Now showing 1 - 10 of 12
  • Publication
    Use of Chemical and Biological Agents to Improve Water Quality of Effluent Discharge from Abattoirs
    (Asian-Australasian Association of Animal Production Societies, 2004) ;
    Murray, P J
    ;
    ;
    Al Jassim, R A M
    Intensive animal industries create large volumes of nutrient rich effluent which, if untreated, has the potential for substantial environmental degradation and to recover valuable nutrients that would otherwise be lost. Members of the family 'Lemnaceae' are widely used in lagoon systems, to achieve inexpensive and efficient remediation of effluent. Only limited research has been conducted into their growth in highly eutrophic media and there has been little done to systematically distinguish between different types of media. This study examined the growth characteristics of duckweed in abattoir effluent and explored possible ways of ameliorating the inhibitory factors to growth on this medium. A series of pot trials was conducted to test the tolerance of duckweed to abattoir effluent partially remediated by a sojourn in anaerobic fermentation ponds, both in its unmodified form and after the addition of acid to manipulate pH, and the addition of bentonite . Unmodified abattoir effluent was highly toxic to duckweed, even at dilutions of 3: 1. Duckweed remained viable and grew sub-optimally in simplified media with total ammonia nitrogen (TAN) concentrations of up to 100 mg/L. Duckweed grew vigorously in effluent diluted 1:4 v/v, containing 56 mg TAN /L when modified by addition of acid (to decrease pH to 7) and bentonite at 0.5%. The results of this study suggest that bentonite plays an important role in modifying the toxicity of abattoir effluent to duckweed.
  • Publication
    Selection for residual feed intake can change methane production by feedlot steers
    (2005) ;
    Herd, RM
    ;
    ;
    McCorkell, B
    ;
    Arthur, PF
    A 70-day residual feed intake (RFI) test on a barley-based feedlot ration was conducted, over which daily feed intake (FI) and weekly liveweight of 91 Angus steers were recorded. Rate of enteric methane production (MPR) was measured in a series of 5×2-day consecutive measurement periods using a marker-based method with the marker gas (SF₆) released from an intraruminal permeation device. Data for 76 steers with 3 or more valid 2-day methane collections were analysed. The 43 low. RFI (high efficiency) line steers (progeny of 9 sires) and the 24 high-RFI (low efficiency) line steers (5 sires) represented approximately 2.4 generations of divergent selection for postweaning RFI. An additional nine intermediate unselected line steers were included. MPR (g/day) was highly, significantly related to daily FI (kg/day) over the 10-day gas-collection period: MPR=13.0±3.0 (se) × FI+34.9, although FI (P<0.0001) explained only 20% of the variance in MPR. From this relationship MPR over the 10-week RFI test was predicted. MPR predicted for the low-RFI line steers was not significantly lower than for the high-RFI line steers (187±4 v 199±4 g/day; P>0.05). Regression analyses showed MPR to be significantly related to genetic variation in RFI (P<0.05), such that a 1 kg/day reduction in estimated breeding value for RFI would be accompanied by a 13.0±5.1 g/day, or 7%, reduction in methane production. This result supports predictions that reduction in methane emissions should accompany the reduction in FI following from selection for lower RFI.
  • Publication
    Intra-ruminal concentrations of SF6 from high release rate permeation tubes
    (University of New England, 2003) ;
    Hegarty, Roger
    ;
    Woodgate, RT
    Sulphur hexafluoride (SF₆) released from permeation tubes is used as a tracer gas for the estimation of ruminal methane emissions and (e.g . Ulyatt et al. 2002) there is usually a wait of seven days or longer after tube insertion to allow intra-rumina] SF₆ to plateau prior to sampling. Our theoretical calculations, however. suggested that intra-rumina] SF₆ would plateau within 2-3 h of permeation tube placement. Because permeation tubes being developed (Hegarty and Woodgate 2003) have release rates ~ I00 times higher than those used in previous studies they run for shorter periods, and the time available for calibration and achieving plateau is critical. Permeation tubes releasing an average of 170 mg SF₆/d (Hegarty and Woodgate 2003) were placed via rumen cannulae into two cows . Rumen gas was regularly sampled (900 ml) through the rumen cannulae over a 5 d period, collected in Tedlar gas sampling bags and immediately analysed for CH₄ and SF₆ concentrations.
  • Publication
    Cattle selected for lower residual feed intake have reduced daily methane production
    (American Society of Animal Science, 2007) ; ;
    Herd, RM
    ;
    McCorkell, B
    Seventy-six Angus steers chosen from breeding lines divergently selected for residual feed intake (RFI) were studied to quantify the relationship between RFI and the daily rate of methane production (MPR). A 70-d feeding test using a barley-based ration was conducted in which the voluntary DMI, feeding characteristics, and BW of steers were monitored. The estimated breeding value (EBV) for RFI (RFI'EBV') for each steer had been calculated from 70-d RFI tests conducted on its parents. Methane production rate ('g'/ d) was measured on each steer using SF⁶ as a tracer gas in a series of 10-d measurement periods. Daily DMI of steers was lower during the methane measurement period than when methane was not being measured (11.18 vs. 11.88 kg; P = 0.001).Asignificant relationship existed between MPR and RFI when RFI (RFI₁₅'d') was estimated over the 15 d when steers were harnessed for methane collection (MPR = 13.3 × RFI₁₅'d' + 179; r² = 0.12; P = 0.01). Animals expressing lower RFI had lower daily MPR. The relationship established between MPR and RFI₁₅'d' was used to calculate a reduction in daily methane emission of 13.38 g accompanied a 1 kg/d reduction in RFI'EBV' in cattle consuming ad libitum a diet of 12.1 MJ of ME/kg. The magnitude of this emission reduction was between that predicted on the basis of intake reduction alone (18 g.d⁻¹kg of DMI⁻¹) and that predicted by a model incorporating steer midtest BW and level of intake relative to maintenance (5 g.d⁻¹.kg of DMI⁻¹). Comparison of data from steers exhibiting the greatest (n = 10) and lowest (n = 10) RFI₁₅'d' showed the low RFI₁₅'d' group to not only have lower MPR (P = 0.017) but also reduced methane cost of growth (by 41.2g of CH₄/kg of ADG; P = 0.09). Although the opportunity to abate livestock MPR by selection against RFI seems great, RFI explained only a small proportion of the observed variation in MPR. A genotype × nutrition interaction can be anticipated, and the MPR:RFI'EBV' relationship will need to be defined over a range of diet types to account for this.
