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The objective of the study was to analyze nonlinear models that best fit the growth of Caracu cows. The experiment was conducted at the Instituto de Zootecnia, Centro APTA Bovinos de Corte, Sertãozinho, SP. Data of weight at birth to 63 months of age, from 500 females of the Caracu breed were used. The mean weight at birth (BW), weaning weight (W7), weight at 26 months (W26) and weight at 63 months (W63) were, respectively, 32 kg, 198 kg, 354 kg and 488 kg, providing an average daily gain (ADG) of 0.241 kg/day. The nonlinear models used were: Brody, Von Bertalanffy, Logistic and Gompertz. All of the models tended to describe accordingly the growth curve of these animals, but, according to the mean square residual and coefficient of determination adopted to select the most appropriate model, Brody showed the best fit. All models presented a high and negative correlation between the A and k parameters, indicating that the most precocious animals are less likely to reach elevated weights at 63 months of age. The effect of year of birth significantly affected (P 0.01) the parameters A and k, concluding that the animal selection based on growth traits favored the increase of mature weight and growth precocity over the generations.
O objetivo do estudo foi analisar os modelos não-lineares que melhores se ajustam ao crescimento de fêmeas da raça Caracu. O experimento foi conduzido no Instituto de Zootecnia, Centro APTA Bovinos de Corte, Sertãozinho, SP. Dados de peso ao nascimento até os 63 meses de idade de 500 fêmeas da raça Caracu foram utilizados. A media de peso ao nascer (PN), peso a desmama (P7), peso aos 26 meses (P26) e peso aos 63 meses (P63) foram, respectivamente, de 32 kg, 198 kg, 354 kg e 488 kg, fornecendo um ganho médio diário (GMD) de 0,241 kg/dia. Os modelos não-lineares utilizados foram: Brody, Von Bentarlanffy, Logístico e Gompertz. Todos os modelos descreveram adequadamente a curva de crescimento destes animais, porém de acordo com o quadrado médio do resíduo e coeficiente de determinação, adotados para escolha do modelo mais apropriado, Brody mostrou o melhor ajuste. Todos os modelos apresentaram alta e negativa correlação entre os parâmetros A e k, indicando que animais mais precoces possuem menor probabilidade de atingir pesos mais elevados aos 63 meses de idade. O efeito de ano de nascimento afetou significativamente (P 0,01) os parâmetros A e k, sugerindo que a seleção dos animais com base em características de crescimento favoreceu o aumento do peso adulto e a precocidade, com o passar das gerações.
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The present study aimed to evaluate feed intake and behavior during the efficiency test of Nellore males. Efficiency test was conducted from June to October of 2012, during 119 days. Registers of 85 Nellore males, with initial averages age of 270 ± 23 days and body weight of 239 ± 41 kg were used. Animals were fed ad libitum at GrowSafe System® with 10 feeders, which individual recorded bunk attendance (BA), frequency of visits (FV) and feed intake (FI). The first 28 days of test were for adaptation to diet and environment, and the subsequent 91 days were considered as experimental period. Experimental period was divided in three sub periods (28, 28 and 31 days, respectively). Data were analyzed by PROC MIXED (SAS Inst., Inc., Cary, NC), including in the model period effects (adaptation - 1 and experimental periods - 2, 3 or 4) and animal age as linear covariate. During the adaptation period, low values (P 0.05) were observed of FI, BA and FV (991 ± 40.7 kg/day, 854 ± 33.2 min/day and 1172 ± 49.4 visits/day, respectively) in relation experimental period (1091 ± 18.5 kg/day, 965 ± 15.1 min/day and 1217 ± 22.5 visits/day, respectively). Feeding behavior traits were analyzed in four test periods (Figure 1), and a reduction (P 0.05) in FI (from 1162 ± 39.2 to 984 ± 77.6 kg/day) and BA (from 992 ± 32.1 to 866 ± 63.6 min/day) was observed in the third period. Additionally, FV m
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The direct determination of carcass composition as experimental routine, despite being the most accurate method, is time consuming, laborious and expensive. Indirect methods have been developed to estimate on quick, simple, economical and reliable ways empty body composition of beef cattle. This study was performed with the objective of developing accurate regression equations to predict carcass composition of Nellore animals using 9-10-11th ribs chemical composition and performance measures as independent variables. Sixty-seven non-castrated Nellore bulls were randomly selected for finishing period in two consecutive years (2008 and 2009) and were finished in individual pens for approximately 100 days, until they reached four millimeters of subcutaneous fat thickness over Longissimus muscle. They were slaughtered at 540 days of average age and body weight at slaughter (BW) and carcass weight (CW) were taken. The 9-10-11th ribs cut was obtained according to Hankins and Howe (1946) and weighted (RW). The carcass composition was obtained after grinding, homogenizing, sampling and analyzing the left side of the carcass. Chemical analysis of 9-10-11th ribs cut and carcass were carried for protein (RP and CP), fat (RF and CF), ashes (RA and CA) and water (RWt and CWt). Stepwise and Mallows Cp options were used in PROC GLMSELECT (SAS Inst., Inc., Cary, NC) to determine significant (
O artigo não apresenta resumo em português.
