Characterization of the dynamics of fat cell turnover in different bovine adipose tissue depots

In many but not all high producing cows, the energy requirements for milk yield and maintenance exceed energy intake by voluntary feed intake during early lactation. Prioritizing milk secretion, body reserves mainly from adipose tissue are mobilized and imply an increased risk for metabolic diseases. Reducing the energy output via milk by decreasing the milk fat content through feed supplements containing conjugated linoleic acids (CLAs) may attenuate the negative energy balance during this period. In two separate trials, variables characterizing fat cell turnover were investigated in different subcutaneous and visceral fat depots from primiparous heifers (n = 25) during early lactation, and subcutaneous fat from non-lactating, over-conditioned heifers (n = 12) by immunohistochemistry. The portion of apoptotic adipocytes was consistently greater than that of proliferating cells and preadipocytes; the sporadically observed effects of CLA were limited to visceral fat. Lactating heifers had more apoptosis and less preadipocytes than non-lactating heifers.