Genetic parameters for production, quality, and colors from eggs in Brazilian lineages of chickens.

Genetic parameters were estimated for egg production, egg quality, and eggshell colors in eight lineages of Brazilian laying hens. Age at first egg (AFE), total egg production up to the 45th week (PROD), egg weight (EW), albumen height (AH), yolk color (YC), the Haugh units (HU), eggshell strength (ESS), eggshell thickness (EST), yolk weight (YW), eggshell weight (ESW), and eggshell color (L*, a*, and b*) were measured in 2030 eggs obtained from 645 laying hens. Variance components were estimated from a mixed animal model, which included the fixed effects of contemporary groups, cage location, and hen line, and the additive genetic, permanent environmental, and residual as random effects. In general, heritabilities were low to moderate (h2 = 0.11 to 0.48). Genetic correlations among eggshell quality traits were moderate to high (0.36 and 0.69). High genetic correlations were obtained between the eggshell color traits [rg = -0.90 (L* and a*); rg = -0.64 (L* and b*); and rg = 0.65 (a* and b*)]. Results suggest that EW is strongly correlated with ESW, but the genetic correlations between EW and ESS and between EW and EST were low. Genetic correlations between L* and eggshell quality traits were low to moderate, suggesting that L* has little or no relation with external egg quality. However, genetic correlations between a* and b* values and eggshell quality traits were high. The genetic correlations between eggshell color and eggshell quality traits were low, suggesting that the eggshell color does not influence external egg quality. Genetic correlations between PROD and egg quality traits were negative and varied between -0.42 and -0.05. This antagonistic relationship emphasizes the importance of adopting breeding schemes that allow the simultaneous genetic progress of these traits by considering their genetic correlation and economic relevance, such as the selection index.

Heat stress on breeding value prediction for milk yield and composition of a Brazilian Holstein cattle population.

Due to the high milk production of Holstein cows, many countries have chosen to import semen to improve local dairy herds. This strategy would be more effective if this semen was used in the same environment conditions in which the bulls were selected. If the effect of genotype by environment (G × E) interaction is not considered, the estimated breeding values (EBVs) may vary, potentially reducing the selection response. We evaluate the impact of heat stress on selection for milk yield and composition of Holstein cows using random regression models. To verify the interference of heat stress in milk yield (MY) and composition traits (fat, protein, total saturated, and total unsaturated fatty acids content in milk), temperature-humidity index (THI) on test-day milk records was used. The threshold value to divide the environments using test-day information from Brazilian Holstein cows was 72 units of THI, i.e., < 72 represented no heat stress and > 72 represented heat stress. Legendre polynomials of second-order (Leg 2) model and two lactation points (33 and 122 DIM) were used to estimate heritabilities and EBVs for five important dairy traits. The heritabilities of milk components and fatty acids were low (0.09-0.29), regardless of lactation period and degree of heat stress, with the exception of protein content (0.30-0.35). Fat content was the only milk component that was reduced according to the degree of heat stress and lactation period. The EBVs tended to decrease in heat stress conditions, thus animals with high genetic potential demonstrated evidence of G × E interaction. However, acclimatization of dairy cows to heat stress in the farm production systems may have been responsible for the low differences among genetic parameters and EBVs with and without heat stress found in this study.

Genetic parameters for milk yield and quality traits of Brazilian Holstein cows as a function of temperature and humidity index.

Measurements of milk yield (MY), somatic cell score (SCS), percentage of fat (FP), protein (PP), lactose (LP), casein (CP) and percentage of palmitic (C16:0), stearic (C18:0), oleic (C18:1), total saturated (SFA), unsaturated (UFA), monounsaturated (MUFA) and polyunsaturated (PUFA) fatty acids in milk from 5,224 Holstein cows were evaluated as a function of a temperature and humidity index (THI). Legendre orthogonal polynomials from second to seventh order were tested. The best fit order for MY, PP and C18:0 was the third, whereas the second for all other traits. The heritability estimates decreased for MY (0.31 to 0.14), FP (0.28 to 0.16), LP (0.43 to 0.30), SCS (0.14 to 0.09), SFA (0.33 to 0.22) and C16:0 (0.31 to 0.26), whereas increased for CP (0.32 to 0.42), MUFA (0.08 to 0.13), UFA (0.07 to 0.11) and C18:1 (0.07 to 0.11) as the THI level increased. For PP, heritabilities (0.26 to 0.39) presented larger values in intermediate THI. For PUFA and C18:0, heritabilities were approximately constant (0.13 to 0.14 and 0.15, respectively). However, the greatest variations may have been the result of the limitations of Legendre polynomials at the extreme points of the curve, and the pattern of heritabilities curves was approximately constant for the evaluated traits. Spearman's rank correlations between breeding values in extreme THI levels were greater than 0.80 for all traits considering all animals, only cows and only bulls. When considering the top 1% and the top 50% animals (only cows, only bulls and all), Spearman correlations smaller than 0.70 were found, suggesting reranking of the animals. Although there was little variation in the variance components over THI, it is possible that there is no heat stress in the animals studied, because, on average, there was no great impact of the thermal load on the traits. One possible explanation is the use of herds with little climatic difference among herds, as well as the use of fans and sprinklers into the barns. However, the THI levels may be important factors in the selection process, as reranking of animals was verified.