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This study aimed to evaluate feed intake and behavior during feed efficiency test of Nellore males from different residual feed intake (RFI) classes. Data from 85 Nellore males, with initial average age of 270 ± 23 days and body weight of 239 ± 41 kg were used. The feed efficiency test was performed during 119 days, divided in four periods. The first period (adaptation) had 28 days, and the three subsequent periods had, respectively, 28, 28 and 31 days. Animals were fed ad libitum at GrowSafe System® with 10 feeders, which recorded bunk attendance (BA), frequency of visits (FV) and feed intake (FI) individual data. After test end, RFI was calculated by the difference between observed and predicted feed intake, based on average daily gain and metabolic body weight. Then, animals were classified into low ( mean - 0.5 standard deviation-SD), medium (± 0.5 SD from mean) and high (>mean + 0.5 SD) RFI. Statistical analyzes were performed by PROC MIXED (SAS Inst., Inc., Cary, NC), including in the model effects of test period (1, 2, 3 or 4), RFI classes (low, medium or high) and interaction, being animal age considered as linear covariate. Feeding behavior pattern was not different among the efficiency test periods (P>0.05), however differences were detected among RFI classes inside the periods (P 0.01) (Figure 1). Low RFI animals, when compared to the medium and high RFI
O artigo não apresenta resumo em português.
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This study was carried out to identify associations among carcass traits and residual feed intake (RFI) in young Nellore males feedlot finished. Data was obtained in four experiments, after the animals had been evaluated in individual pens and classified in low RFI( mean - 0.5 standard deviation), medium RFI (± 0.5 standard deviation from mean) and high RFI (> mean + 0.5 standard deviation). One hundred-sixteen non castrated males from low and high RFI classes, with 369 kg of initial body weight and 439 days of initial age, were used for finishing phase. Animals were distributed in individual pens for 100 days and weighed at the beginning and end of experimental period after 16 hours solids fasting. Animals were slaughtered with a minimum of 4 mm for subcutaneous fat thickness over Longissimus muscle between the 12th and 13th ribs. Slaughter was carried out in experimental slaughter houses following the normal procedures of Federal inspection. After slaughter, carcasses were weighed (hot carcass weight) and transferred to chilling room where they were kept at 2C for 24h. Dressing percentage was calculated as the ratio between hot carcass weight and slaughter body weight. After chilling, carcasses right halves were divided into carcass primary cuts: forequarter, hindquarter and spare ribs, which were also weighed. Data were analyzed using the SAS MIXED procedure (SAS Inst
O artigo não apresenta resumo em português.
