Effects of the initial level of milk production and of the dietary proteinintake on the course of natural nematode infection in dairy goats

The level of dietary protein is known to alter the establishment and the pa thophysiology of gastrointestinal nematodes in sheep. On the other hand, hi gh-producing dairy goats are less resistant and/or resilient than low-produ cing ones to experimental nematode infection. During a a-year study, we hav e investigated the course of a natural nematode infection (mainly T. colubr iformis) in a high-producing dairy goat flock. In year 1, 50 grazing goats divided in high (HP) or low producer (LP) were compared from April to Octob er for parasitological and milk parameters. In year 2, the 25 HP goats were only considered and were allocated to two levels of dietary protein, high level (HPr) with a protein coverage of 125% or normal level (NPr) with a pr otein coverage of 106%. They were monitered as above. In year I, HP goats s howed a greater nematode egg output (1856 vs. 1000 epg) associated with hig her values in I: colubriformis IgG in autumn than LP ones whereas the decre ase in serum phosphate concentration was similar in both groups. In year 2, HPr goats exhibited lower egg output in autumn (2219 vs. 2817) vs. NPr one s, Moreover, milk yield and fat content were significantly higher in HPr vs . NPr in the 2nd part of the study. HP goats are less resistant to nematode infection in natural conditions. Resistance and resilience of HP goats may partially be improved by a protein supplementation in the diet. (C) 2000 E lsevier Science B.V. All rights reserved.