عنوان مقاله [English]
نویسندگان [English]چکیده [English]
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.