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Feed efficiency is difficult to evaluate because individual feeding are required. An alternative is selecting animals based on traits easier to obtain and genetically favorably correlated with feed efficiency traits. This study aimed to estimate genetic and phenotypic correlations between feed efficiency traits (residual feed intake RFI, feed efficiency FE and residual BW gain RG) with yearling weight (YW), hip height (HH) and girth circumference (GC) in Nellore cattle. Feed efficiency data set consisted of 887 records of DMI, ADG and BW0.75 obtained during performance tests (83 ± 15 d) to calculate RFI (0.005 ± 0.58 kg DM/d), FE (0.14 ± 0.03) and RG (0.00 ± 0.11 kg/d). FE was calculated as ADG and DMI ratio, RFI was estimated as the error of multiple regression of DMI on ADG and BW0.75, and RG was estimated as the error of multiple regression of ADG on DMI and BW0.75. The YW data set consisted of 7,948 records of males (314.45 ± 45.85 kg) and females (282.68 ± 48.19 kg) adjusted to 378 and 550 d of age, respectively. The HH consisted of 6,418 records of males (131.80 ± 5.40 cm) and females (132.51 ± 5.38 cm), and 3,745 records of GC of males (162.56 ± 8.48 cm) and females (167.72 ± 8.08 cm). Pedigree file contained 9,830 animals. Growth traits were analyzed as unit standard deviation of each sex/age. (Co)variance components were estimated through two-trait animal models
O artigo não apresenta resumo em português.
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Recent advances in the field of animal assisted reproduction have allowed faster dissemination of animals with superior genetics. In cattle, the development of some biotechnologies such as the in vitro production (IVP) of embryos optimized the use of oocytes, which represents a great improvement in embryo production world-wide. Therefore, females with high net merit can be multiplied more efficiently to maximize the number of their offspring. The use of ultrasound-guided transvaginal follicle aspiration combined with IVP allowed wide commercial transfer of IVP-embryos with satisfactory pregnancy results. Yet, there are a number of unanswered areas including the level of repeatability and predictability in IVP systems. Thus, the aim of this study was to evaluate the repeatability of some variables related to IVP of bovine embryos from Nellore breed. The study was conducted from 2011 to 2012 using 42 Nellore cows housed at the Centro APTA Bovinos de Corte located in Sertãozinho-SP, Brazil. Donors were kept under the same management throughout the entire experimental period. All animals underwent a total of 25 transvaginal ultrasound-guided follicular aspiration sections. Oocytes were retrieved and handled similarly by Sexing Technologies using semen from 11 sires. Repeatability was evaluated in the following variables: total number of oocytes, embryos and viable oocytes, viable o
O artigo não possui resumo em português.
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Several factors can influence the recovery of the amount of oocytes for in vitro embryo production (IVEP), including the age of the donor, the time and the frequency at which the animal is collected and climate station year. Another factor is the individual variation of each animal in the number of oocytes and embryos. Thus, the aim of this work was to evaluate the effect of the number of aspirations and the influence of the months of the year in the amount of total and viable oocytes in Nellore cows. The date was collected from January 2011 to December 2012. Non-lactating, cycling Nellore cows (n = 42) of high genetic value were used as oocyte donors. The procedures were carried out in a farm in southeast Brazil (21816S/48582W), located in humid tropical climate. All the donors were maintained on pasture consisting of guinea grass (Panicum maximum and Urochloa brizantha), getting protein mineral supplement energy and water ad libitum daily. The analyzes were performed by proc GLIMMIX of SAS 9.3 (SAS Inst., Inc., Cary, NC). The amount of total oocytes (P=0.16) and viable (P=0.11) did not influenced by the number of aspirations. However, the months of the year have an effect on the amount of total and viable (P 0.0001) oocytes. Probably the production of oocytes did not suffer influences the number of aspirations performed mainly because the intervals between each OPU
O artigo não possui resumo em português.
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The direct determination of carcass and empty body composition as experimental routine, despite being the most accurate method, is time consuming, laborious and expensive. Therefore, indirect methods have been developed to estimate on quick, simple, economical and reliable ways for the compositions of carcass and empty body of beef cattle. This study aimed to obtain the correlations among the compositions of 9-10-11th ribs, carcass and empty body for protein, fat, ashes and water contents, expressed in percentage and kilograms, in young Nellore bulls. Sixty-seven non-castrated Nellore bulls were randomly selected for confining period in two consecutive years (2008 and 2009) and were confined in individual pens for approximately 100 days, until they reached a subcutaneous fat thickness of 4 mm over the Longissimus muscle. They were slaughtered at an average age of 540 days and body weight of 398 kg. Chemical analysis of the 9-10-11th ribs, carcass and empty body were carried for protein, fat, ashes and water. The 9-10-11th ribs cut was obtained according to Hankins and Howe (1946). Carcass composition was obtained after grinding, homogenizing, sampling, analyzing and combining edible portions and bones. Empty body composition was obtained after grinding, homogenizing, sampling, analyzing, and combining blood, hide, head + feet, viscera, and carcass. The correlation coefficients
O artigo não apresenta resumo em português.
