The effect of stocking rate on the performance of ewes and lambs on Italian ryegrass

Author: J.F. de Villiers, W.A. Botha and M.F. Smith
Year: 1993
Issue: 2
Volume: 23
Page: 43 - 50

Italian ryegrass was evaluated over four seasons at stocking rates (SR) of 20, 24, 28, 32 and 36 ewes with lambs/ha. During each of three seasons, between 19 and 24 ewes per SR were milked for 10 weeks, from three weeks post partum until the lambs were weaned at approximately 100 days of age. The ewes and lambs were kept on pasture for 12 weeks. An eight-camp rotational grazing system was applied with a fixed period of grazing of 3.5 days per camp. Ewes with twins lost between 2.2 and 15.7% and ewes with single lambs between 1.6 and 11.0% of live mass at the SR of 20 or 36 ewes with lambs/ha, respectively. SR exerted a significant (P 0.05) effect on lamb growth. At an SR of 20 ewes with lambs/ha, lambs gained mass 35% (single and twin lambs), 40% (twin lambs) and 29% (single lambs) faster than those at an SR of 36 ewes with lambs/ha. A highly significant (P 0.001) relationship was found between average daily gain and the post-grazing pasture height. The average weaning mass of lambs declined from 22.9 to 17.2 kg (P 0.05) at an SR of 20 or 36 ewes with lambs/ha, respectively. The relationship between lamb growth and milk production was strongest during the first 6 weeks on pasture. A multiple regression analysis showed that SR accounted for 22.5% (P 0.001), ewe mass 13.5% (P 0.001), mean milk production 12.1% (P 0.001), birth status 5.8% (P 0.001), ewe mass change 2.3% (P 0.01) and initial lamb mass 1.8% (P 0.05) of the variation in lamb growth.



Keywords: Average daily gain, ewe mass change, Italian ryegrass, milk production, stocking rate
Read article