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Asparagopsis taxiformis(Asparagopsis) has been shown to be highly efficacious at inhibiting the production of methane (CH4) in ruminants. To date, Asparagopsishas been primarily produced as a dietary supplement by freeze-drying to retain the volatile bioactive compound bromoform (CHBr3) in the product. Steeping of Asparagopsisbioactive compounds into a vegetable oil carrier (Asp-Oil) is an alternative method of stabilizing Asparagopsisas a ruminant feed additive. A dose–response experimental design used 3 Asp-Oil-canola oil blends, low, medium, and high Asp-Oil which provided 17, 34, and 51 mg Asparagopsisderived CHBr3/kg dry matter intake (DMI), respectively (in addition to a zero CHBr3canola oil control), in a tempered-barley based feedlot finisher diet, fed for 59 d to 20 Angus heifers (five replicates per treatment). On four occasions, live weight was measured and CH4emissions were quantified in respiration chambers, and blood, rumen fluid, and fecal samples were collected. At the end of the experiment, all animals were slaughtered, with carcasses graded, and samples of meat and edible offal collected for testing of consumer sensory qualities and residues of CHBr3, bromide, and iodide. All Asp-Oil treatments reduced CH4yield (g CH4/kg DMI, P= 0.008) from control levels, with the low, medium, and high Asp-Oil achieving 64%, 98%, and 99% reduction, respectively. Dissolved hydrogen increased linearly with increasing Asp-Oil inclusion, by more than 17-fold in the high Asp-Oil group (P= 0.017). There was no effect of Asp-Oil treatment on rumen temperature, pH, reduction potential, volatile fatty acid and ammonia production, rumen pathology, and histopathology (P> 0.10). There were no differences in animal production and carcass parameters (P> 0.10). There was no detectable CHBr3in feces or any carcass samples (P> 0.10), and iodide and bromide residues in kidneys were at levels unlikely to lead to consumers exceeding recommended maximum intakes. Overall, Asp-Oil was found to be safe for animals and consumers of meat, and effective at reducing CH4emissions and yield by up to 99% within the range of inclusion levels tested.A feed ingredient containing bioactive metabolites of Asparagopsisstabilized in canola oil was able to virtually eliminate methane emissions from grain-fed cattle, without impacting animal health or production, or consumer safety.Red seaweed, Asparagopsis taxiformis(Asparagopsis), has been shown to be highly effective at inhibiting the production of methane (CH4) in ruminants. An alternative to feeding whole, freeze-dried Asparagopsisis steeping the biomass in vegetable oil to stabilize the bioactive compounds (Asp-Oil) and feeding Asp-Oil to ruminants as a component of their dietary intake. This experiment measured the CH4reduction potential and safety of Asp-Oil in a trial with 20 Angus heifers, fed iso-fat feedlot diets containing one of the three levels of Asp-Oil, or a control oil. Compared to the control, bromoform inclusion levels of 17, 34, and 51 mg/kg of dry matter (DM; low, medium, high) reduced CH4yield (g CH4/kg DM intake) by 64%, 98%, and 99%, respectively. There were no effects on animal production or carcass characteristics. There were no impacts on animal health, welfare, or rumen function. Carcasses were safe for human consumption, and there was no bromoform detected in any carcass samples. Overall, Asp-Oil was found to effectively reduce CH4emissions and is safe for animals and consumers of meat and edible offal.

A dose-response experiment was designed to examine the effect of 3-nitrooxypropanol (3-NOP) on methane (CH4) emissions, rumen function and performance of feedlot cattle fed a tempered barley-based diet with canola oil. Twenty Angus steers of initial body weight (BW) of 356 ± 14.4 kg were allocated in a randomized complete block design. Initial BW was used as the blocking criterion. Cattle were housed in individual indoor pens for 112 d, including the first 21 d of adaptation followed by a 90-d finishing period when five different 3-NOP inclusion rates were compared: 0 mg/kg dry matter (DM; control), 50 mg/kg DM, 75 mg/kg DM, 100 mg/kg DM, and 125 mg/kg DM. Daily CH4production was measured on day 7 (last day of starter diet), day 14 (last day of the first intermediate diet), and day 21 (last day of the second intermediate diet) of the adaptation period and on days 28, 49, 70, 91, and 112 of the finisher period using open circuit respiration chambers. Rumen digesta samples were collected from each steer on the day prior to chamber measurement postfeeding, and prefeeding on the day after the chamber measurement, for determination of rumen volatile fatty acids (VFA), ammonium-N, protozoa enumeration, pH, and reduction potential. Dry matter intake (DMI) was recorded daily and BW weekly. Data were analyzed in a mixed model including period, 3-NOP dose and their interaction as fixed effects, and block as a random effect. Our results demonstrated both a linear and quadratic (decreasing rate of change) effect on CH4production (g/d) and CH4yield (g/kg DMI) as 3-NOP dose increased (P< 0.01). The achieved mitigation for CH4yield in our study ranged from approximately 65.5% up to 87.6% relative to control steers fed a finishing feedlot diet. Our results revealed that 3-NOP dose did not alter rumen fermentation parameters such as ammonium-N, VFA concentration nor VFA molar proportions. Although