Effect of feeding Ca salts of trans-octadecenoic fatty acids and linoleic acid on productive and metabolic responses of dairy cows during the transition period.

Fifty-eight multiparous Holstein cows were used in a completely randomized block design to evaluate the effects of feeding Ca salts of trans-octadecenoic fatty acids and linoleic acid on animal performance and lipid metabolism during the transition period. Three weeks before expected calving, cows were fed 1% of the diet dry matter (DM) as Ca salts of palm oil (PFA) or as Ca salts of trans-octadecenoic fatty acids and linoleic acid (TFAL). After calving and until d 28 postpartum, half of the cows from each prepartum treatment were assigned to a diet containing PFA or TFAL at 2% of dietary DM. Pre- and postpartum diets differed only in the type of supplemental fatty acids. After d 28 postpartum, all cows were fed the PFA lactation diet until d 42. Fatty acid supplementation had no effect on pre- or postpartum DM intake or milk production. Milk fat % was lower (P < 0.01) and milk fat yield tended to be lower (P < 0.15) for cows fed TFAL than for cows fed PFA prepartum (3.8 vs. 4.1%, and 1.51 vs. 1.39 kg/d, respectively). Cows fed TFAL postpartum had lower (P < 0.03) milk fat test than cows fed PFA (3.8 vs. 4.0%, respectively), but no effect of postpartum treatment was observed for milk fat yield. Prepartum plasma concentration of nonesterified fatty acids (NEFA) tended to be lower (P < 0.10) for cows fed TFAL than for cows fed PFA (369 vs. 451 μEq/L, respectively). Cows fed TFAL prepartum tended to have lower (P < 0.11) plasma NEFA concentration at d 1 postpartum than cows fed PFA prepartum (792 vs. 989 μEq/L, respectively). Postpartum treatments had no effect on plasma NEFA concentration. No effect of prepartum treatment was observed for liver triglyceride content at d 1 postpartum. Results of this study suggest that feeding Ca salts of trans-octadecenoic acids and linoleic acid during late gestation may cause milk fat depression and lower NEFA mobilization at parturition compared to feeding palm oil fatty acids. [ABSTRACT FROM AUTHOR]