Essential oils have proven efficacious in some feeding trials, but more research is needed, say dairy nutritionists at the University of Wisconsin-Madison.

Recently, the UW-Madison researchers conducted their own feeding trial on transition and early-lactation cows and found that treatment cows (i.e., those receiving essential oils) had lower milk yield than control cows in weeks 1 through 5 postpartum, similar milk yield in weeks 6 through 10, and greater milk yield in weeks 11 through 15. Unfortunately, the feeding trial was not continued any further into lactation, the researchers noted in a paper presented last fall at the Cornell Nutrition Conference. More research regarding potential interactions between basal diet, stage of lactation and dietary essential oil supplementation is needed before essential oils can be used with confidence in commercial practice, they added. To read their paper, click here.

Another paper on essential oils was presented in the December Journal of Dairy Science. That study, conducted by the University of Delaware, found that mid-lactation cows fed essential oils ate 4.2 pounds more dry matter per day and produced 5.9 pounds more 3.5 percent fat-corrected milk per day than cows fed the control diet. Note that the animals in the Delaware study were further along in lactation than the Wisconsin study. It would have been interesting if the Wisconsin study had followed cows well into mid-lactation, because the treatment cows did start to show a milk-yield advantage as they approached the mid-lactation stage. That is why the UW-Madison researchers are correct in saying that more research is needed.