splines (SPL), Cubic Splines (SPC), Quadratic Splines (SPQ), Cobby and Le Du, Ali Schaeffer and Legendre Polynomial (LEG), in random regression model (RRM) for milk production traits of Iranian Holstein dairy cattle. For this purpose the records obtained from Test-day (TD) regarding milk (928513), fat (788577) and protein (653317) yields related to their first parity were used. These data collected from the years of 2003 to 2011 by the Karaj breeding center of Iran. The genetic parameters were estimated using REML method using WOMBAT software. Based on obtained results, RRM with SPL6 (6,6), SPC6 (6,6) and LEG (3,5) for milk yield, SPL6 (6,6), SPQ6 (6,6), LEG (3,5) for fat yield and SPL5 (5,5), SPQ4 (4,4) and LEG (3,4) for protein yield, were selected as better model to describe the lactation curves. The estimated heritabilities by best models were lower in the beginning lactation than other during lactation. The genetic trend of milk yields was showed an increasing during the 10 past years, which indicated Iranian Holstein dairy cattle population genetically was improved for milk yields.

O objetivo deste estudo foi comparar a qualidade de ajustes dos modelos da curva de lactação, Wood Wilmink, Spline Linear (SPL), Spline Cúbico (SPC), Spline Quadrático (SPQ), Cobby e Le Du, Ali Schaeffer e os Polinômios de Legendre (LEG), em um modelo de regressão aleatória (RRM) para as características da produção de leite do gado Holstein iraniano. Para este propósito os registros obtidos no teste, foram referentes ao leite (928513), gordura (788577) e proteína (653317) e os rendimentos relacionados as suas primeiras paridades foram usadas. Estas informações foram coletadas durante 2003 até 2011 por Kraj em um centro de criação no Iran. Os parâmetros genéticos foram estimulados usando o método REML WOMBAT. Baseado nos resultados obtidos, RRM com SPL6 (6.6), SPC6 (6,6) e LEG (3,5) por produção de leite, foram selecionados os melhores modelos para descrever as curvas de lactação. A hereditariedade estimada por esses melhores modelos foi menor no início da lactação do que durante outra lactação. A tendência genética da produção de leite mostrou um aumento ao longo de 10 anos, na qual indicou o melhoramento genético do gado Holstein Iraniano no que diz respeito à produção de leite.