Effect of stocking rate on pasture and sheep production in winter and spring lambing systems

Abstract

A 2-year study was conducted to quantify the effect of stocking rate on pasture and sheep production in winter and spring lambing systems. Pastures were set-stocked with ewes and their winter-born single lambs at low (20 ewes + lamb ha(-1)), medium (28 ewes + lamb ha(-1)), and high (36 ewes + lamb ha(-1)) stocking rates in spring 2012 and by ewes and their spring-born lambs at low (16 ewes + lamb ha(-1)), medium (24 ewes + lamb ha(-1)), and high (32 ewes + lamb ha(-1)) stocking rates in spring 2013. Annual pasture dry matter production ranged from 8.9 to 10.2 t ha(-1) but was not affected by the spring stocking rates. The average live weight gains of the winter-born lambs were 73 and 10 g head(-1) day(-1) for low and medium stocking rates, respectively, while the lambs at the high stocking rate lost 10 g head(-1) day(-1) in spring 2012. The spring-born lambs grew at 245, 189, and 133 g head(-1) day(-1) for low, medium, and high stocking rates, respectively, in spring 2013. High stocking rates did not have any negative effects on the pasture production or botanical composition but they resulted in poor sheep performance, particularly in the winter lambing system.