Lactational oestrus in the sow 4. Variation in the incidence and timing of lactational oestrus in groups of sows

Abstract

ABSTRACTEighty multiparous Camborough hybrid female pigs (sows) and their litters, on average 15 days post partum, were housed in groups of five in multi-accommodation pens. The sows were fed ad libitum on a proprietary diet containing 160 g crude protein per kg from grouping to 30 days post partum, when they were fed to scale twice daily in individual feeders until weaning at 42 days post partum. One of four Large White male pigs (boars) was introduced to each group on the day following grouping, each boar being run with four groups.Oestrus occurred in 62 sows, on average 10·2 ± 3·3 days after grouping. The differences between groups in the interval from grouping and boar introduction to the onset of oestrus were statistically significant (P < 0·01). Neither the incidence nor the timing of oestrus could be related to the identity of the boar.Regression analysis revealed relationships between a number of independent variables and the incidence and timing of lactational oestrus. Sows which gained more live weight from farrowing to weaning and whose litters consumed more creep food were more likely to show lactational oestrus. Sows were slower to show lactational oestrus when they gained little weight from farrowing to weaning, had lower live weights at weaning and gained less weight from the previous weaning, despite eating comparatively more food during grouping. The sows which took longer to show lactational oestrus also had heavier piglets at grouping and more piglets in their litters at weaning. The difficulties arising in the interpretation of these results are discussed.