Resumo
Investigating factors that could affect milk production of cows is an important way to improve the efficiency of production systems. This purpose of this study was to verify and quantify the influence of calf sex on milk production and lactation length in herds of Holstein, Gir, and Guzera cows. Data from 10,780 lactations of 4,807 Holstein cows that calved between 2001 and 2013; 18,898 lactations of 13,172 Gir cows that calved between 1985 and 2013; and 5,277 lactations of 3,972 Guzera cows that calved between 1987 and 2013 were used. Both the accumulated 305-day milk yield (P305) and the length of the lactation period up to 305 days (DL305) were evaluated. Analysis of variance was performed by the least squares method using the GLM procedure in the SAS statistical program. The P305 was not influenced by the sex of the calf in the Holstein breed. However in the zebu breeds (Gir and Guzera), both P305 and DL305 were significantly affected (P 0.01) by the sex of the calf, with higher production and average length of lactation in cows that calved males. In addition, a significant difference was also nested within sex of calf and age at first calving (P 0.05) in the Gir breed. The results indicate that for the zebu breeds, calf sex influences production characteristics.
A investigação de fatores que interferem na produção de vacas leiteiras é de grande importância para eficiência dos sistemas de produção. O objetivo do trabalho foi verificar e quantificar a influência do sexo do bezerro sobre produção de leite e sobre a duração da lactação em rebanhos das raças Holandesa, Gir Leiteiro e Guzerá. Foram avaliadas 10.780 lactações de 4.807 vacas Holandesas, paridas entre 2001 e 2013; 18.898 lactações de 13.172 vacas Gir Leiteiro paridas de 1985 a 2013 e 5.277 lactações ocorridas entre 1987 e 2013, de 3.972 vacas Guzerá. As características estudadas foram produção de leite acumulada em 305 dias e duração da lactação (até 305 dias). A análise de variância foi realizada pelo método de quadrados mínimos, através do procedimento GLM do programa estatístico SAS. A produção de leite acumulada aos 305 dias (P305) na raça Holandesa não foi influenciada pelo sexo do bezerro. Entretanto, para os animais de origem zebuína (Gir leiteiro e Guzerá), ambas as características foram significativamente influenciadas (P 0,01) pelo sexo do bezerro, sendo observadas maiores produções de leite e duração de lactação para vacas que pariram machos. Também foi observada diferença significativa do sexo do bezerro aninhado dentro de idade da vaca ao parto (P 0,05) para a raça Gir leiteiro. Estes resultados indicam que para as raças zebuínas, o sexo do bezerro influe
Resumo
Performance evaluation of adapted animals to local conditions for economic traits is essential for the preservation of species and their genetic resources. The size of Morada Nova breed herds have decreased over time, becoming restricted to a few regions. Other races have been used with higher frequency because of their production and adaptation, and are important as a source of food and income for local communities. The objective of this research was to evaluate the application of nonlinear models to describe the growth curve of Morada Nova sheep. Records of 1604 weights of 250 lambs from Nova Odessa municipality, being 934 repeated measurements of female and 670 repeated measurements of male, obtained between 2012-2013 were used. The average birth weight observed was 2.50 ± 0.690 kg. The nonlinear models used to adjust the data were Brody Yt = A (1 - be-kt); Von Bertalanffy Yt = A (1 - be-kt)3; Richards Yt = A (1 - be-kt)m; Logistic Yt = A (1 + e-kt)-m and Gompertz Yt = Ae -be(-kt). The models were fitted by Gauss-Newton using the NLIN procedure of SAS (SAS Inst., Inc., Cary, NC). The parameters that make up the functions are Y = body weight at the age t; A = asymptotic weight that represents the average adulthood weight; K = Maturation rate, an indicator of the speed with which the animal approaches its adult size, maturity of the individual in relation to age is the fractio
O artigo não apresenta resumo em português.
