Poster presentations (Monday)
Advances in Animal Biosciences
Introduction Many potential approaches for reducing methane (CH 4 ) emissions from cattle are at present under development. The promising ones will require verification of their efficacy at the production scale (e.g. paddock scale). We report an experiment to test whether a difference in CH 4 emissions between two grazing groups of cattle could be detected by 1) a micrometeorological technique using line-averaged concentrations up-and downwind of the cattle, and 2) by the sulfur hexafluoride
... 6 ) tracer-ratio technique. Material and Methods Two groups, of 30 one-year old Hereford x Friesian steers each, were formed with equal mean liveweight. In a flat uniform paddock composed predominantly of ryegrass (Lolium perenne), 32 rectangular strips were fenced, each 40 m by 25 m in size. Paired strips were allocated to the two groups on a daily basis, such that one group was always 65 m north of the other. First, for 6 days (Period 1) no treatment was applied, in order to test whether the emissions from the two groups were indistinguishable. For the following 10 days (Period 2), the grazing strip for the Northern group was sprayed with canola oil at a rate of 120 L ha −1 . This was expected to cause a reduction in CH 4 emissions, compared to the Southern group which did not receive any oil. For 3 days in Period 1 and for 4 days in Period 2, individual CH 4 emissions over 24 h from all steers were measured with the SF 6 tracer-ratio technique (Johnson et al., 1994). Group dry-matter intakes (DMI) were estimated from daily platemeter measurements before and after grazing. Individuals' DMI were estimated in Period 2, based on faecal outputs and invitro feed digestibility. Faecal output was estimated using titanium dioxide (TiO 2 ) as external faecal marker (Pinares-Patiño et al., 2008). CH 4 emission rates were tested for group effects with ANOVA. Concentrations of CH 4 in air were measured along lines parallel to the W and E fences of each rectangle, as 20-minute averages. For this, air was drawn into 44 m long perforated alkythene pipes mounted 0.7 m above ground, and from each of these four intake pipes via a switching manifold into a CH 4 analyser (DLT-100, Los Gatos Research, Mountain View, California, USA). The collective CH 4 emissions from each group were computed from downwind-upwind concentration differences, using a backward-Lagrangian stochastic model (WindTrax software, www.thunderbeachscientific.com; Flesch et al., 2004). Periods of unsuitable wind direction (outside ±40°of due W or due E), low wind speed or systematically turning direction were excluded from the analysis. The differences in CH 4 emissions between the groups, for each valid 20min run, were the input data for statistical analysis with a linear mixed-effects model, using days as the random effect. Results In Period 1 (no treatment), CH 4 emissions from the two groups did not differ, according to both the micrometeorological technique (Table 1 ) and the SF 6 technique ( Table 2 ). The groups' DMI did not differ, either. By contrast, in Period 2 both techniques showed significant differences (P < 0.01) for the CH 4 emissions. Mean emissions from the oil-treated group were obtained as 0.92 and 0.89 of those from the control group, with the micrometeorological technique and the SF 6 technique, respectively. The oil-treated group had a significantly higher DMI than the control group, 8.29 (±1.43) kg d −1 animal −1 versus 7.51 (±0.90) kg d −1 animal −1 , P = 0.02. Consequently, the mean CH 4 yield (emissions per DMI) of the oil-treated group was obtained as 0.83 and 0.80 of that of the control group with the micrometeorological and SF 6 techniques, respectively. Introduction Sheep production in the UK is stratified into systems that utilize smaller, hardier breeds in the hills, their crossbreds in the uplands, and heavier, more productive breeds and their crossbreds in the lowlands. This experiment tested the hypothesis that body mass and associated allometric relationships, rather than breed type, determines enteric methane production in sheep. Materials and methods Methane emission measurements were made on mature, barren ewes of four different breed types: Welsh Mountain (WMO), Scottish Blackface (SBF), Welsh Mule (WMU) and Texel (TEX) (n = 8 per breed). Data were collected during two separate experiments in which the animals were offered fresh herbage cut from: 1) an intensively managed perennial ryegrass sward (RG), and 2) a long-term permanent pasture (PP). A zero-grazing approach was chosen to minimise potential confounding of differences in enteric methane production with differences in grazing behaviour. The experimental procedure adopted was similar for both experiments. The ewes were initially housed in a group pen and offered the experimental diet. Following an initial adaptation period of at least three weeks they were transferred to individual pens for a further three days acclimatisation. The ewes were then individually housed in one of four calibrated methane chambers and data were collected for three consecutive days for each individual animal. Throughout the experiment the ewes were fed on an ad libitum basis, with two equal portions of feed offered at 0900 and 1600. Stored forage was kept refrigerated at approximately 4°C. Fresh water was available continuously. All experimental animals were drenched with an anthelmintic prior to each experiment commencing. The weights of feed offered and feed refused were recorded on a daily basis. Methane production was determined by comparing methane concentrations in air entering and