Browsing by Browse by SEO 2020 "100101 Management of gaseous waste from animal production (excl. greenhouse gases)"

Ruminants are central to the economic and nutritional life of much of sub-Saharan Africa, but cattle are now blamed for having a disproportionately large negative environmental impact through emissions of greenhouse gas (GHG). However, the mechanism underlying excessive emissions occurring only on some farms is imperfectly understood. Reliable estimates of emissions themselves are frequently lacking due to a paucity of reliable data. Employing individual animal records obtained at regular farm visits, this study quantified farm-level emission intensities (EIs) of greenhouse gases of smallholder farms in three counties in Western Kenya. CP was chosen as the functional unit to capture the outputs of both milk and meat. The results showed that milk is responsible for 80-85% of total CP output. Farm EI ranged widely from 20 to >1 000 kg CO₂-eq/kg CP. Median EIs were 60 (Nandi), 71 (Bomet), and 90 (Nyando) kg CO₂-eq/kg. Although median EIs referenced to milk alone (2.3 kg CO₂-eq/kg milk) were almost twice that reported for Europe, up to 50% of farms had EIs comparable to the mean Pan-European EIs. Enteric methane (CH₄) contributed >95% of emissions and manure ~4%, with negligible emissions attributed to inputs to the production system. Collecting data from individual animals on smallholder farms enabled the demonstration of extremely heterogeneous EI status among similar geographical spaces and provides clear indicators on how low EI status may be achieved in these environments. Contrary to common belief, our data show that industrial-style intensification is not required to achieve low EI. Enteric CH₄ production overwhelmingly drives farm emissions in these systems and as this is strongly collinear with nutrition and intake, an effort will be required to achieve an "efficient frontier" between feed intake, productivity, and GHG emissions.

Australia is a major exporter of live animals, and around half a million sheep were exported in both 2021 and 2022. Countries of the Middle East represent the largest market demand for live Australian sheep, and most sheep exported to these destinations depart from Fremantle, WA, for a sea voyage that generally lasts between 14 to 21 days. In recent years, there has been extensive public concern regarding the welfare of animals, including sheep, on live export ships. The live export process is complex and involves various stages, including sourcing, handling, loading and the sea transport phase, which was the focus of the work described in this research. Specifically, this research investigated how sheep welfare is impacted by the quantity and quality of pen space during periods of intensive housing, such as what is experienced during live export voyages. An accumulated stressors approach was implemented to first investigate the impacts of stocking density severally, and then also in combination with restricted feed trough space, and then in combination with hot and humid conditions.

Chapter 3 of this thesis examined how the quantity of pen space (i.e., stocking density) and the quality of pen space with regards to feed trough space restriction, impact the welfare of intensively housed sheep in a land-based experiment conducted in thermoneutral conditions. The provision of additional pen space was beneficial in reducing the time taken for sheep to behaviourally adapt to their environment, and in facilitating the expression of some preferred lying positions. Despite this, a lack of important impacts on the stress physiology and biological fitness characteristics of the sheep was observed. Unlike pen space, the trough space allowances investigated here had no important effects on the behaviour, stress physiology or biological fitness characteristics.

Chapter 4 of this thesis built upon the findings from Chapter 3, to investigate the potential impacts of stocking density on the biological functioning and thermoregulation of sheep housed intensively on land, under continuously hot and humid conditions. The climatic conditions imposed were similar to what would be experienced by sheep travelling from Australia to the Middle East at certain times of the year that have been identified as problematic by the industry and the public, with regards to heat stress risk. Similar to the work described in Chapter 3, additional pen space facilitated the ability of sheep to lie in preferred positions, such as with legs outstretched from their body or in physical isolation from conspecifics in their pen, but the effects on stress physiology and biological fitness characteristics were limited. Stocking density did not have an effect on the thermoregulatory ability of the sheep, although results did indicate that the reliance on evaporative cooling through the respiratory tract may be reduced by providing more space at high temperatures. Importantly, individual variation and maximum rumen temperature and respiration rate values suggested that not all wethers were able to effectively regulate their core temperature under these conditions.

In chapter 5, the presence and consistency of individual differences in aggressive behaviours expressed by wethers in a competitive feeding environment was investigated. Sheep were provided with restricted feed trough space and fed a maintenance quantity of pelleted feed, and the results indicated that sheep that displayed more aggression were at an advantage for accessing feed faster and more frequently within each feeding period. As such, the attempts of individuals to cope with the competitive feeding environment were not equal.

