Effects of chopping grass silage and of mixing silage with concentrate on feed intake and performance in pregnant and lactating ewes and in growing lambs

Abstract

The effects of chopping grass silage and of mixing grass silage with concentrate on feed intake and performance in pregnant and lactating ewes, and in growing lambs were studied in two experiments (Exp. 1 and Exp. 2). The three experimental diets used in both experiments were: (1) unchopped grass silage and 0.8kg/d concentrate, fed separately (US); (2) chopped grass silage and 0.8kg/d concentrate, fed separately (CS); and (3) chopped grass silage mixed with concentrate to the same forage:concentrate ratio as in the CS treatment (CM). Twin bearing/suckling ewes (n=7 per treatment) were individually penned and individually fed during the experiments. The lambs were penned and fed in twin pairs after weaning. The silages used in Experiments 1 and 2 contained 583 and 353g dry matter (DM) per kg, and 10.9 and 11.4MJ ME, 139 and 193g CP, and 580 and 483g NDF per kg DM, respectively. In Exp. 1, daily DM intake (DMI) by ewes and LWG of lambs were unaffected by chopping silage or mixing silage and concentrate (P>0.05). In Exp. 2, the daily DMI by lactating ewes was 0.6kg higher in the mixed diet compared with the separate diets (4.4 vs. 3.8kg; P<0.05). Suckling lambs on the chopped diets in Exp. 2, had 38g higher daily live weight gain (LWG) than those on the unchopped diet (424 vs. 386g; P<0.05), whereas suckling lambs on the mixed diet had 63g higher daily LWG than those on the separate diets (454 vs. 391g; P<0.001) resulting in 11 days younger age at slaughter (P<0.01). Weaned lambs fed the chopped diets in Exp. 2, had 71g higher daily LWG than those on the unchopped diets (444 vs. 373g; P<0.01) resulting in 9 days younger age at slaughter (P<0.05). Averaged over treatments, the daily silage DMI of ewes increased from 1.9 to 2.8kg in Exp. 1 and from 2.0 to 3.3kg in Exp. 2 from late pregnancy to lactation. It was concluded that chopping highly digestible grass silage and mixing it with concentrate can increase the DMI of ewes and improve the performance of their lambs.