Determination of maintenance energy requirement and responses of dry ewes to dietary inclusion of lucerne versus concentrate meal

An accurate value for metabolizable energy (ME) requirement for maintenance (ME_m) is essential to enable sheep husbandry practice to reach its potential. The objectives of the study were to use calorimetry chamber data of dry ewes (Hu × thin-tail Han F1 crossbred) to develop updated ME_m, examine effects of substituting concentrate feed with lucerne hay on energy partitioning, and explore the relationships between energy utilization and fasting heat production (FHP). Data were collected from three experiments. In Exps. 1, 2a and 2b, lucerne hay was used to replace concentrates in three levels (0:40%, 15:25% and 30:10%), with diets containing 60% maize stover (Exp. 1), fresh rye forage (Exp. 2a) or dry rye forage (Exp. 2b). Within each experiment, diets were isoenergetic (digestible energy, DE) and isonitrogenous. Exp. 3 aimed at evaluating effects of three BW levels on nutrient utilization of dry ewes offered diets containing 60% maize stover, 15% lucerne hay and 25% concentrates. Energy metabolism data were measured using the respiration calorimeter chamber technique in all three experiments, followed by the measurement of FHP in Exps. 1, 2b and 3. The ME_m derived from the linear regression between energy balance (EB) and ME intake was 0.440 MJ/kg BW^0.75. The average FHP was 0.326 MJ/kg BW^0.75. The fasting metabolism, net energy requirement for maintenance (NE_m) and ME_m were estimated to be 0.336, 0.359 and 0.511 MJ/kg BW^0.75, respectively, through adjustment of FHP using fasting urinary energy output, activity allowance and efficiency of ME use for maintenance. The FHP was negatively correlated to EB/metabolic BW, ME/gross energy (GE), ME/DE, EB/GE intake and EB/ME intake, while positively correlated to HP/GE intake, HP/ME intake and CH₄-E/GE intake. Compared to zero lucerne hay diet, the 15% lucerne hay intake decreased HP (MJ/d), and had no negative effects on EB (MJ/d) or energy utilization efficiencies. The results indicate that nutrient requirement standards currently used across the world are likely to underestimate ME_m for dry ewes, and the selection of low FHP ewes for breeding has the potential to improve sheep production efficiency.     

Improving productivity reduces methane intensity but increases the net emissions of sheepmeat and wool enterprises

Greenhouse gas emissions from Western Australia’s sheep flock account for 26% of the state’s agricultural emissions, principally as a result of enteric methane emissions. A decrease in emissions between 2005 and 2019 can be partly explained by a 44% drop in sheep numbers over that period, but less is known about potential changes in the methane intensity of sheepmeat and wool kg CO₂ equivalents/kg product. Using the livestock systems modelling software GrassGro?, we assessed the changes in methane intensity of sheepmeat and wool produced in two major sheep-producing regions in Western Australia. We also evaluated a series of future scenarios. Our results demonstrate that the observed emissions reductions are largely a result of a decrease in flock size, although methane intensity has also decreased somewhat by 11.1%. Simulation of future trajectories indicates that methane intensity could be as much as 18.8% lower by 2030, compared to 2005, with further reductions of up to 42% considered possible. The primary driver of the decreased methane intensity to date is increased flock reproductive performance through increased marking rates, higher rates of ewe lamb mating, and lower ewe death rates. However, despite reductions in methane intensity per kg of product, net emissions per ewe have risen 11.6% since 2005 and are forecast to rise by up to 21.8% by 2030, with potential further increases of up to 61% considered possible. This is driven by increased feed intake due to an increased number of lambs produced per ewe, higher ewe standard reference weights, and lower ewe death rates. Therefore, achieving absolute net reductions in the methane emissions through productivity improvements is unlikely to be prospective. Reducing net emissions is instead likely to be contingent on a reduction in flock numbers, breakthroughs in anti-methanogenic research, or via emissions offsetting. Our approach can be applied in other major livestock producing regions to evaluate emissions performance, with potential implications for agricultural and trade policy as markets increasingly seek lower emissions product.     