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This study was conducted to describe the ingestive behavior in Nellore and Bonsmara cattle during the feed efficiency test. The test was performed at the Centro APTA Bovinos de Corte Instituto de Zootecnia, Sertãozinho, São Paulo State. Twenty-three Nellore and 19 Bonsmara calves, aging 276 ± 19.2 and 278 ± 29.2 days and weighing 246 ± 26.7 and 273 ± 30.7 kg, on average, at the beginning of the test, respectively, were used. Animals were randomly located in individual pens, during four periods of 28 days, being the first period a pre-test adjustment period. Calves were fed twice a day, with the same diet. Daily the amount of food offered was adjusted in order to maintain 5 to 10% of refusals. Dry matter intake (DMI) was calculated by the difference between food offered and refusals. Animals were weighed each seven days. Average daily gain (ADG) was obtained by linear regression of weights in days in test. Feed conversion was obtained by the DMI:ADG ratio. Ingestive behavior was measured three times, every 28 days, excluding de pre-test period. Observations lasted 24 hours, with records at intervals of five minutes. The behavioral traits analyzed were: bunk attendance duration (BAD), rumination time (RT) and idle time (IT) expressed in minutes per day. Data were analyzed using the PROC MIXED procedure (SAS 9.3). The model included the fixed effects of period, breed and weight
O artigo não apresenta resumo em português.
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Several studies have reported relationship between eating behavior and performance in feedlot cattle. The evaluation of behavior traits demands high degree of work and trained manpower, therefore, in recent years has been used an automated feed intake measurement system (GrowSafe System ®), that identify and record individual feeding patterns. The aim of this study was to evaluate the relationship between feeding behavior traits and average daily gain in Nellore calves undergoing feed efficiency test. Date from 85 Nelore males was recorded during the feed efficiency test performed in 2012, at Centro APTA Bovinos de Corte, Instituto de Zootecnia, São Paulo State. Were analyzed the behavioral traits: time at feeder (TF), head down duration (HD), representing the time when the animal is actually eating, frequency of visits (FV) and feed rate (FR) calculated as the amount of dry matter (DM) consumed by time at feeder (g.min-1). The ADG was calculated by linear regression of individual weights on days in test. ADG classes were obtained considering the average ADG and standard deviation (SD) being: high ADG (>mean + 1.0 SD), medium ADG (± 1.0 SD from the mean) and low ADG ( mean - 1.0 SD). Data were analyzed using the PROC MIXED procedure (SAS 9.3). The model included animal and residue as random effects and the fixed effects of ADG class (1, 2 and 3) and age at the middle of t
O artigo não apresenta resumo em português.
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Several studies have reported relationship between eating behavior and performance in feedlot cattle. The evaluation of behavior traits demands high degree of work and trained manpower, therefore, in recent years has been used an automated feed intake measurement system (GrowSafe System ®), that identify and record individual feeding patterns. The aim of this study was to evaluate the relationship between feeding behavior traits and average daily gain in Nellore calves undergoing feed efficiency test. Date from 85 Nelore males was recorded during the feed efficiency test performed in 2012, at Centro APTA Bovinos de Corte, Instituto de Zootecnia, São Paulo State. Were analyzed the behavioral traits: time at feeder (TF), head down duration (HD), representing the time when the animal is actually eating, frequency of visits (FV) and feed rate (FR) calculated as the amount of dry matter (DM) consumed by time at feeder (g.min-1). The ADG was calculated by linear regression of individual weights on days in test. ADG classes were obtained considering the average ADG and standard deviation (SD) being: high ADG (>mean + 1.0 SD), medium ADG (± 1.0 SD from the mean) and low ADG ( mean - 1.0 SD). Data were analyzed using the PROC MIXED procedure (SAS 9.3). The model included animal and residue as random effects and the fixed effects of ADG class (1, 2 and 3) and age at the middle of t
O artigo não apresenta resumo em português.
