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Performance by Holstein Steers Offered Hay and Supplement With or Without Added Methionine
Recently, amino acid supplementation by forage-fed cattle has been examined in greater detail. Methionine can restrict productivity of many ruminant animals, chiefly because microbial protein, the main source of metabolizable protein in forage-based ruminant diets, is most limiting in methionine. The objective of this study was to evaluate steer performance when offered hay and a supplement with or without added methionine as MFP® (MFP). On October 24th, 2013, a total of 90 (230 ± 2.2 kg body weight) Holstein steers were stratified by body weight within 5 blocks and were allocated randomly to 1 of 2 treatments: 1) control supplement (C; 15 replications) or control supplement plus MFP (15 replications). Each replication had access to a 0.4-ha pasture with limited forage available for grazing and were offered ad libitum access to medium quality hay, water, and shelter. A soybean hull and wheat middling based, pelleted supplement was offered daily at 0.5% of body weight for each replication; in addition the supplement contained minerals, and vitamins. Treatment was provided at 1.17% of supplement DM resulting in an average intake of approximately 15 g/d of MFP. Hay offered did not differ (P = 0.62) across treatments. Initial, d 14, and d 28 body weights did not differ (P ≥ 0.11) across treatments, but d 42 and d 56 body weights were greater (P ≤ 0.05) from pastures receiving MFP compared with C. Average daily gain and gain at d 14 did not differ (P ≥ 0.27) across treatments. However, d 28 ADG and gain tended (P ≤ 0.07) to be greater from MFP compared with C and were greater (P ≤ 0.03) at d 42 and d 56 from MFP compared with C. Through 56 d, steers in pastures offered MFP gained 5.0 ± 2.1 kg/hd more (P < 0.03) body weight than steers fed C. It is concluded that, when steers were offered medium quality hay, providing a supplement that contained MFP®showed improved body weights, ADG, and total gain through the backgrounding phase.
Keywords: Methionine, Backgrounding, Steers