Linkage disequilibrium in Brazilian Santa Inês breed, Ovis aries.

For genomic selection to be successful, there must be sufficient linkage disequilibrium between the markers and the causal mutations. The objectives of this study were to evaluate the extent of LD in ovine using the Santa Inês breed and to infer the minimum number of markers required to reach reasonable prediction accuracy. In total, 38,168 SNPs and 395 samples were used. The mean LD between adjacent marker pairs measured by r2 and |D'| were 0.166 and 0.617, respectively. LD values between adjacent marker pairs ranged from 0.135 to 0.194 and from 0.568 to 0.650 for r2 for |D'| across all chromosomes. The average r2 between all pairwise SNPs on each chromosome was 0.018. SNPs separated by between 0.10 to 0.20 Mb had an estimated average r2 equal to 0.1033. The identified haplotype blocks consisted of 2 to 21 markers. Moreover, estimates of average coefficients of inbreeding and effective population size were 0.04 and 96, respectively. LD estimated in this study was lower than that reported in other species and was characterized by short haplotype blocks. Our results suggest that the use of a higher density SNP panel is recommended for the implementation of genomic selection in the Santa Inês breed.

Genome-wide association study for performance traits in chickens using genotype by sequencing approach.

Performance traits are economically important and are targets for selection in breeding programs, especially in the poultry industry. To identify regions on the chicken genome associated with performance traits, different genomic approaches have been applied in the last years. The aim of this study was the application of CornellGBS approach (134,528 SNPs generated from a PstI restriction enzyme) on Genome-Wide Association Studies (GWAS) in an outbred F2 chicken population. We have validated 91.7% of these 134,528 SNPs after imputation of missed genotypes. Out of those, 20 SNPs were associated with feed conversion, one was associated with body weight at 35 days of age (P < 7.86E-07) and 93 were suggestively associated with a variety of performance traits (P < 1.57E-05). The majority of these SNPs (86.2%) overlapped with previously mapped QTL for the same performance traits and some of the SNPs also showed novel potential QTL regions. The results obtained in this study suggests future searches for candidate genes and QTL refinements as well as potential use of the SNPs described here in breeding programs.

Perfil genético das linhagens de touros leiteiros Holandês e Jersey disponíveis no Brasil / Genetic profile of Holstein and Jersey dairy bull lines available in Brazil

As raças de bovinos de leite Holandesa e Jersey estão entre as mais prevalentes no Brasil. Para avaliar as diferenças entre as PTAs (habilidades de transmissão preditas) destas raças e suas linhagens, foram coletadas informações de 385 touros Holandês e 82 touros Jersey disponibilizados por nove empresas comercializadoras de sêmen no Brasil. Três diferentes linhagens de cada raça foram encontradas. O método dos modelos lineares generalizados foi utilizado para a comparação entre linhagens e entre raças. As duas linhagens da raça Holandesa mais prevalentes apresentaram as maiores PTAs médias para produção de leite (1.061,04 libras e 975,32 libras) e as menores PTAs para a porcentagem de sólidos no leite (de -0,05% a -0,0003%)

The Holstein and Jersey dairy cattle breeds are among the most prevalent in Brazil. To evaluate differences among the PTAs (predicted transmitting abilities) of these breeds and their lines, data were collected on 385 Holstein bulls and 82 Jersey sires with semen commercially available from nine Brazilian companies. Three different sire lines for each breed were found. The general linear models method was used for the comparison among lines and between breeds. The two most prevalent lines of Holstein breed presented higher average PTAs for milk yield (1,061.04 pounds and 975.32 pounds) and lower PTAs for percentage of milk solids (from -0.05% to -0.0003%)

Correlated responses and genetic parameters for performance and carcass traits in a broiler line / Respostas correlacionadas e parâmetros genéticos para características de desempenho e de carcaça em uma linha de frangos de corte

