The effects of feed restriction on energetic metabolism and inflammation in under- and over-conditioned mid-lactation dairy cows

Abstract

he transition cow’s ability to homeorhetically adapt and meet the demands of lactation ultimately determines her ability to maintain optimal health, become pregnant and synthesize copious amounts of milk. Over-conditioned cows tend to be more susceptible to health problems during the transition period, but the mechanism behind why fat cows transition poorly is currently ill-defined. This phenomenon was first described as “Fat Cow Syndrome” where corpulent transition cows experience metabolic disorders or infectious diseases and infertility at increased rates. Some investigators have reported that excessive lipid mobilization, decreased appetite, and excessive inflammation are responsible for Fat Cow Syndrome. As part of this dissertation, we used under- and over-conditioned mid-lactation cows to evaluate the whole-body response to feed restriction as a model for periparturient cow energetics and inflammation. To assess this acute phase proteins and metabolites associated with basal and stimulated carbohydrate and lipid metabolism were evaluated. This experiment suggests that carbohydrate and lipid metabolism were affected by feed restriction similarly between thin and fat cows. Unexpectedly, thin cows had a more inflammatory response to feed restriction than fat cows. While this thesis did not identify the physiological mechanism(s) that explain why over-conditioned cows underperform during the transition period, it does provide strong evidence that excessive adipose tissue mobilization and hyperinflammation are not responsible.