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In study of more efficient animals for food utilization, it is of great importance to know differences between genders. There are differences between male and female cattle in growing and body composition, mainly those related to the action of sex hormones. This study aimed to evaluate the sex effect on feed efficiency traits in young Nellore animals. Individual feed intake data from eight tests, performed from 2005 to 2012 at Centro APTA Bovinos de Corte-Instituto de Zootecnia-Sertãozinho-SP were utilized. The tests began after weaning, when the animals had, on average, 286 days of age and 229 kg of body weight. The tests duration ranged from 56 to 112 days, depending on the year. Traits analyzed were final body weight (FBW), dry matter intake (DMI), average daily gain (ADG), feed conversion ratio (FCR), feed efficiency ratio (FER), residual feed intake (RFI) and Kleiber ratio (KR). Data were analyzed using the MIXED procedure of SAS. The model included the fixed effect age at the test beginning as linear covariate and the random effects: sex, facilities and year. Least square means were calculated and compared by t test. Males had greater FBW than females, what was expected, due to the action of male hormones which benefits the muscle deposition. Greater means of ADG and DMI were also detected for males, when compared to females, because heavier animals have higher gains and
O artigo não apresenta resumo em português.
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Studies have shown associations between temperament traits and productivity on cattle industry, some results indicate that animals which adapt easily are less agitated, therefore there will be fewer losses in carcass due to the low incidence of hematomas and higher weight gain. The objective of this study was to associate the average daily gain in Caracu animals, subject to performance test (PT), with reactivity measured by flight speed test. The average daily gain was divided in three classes, considering 0.5 standard deviation below and above the average. The average gain classes 1, 2 and 3 was 1158.55 ± 89.48, 957.14 ± 54.77, 620.88 ± 127.41 g/day, respectively. The flight speed test (FS) measures how long the animal takes to cover a known distance after the release of the squeeze chute. Faster animals were considered more reactive. The study was performed at Centro APTA Bovinos de Corte from Instituto de Zootecnia-Sertãozinho, SP, in which were used 109 flight speed records, of 56 animals, obtained in the beginning and at the end of PT. Data were analyzed using the PROC MIXED (SAS 9.3). The model of analyses included the fixed effects of average daily gain classes (1, 2 and 3) and measures (1 and 2), besides the random-effects of animal and residue. The interaction classes measures, even as age as covariate, were excluded from the initial model, because they didnt show sig
ês.
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Several studies have reported differences between male and female cattle in growing and body composition. The differences occur mainly by hormonal factors, however, there is little information about the relationship between sex and feed efficiency traits in beef cattle. The residual feeding intake (RFI) is a feed efficiency measurement and has been an alternative to improve the profit in beef production system. It is defined as the difference between dry matter intake observed and estimated by regression in function of weight gain and metabolic body weight. More efficient animals have the intake observed smaller than the predicted (low RFI), unlike the less efficient ones have the intake bigger than predicted (high RFI). This study aimed to evaluate the sex effect (male and female) on growing and feeding efficiency traits in young Nellore bulls selected for post weaning weight. Data from males and females Nellore animals obtained during RFI evaluation tests were utilized. The tests were performed at Centro APTA Bovinos de Corte Instituto de Zootecnia - Sertãozinho-SP, between 2005 and 2011. The tests duration ranged from 56 to 112 days, with the adaption period raging from 28 to 56 days, depending of the year. At the tests beginning the animals had, on average, 286 ± 42 days of age. The traits analyzed were initial body weight (IBW), final body weight (FBW), average daily gai
O artigo não apresenta resumo em português.