The growth rate of broilers has triplicated in the last decades. The body weight is used as one of the selection criteria whereas the carcass traits are valuable market requirements. Thus, the meat industry like animals with high weights at slaughter and better carcass traits. However, the genetic relation of carcass traits with several body weights is unknown. Therefore, we established genetic associations among performance and carcass traits in a broiler chicken line and estimated genetic gain and trends. We also evaluated what age of selection would lead to a more efficient indirect selection of carcass traits. The data set with information of weights in different ages and carcass traits of 128,459 chickens was used. The pedigree data used contained 132,442 chickens. Genetic analysis were realized using ASREML® software applied a restricted maximum likelihood method. Heritability estimates ranged from moderate to high, which indicates that these traits can have high selection response. Genetic correlations between performance and carcass traits varied from moderate to high, which indicates the presence of a genetic association whereas genetic trends indicated that direct selection is occurring for body weight at different ages. Theselection at 30 and 38 days should be considered instead of the slaughter weight, as it anticipates selection in around 12 days.

A taxa de crescimento de frangos de corte foi triplicada nas últimas décadas. O peso corporal é utilizado como um dos principais critérios de seleção, enquanto que as características de carcaça são essenciais para o mercado. Assim, a indústria avícola busca animais com pesos altos ao abate e excelentes características de carcaça. Contudo, a associação genética entre as características de carcaça e desempenho é desconhecida. Deste modo, foram estabelecidas associações genéticas entre estas características, além das estimativas do progresso genético e as tendências genéticas para uma linhagem comercial de frango de corte. Avaliou-se a idade ideal para a seleção indireta, visando a melhoraria das características de carcaça. Foram utilizadas informações de pesos em diferentes idades e características de carcaça de 128.459 frangos em diferentes idades ao passo que o pedigree dispunha de 132.442 aves. As análises genéticas foram realizadas por meio do software ASReml®, utilizando o método da máxima verossimilhança restrita, sob o modelo animal. As estimativas de herdabilidade variaram de moderadas a altas, sendo indicativo de que estas características podem ter alta resposta à seleção.

Perfil genético das linhagens de touros leiteiros Holandês e Jersey disponíveis no Brasil / Genetic profile of Holstein and Jersey dairy bull lines available in Brazil

As raças de bovinos de leite Holandesa e Jersey estão entre as mais prevalentes no Brasil. Para avaliar as diferenças entre as PTAs (habilidades de transmissão preditas) destas raças e suas linhagens, foram coletadas informações de 385 touros Holandês e 82 touros Jersey disponibilizados por nove empresas comercializadoras de sêmen no Brasil. Três diferentes linhagens de cada raça foram encontradas. O método dos modelos lineares generalizados foi utilizado para a comparação entre linhagens e entre raças. As duas linhagens da raça Holandesa mais prevalentes apresentaram as maiores PTAs médias para produção de leite (1.061,04 libras e 975,32 libras) e as menores PTAs para a porcentagem de sólidos no leite (de -0,05% a -0,0003%)(AU)

The Holstein and Jersey dairy cattle breeds are among the most prevalent in Brazil. To evaluate differences among the PTAs (predicted transmitting abilities) of these breeds and their lines, data were collected on 385 Holstein bulls and 82 Jersey sires with semen commercially available from nine Brazilian companies. Three different sire lines for each breed were found. The general linear models method was used for the comparison among lines and between breeds. The two most prevalent lines of Holstein breed presented higher average PTAs for milk yield (1,061.04 pounds and 975.32 pounds) and lower PTAs for percentage of milk solids (from -0.05% to -0.0003%)(AU)

Correlated responses and genetic parameters for performance and carcass traits in a broiler line / Respostas correlacionadas e parâmetros genéticos para características de desempenho e de carcaça em uma linha de frangos de corte

The growth rate of broilers has triplicated in the last decades. The body weight is used as one of the selection criteria whereas the carcass traits are valuable market requirements. Thus, the meat industry like animals with high weights at slaughter and better carcass traits. However, the genetic relation of carcass traits with several body weights is unknown. Therefore, we established genetic associations among performance and carcass traits in a broiler chicken line and estimated genetic gain and trends. We also evaluated what age of selection would lead to a more efficient indirect selection of carcass traits. The data set with information of weights in different ages and carcass traits of 128,459 chickens was used. The pedigree data used contained 132,442 chickens. Genetic analysis were realized using ASREML® software applied a restricted maximum likelihood method. Heritability estimates ranged from moderate to high, which indicates that these traits can have high selection response. Genetic correlations between performance and carcass traits varied from moderate to high, which indicates the presence of a genetic association whereas genetic trends indicated that direct selection is occurring for body weight at different ages. Theselection at 30 and 38 days should be considered instead of the slaughter weight, as it anticipates selection in around 12 days.(AU)

