Responses of Bos indicus cattle to phytogenic feed additives compared with monensin in feedlot diets

Abstract

Two experiments assessed the responses of Bos indicus cattle fed monensin (MON), Stryphnodendron adstringens extract (BBT), a blend of essential oils (BEO), and a blend of functional oils (BFO). Feed additives were added to a total mixed ration (TMR) with a 20:80 roughage to concentrate ratio. Experiment 1, lasting 104 d, used a randomized complete block design. One hundred fourteen (114) crossbred bulls (336 ± 26 kg BW) were assigned to four treatments: MON (30 mg/kg DM), BBT (1500 mg/kg DM), BEO (118 mg/kg DM), and BFO (250 mg/kg DM). MON resulted in the lowest dry matter intake. Average daily gain, final body weight, and carcass traits were similar across treatments. Feed efficiency was 13 %, 11 %, and 4 % greater with MON compared to BBT, BEO, and BFO, respectively. Experiment 2 employed a 5×5 Latin square with five ruminally fistulated Bos indicus steers to test the same four treatments and a control diet without additives. Each period lasted 14 d. Apparent nutrient digestibility and concentrations of volatile fatty acids and NH3-N were similar among treatments. BBT and BFO had the lowest (6.54) and highest (6.75) ruminal pH values, respectively. Monensin showed superior feed efficiency despite similar nutrient digestibility and rumen fermentation profiles compared to phytogenic additives.