Effect of lactation length caused by the management production system on piglet performance until slaughter

Since weaning in commercial conditions is usually done on a fixed day for all sows belonging to the same parturition batch, litters have differences in days of lactation, depending on the farrowing date. Days of lactation affect the piglet's weaning body weight (BW), and it is hypothesized that it may also affect the slaughtering BW. The objective of this study is 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 days of age. A total of 796 male and female crossbreed piglets [Pietrain x (Landrace x Large White)] from 92 sows (parities ranging from 1 to 7) were used and individually weighed 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 day 165 of age was estimated for each pig using this model to correct for the age effect among pigs. Means were calculated as LSmeans. Birth body weight (BBW) was added as a covariate and lactation length as a factor using the Proc GLM of SAS. The effect of days of lactation was found to be significant at weaning (P < 0.001) and at the end of the cycle (P < 0.001). Results (kg of SW) for weaning were 4.7(a), 5.3(b), 5.6(c), 6.0(c), and 7.2(d) kg, and for 165 days of age they were 92.3(a), 96.4(b), 98.0(bc), 102.9(d), and 101.7(cd) kg for 18, 19-20, 21-22, 23-24, and > 25 days of lactation, respectively. The consequence was that a difference of 2.4 kg at weaning increased to 9.4 kg at day 165. Increasing the length of lactation from 18 days to more than 25 days caused a significant linear BW increase at weaning (P < 0.001) and a quadratic response at 165 days of life (P < 0.001). It is concluded that piglets coming from sows that farrow earlier in a batch increase the days of lactation and produce heavier pigs at 165 days of age; consequently, shortening the farrowing period within a batch, without necessarily using artificial farrow synchronization, could help to reduce the differences in BW at the end of the cycle, and may help producers to increase farm efficiency.