Effects of maize maturity at harvest and dietary proportion of maize silage on intake and performance of growing/finishing bulls

•We test maize and grass silage-based diets on intake and performance of growing bulls.•We examine changes in intake and performance due to maize maturity stage at harvest.•Maize silage promotes higher intakes of Metabolisable Energy in finishing bulls.•Maize maturity at harvest and maize silage ratio in diets do not affect DM intake.•Early harvested maize can affect positively carcass fatness and performance.

Whole-crop maize silage as forage in diets of finishing cattle can promote high intakes and thus, enhances animal performance. In the present study we evaluated the effect of whole-crop maize maturity at harvest and the proportion of maize-silage in diets of finishing bulls, on feed intake and performance. An indoor experiment with 64 dairy bulls was replicated over two consecutive rearing periods, under the same experimental design. Two groups of 4 light and two groups of 4 heavy bulls were randomly allocated into one of the 4 dietary treatments, which formed a 2×2 factorial arrangement of treatments, involving two maturity stages of maize at harvest (i.e. dough stage or dent stage) and two maize silage proportions (i.e. 100% maize silage or 50% maize and 50% grass silage). The diets were offered ad libitum as total mixed rations (TMRs) with inclusion of concentrates (i.e. rolled barley; dried distillers’ grain plus soluble; cold-pressed rapeseed cake) in a 40% proportion on DM basis. All animals were slaughtered at a target body weight of 630 kg. Bulls fed on diets containing maize silage as sole forage achieved higher live-weight gain (P<0.01) compared to their counterparts. This is likely due to the higher ME (P<0.01) and CP (P<0.001) intakes they achieved. Interestingly, the dough stage compared to dent stage maturity of maize at harvest tended to increase live-weight gain (P=0.06).