Resumo
The body weight (BW) determination is important to evaluate the growth of animals, their nutritional condition and reproduction and to establish the slaughter time and the sale value of the animal. The chest girth (CG) could be an alternative to determine the body weight of sheep on properties that do not have scales. The objective of this study was to investigate the feasibility of using chest girth to determine the estimated body weight (EBW). The data file contained 1762 records of body weight (BW) and chest girth (CG) from 426 Santa Ines breed sheep, belonging to eight herds located in Southeastern Brazil. The chest girth was measured using the sternum and the withers as base, passing the tape measure behind the shoulder. Body weights were related to CG values through linear regressions using the software Statistical Analysis Systems (SAS Inst., Inc., Cary, NC). The age classes 1, 2, 3, were defined respectively as: 0 to 12 months; 13 to 22 months; over 34 months. The regression equation used to predict the body weight through chest girth in different age classes was y = b0 + b1x, where y is the dependent variable EBW, x is the independent variable CG, b0 is the intercept, b1 is the slope of the equation that defines the relationship between EBW and CG. The other variables were constant. The regression equations for specific age groups of animals were: Class 1 EBW = -42.201
O artigo não apresenta resumo em português.
Resumo
In dairy farming, the productive performance of lactating cows is directly related to the efficiency of the production system. In this respect, studies in different areas investigating animal production try to understand the determinant factors of milk production. Many studies have shown a high correlation between milk production of cows and performance of their calves; however, few studies have addressed the influence of calf sex on milk production. With the objective to evaluate the influence of fetal sex on the milk production of Holstein cows, the present study analyzed cumulative milk yield data provided by the Agrindus Farm in Descalvado, São Paulo. A total of 10,780 calvings of 4,807 cows that had calved between April 2001 and October 2013 and their cumulative yields during lactation according to offspring sex were evaluated. The PROC GLM procedure of the SAS software (SAS Inst., Inc., Cary, NC) was used for analysis. The contemporary group was defined as year and month of calving, with a minimum of 5 observations per group. In addition to contemporary group, the effects of management group and calving order of the cow were included in the model. Mean cumulative yields were 9,800.79 and 9,802.95 kg for cows that had given birth to males and females, respectively. There was no significant difference (P=0.9519) in cumulative milk yield of cows during the study period as a
O artigo não apresenta resumo em português.
Resumo
Mastitis is an inflammation of the mammary gland, caused by bacteria, viruses, fungi and yeasts. During the processes of inflammation, chloride (Cl) and sodium (Na) ions, immunoglobulins and other serum proteins present in blood, flow through capillaries direct to the alveoli lumen of the gland, thus increasing its concentration. This is due to the increase of vascular permeability, the destruction of tight junctions and the active ion-pumping system, while the concentration of casein, lactose, triglycerides and potassium (K) decreases. This work aimed to study a method to evaluate mastitis in Gir dairy cattle, where the milk electric conductivity (EC) was correlated to milk somatic cell count (SCC). This method will provide an early diagnosis, which can be used daily with conductivity meter in mechanical milking machine or weekly in properties with manual milking. The measurement of EC in milk was accomplished through the appliance of AK83 BENCHTOP PORTATIL. The experiment was conducted in two farms: Calciolândia, Arcos/MG and Bom Jardim da Serra, Mococa/SP, totaling 123 Gir cows. In Calciolândia farm, milking was manual and in Bom Jardim da Serra milking was manual and mechanical but both with the presence of the calf . The milk collection took place in 10 ml bottles at ambience temperature, and the samples were in duplicate, one to measure the EC and the other for SCC and co
O artigo não apresenta resumo em português.
