Abstract
The objective of the study was to estimate genetic and phenotypic parameters for sow productivity traits of South African Large White pigs, using data from the Integrated Registration and Genetic Information Systems. The analyses were done on 29 719 records for 7 983 sows from 29 herds, which farrowed between 1990 and 2008. Data were analysed as a sow trait using a repeatability animal model. The traits analysed were number of piglets born alive (NBA), litter birth weight (LBWT), 21-day litter size (D21LS) and 21-day litter weight (D21LWT). Estimates of heritability for these traits were 0.07 ± 0.01, 0.11 ± 0.01, 0.03 ± 0.01 and 0.06 ± 0.01, respectively. The respective repeatability estimates for the traits were 0.15 ± 0.01, 0.16 ± 0.01, 0.11 ± 0.01 and 0.12 ± 0.01. Genetic correlations among the traits ranged from 0.32 ± 0.07 between NBA and D21LWT to 0.88 ± 0.04 between NBA and D21LS. The phenotypic correlations ranged from 0.35 ± 0.01 between NBA and D21LWT to 0.75 ± 0.01 between NBA and LBWT. Litter traits at birth were more heritable and repeatable than traits measured at 21 days of age. In general, all traits showed positive genetic and phenotypic trends for the period studied. The heritability of sow productivity traits was low and less repeatable, which suggests that response to selection may be slow and that the performance in the first parity may not always predict future performance. However, because of their economic importance, an attempt should always be made to keep these traits at their optimum.Keywords: Reproductive traits, pigs, genetic progress, phenotypic performance, correlations
Highlights
In pig production systems, enterprise revenue and costs depend on the weight and number of animals raised to marketing
Heritability estimates for the variation in litter sizes and weights among sows ranged from 0.03 ± 0.01 for D21LS to 0.11 ± 0.01 for litter birth weight (LBWT)
The generally low heritability estimates for sow productivity traits are in agreement with most results in literature reported for other breeds (Noguera et al, 2002; Chimonyo et al, 2006; Roehe et al, 2009)
Summary
Enterprise revenue and costs depend on the weight and number of animals raised to marketing. Sow productivity contributes most to the revenue and costs of any pig enterprise. To improve the profits obtained from an enterprise, the number of live piglets born should be improved. The survival of these piglets until weaning is important, after which they do not depend on the sow for survival. Improvement of sow productivity substantially reduces production costs per pig marketed (Irgang et al, 1994). The cumulative and permanent nature of genetic improvement is an important motive to consider sow productivity traits in a selection programme to improve the efficiency of pig enterprises
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