46- Verminous gastroenteritis, measured by EPG, reduced milk yield in a grazing system in Argentina¹s Humid Pampa. (Hormonal control of milk production in bovines. Effect of verminous nematodiasis during the cow¹s development and reproductive stages Part

MEJIA, ME; PERRI, AF; LICOFF, N; LAZARO, L; MIGLIERINA, M; FERNÁNDEZ-FRANCIA, G.; BECU-VILLALOBOS, D; LACAU-MENGIDO, I

Calgary, Canada

Congreso; 22nd WAAVP conference; 2009

World Association for the Advancement of Veterinary Parasitology

Gastrointestinal parasitism is a major constraint in grazing livestock production systems. Most studies on the effects of these parasites in bovines have been performed on beef herds. In dairy systems the importance of verminous gastroenteritis is well documented in growing animals, but there are few studies on adult dairy cows, with confusing results. As a part of a multi-disciplinary study, milk production of each cow (n=200) was daily measured from a dairy herd in a grazing system in the province of Buenos Aires. Parasitism was evaluated through monthly EPG of every animal within the system, and larval cultures were performed to determine the genera involved. Also grass forage samples were taken every 14 days from every paddock where each herd grazed, in order to obtain, identify and count infective larvae. Cows with positive EPG, whether from the pre-calving sample (29.21 %), the first post-calving sample (33.33 %) or both (14.60 %) showed a decrease in milk production of 2.38 l/d,  0.93 l/d and  2.41 l/d respectively, throughout lactation. The difference was pronounced during the first five months of lactation (2.98 l/d,  2.23 l/d  and  3.88 l/d). Nematodes of the genera Ostertagia, Cooperia, Haemonchus and Trichostrongylus were identified in fecal egg cultures and grass samples, showing regional normal prevalence curves and seasonal variability. These data show that gastrointestinal nematodiasis dramatically affects milk production and suggests that EPG can be a useful diagnostic tool. Further studies are being performed with treated and untreated cows with anthelmintic drugs.