A taxa de crescimento de frangos de corte foi triplicada nas últimas décadas. O peso corporal é utilizado como um dos principais critérios de seleção, enquanto que as características de carcaça são essenciais para o mercado. Assim, a indústria avícola busca animais com pesos altos ao abate e excelentes características de carcaça. Contudo, a associação genética entre as características de carcaça e desempenho é desconhecida. Deste modo, foram estabelecidas associações genéticas entre estas características, além das estimativas do progresso genético e as tendências genéticas para uma linhagem comercial de frango de corte. Avaliou-se a idade ideal para a seleção indireta, visando a melhoraria das características de carcaça. Foram utilizadas informações de pesos em diferentes idades e características de carcaça de 128.459 frangos em diferentes idades ao passo que o pedigree dispunha de 132.442 aves. As análises genéticas foram realizadas por meio do software ASReml®, utilizando o método da máxima verossimilhança restrita, sob o modelo animal. As estimativas de herdabilidade variaram de moderadas a altas, sendo indicativo de que estas características podem ter alta resposta à seleção.(AU)

Modelos de curvas de crescimento e regressão aleatória em linhagens nacionais de frango caipira / Models of growth curves and random regression lines in national free-range chickens

A avicultura é uma das principais atividades agropecuárias do Brasil, em 2011 o país produziu 12.230 toneladas de carne de frango, sendo o 3º maior produtor de frango do mundo, apenas atrás dos EUA e China. Parte deste êxito se deve principalmente ao melhoramento genético animal implantado nas últimas décadas. Os objetivos nesse estudo foram: 1º - Comparar as funções das curvas de crescimento: von Bertalanffy, Gompertz, Logística, Richards e Brody, pelo método dos Mínimos Quadrados Ordinários (QMO) e Quadrados Mínimos Ponderados (QMP) a dados de peso vivo para as linhagens experimentais de frango caipira (7P, Caipirão da ESALQ, Caipirinha da ESALQ e Carijó Barbado) e selecionar uma curva de crescimento que melhor descreva o padrão de crescimento para cada linhagem, e estimar os componentes genéticos (herdabilidades e correlações genéticas) dos parâmetros destas funções sob análise bicaracterística; 2º - Comparar modelos com diferentes ordens de ajuste por meio de funções polinomiais de Legendre, sob modelos de regressão aleatória, com variância residual heterogênea, para a estimação dos componentes de (co) variância e avaliação genética de linhagens experimentais de frango caipira (7P, Caipirão da ESALQ, Caipirinha da ESALQ e Carijó Barbado). [...] As correlações genéticas e fenotípicas entre as características e foram negativas e altas. Indicando que quanto maior o peso assintótico menor a taxa de crescimento. Dentre os modelos de Regressão Aleatória estudados o polinômio de 3ª ordem foi o que melhor se adequou para descrever as curvas de crescimento das linhagens estudadas. As estimativas de variâncias, herdabilidades foram afetadas pela modelagem da variância residual. Em geral as herdabilidades estimadas para as idades de 1 a 84 dias variaram de moderadas a altas para as linhagens estudadas, indicando que qualquer idade pode ser utilizada como critério de seleção. A seleção aos 42 dias de idade pode ser mantida como critério de seleção

Aviculture is one of the main agribusiness activities in Brazil, in 2011 the country produced 12,230 tons of broiler meat, was the 3rd largest producer of broiler in the world, only behind the USA and China. Part of this success is mainly due to animal genetic improvement implemented in recent decades. In this study, our objectives were: 1 - to compare the functions of the Von Bertalanffy, Gompertz, Logistic, Richards and Brody growth curves by the Ordinary Least Squares and Weighted Least Squares method, from data for body weight from experimental free-range chicken lines (7P, Caipirão da ESALQ, Caipirinha da ESALQ and Carijó Barbado) and select a growth curve that best describes their growth. From this, estimates of the genetic components (heritability and genetic correlations) of the parameters of these functions under bivariate analysis; 2 - Comparing models with different orders of adjustment by means of Legendre polynomial functions under random regression models with heterogeneous residual variance for the estimation of (co) variance and genetic evaluation of experimental free-range chicken lines (7P, Caipirão da ESALQ, Caipirinha da ESALQ and Carijó Barbado). [...] The genetic and phenotypic correlations between traits and were negative and high, indicating that the higher the asymptotic weight, the lower the growth rate. Among the Random Regression models studied the 3rd order polynomial was best adapted to describe the growth curves of the lines studied. Estimates of variances and heritabilities were affected by residual variance modeling. Overall heritability estimates between 1 to 84 days of age ranged from moderate to high for all lines, indicating that any age can be used as a selection criterion, including maintaining the current selection at 42 days of age