NURSING BEHAVIOUR AND NURSING VOCALISATIONS IN DOMESTIC SOWS: REPEATABILITY AND RELATIONSHIP WITH MATERNAL INVESTMENT

Abstract

We examined the repeatability of pig nursing behaviour and its relationship with maternal investment (measured in piglet growth) in two experiments. In Experiment 1, eleven sows were followed for 2-5 (median 3) lactations, and their nursing behaviour was recorded on Day 11 post partum during each of these lactations. In Experiment 2, fourteen sows were followed for two consecutive lactations, and their nursing behaviour recorded on Days 7 and 28. In Experiment 2, the data on piglet growth between Days 1 and 6, and between Days 6 and 28 were also recorded, and mortality data were available in both experiments. We evaluated the data in order to get answers to three basic questions: First, was the nursing behaviour repeatable within and across lactations, i.e. did the sow have individually stable nursing styles? Second, was the variability in nursing behaviour related to piglet growth or mortality? Third, were the sows inclined to nurse repeatedly on one side and if so, did this result in faster growth and/or lower mortality in the piglets suckling the 'upper row' teats? We found that the pattern of grunting vocalisation emitted by the sow was highly repeatable both within and across lactations. We hypothesise that this individual acoustic signal may be used by piglets to locate their mother during synchronised nursings in the group living female pigs. However, the variables characterising nursing frequency, the willingness of the sow to allow udder massage by the piglets, and the laterality of nursing had low or no repeatabilities within and across lactations. Piglet growth was only loosely, and piglet mortality not at all, related to the quantitative variability in nursing behaviour casting doubts on whether nursing behaviour variables are suitable for selection programs. Although some sows preferred to nurse while lying on the left, and others on the right side, this laterality did not result in faster growth of piglets suckling the upper row of teats.