Supplementing a Phytogenic Feed Additive Modulates the Risk of Subacute Rumen Acidosis, Rumen Fermentation and Systemic Inflammation in Cattle Fed Acidogenic Diets

SIMPLE SUMMARY: The present study evaluated the hypothesis that phytogenic supplementation in the diet will reduce the negative impacts of subacute ruminal acidosis and modulate rumen fermentation. A control group of cows with no supplementation was compared to a group supplemented with 0.04% (DM basis) of a phytogenic feed additive. We observed that after the high-concentrate diet was implemented with the phytogenic blend based on L-menthol, thymol, eugenol, mint oil (Mentha arvensis) and cloves powder (Syzygium aromaticum), the mean ruminal pH increased and the time for pH to reach below 5.8 decreased during the last two weeks of the experiment. Phytogenic feed supplementation also increased ruminal acetate and butyrate and reduced propionate, promoting more stable rumen fermentation compared to no supplementation (Control). Acute phase proteins decreased with the phytogenic feed additive from week 3 of high concentrate feeding. Nevertheless, liver enzymes did not seem to be affected by supplementation. Our study demonstrated that acidogenic diets supplemented with a phytogenic compound can reduce the risk of subacute ruminal acidosis. ABSTRACT: Feeding with high-concentrate diets increases the risk of subacute ruminal acidosis (SARA). This experiment was conducted to evaluate whether supplementing a phytogenic feed additive based on L-menthol, thymol, eugenol, mint oil (Mentha arvensis) and cloves powder (Syzygium aromaticum) (PHY) can amend the ruminal fermentation profile, modulate the risk of SARA and reduce inflammation in cattle. The experiment was designed as a crossover design with nine non-lactating Holstein cows, and was conducted in two experimental runs. In each run, cows were fed a 100% forage diet one week (wk 0), and were then transitioned stepwise over one week (0 to 65% concentrate, wk adapt.) to a high concentrate diet that was fed for 4 weeks. Animals were fed diets either with PHY or without (CON). The PHY group had an increased ruminal pH compared to CON, reduced time to pH < 5.8 in wk 3, which tended to decrease further in wk 4, reduced the ruminal concentration of D-lactate, and tended to decrease total lactate (wk 3). In wk 2, PHY increased acetate, butyrate, isobutyrate, isovalerate, and the acetate to propionate ratio compared to CON. Phytogenic supplementation reduced inflammation compared to CON in wk 3. Overall, PHY had beneficial effects on ruminal fermentation, reduced inflammation, and modulated the risk of SARA starting from wk 3 of supplementation.