摘要
Negative energy balance in early lactating dairy cows results in a massive release of fatty acids （FA） into the blood in nonesterified fatty acids （NEFA） form. Large quantities of circulating NEFA may alter the serum FA profile of phospholipids （PL） fraction, which is responsible for cellular plasma membrane integrity and intercellular signaling. The objective of this study was to determine the effects of subcutaneous fat stores, as assessed by body condition score （BCS） on a scale of one to five, around the time of calving and the subsequent lipomobilization on FA profile of serum NEFA and PL lipid fractions, and on productive performance. Based on BCS, cows were retrospectively dichotomized into two groups： over-conditioned （BCS _〉 3.25） and control （BCS _〈 3.0）. 22 cows had serum samples obtained at -28, -7, 8, 18 and 28 d relative to parturition and analyzed for the FA profile of the NEFA and PL fractions. As expected, over-conditioned cows had greater total plasma NEFA concentrations and decreased dry matter intake. Milk yield and composition did not differ between groups. More importantly however, several FA in the NEFA fraction of plasma lipids varied significantly, including C14：1, C16：0, C18：0 and C20：3n3. In the PL fraction, other FA varied significantly by BCS around time of parturition, including C16：0, C17：0, total C18：2 cis, and C20：2. In summary, BCS did affect FA profile of serum NEFA and PL lipid fractions. This may have drastic consequences for circulating immune cells and their ability to fight infection by altering their FA profile.
