Effects of gastrointestinal infections caused by nematodes on milk production in goats in a mountain ecosystem : comparison between a cosmopolite and a local breed

Alpine goats, a cosmopolite breed, and Nera di Verzasca, an autochthonous breed, reared in a mountain ecosystem of Lombardy, northern Italy, were tested for the effect of gastrointestinal nematode-sustained natural infections on both yield and quality of their milk. The survey was based on to the hypothesis that high levels of gastrointestinal nematode infection might affect milk yield, milk quality and lactation period length, and that the animal breed might influence such an effects. Seventy-one adult goats reared in the same farm were used in the study. From February to September 2010, 37 Alpine and 34 Nera di Verzasca goats were sampled for milk and feces monthly. Milk quantity, fat and protein contents, and somatic cell counts (SCC) were determined. The gastrointestinal parasitic infections were evaluated by fecal egg count (EPG) and animals were ranked into five classes according to their mean EPG: Le0 (Level0): <100 EPG; Le1 (Level1): 101-200 EPG; Le2 (Level2): 201-600 EPG; Le3 (Level3): 601-1500 EPG; Le4 (Level4): >1500 EPG. EPG counts and infection prevalence showed a high variability in both breeds, however the mean EPG values in Alpine goats were higher more than twice in comparison with Nera di Verzasca. Milk yield decreased in both breeds as the infection level increased. It occurred when Alpine goats reached level 3 of EPG counts while no decrease was found in Nera di Verzasca goats before reaching EPG level 4. Protein and fat contents were influenced by breed, level of EPG and milking days. Nematode infection was found to affect SCC values only at greatest levels of EPG counts. The results supported a different host-parasite relationship in the two goat breeds. In fact, though a reduction in milk yield, protein and fat contents was observed in both breeds, Alpine goats were found to be weaker in contrasting the effects of gastrointestinal nematodes than the more resilient Nera di Verzasca. The results of this survey can contribute to develop proper strategies in controlling goat parasitism by exploiting resilient breeds and improving sustainable rearing of local breeds.