effects of protected fat supplements on performance of early lactating holstein cows

this study was conducted to evaluate production response of early lactating cows to rumen protected fats. twelve (nine multiparous and three primiparous) holstein cows (26±4 d in milk) were empolyed in a replicated 3×3 latin square design of 21-d periods. each period consisted of 14 days of adaptation and 7 days of sampling. cows received diets containing either one of two types of protected fats or no supplemental fat. cows in group 1 (control) were fed total mixed ration (tmr) of 20% corn silage, 20% alfalfa hay, and 60% concentrate mix. cows in group 2 were fed the tmr containing 3% prilled protected fat (energizer-10). cows in group 3 were fed the tmr containing 3.5% ca salt of protected fat (magnapac). intake of dry matter (dm), organic matter (om) and neutral detergent fiber (ndf) were decreased by rumen protected fat (p < 0.05) in multiparous cows (dmi: 25.7, 24.1, and 23.9 kg/d for control, prilled fat, and ca salt of fat, respectively); intake of nel in all the cow population and intake of dm, om and ndf in primiparous cows were similar for all diets (p > 0.05). production of milk and 3.5% fcm in primiparous and multiparous cows as well as milk protein, fat, lactose and total solid percentages and yields (kg/d) were not affected by fat supplements (p > 0.05). the bcs and bw changes were similar for all diets in multiparous and primiparous cows (p > 0.05). in multiparous cows, feed efficiency (3.5% fcm/dmi) was higher for cows fed supplemental fat diets (p < 0.05) than for control samples. fat fed cows were more efficient than those fed with control diet. in primiparous cows supplemental fat did not influence feed efficiency (p > 0.05). fat supplements did not influence either chewing behavior or total time spent ruminating and eating (p > 0.05). the results indicate that supplementation of early lactating diet with rumen protected fat decreases feed intake and improves milk efficiency but this is not true for primiparous cows.