Evaluation of Agolin® Ruminant, an Essential Oil Blend, as a Feed Additive for Cows at Two Levels of Production

Agolin® Ruminant is a commercially available blend of essential oils which has been demonstrated to reduce greenhouse gas emissions in dairy cows and improve energy corrected milk and feed efficiency. Further trials are needed with large numbers of cows to confirm the magnitude of effect of this feed additive on milk production under differing feeding conditions and stages of lactation. Information that can be quantified from newer on-farm systems of measurement is likewise needed. This study was conducted to determine the effects of this additive on high producing (48 kg of milk/day average) just past peak lactation and medium producing dairy cows (43 kg of milk/day average) further along in lactation under commercial conditions that would typically occur in the Pacific Northwest USA. Four pens of approximately 400 Holstein cows/pen (two high producing pens and two medium producing pens) were available for this side-by side study. Performance results were determined using data derived from a subscription standardized monitoring system (High Desert Dairy Laboratory, Inc, Nampa, ID, USA) that provided results for milk yield, fat percentage and protein percentage. As well daily in-stall electronic monitoring of milk only was available. All pens received a common total mixed ration typical of rations fed in the Pacific Northwest, USA. The Agolin feed additive was dispensed through the bulk mineral supply with control cows receiving the normal minerals and the treatment cows receiving the normal minerals plus Agolin. The trial began on August 24, 2021, with treatment cows provided with 1g/head/day for the duration of the 8-week long study. Dry matter intakes were determined daily for the week before the trial was conducted and the last week of the trial. Treatment results were compared using a general linear model that considered pretrial milk, fat yield and protein yield, days in milk and lactation number. There were 678 high producing cows available for the duration of the study. Based on the standardized testing results, milk yield was greater (1.12 kg/cow/day; P < 0.05) for the cows in the treatment group. There was a tendency for fat corrected milk (FCM) and energy corrected milk (ECM) to be greater for the cows receiving the Agolin feed additive (0.96 and 0.86 kg/cow/day for FCM and ECM respectively, P < 0.10). There were 646 medium producing cows that participated in the trial. There was no treatment effect upon milk production (P = 0.27). There was a significant (P < 0.05) increase in milk fat yield and no change (P = 0.33) in protein yield for the treatment cows in this test group, resulting in greater FCM and ECM (1.12 and 0.95 kg/cow/day; P < 0.05). Daily milk monitoring resulted in a reduced decline in milk yield from the week before to the final week of the trial revealing greater persistency of milk for Agolin-fed cows in both high and medium production pens (1.58 and 2.13 kg/cow/day;
P < 0.01). Likewise, overall feed efficiency was improved by 5.3% (P < 0.05) with the test product.