Abstract
Studying the Santa Ines sheep breed is important, as it is the most prevalent breed in Brazil and can adapt to many environments. This study included data were collected over a period of 12 years from 33 flocks in 10 Brazilian States. The estimation of variance components, genetic parameters and breeding values were obtained by DFREML method, using lineal mixed model in single-trait analysis. Traits of age at first lambing (AFL), lambing interval (LI), survivability (SU), litter size at birth (LSB), litter size at weaned (LSW),total litter weight at birth (TLWB) and total litter weight at weaning (TLWW) were assessed. The significance of the fixed effects to be included in the model was performed using statistic program R. The effects of breeder and lambing year were significant (P<0.001). A remarkable phenotypic and permanent environmental variability were found in all traits. Direct heritability estimates were 0.13, 0.04, 0.01, 0.12, 0.03, 0.16 and 0.18 for AFL, LI, SU, LSB, LSW, TLWB and TLWW, respectively. The estimated fractions of variance due to the permanent environmental effects in any traits were high magnitude (0.79 to 0.97). The annual genetic gain has a slightly negative trend in all of them except for AFL and SU. Results indicate that change in environmental conditions of flock in addition to the direct selection for TLWB and TLWW, can be used as selection criteria for improving the productivity of this sheep.
Highlights
The Santa Ines hair sheep has its origin in the state of Bahia and other states of Brazilian Northeast, from crossbreeding mainly among the breeds Bergamácia, Morada Nova and Somalis
Contemporary group (CG) definition varied from trait to trait, including: flock-year-season of ewe birth for lambing interval (LI), flock-year of ewe birth for at first lambing (AFL), flock-year of ewe lambing for litter size at birth (LSB), litter size at weaned (LSW),total litter weight at birth (TLWB) and SU, and flock-year-season of ewe lambing for total litter weight at weaning (TLWW)
Comparing those performances with the obtained from other Brazilian sheep breeds, observations for LI, AFL and LSB were similar to the ones reported by Quesada et al [23]
Summary
The Santa Ines hair sheep has its origin in the state of Bahia and other states of Brazilian Northeast, from crossbreeding mainly among the breeds Bergamácia, Morada Nova and Somalis. The current animal production systems are intensifying livestock, become more sophisticated and seeking increase productivity with better link to animal’s genetics, so only the most productive breeds have been selected [2]. This led in last decade the gradual decrease on genetic variability and reduction or disappearance of breeds “less productive” due to the vision of intensification [3]. An efficient lamb production cannot be performed without controlling reproductive indices such as survivability, age at first lambing, lambing intervals and prolificacy. We consider those traits become invariably relevant as selection criteria for animal breeding programs involving sheep breeds
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