On-Farm Methane Mitigation and Animal Health Assessment of a Commercially Available Tannin Supplement in Organic Dairy Heifers.

Simple Summary: On-farm research that investigates commercially relevant climate-smart conservation practices is critical in order to develop practical sustainability strategies in agricultural production systems. The purpose of this study was to investigate on-farm methane (CH4) mitigation potential and animal health outcomes using a commercially available tannin as a feed additive in dairy heifers reared under an organic production system. Enteric CH4 was measured using one GreenFeed and animal health was evaluated via select antioxidant enzyme and oxidate stress biomarker concentrations. No effect was observed for daily enteric CH4 production, average daily gain (ADG), dry matter intake (DMI), or oxidative stress biomarker concentration. Tannin supplementation did have an effect on the concentration of the antioxidant-enzymes-reduced glutathione (GSH) and superoxide dismutase (SOD). Future research may consider the investigation of animal health benefits due to tannin supplementation, such as linking the effect of tannins to the improved antioxidant status of heifers, which may be of particular interest in organic dairy production systems. The observations from this study highlighted the challenges for future on-farm sustainability research and the scalability of potential CH4 mitigation strategies. The objective of this experiment was to demonstrate the effectiveness of a commercially available tannin product (Silvafeed® ByPro, 70% tannic acid) as an enteric methane (CH4) mitigation and preventative animal health strategy in Holstein heifers (BW = 219 ± 17 kg; 9 mo), reared under organic production system requirements. Twenty heifers were randomly assigned to one of four commercial tannin supplementation treatments as follows: 0% (0 g/hd/d; CON), 0.075% (~5 g/hd/d; LOW), 0.15% (~10 g/hd/d; MED), and 0.30% (~21 g/hd/d; HIG) of dry matter intake (DMI). Heifers received their treatment in individual animal feeding stanchions and were fed a basal total mixed ration (TMR) through four SmartFeed Pro intake measurement bunk systems (C-Lock Inc., Rapid City, SD, USA) for 45 d. An automatic head chamber system (AHCS; i.e., GreenFeed, C-Lock Inc., Rapid City, SD, USA) was used to continuously evaluate enteric CH4 production. No effect was observed among the treatments for CH4 emissions (p ≥ 0.55), animal performance (p ≥ 0.38), or oxidative stress biomarker concentration (p ≥ 0.55). Superoxide dismutase (SOD) and reduced glutathione (GSH) concentrations exhibited a linear response to increasing tannin dose (p = 0.003), indicating a potential tannin effect on the antioxidant status of dairy heifers. This observation may encourage future tannin research relating to animal health, which may be of particular interest to organic dairy systems. The results of this study suggest that tannin supplementation at 0%, 0.075%, 0.15%, and 0.30% of DMI, did not alter CH4 emissions, animal performance, or oxidative stress biomarker concentration in organic Holstein heifers when assessed under an on-farm research approach. Further, the results of this study affirm the challenges associated with on-farm research and the development of climate-smart strategies that are capable of mitigating climate impacts in less controlled environments under standard working conditions. [ABSTRACT FROM AUTHOR]