Supplemental fish oil does not alter immune competence or the pathophysiological response to an intramammary infusion of endotoxin in peri-partum multiparous Holstein cows

The objective was to determine the effects of supplementing the diet with fish oil during the peri-partum period on the immune competence and the pathophysiological response to a lipopolysaccharide-induced mastitis challenge. Multiparous Holstein cows (n=30) were completely randomized to one of two treatments at 3 weeks pre-partum. Treatments differed only in the source of supplemental lipid and included either Energy Booster® or fish oil. Treatment diets were fed from −21 d relative to expected date of parturition until 10 d post partum. Treatments were fed as a bolus prior to the a.m. feeding. The dose of lipid during the pre-partum period was 250 g/d, whereas the amount of lipid supplemented post partum was adjusted to the level of intake, approximately 0·92% of the previous day's dry matter intake. Ex-vivo analyses of immune competence were measured including the antimicrobial activity of whole blood against Escherichia coli, Salmonella typhimurium and Candida albicans as well as the production of interferon-γ by peripheral blood mononuclear cultures. At 7 days in milk cows were infused with 100 μg of Esch. coli lipopolysaccharide into one rear quarter. Supplementing fish oil increased plasma concentrations of eicosapentaenoic and docosahexaenoic acids, but had no affect on the proportions of arachidonic acid at calving. Fish oil did not influence the production of interferon-γ or the antimicrobial activity of whole blood against any of the microorganisms. Furthermore, fish oil had no ameliorative effect on either the local or the systemic acute phase response following an intramammary lipopolysaccharide challenge in early lactating Holstein cows. Supplementing fish oil in the diet of peri-partum cows will not protect them from deleterious effects of an excessive acute phase response.