[Effects of alternate grazing on faecal egg output of gastrointestinal nematodes and on the growth of calves and lambs].

During the period from 1975 to 1977, the faecal egg output of gastrointestinal nematodes and the gain in weight of a group of calves and a group of ewes with lambs on pastures alternately grazed by the two groups, were compared with the egg output and the gain in weight of a group of calves and a group of ewes with lambs not grazed alternately. The annual level of the egg output was identical in each comparable group. Variations in larval differentiation were observed between the groups grazed alternately or not. More host-specific species of worm showed a higher egg output in the calves and lambs which were not alternately grazed. Both calves and lambs, which were not grazed alternately, showed a higher host-specific Ostertagia-egg output. Less host-specific species were easily transferred to another host. Haemonchus contortus was frequently found to be present in calves and Cooperia oncophora in lambs. The annual gain in weight of the calves in the comparable groups was the same throughout the years. Each year lambs grazed alternately showed higher gains in weight compared with animals not alternately grazed. However, it is apparent from the literature that management systems are an important factor and therefore these results merely suggest that more satisfactory results may be obtained by alternate grazing.