Grape marc and maize cobs in heavy lamb diets

The effect of the introduction into mixed diets of grape marc (GM) or maize cobs (MC) in partial or total substitution for lucerne hay was evaluated in 2 experiments with heavy Bergamasca lambs. The diets were pelleted and contained 40% (DM basis) concentrate and 60% hay and/or by product: GM(0), GM(30) and GM(60) first experiment and MC(0), MC(30) and MC(60) in the second. For each diet, the voluntary intake and live weight gain were measured with 3 lambs, initially 2 months old, over a period of 50 d. Digestibility was measured by intake/excretion balance in 4 4-month-old lambs. The digestibility of the dry matter (DM), organic matter (OM), gross energy (GE), crude protein (CP) and NDF in diets GM(0), GM(30) and GM(60) decreased (P < 0.05) with the increasing percentage of grape marc. Generally smaller and non-significant differences were observed in the second experiment, but in diets MC(30) and MC(60) the digestibility of GE was lower (P < 0.05) than in MC(0). In both trials there was a modest non-significant negative digestive interaction between the hay and the by-product. The maximum DM intake was recorded in diets containing both luceme and the by-products: 147 g/LW(0.75) for the GM(30) diet and 139 g/LW(0.75) for the MC(30) diet. The GM(60) diet produced a lower daily gain than the GM(0), diet (-98 g/d), while GM(30) had an intermediate gain. In the MC diets the best result was obtained with the MC(30) diet (70 g/d higher than MC(0)).