The objective was to evaluate effects of adding a blend of essential oil compounds on ruminal fermentation and animal performance of feedlot cattle in comparison to sodium monensin. In Exp. 1, 24 angus steers [initial weight 141 more or less 6.6kg] were blocked by weight into 4 groups and randomly allocated to 8 pens of 3 steers. Treatments were monensin [46.7mg/kg dietary dry matter [DM]], or plant extracts [PE; 266mg/steer/d of cinnamaldehyde and eugenol+133mg/steer/d of capsicum oleoresin] added to a mineral mixture. The experiment lasted 84d and was divided in 2 periods of 0-44 and 45-84d. Diets were fed once daily and consisted of a corn grain based concentrate fed ad libitum, plus 200g alfalfa hay/steer/d as fed. The DM intake, average daily gain [ADG], feed conversion ratio [FCR] and rate of backfat deposition [BFD] were determined throughout the study. Short term intake patterns were evaluated by visual appraisal. In Exp. 2, two ruminally fistulated steers were used in a crossover design to determine how the ruminal fermentation variables pH, NH 3-N and volatile fatty acids [VFA] were affected by PE or monensin. Compared to monensin, PE did not alter overall DM intake [0.124kg/BW 0.75 versus 0.123kg/BW 0.75], FCR [0.21 versus 0.20], BFD [1.87mm/mo versus 1.76mm/mo], or longissimus dorsi muscle [LM] area [6.56cm 2/mo versus 6.69cm 2/mo] for PE and monensin, respectively. However, a treatmentÃ-period interaction occurred [P=0.02] for ADG, with steers fed PE having a higher [P=0.01] ADG in the second period [1.43kg/d versus 1.23kg/d for PE and monensin, respectively]. Short term intake patterns were not altered by PE compared to monensin, as steers visited the feeders a similar number of times and the length of each visit was also similar [11.5min versus 10.6min and 8.28min versus 9.57min for PE and monensin, respectively]. Although ruminal pH was not affected [5.55 versus 6.05 for PE and monensin, respectively], ruminal NH 3-N was lowered by PE [10.78mg/dl versus 20.05mg/dl, P=0.02]. Ruminal total VFA concentrations did not differ between treatments [80.7mM versus 62.5mM], and feeding PE did not alter ruminal acetate [48.5mol/100mol versus 58.2mol/100mol], or propionate [32.8mol/100mol versus 25.2mol/100mol, P=0.65] proportions. Results show that steers fed PE performed equivalently to those fed monensin in a high concentrate diet, and that some productive variables were improved with PE feeding.
FEEDLOT INTAKE PATTERN PERFORMANCE PLANT EXTRACTS ANIMALIA BOS CAPSICUM OLEORESIN MEDICAGO SATIVA ZEA MAYS