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During three consecutive years a total of 144 bull records from the Zebu breeds Nellore, Guzerah and Caracu breed, selected for post-weaning weight, finished in feedlot and slaughtered at an average age of 19 months, with three different degrees of maturity, were analyzed. Multivariate procedure (MANOVA) was used to estimate the residual correlations between body measurements and carcass traits. The model fitted the effects of genetic groups, order of slaughter and year of birth. Correlation coefficient between hip height and carcass weight was 0.37, antagonistic to the amount of kidney fat (-0.14). High correlation coefficients were estimated between chest girth and carcass weight (0.77), blade (0.57), and chuck (0.67) and positive correlations were estimated between chest girth and kidney fat (0.38) and carcass fat (0.52). The estimated correlation coefficient between body length and carcass weight was 0.38. Correlation coefficients between dorsal line length, rump length and distance among pin bones and all the meat cuts of commercial interest analyzed ranged from 0.24 to 0.56. In addition to live body weight, chest girth and distances between hip bones can be considered an auxiliary tool for evaluation of carcass traits in Zebu and Caracu bulls. Other body measurements analyzed resulted in low or null relationship to carcass traits.
Em três anos consecutivos foram analisados registros de 144 bovinos machos das raças zebuínas Nelore, Guzerá e da raça Caracu, selecionados para peso pós-desmame, terminados em confinamento e abatidos com idade média de 19 meses, em três diferentes graus de maturidade. A análise multivariada (MANOVA) foi utilizada com o objetivo de estimar as correlações residuais entre medidas corporais e características de carcaça. O modelo de ajuste incluiu os efeitos de grupos genéticos, ordem de abate e ano de nascimento. O coeficiente de correlação entre a altura na garupa e peso de carcaça foi de 0,37, sendo antagônico à quantidade de gordura renal (-0,14). Altos coeficientes de correlação foram estimados entre perímetro torácico e peso de carcaça (0,77), paleta (0,57) e acém (0,67) e correlações positivas foram estimadas entre perímetro torácico e gordura renal (0,38) e gordura na carcaça (0,52). O coeficiente de correlação estimado entre comprimento do corpo e peso de carcaça foi 0,38. Os coeficientes de correlação estimados entre comprimento do dorso, comprimento da garupa e distância entre ísquios e todos os cortes cárneos comerciais analisados variaram de 0,24 a 0,56. Além de peso vivo, o perímetro torácico e a distância entre os íleos podem ser considerados auxiliares na avaliação de características de carcaça de bovinos Zebu e Caracu. As outras medidas corporais analisadas resulta
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Data from nine studies were compiled to evaluate the effects of selection for postweaning weight on some carcass characteristics in experimental herds of selected Nellore (NeS), control Nellore (NeC), Caracu (CaS), Guzerah (GuS) and Gir (GiS) breeds from Instituto de Zootecnia genetic selection program. After the feeding performance test (168 days after weaning), samples of bulls (n=490) from the progeny groups born between 1992 and 2000 were selected for finishing period and slaughtered. Treatments were different across studies. Meta-analysis was conducted with a random coefficients model in which herd was considered a fixed effect and treatments within year and progeny groups as random effects. Slaughter, empty body, hot carcass and cold carcass weights were higher for NeS and CaS, intermediate for GuS and lower for NeC e GiS. CaS bulls had higher proportions of forequarter and spare ribs and lower proportion of hindquarter than the other groups. No significant differences were found for percentage of edible portion among the genetic groups. Selection for postweaning weight in Nellore increased carcass, hindquarter, forequarter, and spare ribs weights without altering dressing percentage, carcass quarter, and hindquarter prime meat cuts proportions.
