The effect of feed restriction on belly nosing behaviour in weaned piglets

Belly nosing is an abnormal behaviour pattern most commonly seen in early-weaned piglets. Because belly nosing resembles massaging the sow's udder, it has been suggested that the behaviour is redirected suckling and may be associated with hunger or feeding motivation. The objective of this study was to determine the effect of feed restriction on the behaviour of newly weaned piglets. Eight groups of four piglets were fed ad libitum during weeks 1, 2 and 3 post-weaning (control), while treatment piglets (eight groups of four) were fed ad libitum during weeks 1 and 3, and feed restricted during week 2. During restriction, ad libitum intake from the previous day was determined from control groups (voluntary intake of 1.9 times maintenance energy requirement), averaged, and treatment piglets were provided with 65% of this amount (1.2 times maintenance energy requirement). While both groups continued to gain weight during the restriction period, weight gain was significantly lower for restricted piglets compared to controls (P < 0.05). Behaviour was observed on days 5, 7, 9, 12, 14, 17, and 20 post-weaning using a 5-min scan sampling method for 6 h/day. During the period of restriction, treatment piglets spent less time at the feeder (5.3 ± 0.9%; controls, 8.3 ± 0.6%, P < 0.05) and more time nosing and chewing at the pen (4.1 ± 1.0%; controls 1.4 ± 0.4%, P < 0.05) compared to controls. Mean percentage of time spent belly nosing was not statistically different (3.5 ± 0.89%; controls 2.1 ± 0.53%, P = 0.13), but the variation among piglets was significantly greater in treatment groups (P < 0.05) during the restriction period. During the post-restriction period, treatment piglets engaged in significantly more belly nosing behaviour (1.8 ± 0.6%; controls, 0.5 ± 0.2%, P < 0.05), while nosing and chewing at the pen was similar between the two groups. Feed restriction stimulated foraging-type behaviour directed at the pen during the period of restriction, and increased and altered the time course for belly nosing, but it did not elicit belly nosing in all pigs. Individual differences in response to feed restriction suggest that there is a causal relationship between low feed intake and belly nosing, but only in piglets with a predisposition for the behaviour.