Effects of feeding rumen protected amino acids in finishing cattle diets on performance and carcass characteristics

Abstract Text:

A 190-d calf fed finishing study, utilizing 240 steers, was conducted to evaluate growth implications of supplementing finishing cattle with bypass amino acid products, MetiPEARL™ and USA Lysine^® of Kemin Industries, Inc. (Des Moines, Iowa). Three treatments were evaluated with 8pens/treatment. Treatments consisted of a control (CON) diet; 8 g methionine/steer daily (26 g MetiPEARL/steer daily; MET); and 8 g methionine and 12 g lysine/steer daily (26 g MetiPEARL and 28 g USA Lysine/steer daily; MetLys). The common finishing diet for all treatments consisted of 40% Sweet Bran (Cargill Corn Milling; Blair, NE), 50% high moisture corn, 5% wheat straw, and 5% supplement (DM basis). All diets contained monensin (330 mg Rumensin^®/steer daily) and tylosin (90 mg Tylan^®/steer daily), and all cattle were fed ractopamine hydrochloride (300 mg Optaflexx^®/steer daily) the final 28 d from Elanco Animal Health (Greenfield, Indiana). All cattle received a Revalor^®-XS (Merck Animal Health Madison, New Jersey) implant on d 0. Cattle performance was measured throughout the study with 4 pen weights recorded throughout the trial and carcass data collected upon harvest. There was no difference in DMI (P = 0.46) among the three treatments, averaging 10.2 kg/d. No differences in ADG during the feeding period were observed using interim pen weights (P ≥ 0.41). Using carcass-adjusted performance, no differences were observed in final BW (P = 0.79), averaging 615 kg, or ADG (P = 0.77), averaging 1.76 kg due to treatment. Therefore G:F was also unaffected (P = 0.79) by treatment. While no differences were observed for HCW (P = 0.78) or LM area (P = 0.33), averaging 388 kg and 86.5 cm², respectively, there was a difference in USDA marbling score (P ≤ 0.01). The CON and MetLys treatments were similar with scores of 508 and 498, respectively (P = 0.38), while the MET treatment had a score of 465 (P ≤ 0.01). Fat thickness among treatments also varied slightly. The CON had the greatest 12^th rib fat thickness (P = 0.02). However, all cattle were well finished, with an average fat thickness of at least 1.5 cm. Bypass amino acid supplementation did not affect cattle performance. Although gluten feed provides less bypass protein than distillers grains, it appears that a 40% Sweet Bran, 50% high moisture corn diet provides sufficient lysine, methionine, and metabolizable protein to meet finishing steer requirements.

Keywords:

Amino Acid, Bypass protein, Supplementation