Dados de nove estudos foram compilados com o objetivo de avaliar os efeitos da seleção para peso pós-desmame em algumas características de carcaça de rebanhos experimentais Nelore Seleção (NeS), Nelore Controle (NeC), Caracu (CaS), Guzerá (GuS) e Gir (GiS) do programa de melhoramento genético do Instituto de Zootecnia. Após a Prova de Ganho de Peso (168 dias pós-desmame), amostras de machos (n=490) de progênies nascidas entre 1992 e 2000 foram selecionadas para o período de terminação e posterior abate. Em cada estudo os animais foram submetidos a diferentes tratamentos de terminação. Foi conduzida meta-análise com modelo de coeficientes aleatórios, onde rebanho foi considerado efeito fixo e tratamentos dentro de ano e progênie foram considerados efeitos aleatórios. Os pesos de abate, do corpo vazio, da carcaça quente e da meia carcaça direita resfriada foram maiores para NeS e CaS, intermediários para GuS e menores para NeC e GiS. O CaS apresentou maiores proporções de dianteiro e ponta-de-agulha e menor proporção de traseiro que os outros grupos genéticos estudados. Não foram encontradas diferenças significativas entre as porcentagens de porção comestível das carcaças dos grupos genéticos estudados. A seleção para peso pós-desmame aumentou os pesos de carcaça, traseiro, dianteiro e ponta-de-agulha no Nelore sem alterar o rendimento de carcaça, as proporções dos quartos da car
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Data from three experimental herds of Nelore cattle were analyzed to estimate genetic parameters for three fertility traits of cows: days to calving (DIAP), calving date (DATAP) and calving success (SP). The 7,951 records of 1,575 cows were obtained from 1978 to 2000 and up to 12 records by animal were available. DIAP was computed as the interval between calving date and the date of the beginning of the breeding season, DATAP was computed designing 1 to the first calving of the year and then successively, and non-calved cows received a predicted record according to higher observed record within breeding group. SP was considered as binomial trait (one for calving and zero for failure to calve). The three traits were analysed assuming a repeated model in single-trait analysis. The model included additive genetic effects, permanent environment and error as random, year of the beginning of the breeding season, herd, age, previous reproductive status and cow weight at the beginning of the breeding season as fixed effects. The variance components were estimated using REML methodology for DIAP and DATAP and quasi-REML in threshold model for SP. Estimates of heritabilities were 0.15±0.02; 0.16±0.02 and 0.19±0.03 for DIAP, DATAP and SP, respectively. The rank correlations between the expected breeding values for the DIAP and SP were -0.89 for sires and -0.90 for all animals. The high an
Dados de três rebanhos experimentais de bovinos Nelore foram analisados para estimar parâmetros genéticos de três características de fertilidade de matrizes: dias ao parto (DIAP), data do parto (DATAP) e sucesso ao parto (SP). Os 7.951 registros de 1.575 vacas foram obtidos de 1978 a 2000 e até 12 registros estavam disponíveis por animal. DIAP foi calculado como o intervalo da data do parto e a data do início da estação de monta, DATAP foi calculado como sendo 1 a data do primeiro parto do ano e assim sucessivamente dentro de ano, e para ambas características as vacas que participaram da estação de monta e não pariram receberam um registro predito, com base no maior valor de DIAP ou DATAP observado no grupo de monta. SP foi considerado como característica binomial (1 para parto e 0 para falha ao parto). As três características foram analisadas assumindo um modelo de repetibilidade em análises univariadas. O modelo incluiu os efeitos genético aditivo direto, ambiente permanente do animal e erro como aleatórios, e os efeitos de ano de entrada na estação de monta, rebanho, idade, estado reprodutivo anterior e peso da vaca no início da estação de monta como fixos. Os componentes de variância foram estimados usando metodologia de máxima verossimilhança para DIAP e DATAP e metodologia de máxima verossimilhança aproximada, em modelo de limiar, para SP. As estimativas de herdabilidade
Resumo