Resumo
The electrical conductivity of milk is an indirect method of mastitis diagnosis and can be used as selection criterion in breeding programs to obtain resistant animals to infection. For the present study data from 9,302 milk electrical conductivity measurements in the morning (ECM), from 1,129 Holstein cows in first lactation, calving between 2001 and 2011, belonging to eight herds in the Southeast of Brazil, obtained from automated milking equipment WESTFALIA® with system management "Dairyplan" was utilized. Classes of ECM were formed at weekly intervals, representing a total of 42 classes. The model included direct additive genetic, permanent environmental and residual effects as random and the fixed effects of contemporary group (herd - year and season of the control), age at calving as a covariate (linear and quadratic). Mean trends were modeled by an orthogonal Legendre polynomial with three coefficients of days in milk. The residual variance was considered homogeneous throughout lactation. Variance components were estimated by restricted maximum likelihood method (REML), using the statistical package Wombat (Meyer, 2006). The mean and standard deviation of the electrical conductivity of milk were 4.799 ± 0.543 ms/cm. The heritability for ECM were increased from the beginning to the middle of lactation (154 days), when it reached the maximum value (0.44), decreasing therea
O artigo não apresenta resumo em português.
Resumo
Electrical conductivity of milk is an indirect method for diagnosis of mastitis that can be used as criterion of selection in breeding programs, to obtain more resistant animals to infection. Data from 9,302 records of electrical conductivity from the morning milking (ECM), 13,070 milk yield records (MY) and 11,560 records of milking time (MT), of 1,129 first lactation Holstein cows, calving from 2001 to 2011, were used in statistical analysis. Data of eight herds of Southeast region of Brazil were obtained by the WESTFALIA® electronic milking machines, with Dairyplan management system. Two analysis were performed: a multitrait, including MY, MT and ECM, and an unitrait, considering only test-day morning electrical conductivity. The model included additive genetic, permanent environmental and residual effects as random. Additionally, contemporary groups (CG), the age of cow at calving (AGC) and days in milk (DIM) (linear and quadratic regression) were included as fixed effects. The CG was composed by herd, year and month of test. DIM classes were formed with weekly intervals, constituting a total of 42 classes. The variance components were estimated by Restricted Maximum Likelihood Method (REML), using the Wombat software. The average and standard deviation of ECM were 4.80 mS cm-1 and 0.54 mS cm-1, respectively. The heritability estimates by multitrait model and their standa
O artigo não apresenta resumo em português.
Resumo
The Zebu breeds were introduced in Brazil mainly in the last century by imports from the Indian subcontinent. When the Zebu cattle arrived, the national herd suffered a significative change by backcrossing the national cows of taurine origin with Zebu sires. These processes created a polymorphism in the mitochondrial DNA (mtDNA) in the Zebu animals with are in a major part derived from backcrossing and sharing mtDNA of taurine origin. To verify the maternal origin of cows belonging to the Dairy Gyr herd of APTA, Mococa 60 females were analyzed and 33 presented mtDNA from Bos taurus origin and 27 presented mtDNA from Bos indicus origin. None of these animals presented patterns of both mtDNA origins, indicating absence of heteroplasmy for these mitochondrial genotypes.
As raças zebuínas entraram no Brasil principalmente no século passado através de importações do continente indiano. Com a chegada do gado zebu, o rebanho nacional sofreu profunda modificação pelo processo de cruzamento absorvente e foi sendo gradativamente azebuado com a utilização de touros das raças zebuínas. Com isso, criou-se um polimorfismo quanto à origem do DNA mitocondrial (mtDNA) nos animais zebuínos visto grande parte serem oriundos de cruzamentos absorventes a partir de vacas taurinas. Para verificação da origem materna das matrizes do rebanho Gir Leiteiro da APTA, Mococa foram analisadas 60 fêmeas sendo que, 33 apresentaram mtDNA de origem Bos taurus enquanto 27 apresentaram mtDNA de origem Bos indicus . Nenhum animal apresentou os dois genótipos, comprovando assim a ausência de heteroplasmia para este marcador.
