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Performance and blood measurements by Holstein steers supplemented with or without MFP® while grazing cool-season forages
Methionine is an amino acid that can limit productivity of many ruminants. Supplemental methionine may be beneficial when the major source of dietary crude protein is provided by forage and by-pass protein is provided by bacteria. Our previous research has shown supplementing with methionine hydroxy analog ( MFP®; Novus International) improved body weight and ADG in steers offered medium quality hay.Our objective was to evaluate the performance by steers supplemented with or without MFP® while rotationally grazing cool-season forages. Holstein steers (n=80; 196 ± 2.1 kg initial body weight) were stratified by body weight and allocated randomly to 1 of 2 treatments: 1) control supplement(C; 5 replications) and 2) control supplement plus MFP® (MFP®; 5 replications). Beginning on May 8, 2014, each replication was rotationally grazed on 3, 0.4-ha pastures of orchardgrass (Dactylis glomerata), alfalfa (Medicago sativa), and bromegrass (Bromus inermis) with ad libitum access to water and shelter for a total of 71 d. A soybean hull- and wheat middling-based pelletedsupplement that contained minerals and vitamins was offered at 0600 daily at 0.5% of body weight for each replication. Treatment was provided at 1.17% of supplement DM resulting in an average intake of approximately 13.5 g/dof MFP®.Steers were weighed and blood was collected approximately every 21 d throughout the study. Body condition scores, body weight, gain, and ADG did not differ (P ≥ 0.22)between treatments throughout the study.Complete blood cell counts did not differ (P = 0.13) between treatments.However,basophil concentrations at d 71tended (P = 0.07) to be higher from C compared with MFP®.Available forage tended (P = 0.10) to be greater from MFP® compared with C. A treatment × date interaction (P = 0.10) was observed for available forage with d 71 C having the lowest available forage compared with all other treatments and dates. Therefore, in this study supplementing steers on pasture with MFP® did not improve gain, but resulted in less consumption of available forage at certain times of the year.
Keywords: methionine, steers, grazing