Abstract #T166

# T166
Effects of methionine coated with vegetable fat on performance and feed intake of mid-lactation dairy cows fed a low-protein diet.
J. M. Ruiz-Rodriguez1, M. Puyalto2, J. J. Mallo2, G. Elcoso3, A. Bach*4,5, 1Universidad Politécnica de Madrid, Madrid, Spain, 2Norel S.A, Madrid, Spain, 3Blanca from the Pyrenees, Hostalets de Tost, Spain, 4Department of Ruminant Production, IRTA, Barcelona, Spain, 5Institució Catalana de Recerca i Estudis Avançats, Barcelona, Spain.

The aim of the study was to evaluate the effects of supplementing Met coated with hydrogenated palm fatty acid distillates (PFAD) on feed intake and milk yield of dairy cows. Fifty Holstein cows (146 ± 39 DIM, 30.9 ± 5.00 kg/d; 44 multiparous; 6 primiparous) were split in 2 groups (n = 25) and exposed for 58 d to 2 treatments following a complete randomized design. Treatments consisted of supplementation with 30 g/d of hydrogenated PFAD plus 20 g/d of DL-Met, where Met 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 contents were determined individually. Individual feed intake was daily monitored using electronic feed bins as cows were freestall housed. As treatments were applied at the animal level, the experimental unit was the animal. Data were summarized by week of study and animal, and analyzed using a mixed-effects model for repeated measures. Dry matter intake was greater (P = 0.01) in MET (23.8 ± 0.42 kg/d) than in CTRL (22.3 ± 0.42 kg/d). Also, milk fat content and milk fat yield were affected (P < 0.001) an interaction between treatment and week, with MET cows producing greater amounts of milk fat and greater content of milk fat after the third week of study. Similarly, yield of ECM was also affected by an interaction between treatment and week (P = 0.02), and progressively increased in MET cows along the study. It is concluded that MET coated with hydrogenated PFAD has the potential to improve DMI of cows in mid-lactation fed low protein diets, and as a result milk fat content, milk fat yield, and yield of ECM may increase after about 3 weeks from the beginning of supplementation.

Key Words: methionine, palm fatty acid distillates (PFAD), milk