Resumo
Using pedigree records of the Polled Gir animals in Brazil born between 1976 and 1998, the inbreeding and effective population size were calculated and genetic variability was determined by parameters based on probabilities of gene origin. The data file was separated in the following periods: 1979-1983, 1984-1988, 1989-1993 e 1994-1998. The total inbreeding increased from 0.22% to 3.06%, the expected inbreeding under random mating increased from 0.07% to 1.54% and the inbreeding due to population subdivision increased from 0.14% to 1.54%, indicating that genetic subdivision in this population is relevant. The effective population size was estimated from the total inbreeding and decreased from 229 to 24. Based on the probabilities of gene origin the effective number of founders, ancestries and remaining genomes decreased over the periods, reaching values of 29, 28 and 19. The results of this study indicate the need for active management to increase genetic variability for conservation and breeding purposes.
Utilizando dados do registro genealógico de animais da raça Gir Mocho, nascidos entre 1976 e 1998, foram calculadas a endogamia, o tamanho efetivo e avaliada a variabilidade genética desta raça por meio dos parâmetros de probabilidade de origem do gene. O banco de dados foi separado nos seguintes períodos: 1979-1983, 1984-1988, 1989-1993 e 1994-1998. A endogamia total aumentou de 0,22% para 3,06%, a esperada sob acasalamento ao acaso aumentou de 0,07% para 1,54%, e a endogamia atribuída a subdivisão populacional aumentou de 0,14% para 1,54% indicando a existência de subdivisão genética na raça Gir Mocho. O tamanho efetivo populacional estimado pelo coeficiente total de endogamia decresceu de 229 para 24. Tendo-se como base a probabilidade de origem do gene foram calculados os números efetivos de fundadores, de ancestrais e de genomas remanescentes. Esses parâmetros decresceram ao longo dos períodos atingindo valores de 29, 28 e 19. Os parâmetros que expressam a variabilidade genética da raça decresceram ao longo dos períodos, indicando a necessidade de monitoração da raça para fins de conserva ção e melhoramento genético.
Resumo
Using pedigree records of the Polled Gir animals in Brazil born between 1976 and 1998, the inbreeding and effective population size were calculated and genetic variability was determined by parameters based on probabilities of gene origin. The data file was separated in the following periods: 1979-1983, 1984-1988, 1989-1993 e 1994-1998. The total inbreeding increased from 0.22% to 3.06%, the expected inbreeding under random mating increased from 0.07% to 1.54% and the inbreeding due to population subdivision increased from 0.14% to 1.54%, indicating that genetic subdivision in this population is relevant. The effective population size was estimated from the total inbreeding and decreased from 229 to 24. Based on the probabilities of gene origin the effective number of founders, ancestries and remaining genomes decreased over the periods, reaching values of 29, 28 and 19. The results of this study indicate the need for active management to increase genetic variability for conservation and breeding purposes.
Utilizando dados do registro genealógico de animais da raça Gir Mocho, nascidos entre 1976 e 1998, foram calculadas a endogamia, o tamanho efetivo e avaliada a variabilidade genética desta raça por meio dos parâmetros de probabilidade de origem do gene. O banco de dados foi separado nos seguintes períodos: 1979-1983, 1984-1988, 1989-1993 e 1994-1998. A endogamia total aumentou de 0,22% para 3,06%, a esperada sob acasalamento ao acaso aumentou de 0,07% para 1,54%, e a endogamia atribuída a subdivisão populacional aumentou de 0,14% para 1,54% indicando a existência de subdivisão genética na raça Gir Mocho. O tamanho efetivo populacional estimado pelo coeficiente total de endogamia decresceu de 229 para 24. Tendo-se como base a probabilidade de origem do gene foram calculados os números efetivos de fundadores, de ancestrais e de genomas remanescentes. Esses parâmetros decresceram ao longo dos períodos atingindo valores de 29, 28 e 19. Os parâmetros que expressam a variabilidade genética da raça decresceram ao longo dos períodos, indicando a necessidade de monitoração da raça para fins de conserva ção e melhoramento genético.