Data from three experimental herds of Nelore cattle were analyzed to estimate genetic parameters for three fertility traits of cows: days to calving (DIAP), calving date (DATAP) and calving success (SP). The 7,951 records of 1,575 cows were obtained from 1978 to 2000 and up to 12 records by animal were available. DIAP was computed as the interval between calving date and the date of the beginning of the breeding season, DATAP was computed designing 1 to the first calving of the year and then successively, and non-calved cows received a predicted record according to higher observed record within breeding group. SP was considered as binomial trait (one for calving and zero for failure to calve). The three traits were analysed assuming a repeated model in single-trait analysis. The model included additive genetic effects, permanent environment and error as random, year of the beginning of the breeding season, herd, age, previous reproductive status and cow weight at the beginning of the breeding season as fixed effects. The variance components were estimated using REML methodology for DIAP and DATAP and quasi-REML in threshold model for SP. Estimates of heritabilities were 0.15±0.02; 0.16±0.02 and 0.19±0.03 for DIAP, DATAP and SP, respectively. The rank correlations between the expected breeding values for the DIAP and SP were -0.89 for sires and -0.90 for all animals. The high an
Dados de três rebanhos experimentais de bovinos Nelore foram analisados para estimar parâmetros genéticos de três características de fertilidade de matrizes: dias ao parto (DIAP), data do parto (DATAP) e sucesso ao parto (SP). Os 7.951 registros de 1.575 vacas foram obtidos de 1978 a 2000 e até 12 registros estavam disponíveis por animal. DIAP foi calculado como o intervalo da data do parto e a data do início da estação de monta, DATAP foi calculado como sendo 1 a data do primeiro parto do ano e assim sucessivamente dentro de ano, e para ambas características as vacas que participaram da estação de monta e não pariram receberam um registro predito, com base no maior valor de DIAP ou DATAP observado no grupo de monta. SP foi considerado como característica binomial (1 para parto e 0 para falha ao parto). As três características foram analisadas assumindo um modelo de repetibilidade em análises univariadas. O modelo incluiu os efeitos genético aditivo direto, ambiente permanente do animal e erro como aleatórios, e os efeitos de ano de entrada na estação de monta, rebanho, idade, estado reprodutivo anterior e peso da vaca no início da estação de monta como fixos. Os componentes de variância foram estimados usando metodologia de máxima verossimilhança para DIAP e DATAP e metodologia de máxima verossimilhança aproximada, em modelo de limiar, para SP. As estimativas de herdabilidade
Resumo
The objective of the study was to analyze nonlinear models that best fit the growth of Caracu cows. The experiment was conducted at the Instituto de Zootecnia, Centro APTA Bovinos de Corte, Sertãozinho, SP. Data of weight at birth to 63 months of age, from 500 females of the Caracu breed were used. The mean weight at birth (BW), weaning weight (W7), weight at 26 months (W26) and weight at 63 months (W63) were, respectively, 32 kg, 198 kg, 354 kg and 488 kg, providing an average daily gain (ADG) of 0.241 kg/day. The nonlinear models used were: Brody, Von Bertalanffy, Logistic and Gompertz. All of the models tended to describe accordingly the growth curve of these animals, but, according to the mean square residual and coefficient of determination adopted to select the most appropriate model, Brody showed the best fit. All models presented a high and negative correlation between the A and k parameters, indicating that the most precocious animals are less likely to reach elevated weights at 63 months of age. The effect of year of birth significantly affected (P 0.01) the parameters A and k, concluding that the animal selection based on growth traits favored the increase of mature weight and growth precocity over the generations.
O objetivo do estudo foi analisar os modelos não-lineares que melhores se ajustam ao crescimento de fêmeas da raça Caracu. O experimento foi conduzido no Instituto de Zootecnia, Centro APTA Bovinos de Corte, Sertãozinho, SP. Dados de peso ao nascimento até os 63 meses de idade de 500 fêmeas da raça Caracu foram utilizados. A media de peso ao nascer (PN), peso a desmama (P7), peso aos 26 meses (P26) e peso aos 63 meses (P63) foram, respectivamente, de 32 kg, 198 kg, 354 kg e 488 kg, fornecendo um ganho médio diário (GMD) de 0,241 kg/dia. Os modelos não-lineares utilizados foram: Brody, Von Bentarlanffy, Logístico e Gompertz. Todos os modelos descreveram adequadamente a curva de crescimento destes animais, porém de acordo com o quadrado médio do resíduo e coeficiente de determinação, adotados para escolha do modelo mais apropriado, Brody mostrou o melhor ajuste. Todos os modelos apresentaram alta e negativa correlação entre os parâmetros A e k, indicando que animais mais precoces possuem menor probabilidade de atingir pesos mais elevados aos 63 meses de idade. O efeito de ano de nascimento afetou significativamente (P 0,01) os parâmetros A e k, sugerindo que a seleção dos animais com base em características de crescimento favoreceu o aumento do peso adulto e a precocidade, com o passar das gerações.