C.S. Pinares-Patiño

Effects of intensification of pastoral farming on greenhouse gas emissions in New Zealand

Abstract In 2007, greenhouse gas (GHG) emissions in New Zealand were 16% higher than in 1990. Agriculture accounts for 48% of GHG emissions in New Zealand, and 10–12% of emissions in most other ‘developed’ countries. Methane (CH4) accounts for 35% of GHG emissions in New Zealand, mostly from ruminal fermentation. Nitrous oxide (N2O) accounts for 17% of GHG emissions in New Zealand, mostly from urinary N, exacerbated by excessive application of nitrogenous fertiliser. GHG are often expressed as carbon dioxide equivalents (CO2-e), and 1 kg CH4 has a similar global-warming potential as 21 kg CO2, whilst 1 kg N2O has the same warming potential as 310 kg CO2. Methane is derived from H2 produced during ruminal fermentation, and losses account for 6–7% of gross energy in feeds. This is about 9–10% of metabolisable energy intake. Methane production tends to be lower when legumes, rather than grasses, are fed, and emissions are greater (per kg dry matter intake; DMI) when mature grasses and silages are fed. There are small differences between individual animals in their CH4 production (g/kg DMI) but there are few profitable options available for reducing CH4 production in ruminants. Emissions of N2O can be reduced by more strategic application of nitrogenous fertiliser, avoidance of waterlogged areas, and use of dicyandiamide in some cooler regions. GHG mitigation should be based on life-cycle analyses to ensure a reduction in one GHG does not increase another. Current and future strategies are unlikely to reduce GHG emissions by >20%. Food production is central to human survival, and should not be compromised to mitigate GHG emissions. Efforts should be directed toward increasing animal efficiency and reducing GHG emissions/unit edible food.

Methane emissions and digestive physiology of non-lactating dairy cows fed pasture forage

The objective of this study was to identify intake and digestion characteristic(s) responsible for variation in methane (CH4) emissions from non-lactating cows fed pasture forage. Nine Friesian × Jersey cows ranked low, medium or high CH4 emitters [group means 15.3, 19.2 and 24.8 g kg-1 dry matter intake (DMI), respectively; P = 0.015] were selected from a herd of 302 lactating cows. The selected cows were dried-off, rumen-fistulated, and fed indoors on fresh pasture forage at 0700 and 1700. Voluntary feed intake (VFI), feeding behaviour and intake rates (IR) were measured over 5 d. Feed allowance was reduced to 90% of VFI for measurement of CH4 emissions and rumen fermentation and digestion kinetics parameters. Although some variation in CH4 yield remained among the animals (26.4 ± 3.6 g kg-1 DMI), the previous ranking of cows during lactation was no longer evident during this study (P = 0.41). The change in CH4 yields may have resulted from lower feed intakes of lower quality pasture compared with grazi...

The SF6 tracer technique for measurements of methane emission from cattle – effect of tracer permeation rate

Previous experiments have suggested that estimates of methane (CH4) emissions from ruminant animals made using the sulphur hexafluoride (SF6) tracer might be influenced by the permeation rate of SF6 (PR). This study examined the latter issue with cattle. For this, analyses of data sets from two grazing trials involving large herds (exps. 1 and 2) and a specifically designed controlled trial (exp. 3) were conducted. Individual daily CH4 emissions from 296 (exp. 1) and 388 (exp. 2) Friesian × Jersey cows in mid-lactation were measured with herds subdivided into four (exp. 1) or five (exp. 2) measurement groups and dry matter intake (DMI) estimated by energy metabolism algorithms. The ranges of tracer PR in exps. 1 and 2 were 2.624–5.689 and 2.214–3.594 mg d-1, respectively. Experiment 3 was conducted using 12 rumen-fistulated beef steers pen-fed on lucerne silage and design arranged as a 4 × 4 Latin square with three replications. Permeation tubes with four levels of nominal PR (three tubes each): low (L), ...

The possible influence of intra-ruminal sulphur hexafluoride release rates on calculated methane emissions from cattle

Estimates of methane (CH4) production from grazing animals are routinely made using the sulphur hexafluoride (SF6) tracer technique. While this technique is generally regarded as useful, some investigators report a higher variability in measurements when compared with calorimetry. The SF6 technique is a marker dilution method in which a known release rate of SF6 from an intra-ruminal permeation tube is used to calculate CH4 emissions from the ratio of SF6:CH4 in expired breath. The release rate of SF6 is unique for each tube, and although calculated CH4 emissions should be independent of SF6 release rate, an analysis of research conducted in New Zealand has suggested a possible influence of SF6 release rate upon calculated CH4 emissions. A modified cross-over design, with two groups of six steers given either one (2.878 mg SF6 d-1) or two (7.336 mg SF6 d-1) permeation tubes and offered either energy maintenance (M) or 2 × M levels of feed intake was undertaken to determine the effect of SF6 release rate a...

Methane emissions from dairy cattle divergently selected for bloat susceptibility

Bloat susceptibility is a genetically inherited trait and this study explored whether cattle divergently selected for this trait (low or high bloat susceptibility) also differ in methane (CH4) emissions. Twelve low bloat (402 ± 12 kg liveweight, LW) and 12 high bloat (334 ± 13 kg LW) Friesian × Jersey mixed age (2–4 years old) non-lactating and non-pregnant female cattle were used in a late autumn (June) grazing experiment involving two periods (P1 and P2). Methane emissions were measured during 5 (P1) or 4 (P2) consecutive days using the sulfur hexafluoride (SF6) tracer technique. In P1 only, titanium dioxide (TiO2) was used for faecal output and feed dry matter intake (DMI) estimations and it was found that the selection lines did not differ in DMI per unit of LW (17.3 ± 1.3 v. 15.4 ± 1.3 g DMI/kg LW, P > 0.05; for low and high bloat cows, respectively). In both periods, the mean absolute CH4 emissions from low bloat cows were significantly higher (P   0.05) either at P1 (346 ± 16 v. 312 ± 11 mg/kg LW) or P2 (345 ± 11 v. 347 ± 10 mg/kg LW). In P1, when DMI was estimated using TiO2, the selection lines did not differ (P > 0.05) in CH4 yields per unit of intake (20.6 ± 0.8 v. 21.3 ± 1.4 g/kg DMI for low and high bloat, respectively). Previous studies with the same herd showed that the selection lines did not differ in DMI per unit of LW, which was confirmed by the present study from estimations of DMI by TiO2 dosing in P1. It is concluded that low and high bloat susceptible genotypes did not differ in their CH4 yields per unit of feed intake.