Neonatal piglets are able to differentiate more productive from less productive teats

A previously-validated method to induce variation in milk production between teats of the same udder that is not related to the ante-posterior location of the teat was used. In the first lactation, over half of the sows' teats (teats 1, 2, 5, 6, and 7 from 1 side of the udder, and teats 3, 4, and 7 from the other side) were sealed with tape so that they were non-functional (treated (TRT) teats), whilst the other six unblocked teats were left unblocked so that they were functional (control (CTL) teats). Sixty-four piglets in eight litters were observed on days 2 and 10 of the second lactation when all teats were available. Teat use, piglets' behaviour during nursings and growth performances were analysed according to a 2 × 3 factorial design including the position (anterior, middle and posterior) and the treatment (CTL vs. TRT) of teats as fixed factors. Analysis of the location of piglets along the udder at milk ejection revealed that teat use on day 2 was affected by position and treatment of teats, but teat use on day 10 was only affected by position. Moreover, on day 2, the total number of fights was greater for CTL than TRT teats (9.6 vs. 6.2 fights/day, respectively; P < 0.001) and the percentage of time the teat was suckled during post-massage was longer for CTL than TRT teats (54.9 vs. 44.7%, respectively; P = 0.022). Piglets that suckled preferentially from CTL teats in early lactation had an increased growth rate until the end of the post-weaning period (BW at day 56: CTL = 23.66 vs. TRT = 21.32 kg; P = 0.004). Current results confirmed that teats used in first lactation produce more milk in second lactation, and that piglets are able to detect this difference. When considering the whole litter, piglets had a preference for previously-used teats and competed to get access to them. We conclude that choice and competition of piglets for higher-producing teats happens in the early stage of lactation, during the establishment of the teat order and that suckling preferentially from such teats has long-term positive effects on piglets' growth.