RESUMO
The objectives of this study were to evaluate the influence of inbreeding on growth traits and body measurements, as well as on the estimation of genetic parameters and genetic trends in Guzerá cattle. Phenotypic records of 4,212 animals selected for postweaning weight from Guzerá Breeding Program of Advanced Beef Cattle Research Center were utilized. The pedigree file contained records from 7,213 animals born from 1928 to 2019. The traits analyzed were: birth weight (BW), weights adjusted to 210, 378 and 550 days of age (W210, W378 and W550, respectively), chest girth at 378 and 550 days of age (CG378 and CG550), scrotal circumference (SC), and hip height at 378 and 550 days of age (HH378 and H550). Linear regression was used to evaluate the effects of inbreeding on traits. Genetic parameters were obtained using models including or not the effect of inbreeding as a covariate. Inbreeding had negative effects (P ≤ 0.01) on BW (-0.09 kg), W378 (-2.86 kg), W550 (-2.95 kg), HH378 (-0.10 cm), and H550 (-0.29 cm). The lowest and highest heritability estimates were obtained for W210 (0.21 ± 0.07) and HH550 (0.57 ± 0.06), respectively. The genetic correlations were strong and positive between all traits, ranging from 0.44 ± 0.08 (SC x HH) to 0.99 ± 0.01 (W378 x W550). Spearman correlations between EBVs obtained with or without inbreeding effect ranged from 0.968 to 0.995 (P < 0.01). The results indicate loss of productive performance in inbred animals. However, the inclusion of inbreeding coefficient in genetic evaluation models did not alter the magnitude of genetic parameters or genetic trends for the traits studied.
Assuntos
Endogamia , Clima Tropical , Gravidez , Feminino , Bovinos/genética , Animais , Fenótipo , Parto , Peso ao NascerRESUMO
The objective of the present study was to evaluate the effects of different selection practices on the environmental sensitivity of reproductive and growth traits in males and females of three Nellore selection lines [control (NeC), selection (NeS), and traditional (NeT) lines]. Moreover, genetic trends for the intercept and slope were estimated for each line, and the possible reranking of sires was examined. A total of 8,757 records of selection weight (SW), 3,331 records of scrotal circumference (SC), and 2,311 records of days to first calving (DFC) from Nellore cattle born between 1981 and 2017 were analyzed. (Co)variance components and genetic parameters of all traits were estimated using a reaction norm model with Gibbs sampler. In all cattle lines, the mean heritability of the studied traits ranged from 0.39 to 0.75 for SW in both males and females, from 0.46 to 0.68 for SC, and from 0.06 to 0.57 for DFC along with the environmental descriptor. In all cattle lines, the genetic correlation coefficients between the intercept and slope ranged from 0.03 to 0.81 for SW, from -0.14 to 0.39 for SC, and from -0.87 to -0.42 for DFC. Genetic trends for the slope and proportion of plastic genotypes indicated that the NeS line was more responsive to environmental changes, whereas the NeC and NeT lines tended to respond more modestly. Reranking of sires was observed for all traits, specifically in the NeC and NeT lines, because of the weak correlation between the opposite extreme environments. In the NeS line, reranking of sires was observed for DFC alone. Our results indicate that the effects of genotype-environment interaction are important and should be considered in genetic evaluations of Nellore cattle. Moreover, different selection practices affected the environmental sensitivity of the Nellore selection lines tested in this study.
Assuntos
Bovinos/crescimento & desenvolvimento , Animais , Bovinos/genética , Feminino , Interação Gene-Ambiente , Genótipo , Masculino , Fenótipo , ReproduçãoRESUMO
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
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
Many factors can influence milk yield. Among them are included the environmental, genetics factors and gene-environment interaction. Studies aiming to identify the magnitude of these factors are needed. The effect of calf sex on milk yield is controversial. Therefore, the objective of this work was to investigate the influence of calf gender on milk production along the lactation (P305) of Gyr cows. Data of 18,898 lactation records between the years of 1987 to 2013 were acquired in the official milk control of Brazilian Association of Zebu Breeders (ABCZ) database and analyzed by the least squares method. The linear model for P305 included the fixed effects of calf sex, contemporary group and age of cow at calving within the calf sex as co-variable linear and quadratic. Significant difference was found for the sex of the calf (P 0.01) and the adjusted means of P305 of cows that gave birth to male and female calves were, respectively, 3,565.6 and 3,492.3 kg. Also, there was significant effect of the age of the cow at calving nested within sex of the calf (P 0.01). For female calves the linear and quadratic regression coefficients for the cow age at calving were 17.32 and -0.077 kg, respectively. When the calves were male these coefficients were 21.23 and -0.098 kg, describing a quadratic relation which the production peak was observed at 104 months of age. Hence, Gyr cows
O artigo não apresenta resumo em português.
