Effects of Rearing Methods of Heifers during Milk Replacement Period on their Postweaning Behaviour in the Maze

Brouaek J., M. U hrinaaE, C. W . A rave, T. H . F riend, S. M ihina, P. K i‰ac, A H anus: Effects of Rearing Methods of Heifers during Milk Replacement Period on their Postweaning Behaviour in the Maze. Acta Vet. Brno 2002, 71: 509-516. Fifty-eight Holstein heifer calves were assigned to one out of three treatment groups after having nursed by their mothers for the first week: BN) individual hutch, bucket with nipple n=25; DF) loose housing pen, machine milk feeder, n=16; NC) loose housing pen, nursing cow, n=17. After weaning at 8 weeks, all calves were kept in group pens. At 15 weeks of age, the behaviour in the 6-unit maze (16.4 × 4.5 m) was determined. On the first observation day, the calves were tested five times (the first one for training); on the second day there were four runs. The calves had to solve two tasks. In task A, the passage was open on the left side, and on the right side (task B) on the next day. We were testing the following hypothesis: the speed of traversing the maze is affected by the rearing system. The slowest were NC calves. On the first day (task A), the average time to traverse the maze among treatments DF (43.9 s), BN (53 s) and NC (111.3 s) was different (F = 8.26***, P = 0.0007). On the second day (task B), the averages were: BN 77.1 s, DF 83.8 s and DC 166.6 s (F=8.17***, P = 0.0008). The results indicate that the feeding method and housing used to rear calves may have a significant impact on their maze behaviour. Heifers, behaviour, maze, feeding, housing During the period from birth to weaning, the calf is exposed to several environmental factors that can affect its behaviour in the maze. It is necessary to create an adequate environment that will ensure the welfare of animals during rearing. That means we should apply such systems of rearing which correspond to the physiological and behavioural needs of animals. This is most markedly illustrated with regard to formulas of behaviour and production efficiency of an organism ( Friend 1989; Baranyiova and Holub 1993). The period of liquid feeding represents a critical period of life for calves. This period decides about their health, resistance to diseases and later efficiency. If we ignore nutrition, animals can be influenced by three main factors: manner of housing, method of liquid feeding and time of weaning from mother. The situation at the time of weaning is similar in all countries with advanced agriculture. The majority of calves are removed from mother immediately after birth and fed with milk replacer from the fourth day of life. Only about 10% of calves, particularly from small herds, are fed native milk until weaning, and so one of the basic demands on rearing calves in sustainable agriculture can be fulfilled ( Krohn et al. 1999). For animals used to a social way of life, isolation poses significant psychological stress with an extensive scope of behavioural and physiological responses (A lbright and A rave 1997). Early separation of the calf from the cow is popular in the dairy industry, and is deemed by some to be essential to maximum production. Others consider this practice to be against nature. It is probable that very early weaning from mother reduces adaptive abilities of calves and decreases their resistance to stress during some methods of manipulation and treatment, particularly during group mixing and transport. Stressors operating in the prenatal