this experimental design was not focused on the effect of 3-NOP dose on feedlot performance, no negative effects of any 3-NOP dose were detected on animal production parameters. Ultimately, the knowledge on the CH4suppression pattern of 3-NOP may facilitate sustainable pathways for the feedlot industry to lower its carbon footprint.Rumen fermentation, methane (CH4), and production parameters were investigated in feedlot cattle supplemented with increasing inclusion rates of 3-nitrooxypropanol. Our results revealed a potential CH4abatement of up to 90% during a 90-d finishing period on a tempered barley diet containing monensin and 7% lipid content.Livestock methane (CH4) is the main source of greenhouse gases (GHGs) in agriculture, contributing to 11.6% of global GHGs emissions from human-related activities. Therefore, mitigating CH4emissions from ruminant animals is a great opportunity for meeting the current climate targets. In this experiment, increasing inclusion rates of a promising CH4-mitigating compound, 3-nitrooxypropanol (3-NOP, from 50 to 125 mg of 3-NOP/kg of dry matter [DM]), were added to a barley-based feedlot diet containing 25 ppm of monensin and 7% fat (DM-basis) and fed to Angus steers. Under these conditions, increasing inclusion rate of 3-NOP reduced both production and yield of CH4by up to 90%. Rumen fermentation, feed intake, and average daily gain were not affected by the 3-NOP dose. Our results on the potential CH4suppression of 3-NOP may assist the feedlot industry towards sustainability by lowering its GHG output.

Stocking density may impact sheep welfare during live export voyages that occur under hot and humid conditions. The aim of this study was to assess the welfare implications for sheep housed at three allometric stocking densities (k= 0.030, 0.033, 0.042), while exposed to hot and humid climatic conditions. For 21 d, Merino wethers (n= 216) were housed in 12 pens of 18 wethers, in two climate-controlled rooms where wet-bulb temperature (TWB) mimicked the conditions of a live export voyage with high heat and humidity, and limited diurnal variation. Scan sampling of standing and lying behaviors was conducted on days 2, 5, 8, 11, 15, 18, and 20, at hourly intervals. Agonistic interactions were scored continuously on the same days between 1750 and 1800 h. Liveweights were recorded at the start and end of the study. For a subset of focal wethers (3 per pen), whole blood variables were assessed at the start and end of the experiment, along with fecal glucocorticoid metabolites (FGCM), which were also assessed on days 7 and 14. Rumen temperatures (TRUM) of focal wethers were recorded at 10-min intervals, and their respiration rates (RR) were measured every 2 h on days 1, 3, and from days 7 to 21. Focal wethers were slaughtered for necropsy after the study, and both adrenal glands were excised and weighed. The expression of some lying positions was impaired at high stocking densities, and lying with outstretched legs increased at high TWB. For respiration rates, there was an interaction between stocking density and TWB, such that RR was reduced by the provision of additional space at high TWB. TRUMwas relatively unaffected by stocking density but increased at higher TWB, and any effects of stocking density on FGCM concentrations, liveweights (LW), adrenal gland weights or blood variables were minimal. Necropsy examination showed no indication that the wethers had experienced ongoing respiratory distress. These results suggest that the wethers were able to cope with these increases in stocking density under the conditions imposed. However, based on this evidence, the provision of additional space under hot conditions may be beneficial to facilitating the expression of some lying positions. Whilst the experiment was designed to emulate certain conditions relevant during live export voyages, other factors that may induce stress during this mode of transport were not present, and so the conclusions must be interpreted in the context of the experimental conditions.For sheep housed intensively under hot and humid climatic conditions, stocking density impacted lying behaviors, but had limited important effects on heat stress and physiology in the highly controlled experimental environment.There is a high demand for Australian sheep to be exported to the Middle East, and for live export voyages which depart during an Australian winter, heat, and humidity increase rapidly as ships cross the equator and approach destination countries. Concern about sheep becoming heat stressed during these voyages has increased, and industry attention has focused on the potential role of stocking density in determining heat stress risk in this context. High stocking densities limit the body surface area available for heat loss and can increase heat exchange between individual sheep. This study aimed to assess the welfare implications of three stocking densities, for sheep exposed to climatic conditions similar to those experienced during a live export voyage to the Middle East. Higher stocking densities restricted the ability of sheep to lie in some positions, but stocking density had limited effects on heat stress indicators or the physiology of the sheep. These results suggested that the sheep were able to cope with these increases in stocking density under the conditions imposed, but the conclusions must be interpreted in the context of the controlled experimental conditions.