RESUMO
Many factors can influence milk yield. Among them are included the environmental, genetics factors and gene-environment interaction. Studies aiming to identify the magnitude of these factors are needed. The effect of calf sex on milk yield is controversial. Therefore, the objective of this work was to investigate the influence of calf gender on milk production along the lactation (P305) of Gyr cows. Data of 18,898 lactation records between the years of 1987 to 2013 were acquired in the official milk control of Brazilian Association of Zebu Breeders (ABCZ) database and analyzed by the least squares method. The linear model for P305 included the fixed effects of calf sex, contemporary group and age of cow at calving within the calf sex as co-variable linear and quadratic. Significant difference was found for the sex of the calf (P 0.01) and the adjusted means of P305 of cows that gave birth to male and female calves were, respectively, 3,565.6 and 3,492.3 kg. Also, there was significant effect of the age of the cow at calving nested within sex of the calf (P 0.01). For female calves the linear and quadratic regression coefficients for the cow age at calving were 17.32 and -0.077 kg, respectively. When the calves were male these coefficients were 21.23 and -0.098 kg, describing a quadratic relation which the production peak was observed at 104 months of age. Hence, Gyr cows
O artigo não apresenta resumo em português.
RESUMO
In a sheep production system, the growth-related characteristics have direct relationship to both, quantity and quality of meat. The objective of this study was to evaluate the application of non-linear models to report the growth curve of Santa Inês sheep. Weights of 140 females, born from2010 to 2012, from a single herd at Cravinhos- SP were used. The weights were measured from birth to about one year of age and the ages were grouped together in biweekly classes. The average weight observed at birth was of 3.77±0.92 kg. The non-linear models utilized in the data adjustment were the Brody, Gompertz, Logistic and Von Bertalanffy models, adjusted by the Gauss-Newton method by means of NLIN procedure, available in SAS software. The parameters which compose the functions, Wt (kg) is the weight in time t (days); A (kg) is the asymptotic weight when age tends to infinity; b is an integration constant, related to the initial weights of the animals and not well defined biological interpretation, and k is the maturity rate. The average estimates for A and k, are the most important from an zootechnical parameters point of view, mainly because heavier females tend to create faster growing sheep. All the models evaluated reached convergence. The quality of the models adjustment was done by error mean square (EMS) means. From the EMS results , the Gompertz model showed the best adjustment,
O artigo não apresenta resumo em português.
RESUMO
In a sheep production system, the growth-related characteristics have direct relationship to both, quantity and quality of meat. The objective of this study was to evaluate the application of non-linear models to report the growth curve of Santa Inês sheep. Weights of 140 females, born from2010 to 2012, from a single herd at Cravinhos- SP were used. The weights were measured from birth to about one year of age and the ages were grouped together in biweekly classes. The average weight observed at birth was of 3.77±0.92 kg. The non-linear models utilized in the data adjustment were the Brody, Gompertz, Logistic and Von Bertalanffy models, adjusted by the Gauss-Newton method by means of NLIN procedure, available in SAS software. The parameters which compose the functions, Wt (kg) is the weight in time t (days); A (kg) is the asymptotic weight when age tends to infinity; b is an integration constant, related to the initial weights of the animals and not well defined biological interpretation, and k is the maturity rate. The average estimates for A and k, are the most important from an zootechnical parameters point of view, mainly because heavier females tend to create faster growing sheep. All the models evaluated reached convergence. The quality of the models adjustment was done by error mean square (EMS) means. From the EMS results , the Gompertz model showed the best adjustment,
O artigo não apresenta resumo em português.