  • Publication
    Short-term validation of a rumen indwelling pH meter
    (University of New England, 2009) ;
    Woodgate, R
    Rumen acidosis, acute and sub-acute, is an ongoing bane of the dairy and feed-lot sectors, resulting in animal deaths, morbidity and diminished productivity (Owens et al., 1998). Major impediments to improving understanding of these conditions include the large range of animal responses observed under identical conditions (Schwartzkopf-Genswein et al., 2003) and the difficulty encountered in measuring rumen pH itself, which has historically required either rumen cannulation or oesophageal intubation, both of which are likely to affect animal behaviour.
  • Publication
    The persistence over time of divergent methane production in lot fed cattle
    Steers (12) previously screened using the SF₆ measurement technique and found to have either high or low methane yield (MY: gCH₄/MJ DEI) were re-tested on the same diet. Several steers changed their MY, but the group characteristic of High (1.3 g/MJ) or Low (0.8 g/MJ) MY persisted between the measurement periods as did differences in propionate concentration and protozoal density. This suggests that one or more innate animal attributes must affect MY. The need to consider intake variation of cattle in extrapolating short term measures of methane measurements to annual emission estimates was also highlighted.
  • Publication
    A Review on the Role of Duckweed in Nutrient Reclamation and as a Source of Animal Feed
    (Asian-Australasian Association of Animal Production Societies, 2003) ;
    Murray, P J
    The family of lemnacae colloquially known as duckweed contains the world's smallest species of flowering plants (macrophytes). Aquatic and free-floating, their most striking qualities are a capacity for explosive reproduction and an almost complete lack of fibrous material. They are widely used for reducing chemical loading in facultative sewage lagoons, but their greatest potential lies in their ability to produce large quantities of protein rich biomass, suitable for feeding to a wide range of animals, including fish, poultry and cattle. Despite these qualities there are numerous impediments to these plants being incorporated into western farming systems. Large genetically determined variations in growth in response to nutrients and climate, apparent anti-nutritional factors, concerns about sequestration of heavy metals and possible transference of pathogens raise questions about the safety and usefulness of these plants. A clear understanding of how to address and overcome these impediments needs to be developed before duckweed is widely accepted for nutrient reclamation and as a source of animal feed.
  • Publication
    Repeatability of methane production in cattle fed concentrate and forage diets
    (Polska Akademia Nauk, 2004) ;
    Eight Angus steers whose methane emissions had had been found to be higher or lower than predicted when fed a commercial feedlot diet were re-tested on a medium quality forage diet. Methane emissions were within published ranges (136.4 g d⁻¹), but differences in actual vs predicted production between high and low ranked animals were diminished and several animals changed in rankings. This suggests that methane emission characteristics may not persist over time, and that any selection of animals for low methane emission may need to be diet specific.
  • Publication
    Two hour chamber measurement provides a useful estimate of daily methane production in sheep
    (Wageningen Academic Publishers, 2009) ; ;
    In Australia and New Zealand, the significance of enteric methane (CH₄) production is greater than in many industrialised countries, due to large livestock numbers (AGO, 2005). Consequently, there is considerable interest in both countries in breeding livestock which produce relatively less CH₄ per unit of production, as a mitigation strategy. A necessary step in achieving this aim is acquiring the capacity to quickly and reliably estimate the daily methane production (DMP) of ruminants. Mechanistic models used to predict CH₄ production from animals (e.g. Blaxter and Clapperton, 1965) do not reflect differences that have been observed in individual animals on similar intakes (Goopy et al., 2006); 24 h calorimetry remains the only proven method for discerning these observed differences. Unfortunately, this is difficult, resource intensive, and impractical for screening large numbers of animals. Thus, there is considerable impetus to develop alternative methods which will facilitate estimation of OMP in large numbers of animals. This study assessed six (direct and derived) estimates of enteric methane production against 22 h open circuit calorimetry measurements (CHB₂₂) to determine if a reliable, but less demanding estimate of DMP could be found.
  • Publication
    In vitro ruminal VFA production is unaffected by the presence of sulphur hexafluoride
    (University of New England, 2003) ;
    Bird, SH
    ;
    Hegarty, Roger
    ;
    Since first proposed by Johnson et al. (1994), the sulphur hexafluoride (SF₆) tracer technique has been used to quantify ruminal methane emissions from both cattle and sheep. To make the SF₆ technique more robust, permeation tubes with higher release rates have been developed (Hegarty and Woodgate 2003). Although SF₆ is thought to be an inert and non-toxic marker gas, the higher release rates from the new capsules could invalidate this method of determining methane production if there is any effect on microbial metabolism. The intra-ruminal concentration of SF₆ after inserting capsules releasing 100-200 mg/d was from 1-35μl/l(Goopy et al. 2003). A study was made to determine whether SF₆ had any effect on microbial VFA production in the range of 1-100 μl/l.