Resumo
Electrical conductivity of milk is an indirect method for diagnosis of mastitis that can be used as criterion of selection in breeding programs, to obtain more resistant animals to infection. Data from 9,302 records of electrical conductivity from the morning milking (ECM), 13,070 milk yield records (MY) and 11,560 records of milking time (MT), of 1,129 first lactation Holstein cows, calving from 2001 to 2011, were used in statistical analysis. Data of eight herds of Southeast region of Brazil were obtained by the WESTFALIA® electronic milking machines, with Dairyplan management system. Two analysis were performed: a multitrait, including MY, MT and ECM, and an unitrait, considering only test-day morning electrical conductivity. The model included additive genetic, permanent environmental and residual effects as random. Additionally, contemporary groups (CG), the age of cow at calving (AGC) and days in milk (DIM) (linear and quadratic regression) were included as fixed effects. The CG was composed by herd, year and month of test. DIM classes were formed with weekly intervals, constituting a total of 42 classes. The variance components were estimated by Restricted Maximum Likelihood Method (REML), using the Wombat software. The average and standard deviation of ECM were 4.80 mS cm-1 and 0.54 mS cm-1, respectively. The heritability estimates by multitrait model and their standa
O artigo não apresenta resumo em português.
Resumo
Mastitis is an inflammation of the mammary gland, caused by bacteria, viruses, fungi and yeasts. During the processes of inflammation, chloride (Cl) and sodium (Na) ions, immunoglobulins and other serum proteins present in blood, flow through capillaries direct to the alveoli lumen of the gland, thus increasing its concentration. This is due to the increase of vascular permeability, the destruction of tight junctions and the active ion-pumping system, while the concentration of casein, lactose, triglycerides and potassium (K) decreases. This work aimed to study a method to evaluate mastitis in Gir dairy cattle, where the milk electric conductivity (EC) was correlated to milk somatic cell count (SCC). This method will provide an early diagnosis, which can be used daily with conductivity meter in mechanical milking machine or weekly in properties with manual milking. The measurement of EC in milk was accomplished through the appliance of AK83 BENCHTOP PORTATIL. The experiment was conducted in two farms: Calciolândia, Arcos/MG and Bom Jardim da Serra, Mococa/SP, totaling 123 Gir cows. In Calciolândia farm, milking was manual and in Bom Jardim da Serra milking was manual and mechanical but both with the presence of the calf . The milk collection took place in 10 ml bottles at ambience temperature, and the samples were in duplicate, one to measure the EC and the other for SCC and co
O artigo não apresenta resumo em português.
Resumo
The Zebu breeds were introduced in Brazil mainly in the last century by imports from the Indian subcontinent. When the Zebu cattle arrived, the national herd suffered a significative change by backcrossing the national cows of taurine origin with Zebu sires. These processes created a polymorphism in the mitochondrial DNA (mtDNA) in the Zebu animals with are in a major part derived from backcrossing and sharing mtDNA of taurine origin. To verify the maternal origin of cows belonging to the Dairy Gyr herd of APTA, Mococa 60 females were analyzed and 33 presented mtDNA from Bos taurus origin and 27 presented mtDNA from Bos indicus origin. None of these animals presented patterns of both mtDNA origins, indicating absence of heteroplasmy for these mitochondrial genotypes.
As raças zebuínas entraram no Brasil principalmente no século passado através de importações do continente indiano. Com a chegada do gado zebu, o rebanho nacional sofreu profunda modificação pelo processo de cruzamento absorvente e foi sendo gradativamente azebuado com a utilização de touros das raças zebuínas. Com isso, criou-se um polimorfismo quanto à origem do DNA mitocondrial (mtDNA) nos animais zebuínos visto grande parte serem oriundos de cruzamentos absorventes a partir de vacas taurinas. Para verificação da origem materna das matrizes do rebanho Gir Leiteiro da APTA, Mococa foram analisadas 60 fêmeas sendo que, 33 apresentaram mtDNA de origem Bos taurus enquanto 27 apresentaram mtDNA de origem Bos indicus . Nenhum animal apresentou os dois genótipos, comprovando assim a ausência de heteroplasmia para este marcador.
