Frances C. Cowley’s research while affiliated with University of New England and other places

Context Accurately predicting baseline methane (CH4) emissions from beef cattle is of utmost importance for the beef industry and governments alike. It serves as a vital component for accounting as part of national GHG inventories and enables the development and implementation of greenhouse gas (GHG) mitigation strategies. Aims The aim of this study was to evaluate equations in the literature for predicting CH4 emissions of beef cattle when fed barley and wheat-based diets typical of the Australian feedlot industry. Then, propose the best prediction equation to accurately reflect CH4 emissions of feedlot cattle under Australian conditions. Methods As part of the project, a large database of methane measurements performed in respiratory calorimeters taken from beef cattle fed a range of feedlot diets was assembled. The dataset included a wide range of factors that are known to impact CH4 production, such as dry matter intake (DMI), ether extract (EE), crude protein (CP), and cell wall components, amongst others. The database contained 713 individual measurements, from 175 animals and 12 studies. Key results The equation currently utilised by the Australian National Inventory Report had poor accuracy, with mean bias overprediction of 115 g/day (P < 0.01), along with significant linear bias (P < 0.01) and poor precision (r2 = 0.05). The mean bias was 144% of average observed CH4 production. All evaluated equations lacked accuracy and precision in predicting CH4 emissions for the diets fed in this study. Roughage concentrations (DM basis) ranged from 5.54 to 43.0% with a mean of 20.5 ± 11.1%. Given these findings, two specific equations were developed, (1) a CH4 yield equation based on DMI: CH4 (g/day) = 9.89 ± 1.54 × DMI (n = 384; P < 0.01; root mean square error (RMSE) = 32.6 g/day; r2 = 0.85); and (2) an equation based on DMI, neutral detergent fibre (NDF) and EE: CH4 (g/day) = 5.11 ± 1.58 × DMI − 4.00 ± 0.821 × EE + 2.26 ± 0.125 × NDF (n = 384; P < 0.05; RMSE = 22.2 g/day; r2 = 0.91). When validated, the second equation yielded a mean bias of 6.10 g overprediction, with no linear bias, and better fit than any of the literature equations. Conclusions Based on a thorough model evaluation, our findings support the need to revise current methods to predict CH4 for barley and wheat-based diets. Implications This study contributes to developing accurate estimations of enteric CH4 emissions for cattle fed barley and wheat-based diets.

Stocking density can potentially impact cattle welfare during livestock export voyages. The aim of this study was to assess selected measures that reflect the welfare of cattle housed at three allometric stocking densities (k = 0.027, 0.030, 0.047). Bos indicus cross Bos taurus steers were housed in 12 pens, each with 5 steers, for 10 days. Scan sampling of standing and lying behaviours were conducted on d 2, 5, 7 and 9, at hourly intervals. Continuous observations were conducted on the same days between 1030 and 1130 h, to count aggressive interactions. Liveweights were recorded at the start of the study, and on d 6 and d 10. For a subset of focal steers (3 per pen), white blood cell counts, and faecal glucocorticoid metabolite (FGCM) concentrations were assessed on days 0, 6 and 10. More pen space led to a small increase in the number of steers lying, as well as a small increase in lying synchronicity. Results also indicated that the number of cattle lying in isolation from conspecifics is higher when more space is available. More pen space also resulted in more steers lying with outstretched legs on days 2 and 5, but there was no evidence of this after day 5. Stocking density had no important effect on day 6 or 10 liveweights or FGCM concentrations. Only small decreases in total white blood cell and lymphocyte counts between days 6 and 10 were observed, as well as small increases in neutrophil counts and the neutrophil to lymphocyte ratio, but all mean counts still fell within reference intervals for healthy cattle. The lack of important effects on stress physiology and liveweight suggests that the cost of attempting to adapt to pen space restriction was relatively low, leading to behavioural responses only. Results for lying behaviours also suggest that additional pen space may facilitate adaptation upon introduction to a new housing environment and is beneficial in facilitating the expression of some lying behaviours. While designed to emulate stocking densities applicable to Australian cattle export voyages, other environmental factors that may induce stress during these voyages were not present, and so the conclusions must be interpreted in the context of the controlled experimental conditions.

Context Manure deposition during livestock export voyages contributes to air ammonia levels, potentially affecting human and animal health if not managed. Mitigation strategies may include increased air change rates and application of bedding. Aim This study examined the effect of bedding application rate (BAR) and air change rate (ACH) on air ammonia (NH3) concentrations and pad properties, including pad surface condition, pH, moisture, and pad ammonium (NH4⁺) concentrations, for intensively housed beef cattle. Methods Six 7-day runs were conducted with 72 Bos indicus cross steers (mean liveweight ± s.d. = 338 ± 32 kg) housed in respiration chambers by using a 3 × 3 factorial design. The BARs were set to 0%, 50%, and 100% of the Australian Standards for the Export of Livestock (ASEL), and ACH were varied at 20, 35, and 52. Air NH3 was measured twice daily at three heights. Pad surface condition was collected with the first air NH3 measurement. Video footage captured standing and lying behaviours for each steer. Pad samples were collected on the final day for pad chemical analysis. Key results The ACH of 20 changes per hour resulted in higher air NH3 concentration than ACH of 35 and 52. Higher BAR led to lower pad pH and moisture, with slightly lower pad NH4⁺ concentration in 100% and 50% BAR than 0% BAR. Although air NH3 concentration on Day 7 was positively correlated with pad NH4⁺ concentration, BAR had no marked effect on air NH3 concentration (within the temperature range of this experiment). Drier and firmer pad surfaces were associated with each high BAR and high ACH. Moreover, high BAR increased the frequency of lying behaviour in steers. Conclusions These findings indicated that NH3 can be mitigated by optimising air changes to minimise air NH3 concentration and utilising bedding to minimise pad NH4⁺. This offers practical solutions for intensively housed beef cattle, such as livestock export voyages to improve human and animal welfare onboard. Implications The study results emphasised the importance of optimising ACH to maintain low air NH3 concentrations in livestock export conditions. Although there was no evidence that BAR affects air NH3 directly, it reduced pad NH4⁺ and improved pad conditions for overall animal comfort and environmental quality in confined housing with sufficient air changes.

Asparagopsis taxiformis (Asparagopsis) has been shown to be highly efficacious at inhibiting the production of methane (CH4) in ruminants. To date, Asparagopsis has been primarily produced as a dietary supplement by freeze-drying to retain the volatile bioactive compound bromoform (CHBr3) in the product. Steeping of Asparagopsis bioactive compounds into a vegetable oil carrier (Asp-Oil) is an alternative method of stabilizing Asparagopsis as 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 Asparagopsis derived CHBr3/kg dry matter intake (DMI), respectively (in addition to a zero CHBr3 canola 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 CH4 emissions 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 CH4 yield (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 CHBr3 in 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 CH4 emissions and yield by up to 99% within the range of inclusion levels tested.

The Biennial Conference of Recent Advances in Animal Nutrition – Australia was held on 27–28 July 2023. The special issue contains latest research in the field of animal nutrition across the most economically significant animal species, including poultry, pigs, sheep, cattle, companion animals and aquaculture.