DNA adducts in coal miners: association with exposures to diesel engine emissions

The potential carcinogenic effects of exposure to diesel engine emissions (DEE) are of growing concern. Due to the use of diesel equipment in underground mines, DNA adducts in peripheral blood mononuclear cells have been measured using the ³²P-postlabelling technique in workers from two coal mines (A, B)in NSW, Australia, before and after a period of more intense exposure (long wall change out, LWCO). DNA adducts were readily detected in all workers. At Mine A, in the 89 participants before LWCO, no significant difference was found among the groups categorized by exposure levels. However, significantly higher concentrations of total DNA adducts were observed in the specific job categories, ‘miners and loadmen’, and ‘machinemen, drivers and shiftmen’ and in the smoking group. On comparing total DNA adducts before and after LWCO in a small number of workers, a significant increase was also found. At Mine B, before or after LWCO, the total DNA adduct levels showed no significant difference among groups categorized by exposure conditions, smoking status, job categories and job time length. However, the total DNA adducts for the 61 subjects were significantly increased (geometric means) from 297 to 389 amol lg^?1 DNA after LWCO (p < 0.0001, paired t test). Some individual adducts were also elevated to a greater extent (p < 0.05, paired non-parametric test, Wilcoxon signed rank test). Furthermore, using generalized estimating equations for adjusting all factors across the observation period, no particular factor showed any significant interactive effects. Given the association of exposure to DEE with lung cancer and the apparent increase in adducts during a period of intense DEE exposures it would be prudent to pay particular attention to keeping exposures as low as possible, especially during LWCO operations.     

Applying the Technology Choice Model in Consequential Life Cycle Assessment: A Case Study in the Peruvian Agricultural Sector

Demand for grapes to produce pisco in southern‐coastal Peru is expected to double by 2030. However, the appellation of this beverage confines the production and limits the space for agricultural expansion, leading to a situation in which potential competition for resources with established constraints is foreseen. Hence, the objective of this study is to understand the environmental impacts, focused on climate change and water consumption, linked to the agricultural dynamism in the valleys of Ica and Pisco due to an increase in the demand of pisco. For this, the viticulture system was analyzed regarding predicted changes in terms of expansion, displacement or intensification using a consequential life cycle assessment (CLCA) approach, identifying the environmental consequences of these shifts. A two‐step CLCA model was used based on the results of a previous attributional study, in which marginal effects were estimated following the stochastic technology‐of‐choice model (STCM) operational framework. Results identified a potential for the increase of pisco production based on crop substitution in the valleys of Ica and Pisco and suggest that greenhouse gas emissions and water consumption will be reduced locally, but the displaced agricultural production would reverse this tendency. Regardless of the policy implications of the results in the analyzed system, the proposed methodology constitutes a robust methodology that can be applied to other highly constrained agricultural systems, namely, those regulated by geographic indications.     

The influence of consumer behavior on energy,greenhouse gas,and water footprints of showering

Understanding variability in consumer behavior can provide further insights into how to effectively reduce environmental footprints related to household activities. Here, we developed a stochastic model to quantify the energy, greenhouse gas (GHG), and water consumption footprints of showering in four different countries (Australia, Switzerland, the United Kingdom, and the United States of America). We assessed the influence of two broadly distinct categories of behavior on the footprints of showering: habitual behaviors and one‐off reasoned actions. We also investigated whether changing showering behavior has a substantial impact on the associated energy, GHG, and water footprints. Our results show that the variation in environmental footprints within the countries due to differences in consumer behavior is a factor of 6–17 (95th percentile/5th percentile) depending on the country and the indicator selected. Both consumers’ reasoned actions (especially the choice of a specific heater and shower type) and habitual behaviors (length of showering in particular, are the dominant sources of footprint variability. Significant savings are achievable by making better one‐off decisions such as buying an efficient water heater and by taking shorter showers.     

