Efficacy of 3-NOP applied in drinking water on enteric methane reduction in sheep

Abstract

The most effective strategy to reduce CH₄ emissions is to incorporate CH₄ inhibitors into ruminant diets. However, there is a need to broaden the actual presentation form (i.e., solid powder) of the commercially available products to allow their use in grazing systems. This study aimed to test the efficacy of 3-NOP on enteric CH₄ reduction in sheep when applied in drinking water as a possible delivery system in livestock grazing conditions. The study followed a 4 × 4 Latin square design, enrolling 4 non-lactating female adult sheep with an average body weight (BW) of 44.9 ± 2.6 kg. The study lasted 8 weeks, with 4 experimental periods of 2 weeks each. The experimental periods consisted of 7 days of adaptation to the treatments and 3 days of enteric gas emission measurements (CH₄ and H₂) in open-circuit respiration chambers, followed by a wash-out period of 4 days. Sheep were randomly assigned to 1 of the 4 experimental treatments. The treatments were: i) a basal diet without supplementation (CTL); ii) a basal diet supplemented with 80 mg of 3-NOP per kg of dry matter intake (DMI) (Bovaer® 10); iii) a basal diet supplemented with 80 mg of 3-NOP in the drinking water (DW80) per kg of DMI; and iv) a basal diet supplemented with 120 mg of 3-NOP in the drinking water (DW120) per kg of DMI. There were no significant differences (P > 0.05) in the feed or water intakes across treatments. Methane emissions (g/d) and yield (g/kg DMI) were significantly lower in Bovaer® 10 (-26.8 %), DW80 (-41.4 %), and DW120 (-35.7 %) than in CTL (P < 0.05). Sheep in the Bovaer® 10 treatment had a greater emissions reduction in the first 2 hours after feeding and a smaller reduction in the following 2 hours. In contrast to Bovaer® 10, the impact of treatments in DW80 and DW120 lasted for 4 hours post-feeding. For the second half of the day (i.e., 4 hours after the second feeding), Bovaer® 10, DW80, and DW120 had lower emission values than CTL. The lower emissions in sheep in DW80 and DW120 treatments than Bovaer® 10 is explained by their drinking pattern and, thereby, the supply of 3-NOP into the rumen. Results suggest that adding 3-NOP to the drinking water could be a potential strategy where feed formulation does not necessarily allow for the delivery of 3-NOP mixed with the diet. This strategy requires further research in livestock systems with different drinking water patterns.