Effects of relatedness on the suckling behaviour of calves in a herd of beef cattle rearing twins

Abstract

This study was designed to examine the effects of relatedness on the behaviour, especially suckling behaviour, of twin beef calves. The subjects were 20 twin calves and their 10 dams. Eight of the 10 dams were mothers of twins consisting of one calf which was conceived by artificial insemination (AI) and one calf which was induced by embryo transfer (ET). The remaining two pairs of twins were natural twins conceived by AI. Observations were made in two 10-day periods in early and late summer. Behaviour was recorded using focal-sampling procedures and suckling behaviour was recorded continuously for all calves. No significant differences were found between AI and ET calves, either for general behaviour or for suckling behaviour. The results indicate that social affinity between calves and their dams did not depend on whether the offspring was the dam's own calf or the unrelated ET calf. This is also supported by the finding that AI calves were not found in closer proximity to their mothers than ET calves. Cross-suckling was very frequently recorded in this herd of twin-nursing cows: it was involved in 42% of the nursing bouts of cows in June and in 58% of bouts in September. The duration of cross-suckling was significantly lower than the duration of suckling from calves' own mothers ( P < 0.001), but cross-sucklers were more frequently observed suckling than were non-cross-sucklers ( P < 0.05 and P < 0.01). Suckling from a calf's own mother almost exclusively occurred in the normal opposite parallel position, while cross-sucklers mainly sucked from alien cows from behind.