The current research was conducted to estimate the heritability coefficients and the genetic correlations for performance and carcass and body composition traits in a single sire broiler line. The performance traits analyzed were BW at 38 d, ultrasound records of pectoral muscle depth, feed intake, feed conversion ratio, and BW at 42 d. The carcass traits analyzed were eviscerated BW, breast weight, and leg weight, and the body composition traits analyzed were abdominal fat content, heart weight, gizzard weight, liver weight, and intestine weight. The number of observations varied between 4,120 and 29,040 for each trait. The (co)variance components, heritability, and genetic correlation estimates were obtained by restricted maximum likelihood. The numerator relationship matrix had 42,912 animals. Based on the heritability estimates obtained, the analyzed traits seemed to be able to respond to selection, at variable intensities. The genetic correlation estimates between a great number of performance traits, as well as between a great number of carcass traits, were suggestive of a close genetic relationship between these traits. The genetic correlation estimates between body composition traits were variable. A large genetic association between a great number of performance and carcass traits seemed to exist. The genetic correlation estimates between performance and body composition traits were variable, and important associations between carcass and body composition traits did not seem to exist.
Scrotal circumference data from 47,605 Nellore young bulls, measured at around 18 mo of age (SC18), were analyzed simultaneously with 27,924 heifer pregnancy (HP) and 80,831 stayability (STAY) records to estimate their additive genetic relationships. Additionally, the possibility that economically relevant traits measured directly in females could replace SC18 as a selection criterion was verified. Heifer pregnancy was defined as the observation that a heifer conceived and remained pregnant, which was assessed by rectal palpation at 60 d. Females were exposed to sires for the first time at about 14 mo of age (between 11 and 16 mo). Stayability was defined as whether or not a cow calved every year up to 5 yr of age, when the opportunity to breed was provided. A Bayesian linear-threshold-threshold analysis via Gibbs sampler was used to estimate the variance and covariance components of the multitrait model. Heritability estimates were 0.42 ± 0.01, 0.53 ± 0.03, and 0.10 ± 0.01, for SC18, HP, and STAY, respectively. The genetic correlation estimates were 0.29 ± 0.05, 0.19 ± 0.05, and 0.64 ± 0.07 between SC18 and HP, SC18 and STAY, and HP and STAY, respectively. The residual correlation estimate between HP and STAY was -0.08 ± 0.03. The heritability values indicate the existence of considerable genetic variance for SC18 and HP traits. However, genetic correlations between SC18 and the female reproductive traits analyzed in the present study can only be considered moderate. The small residual correlation between HP and STAY suggests that environmental effects common to both traits are not major. The large heritability estimate for HP and the high genetic correlation between HP and STAY obtained in the present study confirm that EPD for HP can be used to select bulls for the production of precocious, fertile, and long-lived daughters. Moreover, SC18 could be incorporated in multitrait analysis to improve the prediction accuracy for HP genetic merit of young bulls.
The objective of this study was to evaluate the genetic relationship between postweaning weight gain (PWG), heifer pregnancy (HP), scrotal circumference (SC) at 18 months of age, stayability at 6 years of age (STAY) and finishing visual score at 18 months of age (PREC), and to determine the potential of these traits as selection criteria for the genetic improvement of growth and reproduction in Nellore cattle. The HP was defined as the observation that a heifer conceived and remained pregnant, which was assessed by rectal palpation at 60 days. The STAY was defined as whether or not a cow calved every year up to the age of 6 years, given that she was provided the opportunity to breed. The Bayesian linear-threshold analysis via the Gibbs sampler was used to estimate the variance and covariance components applying a multitrait model. Posterior mean estimates of direct heritability were 0.15 6 0.00, 0.42 6 0.02, 0.49 6 0.01, 0.11 6 0.01 and 0.19 6 0.00 for PWG, HP, SC, STAY and PREC, respectively. The genetic correlations between traits ranged from 0.17 to 0.62. The traits studied generally have potential for use as selection criteria in genetic breeding programs. The genetic correlations between all traits show that selection for one of these traits does not imply the loss of the others.
Broiler meat quality is one of the primary factors considered by the poultry industry. This study was conducted to estimate heritability and genetic correlation coefficients for meat quality traits in a single male broiler line. The meat ultimate pH (24 h after slaughter) and lightness presented the highest heritability estimates. Given the estimated genetic correlations, the pH measured at 15 min and 24 h after slaughtering, as well as lightness, were characterized by a close and negative genetic relationship with water holding capacity traits. In contrast, meat quality traits exhibited only non-significant genetic correlations with performance and carcass traits. Noticed exceptions were breast weight, which was genetically and favorably associated with the initial pH and thawing-cooking losses, and ultrasound record of pectoral muscle depth, which was genetically and unfavourably associated with the shear force of meat. Meat pH values at 24 h after slaughtering or lightness may be a favorable selection criterion for the poultry industry for improving meat quality, since these traits are associated with the water holding capacity of the meat. Out of the traits studied, lightness is most easily assessed on the industrial slaughtering line. The direct selection for breast weight could improve the initial pH and thawing-cooking losses of meat, even as selection for ultrasound records of Pectoralis major may affect the meat tenderness in this line.
The aim of this study was to assess the distribution of runs of homozygosity (ROH) and autozygosity islands in the composite Montana Tropical® beef cattle to explore hotspot regions which could better characterize the different biological types within the composite breed. Montana animals (n = 1,436) were genotyped with the GGP‐LD BeadChip (~30,000 markers). ROH was identified in every individual using the plink v1.90 software. Medium and long ROH prevailed in the genome, which accounted for approximately 74% of all ROH detected. On an average, 2.0% of the genome was within ROH, agreeing with the pedigree‐based inbreeding coefficient. The Montana cattle with a higher proportion of productive breed types showed the highest number of autozygosity islands (n = 17), followed by those with a higher proportion of breeds adapted to tropical environments (n = 15). Enriched terms (p < .05) associated with the immune and inflammatory response, homeostasis, reproduction, mineral absorption, and lipid metabolism were described within the autozygosity islands. In this regard, over‐represented GO terms and KEGG pathways described in this population may play a key role in providing information to explore the genetic and biological mechanisms together with the genomic regions underlying each biological type that favoured their optimal performance ability in tropical and subtropical regions.
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