Impact of winter roads on boreal peatland carbon exchange

Across Canada's boreal forest, linear disturbances, including cutlines such as seismic lines and roads, crisscross the landscape to facilitate resource exploration and extraction; many of these linear disturbances cross peatland ecosystems. Changes in tree canopy cover and the compression of the peat by heavy equipment alter local thermal, hydrological, and ecological conditions, likely changing carbon exchange on the disturbance, and possibly in the adjacent peatland. We measured bulk density, water table, soil temperature, plant cover, and CO₂ and CH₄ flux along triplicate transects crossing a winter road through a wooded fen near Peace River, Alberta, Canada. Sample plots were located 1, 5, and 10 m from the road on both sides with an additional three plots on the road. Productivity of the overstory trees, when present, was also determined. The winter road had higher bulk density, shallower water table, higher graminoid cover, and thawed earlier than the adjacent peatland. Tree productivity and CO₂ flux varied between the plots, and there was no clear pattern in relation to distance from the road. The plots on the winter road acted as a greater CO₂ sink and greater CH₄ source compared to the adjacent peatland with plots on the winter road emitting on average (standard error) 479 (138) compared to 41 (10) mg CH₄ m^?2 day^?1 in the adjacent peatland. Considering both gases, global warming potential increased from 70 to 250 g CO₂e m^?2 year^?1 in the undisturbed area to 2100 g CO₂e m^?2 year^?1 on the winter road. Although carbon fluxes on any given cutline through peatland will vary depending on level of compaction, line width and vegetation community shifts, the large number of linear disturbances in Canada's boreal forest and slow recovery on peatland ecosites suggest they could represent an important anthropogenic greenhouse gas source.     

Pioneers of post-agricultural forest successions are adapted for herbivory avoidance but not biotic seed dispersal

Question

Natural reforestation is an important component of climate mitigation and adaptation, but the ecological processes promoting or constraining it are poorly understood. In this study we employ a stand reconstruction approach (which uses ages of extant trees to estimate year of establishment for each individual tree) to test for general trait-based effects on tree species arrival order in post-agricultural forest successions.

Location

Naturally reforesting post-agricultural landscapes throughout New Zealand.

Methods

Ages were obtained for 2434 individuals spanning 30 tree species across a nationwide network of 128 plots in 14 naturally reforesting post-agricultural sites. These ages were used to calculate individual-level arrival times (relative to the oldest individual in each plot). We estimated species-level arrival times by fitting linear mixed-effects (LME) regressions (with species identity as the fixed effect, and plots nested within sites as the random effects) to individual arrival time data. We used back-casting (where arrival time data are used to document individual-level presence in plots through time) to track annual changes in species abundance and community-weighted mean (CWM) trait values. We used standardised major axis (SMA) regressions to examine the effect of traits related to resource use strategy, herbivory avoidance, seed dispersal and disturbance response on species-level arrival times. We used LME regressions to test for changes in CWM trait values with stand age.

Results

The earliest-arriving species had traits associated with herbivory avoidance, were abiotically dispersed and had short predicted dispersal distances. There was no evidence that traits linked to resource use strategy or disturbance response affected species arrival times. Every significant species-level relationship was recovered in community-level LME analyses.

Conclusions

Our findings suggest that mammalian herbivore control and enhancement of biotic (bird) seed dispersal may be key management interventions in realising the full climate mitigation and adaptation potential of natural reforestation in post-agricultural landscapes.     

Distortion-product otoacoustic emissions from the tympanic organ in two noctuoid moths

Distortion-product otoacoustic emissions were measured from the tympanic organ of Ascalapha odorata (Noctuidae, Erebinae) and Empyreuma affinis (=pugione) (Arctiidae, Ctenuchinae) during stimulation with two pure tones of different frequency ( f1, f2) within a frequency range between 5 and 60 kHz. The cubic distortion-product that appears at a frequency of 2f1-f2 showed the largest amplitude and could be used to obtain “distortion audiograms”. In such audiograms, the maximal distortion-product otoacoustic emission levels were measured for stimulus frequencies that correspond to lowest A1-cell thresholds in each of the two species. Newly emerged E. affinis showed very low levels of the 2f1-f2 distortion, most of which were within the noise range. In contrast to vertebrate distortion-product otoacoustic emissions, in neither of the species could an optimum f2/f1 ratio be easily defined, and small ratios were sufficient to induce the distortions. We conclude that the ears of the two moth species exhibit distinctly non-linear mechanical properties. Distortion-product otoacoustic emissions are a good non-invasive method for studying the spectral response characteristics of the mechanics of their auditory organs, despite the fact that their morphological characteristics are very different from those in vertebrates. Accepted: 3 July 1998