Relationship of lymphocyte activation and proliferation with feed efficiency and methane emission in transition cows

摘要

In the transition from late pregnancy to start of lactation, immune function is compromised in mammals. Immune response to mitogens largely differs among cows, especially in early lactation. The lymphocyte activation might be impaired by the limited availability of energy and nutrients in this critical period. We hypothesized that the lymphocyte proliferation (72 h) is related to their activation (24 h) and to the cow's feed intake, feed efficiency, resting metabolic rate (RMR) and mobilization of body reserves. Seventeen multiparous Holstein cows were studied in weeks -2 and +2 around calving. Zootechnical parameters as well as activation and proliferation of lymphocytes were quantified based on their in vitro oxygen consumption rate and 3-[4,5-dimethyldiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT)-reducing activity, respectively. Cows were classified by their proliferative response postpartum as low (L), medium (M), and high (H) responders. Surprisingly, the differences observed in lymphocyte proliferation were not related to activation, feed intake, feed efficiency (milk yield per unit of intake), RMR and body reserve mobilization. However, L cows had smaller levels of methane emission per unit of milk and per unit of body weight after calving compared to H cows. This is indicative of a lower rumen fermentation intensity. It suggests that, in early lactation, low responders might suffer from a smaller availability of digestible energy to sustain immune response consisting of the shift from activation to proliferation. Therefore, the selection of environmentally friendly low methane emitters could favour cows with weak immune response in the critical period of early lactation.