Milk fatty acid composition and mammary lipogenic genes expression in bovine cloned and control cattle

In order to understand the effect of nuclear transfer technology on the physiology of lactation and milk fatty acid composition in dairy cattle (Holstein breed), the present study compares the milk yield and composition from bovine somatic cell cloned (n=5) and control animals (n=5) at 180 days in milk (DIM) maintained together under the same conditions. All cows were offered the same total mixed ration ad libitum. At 180 DIM, the cloned had a higher body weight (BW; P<0.01) compared with control animals, whereas comparable body condition score (BCS) was observed among the 2 groups. The cloned cows had a lower milk yield and milk protein and lactose yields (P<0.05) and had a tendency (P=0.08) for a lower milk fat yield. Conversely, no differences in milk fat, protein and lactose concentrations were observed in cloned compared with control animals. Similar milk fatty acid (FA) concentrations were observed in cloned and control cows except for two minor FA, cis-9 C10:1 and C17:0 (P<0.05) that were higher in the cloned. The milk fat cis-9 C14:1/C14:0, cis-9 C16:1/C16:0, cis-9 C18:1/C18:0, cis-9, trans-11 C18:2/trans-11 C18:1 concentrations ratios were not different in cloned and control. The milk medium-(C10–C16) and long-(∑C18) chain FA yields were lower (P<0.05) in cloned compared with control animals. The mRNA abundance of genes encoding for SCD1, SCD5, ACACA and FABP3 genes in mammary tissue was similar (P>0.05) in cloned and non-cloned animals. Conversely, cloned animals had a lower (P<0.05) mRNA abundance of LPL and a tendency (P<0.10) for lower mRNA abundance of FASN and CD36 genes compared with control. The absence of major differences of milk constituent concentrations, milk FA composition and of the SCD desaturation indices observed between cloned and conventional animals suggest a comparable nutritional quality of milk for these animals. The noticed differences in milk long chain-FA yields were consistent with modulation of mammary lipogenic pathway as suggested by lower mRNA abundance of LPL gene in cloned compared with control. Otherwise, differences in the partitioning of nutrients between the mammary gland and other tissues cannot be excluded as suggested by the higher BW and lower milk yield observed in cloned. Altogether, these observations may be attributed to different genetic background and/or to epigenetic modifications due to the nuclear transfer technology that may affect the growth and the physiological adaptation to lactation and impact the dairy performances. Further investigations are required to identify the mechanisms underlying these differences.