Immune response of cows fed polyunsaturated fatty acids under high ambient temperatures.

The aim of the experiment was to determine the effects of 2 different fat supplementations on immune functions of dairy cows under high ambient temperatures. The experiment involved 24 Italian Friesian cows, divided into 3 groups of 8 animals, that were subjected to fat supplementations based on whole flaxseed (FS) or microencapsulated fish oil (FO). At d 0, 45, and 90 of the experiment, lymphocyte response to phytohemagglutinin (PHA) was determined in vivo on each animal by measurement of skin-fold thickness at the site of PHA injection. A humoral response to chicken egg albumin (OVA) was established following a subcutaneous injection with OVA. To assess cows' immune responses, plasma was prepared from experimental blood samples taken at d 0, 15, 30, 45, 60, 75, and 90 of the experiment. Plasma samples were measured for the presence of anti-OVA IgG, IL-1beta, IL-6, and IL-10. Results revealed greater skin-fold thickness in cows fed FS compared with the FO and the control groups, corresponding to higher mean lymphocyte proliferation following in vivo PHA injection. Cows fed FS displayed higher titers of anti-OVA IgG than the control and FO-fed cows. No effects of the diet on IL-1beta or IL-6 were found, whereas IL-10 secretion was lower in FS-fed cows than in control cows. The present study demonstrates that feed supplementation of n-3 polyunsaturated fatty acids can enhance immune responses of dairy cows exposed to high ambient temperatures.