Effects of maize crop maturity at harvest and dietary inclusion rate of maize silage on feed intake and performance in lambs fed high-concentrate diets

• Maize silage can replace grass silage to finishing lambs.
• Increased maize maturity at harvest did not increased ADG in lambs.
• Increased CP intake increased ADG in lambs.
• Increased dietary MP:ME ratio increased ADG in lambs.
• Increased ADG reduced MJ ME intake per kg ADG.

This study investigated the effects of maize maturity at harvest and dietary inclusion rate of maize silage on feed intake, average daily gain (ADG) and carcass traits of growing ram lambs fed high-concentrate diets. Precision-chopped maize was harvested at two stages of maturity (Early: dough stage and Late: dent stage) and ensiled as round bales. Early or late cut maize silage was fed as the sole forage or together with grass silage, to 40 ram lambs in each of two consecutive years. The four treatments in each year were: (1) early cut maize silage as 50% of the forage dry matter (DM) proportion (E50), (2) early cut maize silage as 100% of the forage DM proportion (E100), (3) late cut maize silage as 50% of the forage DM proportion (L50) and (4) late cut maize silage as 100% of the forage DM proportion (L100). The proportion of forage in each of the diets was on average 42% on a dry matter (DM) basis and the concentrate consisted of dried distillers’ grains plus solubles, rolled barley and cold-pressed rapeseed cake in year 1 (Y1) or heat-treated rapeseed expeller in year 2 (Y2). Daily DM intake (DMI) was 1.24 and 1.40 kg, averaged over treatments, in Y1 and Y2, respectively. Increasing the dietary inclusion rate of maize silage from 50 to 100% of the forage DM proportion resulted in increased DMI in Y1 (P<0.05) and increased carcass fatness in Y2 (P<0.01), whereas increased maturity stage at harvest tended to result in increased DMI in Y2 (P<0.10). Feed conversion ratio (FCR; kg DMI per kg ADG), was lower for the treatments E100 and L50 than for E50 and L100, respectively (P<0.01) in Y2. The body weight of the lambs increased linearly over time, in both years. In conclusion, maize silage can replace grass silage in the diets of high-producing lambs. Increased metabolizable protein (MP) to metabolizable energy (ME) ratio of the diet increased ADG of the lambs. Also, increased ADG decreased mega joule ME intake per kg ADG, in finishing lambs.