368 Effects of Supplemental Methionine Or Choline on Health and Performance of High-Risk Receiving Beef Heifers

Abstract

Abstract Methionine and choline are methyl group sources, and their supplementation improves health and immune function in transition dairy cattle. Our objective was to determine if supplemental methionine or choline could improve health and growth performance of newly received growing cattle. In a 3-year experiment, 1,440 crossbred beef heifers (480 per year; 223 ± 4.4 kg initial body weight; Tennessee origin) were received in 15 truckloads (blocks; 5 per year) in October 2020, 2021, and 2022. Individual body weights were measured at arrival. The following day (day 0) cattle were vaccinated for viral and clostridial diseases, received tulathromycin (2.5 mg/kg body weight; Draxxin, Zoetis Inc., Parsippany, NJ), and were stratified within block by arrival body weight to 1 of 8 pens containing 12 animals each. Cattle (40 pens per year; 120 pens total) were limit-fed at 2.2% of body weight daily (dry matter basis) a ration containing 39.5% dry-rolled corn, 40% Sweet Bran (Cargill Corn Milling, Blair, NE), 13% chopped prairie hay, and 7.5% supplement for 60 days; monensin was included at 25 mg/kg diet dry matter. Pens were assigned to 1 of 5 treatments: Control (nothing), 5 g/d methionine (8.33 g/day Smartamine M; Adisseo USA Inc., Alpharetta, GA), 15 g/day methionine (25 g/day Smartamine M), 1.17 g/day choline (26 g/day ReaShure; Balchem Corp., Montvale, NJ), or 3.5 g/day choline (78 g/day ReaShure); treatments were top-dressed at feeding daily. In each year, there were 8 pens per treatment, for a total of 24 pens per treatment across 3 years. Cattle were revaccinated and weighed on day 14, and pen weights were measured weekly thereafter to adjust feed offered the following week. Heifers were observed twice daily for clinical signs of respiratory illness and treated as follows: first morbidity, florfenicol; second morbidity, enrofloxacin; third morbidity, oxytetracycline. Upon third treatment, heifers were declared chronic and removed from the experiment. Performance data from chronic and dead heifers were removed before analysis. Dry matter intake was not affected by treatment (P = 0.48). There were some minor differences among treatments for final body weight, average daily gain, and gain:feed, but none of the treatments were significantly different from Control for these responses. Overall prevalence of respiratory morbidity and mortality were 29% and 0.69%, respectively. No treatment effects were detected for first, second, or third respiratory morbidity or mortality (P ≥ 0.30). Overall, supplemental methionine and choline did not affect growth performance or health of high-risk, newly received heifers.