Influence of weaning age and an experimental Haemonchus contortus infection on behaviour and growth rates of lambs

Abstract

Four groups of 20 lambs each, differing in weaning age (6 or 13 weeks) and infection with Haemonchus contortus (infection after weaning or simultaneous to weaning), were observed and compared regarding the behaviour before, during and after these procedures. Furthermore the influence on performance, health and welfare was estimated by examining daily weight gains (ADW), haematocrit (HCT), and faecal egg count (FEC). The analysis demonstrates that the exposure through weaning is highest for the youngest lambs. Agitation was higher in lambs that were weaned at the age of 6 weeks, when compared with animals weaned at 13 and 21 weeks of age. ADW at 17 weeks of age were significantly ( p < 0.05) highest in the uninfected control group and in animals which were weaned and infected at the same time (326 ± 10.0 g/day and 305 ± 10.0 g/day). Therefore, infection did not influence ADW significantly. No significant differences between the groups in log FEC could be found. Four weeks after the infection, highest HCT values were measured in the uninfected control animals, whereas lowest HCT values were found in animals which were weaned at the age of 6 weeks. The results show that weaning age had an effect on behaviour alterations after the weaning procedure, as well as on growth rates of lambs. However, grade of parasite infection was not influenced by weaning, but blood loss in lambs due to infection was highest when lambs were weaned at 6 weeks of age. These aspects are important for the experimental design of infection studies in lambs and the assurance of productivity in sheep breeding systems, when lambs weaned and brought on pasture at the same time and therefore exposed simultaneously to two stressors.