Effects of gastrointestinal nematodes on milk productivity in three dairy goat breeds

Resistance and resilience against gastrointestinal nematodes (GIN) in sheep and to a lesser extent in goats have been more and more supported by evidence, recently. Such phenomena can be noted among different breeds as well as within a single breed. This study was performed to test the effect of GIN on qualitative and quantitative productivity of milk, and was prompted by the hypothesis that such effect might be different among goat breeds and their lactations. Thus, fecal samples from goats of three distinct breeds (216 Alpine, 130 Saanen and 33 Nera di Verzasca) were collected; their main GIN eggs were counted using a modified McMaster method. As to milk production, related data were collected monthly; using the routine infrared method they were accounted for milk quantity, fat, protein and lactose contents. Our research highlighted that the emission of parasite eggs was influenced by the goat breed and by the number of lactations. In particular, Verzasca showed the highest quantity of eggs per gram (EPG), while Saanen had the lowest values; in each breed, the number of lactations led to an increase of EPG. On one hand, milk composition showed a reduced variability among breeds, but no effect due to the parasites was observed. On the other hand, daily milk yield was strongly related to parasite burden, breed and number of lactations. In fact during first lactation, parasites had a negative effect on milk production in Alpine breed, caused a slight reduction in Saanen, while they did not affect the production in Verzasca; then, during following lactations the negative effect of parasites showed to be decreasing