The effects of a blend of coriander oil, eugenol, geranyl acetate, and geraniol on bull fattening and carcass quality

A blend of essential oils (eugenol, geranyl acetate, coriander oil, and geraniol) has been earlier shown to improve dairy cow productivity by means of reduced methanogenesis. Thus far, no data is available for beef cattle and a transfer of lessons learned from dairy cows to bulls is difficult. Thirty young bulls (Swiss AA hybrids; 213 ± 32 kg; ∼167 d of age) were assigned to three pens according to live weight. Subsequently, bulls from each pen were randomly assigned to one of two feeding groups receiving 80% maize silage, 20% grass silage, and concentrate according to stage of fattening (up to 2.5 kg/animal*d⁻¹). The control group received 30 g/kg DM of ground wheat as placebo while the treatment group received 30 g/kg DM of a mixture of ground wheat and essential oil product (200 mg product/100 kg of live weight). Live weight, feed intake and feed:gain were monitored weekly for each individual animal. Furthermore, live weight at slaughter, days until slaughter at 500 kg live weight, carcase weight, and carcase quality (CHTAX system) were assessed in the end of the trial. Time (<i>p</i> ≤ 0.0005) but not feeding group (<i>p</i> ≥ 0.26) exerted significant effects on repeated measures. Endpoints measures were also not different between groups (<i>p</i> ≥ 0.14). This outcome conflicts with several earlier reports on positive effects in dairy cows and thereby questions the suitability of the product for beef fattening under the simulated conditions. Further studies including dose-response setups and considering different roughage:concentrate ratios are urgently needed. A controlled bull fattening trial with individual feeding assessed essential oils’ impact on performance and feed conversion.Unlike the positive outcomes reported in dairy trials, no significant effects were observed under the simulated conditions tested in this study.The product’s suitability and effectiveness under Swiss production guidelines remain uncertain based on current findings. A controlled bull fattening trial with individual feeding assessed essential oils’ impact on performance and feed conversion. Unlike the positive outcomes reported in dairy trials, no significant effects were observed under the simulated conditions tested in this study. The product’s suitability and effectiveness under Swiss production guidelines remain uncertain based on current findings.