Effects of alfalfa extract, anise, capsicum, and a mixture of cinnamaldehyde and eugenol on ruminal fermentation and protein degradation in beef heifers fed a high-concentrate diet.

Four Holstein heifers (360 +/- 22 and 450 +/- 28 kg of BW in Exp. 1 and 2, respectively) fitted with ruminal trocars were used in 4 x 4 Latin square designs to evaluate the effects on ruminal microbial fermentation of the following: Exp. 1, no additive, alfalfa extract (30 g/d, AEX), a mixture of cinnamaldehyde (0.18 g/d) and eugenol (0.09 g/d; CIE1), and AEX and CIE1 in combination; and Exp. 2, no additive, anise oil (2 g/d), capsicum oil (1 g/d), and a mixture of cinnamaldehyde (0.6 g/d) and eugenol (0.3 g/d). Heifers were fed a 90:10 concentrate:barley straw diet (16% CP; 25% NDF) for ad libitum intake. Each period consisted of 15 d for adaptation and 6 d for sampling. On d 16 to 18, DM and water intakes were measured. On d 19 to 21 ruminal contents were sampled at 0, 3, 6, 9, and 12 h after feeding to determine ruminal pH and the concentrations of VFA, L-lactate, large peptides, small peptides plus AA (SPep+AA), and ammonia N. On d 20 and 21, samples of ruminal fluid were collected at 0 and 3 h after feeding to determine protozoal counts. In Exp. 1, CIE1 and AEX decreased (P < 0.05) total DMI, concentrate DMI, and water intake. The increase (P < 0.05) in SPep+AA and the decrease (P < 0.05) in ammonia N when supplementing CIE1 suggest that deamination was inhibited. Treatment AEX increased (P < 0.05) the acetate to propionate ratio, which is less efficient for beef production. Treatment CIE1 increased (P < 0.05) counts of holotrichs. Effects of AEX and CIE1 were not additive for many of the measured metabolites. In Exp. 2, treatments had no effect on ruminal pH, total VFA concentration, and butyrate proportion. The capsicum oil treatment increased (P < 0.05) DMI, water intake, and SPep+AA N concentration and decreased (P < 0.05) acetate proportion, branched-chain VFA concentration, and large peptide N concentration. The cinnamaldehyde (0.6 g/d) and eugenol (0.3 g/d) treatment decreased (P < 0.05) water intake, acetate proportion, branched-chain VFA, L-lactate, and ammonia N concentrations and increased (P < 0.05) propionate proportion and SPep+AA N concentration. The anise oil treatment decreased (P < 0.05) acetate to propionate ratio, branched-chain VFA and ammonia N concentrations, and protozoal counts. The results indicate that at the doses used a mixture of cinnamaldehyde and eugenol, anise oil, and capsicum oil may be useful as modifiers of rumen fermentation in beef production systems.