Feeding oregano oil and its main component carvacrol does not affect ruminal fermentation, nutrient utilization, methane emissions, milk production, or milk fatty acid composition of dairy cows

摘要

Because of their antimicrobial properties, essentialoils and their components have been suggested as alternativesto other antimicrobials (e.g., monensin) thatare commonly fed to ruminants to improve nutrientutilization and enhance feed efficiency and milk performance.In this study, we evaluated the potential oforegano oil and its main component (carvacrol) as rumenmodifiers. For this purpose, 8 ruminally cannulatedlactating dairy cows (92 ± 11 d in milk, 36.5 ± 7.6 kg ofmilk yield, and 703 ± 74 kg of body weight) were usedin a double 4 × 4 Latin square (28-d periods). Cowswere fed 1 of the 4 following treatments: (1) control(CTL, no additive); (2) monensin [MON, 24 mg/kg ofdry matter (DM)]; (3) oregano oil (ORE, 50 mg/kgof DM); and (4) carvacrol (CAR, 50 mg/kg of DM).Cows were fed (ad libitum intake) a total mixed rationconsisting of 60% forages (corn silage and alfalfa silage)and 40% concentrates, on a DM basis. Feeding OREand CAR had no effect on nutrient total-tract apparentdigestibility, N utilization, rumen fermentation (i.e.,pH, ammonia, volatile fatty acids), protozoa counts, ormilk performance. Feeding MON increased the molarproportion of propionate and tended to increase totaltractapparent digestibility of crude protein. None ofthe feed additives evaluated affected enteric methaneproduction (491 g/d, 21.1 g/kg of DM intake, 6.14% ofgross energy intake on average). Milk fatty acid compositionwas not changed by ORE or CAR, but MONincreased the proportion of trans-10 18:1, an intermediateof ruminal biohydrogenation. Thus, when includedat 50 mg/kg of dietary dry matter, neither oreganooil nor carvacrol favorably altered rumen fermentation,improved nutrient utilization or milk performance, ormitigated enteric methane emissions in dairy cows.