Abstract
Ruminant livestock turn forages and poor-quality feeds into human edible products, but enteric methane (CH4) emissions from ruminants are a significant contributor to greenhouse gases (GHGs) and hence to climate change. Despite the predominance of pasture-based beef production systems in many parts of Europe there are little data available regarding enteric CH4 emissions from free-ranging grazing cattle. It is possible that differences in physiology or behaviour could influence comparative emissions intensities for traditional and modern breed types depending on the nutritional characteristics of the herbage grazed. This study investigated the role of breed type in influencing CH4 emissions from growing beef steers managed on contrasting grasslands typical of intensive (lowland) and extensive (upland) production systems. Using the SF6 dilution technique CH4 emissions were estimated for a modern, fast-growing crossbred (Limousin cross) and a smaller and hardier native breed (Welsh Black) when grazing lowland perennial ryegrass (high nutritional density, low sward heterogeneity) and semi-improved upland pasture (low/medium nutritional density, high sward heterogeneity). Live-weight gain was substantially lower for steers on the upland system compared to the lowland system (0.31 vs. 1.04 kg d−1; s.e.d. = 0.085 kg d−1; P<0.001), leading to significant differences in estimated dry matter intakes (8.0 vs. 11.1 kg DM d−1 for upland and lowland respectively; s.e.d. = 0.68 kg DM d−1; P<0.001). While emissions per unit feed intake were similar for the lowland and upland systems, CH4 emissions per unit of live-weight gain (LWG) were substantially higher when the steers grazed the poorer quality hill pasture (760 vs 214 g kg−1 LWG; s.e.d. = 133.5 g kg−1 LWG; P<0.001). Overall any effects of breed type were relatively small relative to the combined influence of pasture type and location.
Highlights
The world faces unprecedented challenges with regards to food security for future populations [1]
While beef makes up around 20% of the total meat produced and consumed in the UK, beef cattle account for 27% of the greenhouse gases (GHGs) emissions from UK livestock species [3]
The current study addressed this deficiency, and tested for the first time the role of breed type in influencing CH4 emissions from growing beef cattle when pastured on contrasting pasture types representative of intensive and extensive grazing systems
Summary
The world faces unprecedented challenges with regards to food security for future populations [1]. Ruminant livestock turn forages and poor-quality feeds into human edible products, but there is an inevitable environmental cost in terms of excretion of pollutants [2,3,4]. The output of polluting excretion products on a per unit product basis should be less for modern cattle breeds than traditional British cattle breeds, which are generally smaller and slower-maturing. The latter have frequently been bred under conditions that required them to be hardy and able to survive in exposed conditions on nutritionally poor vegetation [5]. There is a perception that such breeds have an important role to play in terms of maintaining cultural landscapes [5]
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