Suplementação com gordura inerte rica em ácido palmítico para vacas leiteiras expostas ao calor

Abstract

Heat stressed cows have decreased dry matter intake (DMI) and milk yield. The supplementation of fat sources rich in saturated fatty acid can increase the energy density of the diet, without reducing fat synthesis by the mammary gland. We evaluated the response of dairy cows to the supplementation of a basal diet containing oil from whole cottonseed and whole roasted soybeans with two palm oil sources during summer. Thirty cows received a standardization diet for 14 days, formed 10 blocks by lactation order and milk yield, and were assigned to a treatment for 63 days. Treatments were: Control (C, basal diet), Lacfat® (L, control diet plus fractioned palm oil), or calcium salt of palm oil (S, control diet plus calcium salt of palm oil). The ether extract concentration of the diet was 7.3 % of DM in C and 8.4 % in L and S. There were reductions in respiratory rate and rectal temperature in S compared to C, but L reduced only the rectal temperature. The sweating rate and gasometric blood parameters were similar among treatments. The sources of palm oil increased milk yield (31.0 vs. 30.1 kg/d) and reduced DMI (19.2 vs. 19.9 kg/d), increasing feed efficiency (1.54 vs. 1.65). The daily secretions of fat and lactose were increased by S, and L increased fat secretion. Plasma glucose concentration was similar among treatments, as well as the total tract apparent digestibilities of ether extract and neutral detergent fiber. The acetate to propionate ratio in ruminal fluid was greater for L compared to S. The supplementation of dairy cows fed a basal diet of high fat concentration from oilseeds with palm oil increased feed efficiency, by increasing milk and solids yield in reduced DMI.