Total lactational response to added fat during early lactation

The theory that feeding cows additional fat during early lactation will result in greater total lactational production and improved reproductive efficiency was evaluated using 305-d lactational data from 94 cows fed control diets and 96 cows fed additional dietary fat during wk 4 through 16 postpartum. Added fat in diets was supplied by oilseeds, either soybeans or sunflowers, in previously reported studies. Milk yield during wk 4 through 16 postpartum was 2.8% higher for cows fed added fat. Total lactational yield was increased 3.6% for cows fed additional fat in early lactation; 71% of the additional milk production occurred after discontinuing the feeding of additional fat. Percentages of milk fat and protein were lower when cows were fed added fat and remained lower for the remainder of the lactation. Days to first breeding, days open, and services per conception were not reduced by feeding added fat during early lactation. Milk production and persistency for the entire lactation were increased by feeding additional fat during early lactation, but changes in reproductive efficiency were not detected.