Conjugated linoleic acid supplementation during the transition period increased milk production in primiparous and multiparous dairy cows

Trans-10, cis-12 conjugated linoleic acid (CLA), a bioactive fatty acid, has the potential to alter energy metabolism in lactating dairy cows by marginally reducing milk fat synthesis in the mammary gland. The objective of this study was to determine the effects of pre- and postpartum CLA supplementation on lactation performance in a commercial dairy setting. Multiparous (mp) and primiparous (pp) Holstein cows managed in an automatic milking system were blocked by expected calving month, and randomly assigned to either a CLA supplementation (CLA-ME; mp n = 99, pp n = 38) or control (CTL; mp n = 97, pp n = 38) group. Cows were supplemented 100 g/d of lipid encapsulated CLA methyl esters containing 10 g each of cis-9, trans-11 and trans-10, cis-12 CLA, mixed 50:50 with soybean meal, and delivered via an automated mineral dispenser. Supplementation continued from −21 d pre-calving through 30 d in milk (DIM) for mp or 70 DIM for pp. Daily milk yield, fat and protein content, body weight, and rumination minutes were recorded and averaged by wk for the first 100 DIM. Milk yield was increased (P = 0.04) during the supplementation period (44.7 vs. 46.6 ± 0.64 kg/d) for mp CLA-ME cows and was increased (P = 0.03) during the post-supplementation period (31.3 vs. 34.2 ± 0.91 kg/d) for pp CLA-ME cows. Milk fat content was decreased (P = 0.03) during the supplementation period for mp CLA-ME cows and post-supplementation period for pp CLA-ME cows (P = 0.02); but only tended to be decreased (P = 0.09) in the supplementation for pp CLA-ME cows. Fat yield was not altered (P > 0.10) in either period for mp and pp CLA-ME. Supplementation with CLA did not change milk protein content or yield during the supplementation period for either mp or pp CLA-ME. During the post-supplementation period protein content was decreased (P = 0.02); however, yield remained unchanged for mp CLA-ME cows while protein content was unchanged and yield increased for pp CLA-ME cows. Body weight and rumination minutes were unchanged by CLA supplementation. Intervals to first estrus, first service, and conception were similar for CTL and CLA-ME mp and pp cows. First service conception rate was similar for mp CTL and CLA-ME cows; but, tended to be increased (P = 0.10) in pp CLA-ME compared to CTL. These results suggest that transition period CLA supplementation altered energy metabolism to increase milk production during the supplementation period for mp cows and post-supplementation period for pp cows without adversely affecting reproductive performance in mp cows and improving conception in pp cows.