Effect of the Lactation Length of Piglets on Their Later Performance

The lactation period, besides being only a slight fraction of the total cycle up to slaughtering, plays an important role determining the future performance of piglets. Moreover, since weaning is normally done at a fixed day for all sows belonging to the same parturition batch, it leads to differences in d of lactation depending on the farrowing day. It is hypothesized that little variations in d of lactation could affect both BW at weaning and also at slaughtering. The objective of this study was to observe the effect of the lactation length of sows belonging to the same batch on the subsequent performance of piglets at weaning and at 165 d of age. A total of 702 males and females crossbreed piglets [Pietrain x (Landrace x Large White)] from 70 multiparous sows (parity ranging from 2 to 10) were used and individually weighed every three weeks (from birth to slaughter). Weight data for each pig were adjusted using the double exponential Gompertz model (BW = A*exp(-exp(b-(c*t))), and the BW at d 165 of age was estimated for each pig using this model to correct the age effect among pigs. Means were calculated as LSmeans. The BW at birth (BW0) was added as a covariate using the proc GLM of SAS. The effect of d of lactation was found to be significant at weaning (P<0.001) and at the end of the cycle (P=0.004). Results (in kg of BW) for weaning were 4.54^b, 5.31^a, 5.50^a, 5.64^a and 5.53^a kg and for 165d of age were 93.22^b, 96.54^ab, 96.75^a, 98.01^a and 100.05^a for 18, 19, 20, 21 and 22 d of lactation respectively. The consequence was that a small difference of around one kg at weaning increased to almost 7 kg (6.84 kg) at d 165. Increasing the length of lactation from 18 to 22 d caused a significant linear BW increase in both, at weaning (231g/extra d of lactation; R²= 0.70; P<0.05) and at 165 d of live (1151g/extra d of lactation; R²=0.92, P<0.05). It is concluded that piglets coming from sows that farrow earlier in a batch increase the d of lactation and produce heavier pigs at 165 d of age; consequently, shortening the farrowing period within a batch without using artificially farrow synchronization, could help to reduce the differences in BW at the end of the cycle, and may help producers to increase the farm efficiency.