Supplementing pre- and probiotic ingredients to feedlot steers: effects on health, growth performance, and physiological responses.
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Feedlot diets are often enriched with additives to mitigate health disorders and promote cattle performance, including the feed-grade antimicrobials monensin and tylosin. However, alternative feeding strategies are warranted given the increasing regulations regarding the use of antimicrobials in feedlot diets. This study evaluated the performance, physiological, and health responses of feedlot cattle offered a synbiotic supplement (yeast-derived prebiotic+Bacillus subtilis probiotic), which replaced or was fed in conjunction with monensin and tylosin. Angus-influenced steers (n=192) from four different cowherds were weaned on day -1 and transported (800km) to the feedlot. Steers were allocated to 1 of 24 pens (eight steers/pen) upon arrival on day 0. Pens were assigned to receive (n=8/treatment) a total-mixed ration (TMR) containing: (1) monensin and tylosin (RT; 360mg/steer daily from Rumensin and 90mg/steer daily from Tylan; Elanco Animal Health, Greenfield, IN, USA), (2) yeast-derived ingredient and B. subtilis probiotic (CC; 18g/steer daily of Celmanax and 28g/steer daily of Certillus; Church and Dwight Co., Inc., Princeton, NJ, USA), or (3) a combination of RT and CC (RTCC). Steers were slaughtered according to BW in four groups balanced by treatment and pens and received treatments for 2524days. No treatment effects were detected (P0.17) for steer BW gain and morbidity responses. Mean TMR intake was greater and gain:feed ratio was less (P0.01) in CC compared with RT and RTCC steers. Mean plasma leptin concentration was greater (P0.05) in CC compared with RT and RTCC steers. Steers receiving CC had greater (P0.04) concentrations of plasma cortisol, haptoglobin, glucose, and beta-hydroxybutyrate, and less (P0.05) concentration of non-esterified fatty acids compared with RT and RTCC steers on day 14 of the experiment. Carcass marbling was greater (P=0.01) in CC compared with RT steers and tended to be greater (P=0.07) in RTCC compared with RT steers. Proportion of carcasses that graded Choice or better and Longissimus muscle area were greater (P0.05) in CC and RTCC compared with RT steers. Incidence of liver abscesses was less (P=0.01) in RTCC compared with CC steers and tended to be less (P=0.09) in RT compared with CC steers. Results from this experiment indicate that the synbiotic supplement may replace monensin and tylosin without reducing steer BW gain, with potential improvements to carcass quality traits.
