Responses of piglets to early separation from the sow

Two experiments examined the effect of age and diet on behavioural responses of piglets to separation from the sow. In Experiment 1, the vocalizations of piglets were recorded during short term (10 min) isolation from the sow and litter-mates at 1, 2, 3 and 4 weeks of age. From each of 10 litters, two piglets were assigned to each of the four age groups. Piglets of all ages vocalized intensely during isolation, but call rate was lower with older piglets, especially for high-frequency calls (> 500 Hz). When returned to the sow, piglets made distinctive 'quacking' vocalizations, and older piglets produced fewer of these calls than younger piglets. Experiment 2 involved two treatments: weaning age and diet quality. Piglets were weaned at either 2 weeks of age and onto a diet formulated for piglets of this age, or at 4 weeks of age and fed either a diet typically provided for piglets of this age or a more palatable and nutritionally complex diet. Three piglets from each of 16 litters were assigned to each of the three treatment groups. We monitored vocalizations over the first 3 days after weaning, and measured the incidence of belly-nosing during the subsequent week. Piglets weaned onto the standard diet at 4 weeks produced high-frequency calls (> 500 Hz) at a significantly higher rate than those weaned onto the more complex diet, but there was no effect of diet on the incidence of belly-nosing. Piglets weaned at 2 weeks produced more high-frequency calls and performed more belly-nosing than piglets weaned at 4 weeks onto either diet. Thus the behavioural response to separation is greater at younger ages both when the period of separation is too short for diet to be a factor (Experiment 1) and when younger piglets are provided with a specialized diet that allows them to achieve acceptable weight gain after weaning (Experiment 2). These results indicate that separation distress and frustration of suckling motivation are significant problems when piglets are weaned at less than 4 weeks of age. (C) 1999 Elsevier Science B.V. All rights reserved.