Sheep & Goats

Estimates of variance components and genetic parameters for ewe longevity traits in Santa Inàªs hair-type sheep

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Abstract

Santa Inàªs is a major hair-type sheep breed developed in Brazil and represents the largest effective sheep population in the country. Santa Inàªs is widely used as a maternal breed due to its greater growth rate, tropical climate adaptation, maternal ability, and resistance to gastrointestinal parasites as compared to other local breeds. Ewe longevity, defined based on lifespan and lifetime performance, is directly related to flock profitability and animal welfare. However, genetic parameters for ewe longevity-related traits in Santa Inàªs sheep have not been previously reported. Therefore, the main objective of this study was to estimate genetic parameters and accuracies of estimated breeding values (EBV) for seven ewe longevity indicators in Santa Inàªs sheep, including total number of litters (TNL), age at last lambing (ALL), length of productive life (PL), total number of lambs born (TNB) and weaned (TNW) over the ewe lifetime, and total lamb weight at birth (TLB) and weaning (TLW) over the ewe lifetime. After data quality control, phenotypic records from 2,940 ewes born between 1996 and 2014 in 26 flocks were used. The ewes contributing records were daughters of 421 sires and 2,072 dams and produced 8,284 lambs in 7,089 litters. Only ewes with complete lifetime records were analyzed (i.e., non-censored data). Variance components were estimated using the Average Information Restricted Maximum Likelihood algorithm implemented in the BLUPF90+ software by fitting animal models with the Best Linear Unbiased Prediction method. Age at first lambing and year-season were included as a fixed effect while contemporary group (flock-year-season of ewe birth) was fitted as a random effect, due to the large number of levels and their representativeness of a broader population. EBV and their theoretical accuracies were obtained for all 32,866 animals in the complete pedigree. Bivariate analyses were conducted among traits to estimate genetic and phenotypic correlations. The averages of TNB, TNL, ALL, PL, TNW, TLW, and TLB were 2.82 lambs, 2.23 litters, 1,233.95 d, 781.54 d, 2.26 lambs, 34.46 kg, and 10.07 kg, respectively. The heritability estimates (± s.e.) for ewe longevity traits ranged from 0.15 ± 0.03 (ALL) to 0.25 ± 0.05 (TNW) (Table 1). All genetic and phenotypic correlations among ewe longevity traits were positive (Table 1). Genetic correlations ranged from 0.82 ± 0.08 (PL x TLW) to 0.99 ± 0.001 (ALL x PL) and 0.99 ± 0.002 (TNW x TLW). Phenotypic correlations ranged from 0.62 ± 0.02 (ALL x TLW) to 0.98 ± 0.02 (TLW x TNW). These genetic parameters indicate that direct selection for improved ewe longevity in Santa Inàªs sheep is feasible. Despite low to moderate heritability, the estimated genetic correlations support the use of these traits in genetic improvement programs, with favorable expected correlated responses in ewe longevity.

Keywords: 2026

How to Cite:

Alves, J., Pinto, L., Rocha, A., Pedrosa, V. & Brito, L., (2026) “Estimates of variance components and genetic parameters for ewe longevity traits in Santa Inàªs hair-type sheep”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2285626. doi: https://doi.org/10.31274/wcgalp.23758

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