Resumo
The electrical conductivity of milk is an indirect method of mastitis diagnosis and can be used as selection criterion in breeding programs to obtain resistant animals to infection. For the present study data from 9,302 milk electrical conductivity measurements in the morning (ECM), from 1,129 Holstein cows in first lactation, calving between 2001 and 2011, belonging to eight herds in the Southeast of Brazil, obtained from automated milking equipment WESTFALIA® with system management "Dairyplan" was utilized. Classes of ECM were formed at weekly intervals, representing a total of 42 classes. The model included direct additive genetic, permanent environmental and residual effects as random and the fixed effects of contemporary group (herd - year and season of the control), age at calving as a covariate (linear and quadratic). Mean trends were modeled by an orthogonal Legendre polynomial with three coefficients of days in milk. The residual variance was considered homogeneous throughout lactation. Variance components were estimated by restricted maximum likelihood method (REML), using the statistical package Wombat (Meyer, 2006). The mean and standard deviation of the electrical conductivity of milk were 4.799 ± 0.543 ms/cm. The heritability for ECM were increased from the beginning to the middle of lactation (154 days), when it reached the maximum value (0.44), decreasing therea
O artigo não apresenta resumo em português.
Resumo
Investigating factors that could affect milk production of cows is an important way to improve the efficiency of production systems. This purpose of this study was to verify and quantify the influence of calf sex on milk production and lactation length in herds of Holstein, Gir, and Guzera cows. Data from 10,780 lactations of 4,807 Holstein cows that calved between 2001 and 2013; 18,898 lactations of 13,172 Gir cows that calved between 1985 and 2013; and 5,277 lactations of 3,972 Guzera cows that calved between 1987 and 2013 were used. Both the accumulated 305-day milk yield (P305) and the length of the lactation period up to 305 days (DL305) were evaluated. Analysis of variance was performed by the least squares method using the GLM procedure in the SAS statistical program. The P305 was not influenced by the sex of the calf in the Holstein breed. However in the zebu breeds (Gir and Guzera), both P305 and DL305 were significantly affected (P 0.01) by the sex of the calf, with higher production and average length of lactation in cows that calved males. In addition, a significant difference was also nested within sex of calf and age at first calving (P 0.05) in the Gir breed. The results indicate that for the zebu breeds, calf sex influences production characteristics.
A investigação de fatores que interferem na produção de vacas leiteiras é de grande importância para eficiência dos sistemas de produção. O objetivo do trabalho foi verificar e quantificar a influência do sexo do bezerro sobre produção de leite e sobre a duração da lactação em rebanhos das raças Holandesa, Gir Leiteiro e Guzerá. Foram avaliadas 10.780 lactações de 4.807 vacas Holandesas, paridas entre 2001 e 2013; 18.898 lactações de 13.172 vacas Gir Leiteiro paridas de 1985 a 2013 e 5.277 lactações ocorridas entre 1987 e 2013, de 3.972 vacas Guzerá. As características estudadas foram produção de leite acumulada em 305 dias e duração da lactação (até 305 dias). A análise de variância foi realizada pelo método de quadrados mínimos, através do procedimento GLM do programa estatístico SAS. A produção de leite acumulada aos 305 dias (P305) na raça Holandesa não foi influenciada pelo sexo do bezerro. Entretanto, para os animais de origem zebuína (Gir leiteiro e Guzerá), ambas as características foram significativamente influenciadas (P 0,01) pelo sexo do bezerro, sendo observadas maiores produções de leite e duração de lactação para vacas que pariram machos. Também foi observada diferença significativa do sexo do bezerro aninhado dentro de idade da vaca ao parto (P 0,05) para a raça Gir leiteiro. Estes resultados indicam que para as raças zebuínas, o sexo do bezerro influe
Resumo
