Intake and production of ewes grazing oat stubble supplemented with sweet lupin (Lupinus albus) seed
Oat stubble was grazed continuously during the summer and autumn (December-April) for 154 days by reproducing ewes (n = 48) and rumen fistulated wethers (n = 12) at a stocking rate of 2.4 sheep ha-1. The stubble was supplemented with 0, 200, 400 and 600 g sweet lupin seed per sheep day-1 during the last 6 weeks of pregnancy and the first 5-6 weeks of lactation. An average of 1787 kg DM ha-1 with a mean CP content of 71 g kg-1 and DOM content of 501 g kg-1 was available during the experimental period. A deficiency in CP content of the pasture was indicated by low rumen ammonia-N levels of wethers (3.7-3.9 mg per 100 ml), which progressively increased (P < 0.05) by 3.2 mg per 100 ml (SEb = 0.6; R2 = 0.94) for each 100 g of supplement provided (OM basis). Organic matter intake of ewes from pasture per se during late pregnancy (1063 ± 86 g per ewe day-1) and during lactation (1015 ± 150 g per ewe day-1) declined (P < 0.05) by 42 g day-1 for each 100 g of supplement provided on an OM basis. Sweet lupin supplementation at 400 g day-1 fulfilled requirements for DOM and CP during late pregnancy. During lactation a deficiency in DOM and CP still occurred at a supplementation level of 600 g day-1. The BW loss of ewes during the first 6 weeks of lactation was reduced (P < 0.05) by 2.0% (SEb = 0.5; R2 = 0.91) for each 100 g increase in supplementary feed per day provided on an OM basis. No significant differences between supplementary groups were observed in terms of lamb birth weight, the lamb growth rate up to 42 days of age or in ewe wool growth rate. This was probably due to the high degradability of lupin seed. © 1997 Elsevier Science B.V.