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Research into the potential use of various dietary feed supplements to reduce methane (CH4) production from ruminants has proliferated in recent years. In this study, two 8-wk long experiments were conducted with mature ewes and incorporated the use of a variety of natural dietary feed supplements offered either independently or in combination. Both experiments followed a randomized complete block design. Ewes were offered a basal diet in the form of ad libitumaccess to grass silage supplemented with 0.5 kg concentrates/ewe/d. The entire daily dietary concentrate allocation, incorporating the respective feed supplement, was offered each morning, and this was followed by the daily silage allocation. In experiment 1, the experimental diets contained 1) no supplementation (CON), 2) Ascophyllum nodosum(SW), 3) A. nodosumextract (EX1), 4) a blend of garlic and citrus extracts (GAR), and 5) a blend of essential oils (EO). In experiment 2, the experimental diets contained 1) no supplementation (CON), 2) A. nodosumextract (EX2), 3) soya oil (SO), and 4) a combination of EX2 and SO (EXSO). Twenty ewes per treatment were individually housed during both experiments. Methane was measured using portable accumulation chambers. Rumen fluid was collected at the end of both experiments for subsequent volatile fatty acid (VFA) and ammonia analyses. Data were analyzed using mixed models ANOVA (PROC MIXED, SAS v9.4). Statistically significant differences between treatment means were considered when P < 0.05. Dry matter intake was not affected by diet in either experiment (P > 0.05). Ewes offered EO tended to have an increased feed:gain ratio relative to CON (P < 0.10) and SO tended to increase the average daily gain (P < 0.10) which resulted in animals having a higher final body weight (P < 0.05) than CON. Ewes offered EX1 and SO emitted 9% less CH4g/d than CON. The only dietary treatment to have an effect on rumen fermentation variables relative to CON was SW, which enhanced total VFA production (P < 0.05). In conclusion, the A. nodosumextract had inconsistent results on CH4emissions whereby EX1 reduced CH4g/d while EX2 had no mitigating effect on CH4production, likely due to the differences in PT content reported for EX1 and EX2. SO was the only dietary feed supplement assessed in the current study that enhanced animal performance whilst mitigating daily CH4production.This research highlights the efficacy of including natural feed supplements in a once-a-day feeding strategy to mature ewes by reducing methane emissions and improving animal productivity.Reducing methane emissions from agriculture is vital to minimize the effects of global warming and to meet greenhouse gas reduction targets set by EU policy. In this experiment, a range of natural feed supplements were offered to mature ewes through the concentrated portion of their diet. Soya oil and brown seaweed extract reduced daily methane emissions by 9% when offered independently of each other; however, no reduction in methane was observed when combined. Additionally, inclusion of soya oil improved animal weight gain. Results from the current experiment may contribute to the development of a targeted dietary strategy to reduce methane emissions from livestock.

There is an urgent requirement internationally to reduce enteric methane (CH4) emissions from ruminants to meet greenhouse gas emissions reduction targets. Dietary supplementation with feed additives is one possible strategy under investigation as an effective solution. The effects of the CH4inhibitor 3-nitrooxypropanol (3-NOP) at reducing CH4emissions in beef have been shown mainly in adult cattle consuming backgrounding and high-energy finishing diets. In this study, the effects of dietary supplementation of young growing (≤6 mo) beef cattle with 3-NOP were examined in a 50:50 forage:concentrate diet. A total of 68 Dairy × Beef (Aberdeen Angus and Hereford dairy cross) male calves (≤6 mo of age at the start of experiment, body weight: 147 ± 38 kg) underwent a 3-wk acclimatization period and were then assigned to one of two treatments in a completely randomized block design. Dietary treatments were (1) control, placebo (no 3-NOP), and (2) 3-NOP applied at 150 mg kg−1DM. Calves were fed a partial mixed ration for 12 wk. Body weight was recorded weekly and feed intake daily using the Calan Broadbent feeding system. Methane and hydrogen emissions were measured using the GreenFeed system. Total weight gained, dry matter intake (DMI), and average daily gain were not affected by 3-NOP (P> 0.05) supplementation. On average, the inclusion of 3-NOP decreased (P< 0.001) CH4emissions: g d−1; g kg−1DMI; by 30.6% and 27.2%, respectively, during the study with a greater reduction occurring over time. Incorporating 3-NOP into beef cattle diets is an efficient solution to decrease CH4emissions during indoor feeding and when offered 50:50 forage:concentrate diet.This research highlights the efficacy of the methane (CH4) inhibitor, 3-nitrooxypropanol, in reducing CH4emissions in young growing beef cattle without affecting dry matter intake and animal performance when consuming a 50:50 forage:concentrate diet.Enteric methane (CH4) is a by-product from the fermentation of feed in the digestive tract of cattle. The production of CH4is responsible for the loss of 2% to 12% of the animal’s gross energy intake. A potent greenhouse gas, CH4from ruminant systems accounts for 30% of international anthropogenic CH4emissions. As a result, a significant effort has been made internationally to reduce CH4emissions from ruminants in order to achieve reductions in global greenhouse gas emissions. The supplementation of additives in the feed has been demonstrated to be an effective strategy in reducing CH4emitted from livestock. The purpose of this research was to investigate the effects of supplementing young growing cattle with the CH4inhibitor, 3-nitrooxypropanol (3-NOP), consuming a 50:50 forage:concentrate diet. A total of 68 Dairy × Beef (Aberdeen Angus and Hereford dairy cross) male calves (≤6 mo of age at the start of the experiment) were assigned to one of two treatments: control (no 3-NOP) and 3-NOP. Animals received their diets for 12 wk. Animal performance was recorded weekly, with CH4and hydrogen (H2) emissions recorded daily. Dry matter intake and animal performance were not affected by the inclusion of 3-NOP. Over the duration of this study, the inclusion of 3-NOP decreased daily CH4emissions by 30.6%, with a 227% increase in daily H2emissions.