Abstract
Fifty-nine Angus-cross finishing steers were used to evaluate benzoic acid, active dry yeast (Saccharomyces cerevisiae), or a combination of benzoic acid and active dry yeast when supplemented in a high-grain finishing diet on live animal performance, feeding behaviour, and carcass characteristics. Steers were fed a high-grain diet for the final 106 d of finishing. Treatments were; no additional supplementation (CON), 0.5% benzoic acid (ACD), 3 grams per head per day active dry S. cerevisiae (YST), or both 0.5% benzoic acid and 3 grams/head per day S. cerevisiae (AY). Steers were weighed every 14 d, and ultrasound was performed for rib and rump fat thickness at the beginning (d 1), middle (d 57), and end (d 99) of the experiment. Insert feeding stations were used to collect individual feeding behaviour data and DMI daily throughout. Blood samples were collected on d 21-22 and d 99-101 to assess plane of nutrition and metabolism. Ruminal fluid samples were collected by oral gavage 4 weeks prior to slaughter. Carcass characteristics were examined at a federally inspected slaughter facility. Data were analyzed using PROC GLIMMIX of SAS with initial body weight (BW) as a covariate. Benzoic acid supplementation increased (P = 0.002) overall dry matter intake (DMI) compared to YST and CON steers, which may be due to a faster eating rate (P ≤ 0.008). Animal performance parameters (BW, average daily gain, feed conversion, and ultrasound fat depth) were not different (P ≥ 0.11) among treatment groups. Aspartate aminotransferase concentration was greatest (P ≤ 0.01) for YST steers, which may have been reflected in numerically greater liver abscesses. Carcass traits did not differ (P ≥ 0.33) among treatment groups. Ruminal pH was greater (P = 0.006) for ACD steers than AY steers (pH of 6.16 vs. 5.66, respectively), which indicated that there may be an interactive effect between benzoic acid and active dry yeast. To summarize, steers fed a high-grain finishing diet supplemented with benzoic acid, active dry yeast, or both benzoic acid and active dry yeast had similar growth performance and carcass characteristics compared to those without supplementation. However, the addition of benzoic acid alone increased DMI, variation in DMI, eating rate, and ruminal pH. Future studies are warranted to further investigate the impacts of benzoic acid on the ruminal environment of feedlot cattle
Effect of Dietary Yeast (Saccharomyces cerevisiae) Supplementation on Performance, Carcass Characteristics and Some Metabolic Responses of Broilers
