Effect of calcium salts of fish and palm oils on lactational performance of Holstein cows

Two experiments were conducted to determine the effect of source of fatty acids (FA) fed as tallow or calcium salts of fish and palm oils (CaSFO) on performance of dairy cows. In experiment 1, 738 multiparous Holstein cows were fed a diet with either 18 g/kg of tallow or 19 g/kg of CaSFO to supply equal amounts of FA in two replicates per treatment. In experiment 2, 331 multiparous cows were fed one of the two supplements described previously. In both experiments, all cows received a pre-treatment diet during the first 25 days in milk (DIM) consisting of half of each fat supplement (9 g/kg of tallow + 9.5 g/kg of CaSFO). Thereafter, cows received their respective diets for the first 145 DIM. Yields of milk and milk fat were not affected by dietary source of FA in both experiments. However, feeding CaSFO reduced concentration of true protein and solids-not-fat, as well as yields of true protein. Group and individual dry matter (DM) intakes and feed efficiency were not altered by treatment, but cows fed CaSFO had higher total tract apparent digestibility of DM. Cows fed CaSFO had increased concentrations of eicosapentaenoic, docosahexaenoic, conjugated linoleic acid (cis 9, trans 11), C18:1 trans 9, and C18:1 trans 11 FA in milk fat. Treatment had no effect on blood parameters and estimated energy balance, but cows fed CaSFO lost more body condition. Feeding CaSFO at 19 g/kg of the diet modified the FA composition of milk fat compared with tallow, but did not improve lactational performance of dairy cows. The present findings suggest that supplementation with tallow or CaSFO results in similar lactational performance, with changes in FA profile of milk fat.