Behaviour of group-reared calves fed on acid-milk replacer

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When calves are reared in groups on ad libitum acidified milk, growth rates may be variable and the weaning check in growth may be severe. This study was carried out to identify the behavioural factors responsible for these problems. Eight groups of ten 24-hold Friesian calves were reared on acidified milk via 2 teats. Treatments involved varying the positions of the teats (apart or together), restricted (90 l/day) or ad libitum feeding of milk, 2 types of concentrate (meal or pellets) and 3 weaning methods at 4 weeks (stepwise reduction or flat rate of 30 l/day over 1 week or abrupt). Milk and concentrate intake were measured and video records and direct observational records of behaviour were made. The observed duration of sucking was correlated with daily liveweight gain (DLWG) in 2 of the groups where intragroup age difference was high. Social facilitation was found to be important in the development of ingestive behaviour and rumination, in that calves which joined the group later ate concentrate and ruminated at younger ages than calves joining the group earlier, i.e. calves started to ruminate at the same time irrespective of age. Social factors were also important in determining milk intake. However, dominance order alone could not account for differences in milk intake, since pairs of calves with widely differing durations of sucking were found to have similar dominance values (calculated from the number of displacements at the teat). It seemed to be the individual’s ability to reach, grasp and suck the teat which determined intake. These abilities appeared to be affected by the calf’s motivation in relation to the teat. Motivation was influenced by early training, management and social facilitation. Some calves were never observed to suck alone. When the teats were placed together, the effects of social facilitation were greater and milk intake and uniformity of DLWG were found to be higher. The weaning check was severe in calves reared on ad libitum milk with meal, little of which was eaten before weaning. Flat-rate weaning appeared to result in slightly better DLWG than step-wise reduction. However, calves reared on restricted milk with pellets and weaned abruptly suffered no check although their O-4 weeks DLWG was lower.