Diet composition and gains of escape protein-supplemented growing cattle grazing corn residues.
1991
Gutierrez Ornelas E. | Klopfenstein T.J.
Effect of level and method of escape protein (EP) supplementation on weekly steer performance and their diet composition were evaluated in two corn residue grazing trials. In Trial 1, 60 steers (average weight 239 kg) received 8 kg.animal-1.d-1 of a 50% CP supplement to provide one of six levels of EP (60, 88, 116, 144, 172, or 200 g.animals-1.d-1). Steers grazed (2.2 animals/ha) nonirrigated fields (NIF) for 63 d. In Trial 2, 59 steers (average weight 219 kg) grazed either NIF (1.97 animals/ha) or irrigated fields (IF, 3.96 animals/ha) and were supplemented with 60, 95, 130, 165, or 200 g of EP-animal-1.d-1. In a 2 X 5 X 2 factorial arrangement, treatments were IF vs NIF, level of protein, and two supplementation methods: 1) feeding the lowest level of EP (60 g) for 21 d then for the remaining 42 d feeding one of the five EP levels or 2) feeding each EP level continuously. Weekly diet composition was evaluated using four esophageally fistulated steers. In Trial 1, no EP effect (P > 05) was found up to 20 d, but EP affected (P < 05) ADG from d 20 to 34, resulting in 3.35 g of ADG/g of EP. In Trial 2, steers grazing NIF had higher (P < 01) ADG than those grazing IF (644 vs 414 g/animal). Steer daily gains were increased (P < 05) by level of EP but were not affected (P >.05) by the method of supplementation, indicating that EP supplementation was not needed during the first 21 d. Escape protein in extrusa samples decreased (P <.01) as the grazing season progressed. Better animal performance in NIF than in IF probably was related to higher CP, EP, in vitro DM and OM disappearance, and lower ADF in extrusa from steers grazing NIF.
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