In dairy farming, the productive performance of lactating cows is directly related to the efficiency of the production system. In this respect, studies in different areas investigating animal production try to understand the determinant factors of milk production. Many studies have shown a high correlation between milk production of cows and performance of their calves; however, few studies have addressed the influence of calf sex on milk production. With the objective to evaluate the influence of fetal sex on the milk production of Holstein cows, the present study analyzed cumulative milk yield data provided by the Agrindus Farm in Descalvado, São Paulo. A total of 10,780 calvings of 4,807 cows that had calved between April 2001 and October 2013 and their cumulative yields during lactation according to offspring sex were evaluated. The PROC GLM procedure of the SAS software (SAS Inst., Inc., Cary, NC) was used for analysis. The contemporary group was defined as year and month of calving, with a minimum of 5 observations per group. In addition to contemporary group, the effects of management group and calving order of the cow were included in the model. Mean cumulative yields were 9,800.79 and 9,802.95 kg for cows that had given birth to males and females, respectively. There was no significant difference (P=0.9519) in cumulative milk yield of cows during the study period as a
O artigo não apresenta resumo em português.
Resumo
The body weight (BW) determination is important to evaluate the growth of animals, their nutritional condition and reproduction and to establish the slaughter time and the sale value of the animal. The chest girth (CG) could be an alternative to determine the body weight of sheep on properties that do not have scales. The objective of this study was to investigate the feasibility of using chest girth to determine the estimated body weight (EBW). The data file contained 1762 records of body weight (BW) and chest girth (CG) from 426 Santa Ines breed sheep, belonging to eight herds located in Southeastern Brazil. The chest girth was measured using the sternum and the withers as base, passing the tape measure behind the shoulder. Body weights were related to CG values through linear regressions using the software Statistical Analysis Systems (SAS Inst., Inc., Cary, NC). The age classes 1, 2, 3, were defined respectively as: 0 to 12 months; 13 to 22 months; over 34 months. The regression equation used to predict the body weight through chest girth in different age classes was y = b0 + b1x, where y is the dependent variable EBW, x is the independent variable CG, b0 is the intercept, b1 is the slope of the equation that defines the relationship between EBW and CG. The other variables were constant. The regression equations for specific age groups of animals were: Class 1 EBW = -42.201
O artigo não apresenta resumo em português.
Resumo
Performance evaluation of adapted animals to local conditions for economic traits is essential for the preservation of species and their genetic resources. The size of Morada Nova breed herds have decreased over time, becoming restricted to a few regions. Other races have been used with higher frequency because of their production and adaptation, and are important as a source of food and income for local communities. The objective of this research was to evaluate the application of nonlinear models to describe the growth curve of Morada Nova sheep. Records of 1604 weights of 250 lambs from Nova Odessa municipality, being 934 repeated measurements of female and 670 repeated measurements of male, obtained between 2012-2013 were used. The average birth weight observed was 2.50 ± 0.690 kg. The nonlinear models used to adjust the data were Brody Yt = A (1 - be-kt); Von Bertalanffy Yt = A (1 - be-kt)3; Richards Yt = A (1 - be-kt)m; Logistic Yt = A (1 + e-kt)-m and Gompertz Yt = Ae -be(-kt). The models were fitted by Gauss-Newton using the NLIN procedure of SAS (SAS Inst., Inc., Cary, NC). The parameters that make up the functions are Y = body weight at the age t; A = asymptotic weight that represents the average adulthood weight; K = Maturation rate, an indicator of the speed with which the animal approaches its adult size, maturity of the individual in relation to age is the fractio
O artigo não apresenta resumo em português.