Ruminant Nutrition: Protein and Amino Acid Nutrition 2

摘要

The aim of the study was to evaluate the effects of supplementingMet coated with hydrogenated palm fatty acid distillates (PFAD) onfeed intake and milk yield of dairy cows. Fifty Holstein cows (146 ±39 DIM, 30.9 ± 5.00 kg/d; 44 multiparous; 6 primiparous) were splitin 2 groups (n = 25) and exposed for 58 d to 2 treatments following acomplete randomized design. Treatments consisted of supplementationwith 30 g/d of hydrogenated PFAD plus 20 g/d of DL-Met, whereMet was provided in free form (CTRL), or 50 g/d of coated Met (39%Met; thus providing 20 g of Met/d) by the aforementioned fat (MET),commercially available as Bymet by Norel S.A. Cows were fed a TMR(13.2% CP, 30.1% NDF, 1.63 Mcal of NEl/kg; DM basis) twice daily.On a daily basis, lying time, milk yield, and milk fat and protein contentswere determined individually. Individual feed intake was dailymonitored using electronic feed bins as cows were freestall housed.As treatments were applied at the animal level, the experimental unitwas the animal. Data were summarized by week of study and animal,and analyzed using a mixed-effects model for repeated measures. Drymatter intake was greater (P = 0.01) in MET (23.8 ± 0.42 kg/d) than inCTRL (22.3 ± 0.42 kg/d). Also, milk fat content and milk fat yield wereaffected (P < 0.001) an interaction between treatment and week, withMET cows producing greater amounts of milk fat and greater content ofmilk fat after the third week of study. Similarly, yield of ECM was alsoaffected by an interaction between treatment and week (P = 0.02), andprogressively increased in MET cows along the study. It is concludedthat MET coated with hydrogenated PFAD has the potential to improveDMI of cows in mid-lactation fed low protein diets, and as a result milkfat content, milk fat yield, and yield of ECM may increase after about3 weeks from the beginning of supplementation.