Wool growth in Merino wethers fed lupins untreated or treated with heat or formaldehyde, with and without a supplementation of rumen protected methionine

Lupins were treated by either heat (1158C for 1 h) or by formaldehyde (0.4 g 100 gÿ1 crude protein). The fractional rate of disappearance of N from dacron bags suspended in the rumen of steers was reduced by either treatment. Assuming a rumen outflow rate of 0.03 hÿ1, effective rumen degradability was 0.96, 0.94 and 0.92 for protein and 0.84, 0.82 and 0.81 for dry matter in untreated, heatand formaldehyde-treated lupins. Concentration of acid detergent insoluble nitrogen in lupins was not enhanced by treatment. A 3 2 factorial experiment was performed with Merino wethers to study the effect of treating lupins on wool growth and body weight gain on a feeding level slightly above maintenance. Factors were lupin treatment (untreated, heatand formaldehyde-treated) and supplementation of a rumen protected methionine (3 g methionine per day, yes or no). The diet contained (kgÿ1) 620 g chaffed oaten hay, 350 g broken lupins and 30 g mineral premix and was supplied once daily to sheep at a level of 900 g per day air dry or approximately 8 MJ per day ME. Seventy-two sheep were fed the diet containing untreated lupins without methionine supplementation during a 4 week pretreatment period and were subsequently allocated to one out of the six treatments according to pretreatment wool growth rate (n ˆ 12 sheep per treatment). Treatment lasted for 8 weeks. Comparative clean wool growth rate was determined on mid-side patches of approximately 100 cm shorn in 4 weekintervals. Faeces and urine were collected for 7 days at the end of the experiment with six sheep per treatment. Both body weight gain and clean wool growth were not significantly effected by either treatment of lupins. Supplementation of rumen protected methionine significantly increased both body weight gain (by 27%) and clean wool growth. The effect of supplementary rumen protected methionine on clean wool growth was twice as high in sheep fed either heator formaldehydeAnimal Feed Science and Technology