COMPARATIVE SUSCEPTIBILITY OF PYRENEAN AND BROWN SWISS CALVES TO GASTROINTESTINAL NEMATODES IN SUBCLINICAL NATURALLY ACQUIRED INFECTIONS

The susceptibility of two common breeds of cattle in the Pyrenees, Bro wn Swiss and Pyrenean breed, to parasitism by gastrointestinal nematod es was studied. Twenty-two female calves (13 Brown Swiss and 9 Pyrenea n), 3 months old with a mean weight of 112.8 +/- 18.33 and 103.3 +/- 1 7.11 kg respectively at the start of the study, were used. The calves began their first grazing season grazing with 200 cattle following the traditional grazing system for mountainous areas: Stabling during win ter (December-April), grazing on harvesting meadows at an elevation of 900 m in the spring (May-June) and autumn (October-November), and gra zing areas between 1200-2100 m during the summer (July-September). Fae ces, blood samples and calves growth rate were taken at 2-week interva ls throughout the grazing season, Faecal egg counts of gastrointestina l nematodes, level of serum pepsinogen, total serum protein and blood parameters were measured. The worm egg counts and Cooperia sp, counts were significantly smaller in the calves of Pyrenean breed than in Bro wn Swiss throughout the experiment. Numbers of eggs of the other gener a of parasites found were smaller in the calves of Pyrenean breed than in calves of Brown Swiss breed, but no statistical differences were f ound. Blood was compared during two periods: the prepatent and patent periods. During the first period, no differences were found between th e breeds for any parameter studied. However, during the patent period, Pyrenean animals had significantly greater numbers of erythrocytes, h aemoglobin values and packed cell volume (PCV) values, and smaller num bers of eosinophils than animals of the Brown Swiss breed. No differen ces were found in the level of serum pepsinogen, total serum protein a nd live weight gains between the two breeds.