Abstract

The effects of a supplemental oral drench of rumen-protected methionine (Mepron®) on wool growth and weight gain was studied in 2-3y non-mated Romney ewes during nine months from March to December. Three groups of 20 sheep received either 0, 4 or initially 8 (later 2) g of methionine daily. The ewes were rotationally grazed as a single mob on ryegrass-white clover pasture with winter restrictions. Pasture availability was monitored weekly. Mid-side wool samples were taken at two-monthly intervals and analysed for yield. Full fleece samples were collected during end of trial shearing and analysed for yield, fibre diameter, colour, staple length, crimp and style. Sheep were weighed weekly and herbage intakes estimated in August and November. Blood samples for plasma cysteine determinations were collected in June, August and November. There were no significant differences between the control and 4g/d groups in clean wool growth from mid-side patches (mean 1260 mg/cm²/d), greasy fleece weight (4.12kg) or final live-weights (63.1kg). Average estimates of pasture intake were non-significantly lower in supplemented sheep in August but approached significance in November (P<0.11). There were no treatment effects on wool growth rate or wool characteristics even though Mepron increased (P<0.05) plasma cysteine concentrations (umolar) (control 40.5 vs 4g/d 45.3) in June and in August (25.9 vs 31.1) but not in November. Weight-adjusted back-fats depths were lower in both supplemented groups compared to controls (P<0.05). We conclude that simple deficiencies in sulphur-containing amino acids were not limiting for wool production in these grazing sheep.

BJ, Purchas, GC Waghorn, and GA Wickham

Proceedings of the New Zealand Society of Animal Production, Volume 58, , 189-191, 1998