Population dynamics of gastrointestinal nematodes in lambs and their effect on metabolic profiles and growth in a continuous grazing system

Abstract

A study of gastrointestinal nematodes population in lambs born the 10th September and weaned 28th January, in continuos grazing and on natural pastures was carried out. Animal groups were: 52 ewes, 10 drenched lambs (D) and 22 undrenched lambs (SD), 12 of SD were tracers. Egg counts, parasite autopsy, haematocrito, metabolic profile and weight changes were registered. Ewes had a rise of egg counts 8 weeks postpartum, at weanning lambs SD had 5OOO epg, lambs D 1500 epg. Haematocrito dropped to 23% in SD group, there were no deaths. There were no differences between lambs groups in total proteins, globulins, urea, calcium and phosphorus, at 140 d there was difference in albumin in blood. At 8 weeks, the predominant parasite in lambs was Nematodirus sp. (42%), since 3 months on, Haemonchus contortus prevailed largely over the other parasitary genus, at weanning worm counts was 3200 per lamb. The difference in weanning weight was 8%, but no statistically significant.