This research provides evidence that while the provision of additional pen space may allow sheep to adapt to an intensive housing environment faster, and facilitates the expression of some lying positions, implications for stress physiology and the biological fitness of sheep are limited, at least under highly controlled experimental conditions. In addition, sheep do not have an equal ability to access feed in competitive feeding environments, so the provision of feed trough space which permits synchronous feeding, or an ad libitum quantity of feed are important for industries, such as during livestock export voyages, which feed sheep from troughs. This thesis also identified 5 clear recommendations for future research which continue to accumulate relevant stressors and build on the theories about stocking density reported here, so that potential interactions between stocking density and other relevant factors present during voyages can be explored.

Ammonia (NH₃) is a nitrogenous environmental pollutant that is associated with eutrophication and contamination of terrestrial ecosystems and can have detrimental impacts on human and livestock health. Livestock production is a significant contributor to global NH₃ emissions largely as a result of nitrogen losses from the breakdown of manure. Intensively housed livestock situations, such as exporting live animals, lead to increased concentration of manure and development of the manure pad through accumulation of faeces and urine. This increase in higher concentrations of NH₃ may also lead to health and welfare concerns of both humans and animals. Due to the complex interactions of factors contributing to the volatilsation of NH₃ from manure, NH₃ production in livestock operations is difficult to accurately predict with the various methods and modelling approaches currently utilised. Live export is an example of an intensively housed livestock industry where NH₃ production has the potential to impact health and welfare of humans and animals on board. Quantification of NH₃ using current methods is difficult in this industry due to highly variable conditions and limited understanding of how voyage conditions may affect NH₃ production. Methods to quantify NH₃ emissions from manure have some limitations in adoption and understanding of manure pad variables introduced directly by animals, such as disturbance. Use of in vitro methods rather than large scale animal experiments allows understanding of ammonia and testing of dose rates of ameliorates and also aligns with the animal ethics replace, reduce and refine.

The primary objectives of the current thesis were to develop an inexpensive, high throughput method of quantifying NH₃ in solution, and an in vitro method of quantifying NH₃ production from manure that would (1) evaluate the optimal microchamber design to quantify NH₃ production rates from manure; (2) quantify the effect of disturbance of manure on NH₃ production rates; (3) succeed as an alternative method of testing NH₃ production to reduce the need for, or better inform, large-scale animal experiments (4) successfully evaluate the effectiveness of mitigation techniques.

This thesis includes a review of the available literature and three experimental chapters addressing the development and use of the in vitro method and assessment of an available NH₃ mitigation technique. Findings and implications of this thesis include:

Development of a novel high-throughput plate-based analysis with a high degree of accuracy adapting the Berthelot method of quantifying NH₃-N in solution. Boric acid solution was shown to be an effective eluent for gas trap sampling of NH₃;

Successful development of a novel microchamber system. The microchamber design was evaluated and a standard size chosen for the following experiments. It is hypothesised interactions with pad surface areas and depth were dependent on variables facilitating mass transfer such as air flow and headspace. Microchamber results did not meet hypotheses, as (i) increasing microchamber manure surface area did not result in constant rates of NH₃/m² production, and (ii) increasing manure depth resulted in lower rates of NH₃/m² as opposed to a consistent production relative to surface area. The standard size chosen for the experiment on clinoptilolite (zeolite) was a surface area of 90mm diameter (SA₉₀) and manure depth of 30mm (D₃₀), based on less variation in results and ease of use;

Simulated animal movement through four repeated disturbances of cattle manure in micro-chambers every 90 minutes, resulted in increasing rates of NH₃ production (slope coefficients) with each disturbance over 480 min for all treatments. This suggests cattle movement may generate continual fluxes of NH₃ production from the manure over time;

The application of zeolite was successful in reducing NH₃ production from cattle manure. All treatments achieved an immediate and sustained reduction in NH₃ production over 21 hours. The minimum (1%) and maximum (10%) in-pad application rates resulted in a 32% to 70% reduction in NH₃ emissions over 21 hours, respectively.

Application of zeolite suspended in the microchamber headspace reduced the presence of gaseous NH₃ contamination in the air by 37% over 21 hours, similar to 1% zeolite applied in-pad over 21 hours.

Overall, the high-throughput plate-based methodology and microchamber system provided valuable insight into increasing fluxes of NH₃ volatilsation with disturbance and optimal application rates of zeolite to reduce NH₃ production. The aim of the microchamber design was to standardise headspace and air exchange rates in order to quantify the effect of increasing manure surface area and depth. The results demonstrated air flow dynamics are important and challenging factors when comparing these variables, however a standardised microchamber was successfully deployed to compare and determine an optimal application rate of zeolite for NH₃ reduction.