| dc.description.abstract | In the first 3 days of life, triplet lambs, especially the smaller triplets, are less capable of surviving than twins and singles. However, whether differences in behaviour and survival of lambs within triplet litters persist after this period is unknown. This trial examined the differences in sucking behaviour and milk intake between the light, medium and heavy lambs within a triplet litter at 8-17 days of age, with the lamb rank based on birth weight. Of 28 triplet carrying ewes, only 10 complete litters survived to at least 8 days of age and could be used for this trial. After 4 hours of separation, the lambs were returned to the ewe and the behaviour of the lambs and ewe was observed for a period of 15 minutes. The abdominal girth and body weight of the lambs were measured before and after the sucking period. At 8-17 days of age, triplet lambs still differed in terms of weight (P=0.001) and abdominal girth (P=0.002); the triplet lambs born lightest were still lightest and had the smallest abdominal girth. However, there were no statistical relationships between lamb rank and sucking behaviour. Light, medium and heavy lambs did not differ in the number of sucking bouts, number of attempted bouts, total sucking duration, mean sucking bout duration, relative sucking duration, teat fidelity or number of butts. Nor did lamb rank affect the behaviour of the ewes (kicks or butts, walking away from lambs) or measures of milk intake such as relative weight gain or girth gain. However, there was a tendency for lamb rank to have an effect on one measure of milk intake (weight gain) (P=0.09). The lambs that were lightest at birth tended to gain less weight during the observation period than heavier lambs, particularly those of medium birth weight. There was also a tendency for lamb rank to have an effect on relative girth gain (P=0.08). The lambs born lightest tended to gain more girth relative to their original girth than the heaviest lambs. The only measure of sucking behaviour that tended to differ with lamb rank was the frequency of teat switching (P=0.09); medium lambs tended to switch teats more often than the heaviest lambs. Overall, weight gain is likely to be the most accurate indicator of milk intake; based on this variable, lambs born lightest appear to have ingested less milk than their heavier siblings, despite the lack of differences in sucking behaviour. These lambs were still lighter and smaller at 8-17 days of age, suggesting that they had lower growth rates and potentially lower chances of survival. Further research should aim to determine whether ewes and lambs can adapt their sucking behaviour to cope with triplet litters, instead of twins or singles, or whether ewes should be selected for higher milk production. In addition, the effect of different management strategies (e.g. fostering or weaning of the lightest lamb or providing milk supplement) on triplet lambs’ milk intake, growth and survival should be tested. | |