leaving the chambers at a measured airflow. Live weight was measured prior to the sheep entering the methane chambers and again as they were removed. Pearson's correlation coefficients were used to explore relationships between body mass, herbage intake and methane emissions within each experiment. Analysis of variance was used to investigate breed differences for each forage type. Results A range of body weights was recorded across the four breed types (Table 1) . There was a relatively poor relationship between metabolic live weight (kg) and dry matter (DM) intake (g/d; r = 0.54 for RG, 0.30 for PP), and consequently body mass was a poor indicator of methane emissions (g/d; r = 0.40 for RG, 0.39 for PP). There was a stronger correlation between DM intake and methane emitted (r = 0.74 for RG, 0.81 for PP). These findings are in agreement with results from a separate experiment carried out with replacement ewes (Zhao et al, 2013) . Introduction Larger, faster-growing animals should partition relatively more nutrients into production, and therefore be more efficient. As a result the output of polluting excretion products on a per unit product basis would be expected to be lower for modern cattle breeds. In contrast, native cattle breeds are generally smaller and slower-maturing, but are perceived to have been bred under conditions that ensured they were hardy and able to survive in exposed conditions on nutritionally poor vegetation. Thus it is possible that physiological or behavioural differences may result in them utilising low quality rough grazing more efficiently than modern breeds. The aim of this study was to explore the extent to which breed might influence methane emissions from growing cattle grazing contrasting pasture types Materials and methods Methane emission values were established for steers of contrasting breed types, a modern, fastgrowing cross ((dairy × Belgian Blue) × Limousin) and a smaller and hardier traditional breed (Welsh Black). Separate experiments were conducted with groups of animals grazing contrasting pasture types: 1) intensively managed ryegrass, and 2) hill pasture. The 4.2 ha of monoculture perennial ryegrass that were grazed were located at 140 m a.s.l. near Aberystwyth, Wales. The hill pasture was located at 525 -550 m a.s.l. within the Cambrian Mountains and the vegetation within the 16 ha enclosure consisted of a mosaic of several community types. Around a third of the total area was made up of large patches of semi-improved pasture interspersed to varying degrees with rushes, with the remaining vegetation dominated by Molinia caerulea and rushes. Steers born March -May 2011 were selected for each experiment based on uniformity of age and within-breed live weight (n=9 per breed type for each experiment). Each experiment consisted of three phases: a two-week initial adaptation period, a six-week performance measurement period, and a two-week methane measurement period. During the performance measurement periods live weights were recorded weekly in order to establish individual growth rates. Methane emissions were subsequently estimated during 2 x 4-day sampling periods using the sulphur hexafluoride (SF 6 ) marker dilution technique, and averaged to give one value per animal. The results were analysed using analysis of variance. Results When grazing the ryegrass pasture the liveweight gain of the two breed types was similar, at around 1 kg/d, and there was no effect of breed type on the amount of methane emitted (Table 1 ). The growth rates of the two breed types were also statistically similar when they grazed the hill sward, with the growth rates on this pasture being substantially lower than those achieved on the ryegrass. When grazing the hill sward, methane emissions from the Limousin-cross steers were significantly higher than those from the Welsh Blacks. Introduction Enteric methane (CH 4 ) is one of the major greenhouse gases. The emissions of enteric CH 4 are closely related to rumen fermentation pattern. Chemical composition and ruminal degradation characteristics which differ between legumes and grasses and among common grass species may therefore influence rumen fermentation and thereby enteric CH 4 emission. The main objectives of this experiment were a) to investigate if there are differences in CH 4 emission among common used grass species and b) if legumes differ from grasses in CH 4 emissions. Material and methods The experiment was conducted as a Latin square design with four rumen fistulated lactating multiparous Red Norwegian dairy cows (631 ± 3.3 kg body weight, 118 ± 40.9 days in milk and 22.5 ± 2.7 kg milk/d) at start of the experiment. Each period consisted of three weeks, with the last week as a measurement-and sampling period. The cows were fed four silages: primary growth and second regrowth (1:1 ratio on DM basis) from 1) an organically managed two-year old ley with timothy and red clover (39% on DM basis), 2) organically managed long-term grassland with a high proportion of unsown species (six year old), 3) conventionally managed ley with perennial ryegrass and 4) conventionally managed ley with timothy. All roughages were harvested at the same date, pre-wilted to approximately 30% DM and ensiled in round bales applying an additive (GrasAAT N Lacto) at a rate of 4-5 L/ton fresh weight. The silages were fed at 90% of ad libitum intake, and were supplemented with a barley concentrate, constituting about 30% of the total feed intake. Enteric CH 4 emissions were measured over 5 d in each period using the sulphur hexafluoride tracer technique. Feed intake, milk yield and composition were also determined.