|Journal||Journal of Agricultural Science|
|Early online date||22 Jun 2015|
|Publication status||Published - 2015|
To investigate the extent to which enteric methane (CH4) emissions from growing lambs are explained by simple body weight and diet characteristics, a 2 × 2 Latin square changeover design experiment was carried out using two sheep breeds and two fresh pasture types. Weaned lambs of two contrasting breed types were used: Welsh Mountain (a small, hardy hill breed; WM) and Welsh Mule × Texel (prime lamb; TexX) (n = 8 per breed). The lambs were zero-grazed on material cut from recently reseeded perennial ryegrass and extensively managed permanent pasture. In each experimental period, individual ad libitum dry matter intake (DMI) was determined indoors following an adaptation period of two weeks, and CH4 emissions were measured individually in open-circuit respiration chambers over a period of 3 d. Although total daily CH4 emissions were lower for the WM lambs than for the TexX lambs (13.3 vs 15.7 g/d respectively; s.e.d. = 1.01; P < 0.05) when offered fresh forage, the yield of CH4 per unit DMI was similar for the two breed types (16.4 vs 17.7 g CH4/kg DMI; s.e.d. = 0.79; NS). Total output of CH4 per day was higher when lambs were offered ryegrass compared to permanent pasture (16.1 vs 12.9 g/d respectively; s.e.d. = 0.49; P < 0.001) which was likely driven by differences in DMI (986 vs 732 g/d; s.e.d. = 22.4; P < 0.001). Methane emissions per unit DMI (16.4 vs 17.7 g CH4/kg DMI; s.e.d. = 0.37; P < 0.01) and percentage of gross energy (GE) intake excreted as CH4 (5.2 % vs 5.6 %; s.e.d. = 0.11; P = 0.02) were both higher on the permanent pasture. No forage × breed type interactions were identified. The results indicate that forage type had a greater impact than breed type on CH4 emissions from growing weaned lambs. It can be concluded that when calculating CH4 emissions for inventory purposes, it is more important to know what forages growing lambs are consuming than to know what breeds they are.
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