Genetic and Environmental Factors Affecting Weaning-to-First Service Interval in a Landrace-Large White Swine Population in Northern Thailand

Abstract

Non-productive sow days measured as weaning-to-first service interval (WSI) is an economically important trait in commercial swine production. A reduction in WSI would increase efficiency and decrease production costs. The aim of this study was to characterize genetic and environmental factors affecting WSI in a Landrace-Large White commercial swine population in Chiang Mai, Northern Thailand. The dataset contained information from 11,737 litters and 2,468 sows collected from 1989 to 2008. Sows were raised in an open-house system and received the same feeding and
management. Four breed groups were represented: Landrace (L), Large White (T), L × T (LT), and T × L (TL). Parity of sow was classified as 1, 2, 3, 4, 5, 6, and ≥ 7. Seasons were winter (November to February), summer (March to June), and rainy (July to October). Year-season of farrowing was important source of variation (P < 0.0001). The WSI ranged from 4.38 ± 0.67 d (1991-winter) to 9.68 ± 1.14 d (1989-rainy). Gilts had longer WSI (8.54 ± 0.14 d) than multiparous sows (5.80 ± 0.19 d to 6.33 ± 0.14; P < 0.0001). Landrace had similar WSI (6.10 ± 0.10 d) to T sows (6.00 ± 0.09 d). Crossbred LT sows (6.43 ± 0.20 d) and TL sows (7.04 ± 0.20 d) had longer WSI than purebreds sows (P < 0.0001). Heterosis estimates for WSI were 0.31 ± 0.20 d (P < 0.12) for LT sows and 0.91 ± 0.20 d (P < 0.0001) for TL sows. The WSI heritability estimate was low (0.024 ± 0.010) due primarily to a low estimate of additive genetic variance. Introduction of unrelated animal to the population may increase additive genetic variation and increase potential for genetic improvement for WSI.