ENERGY AND PROTEIN VALUE OF COMBINATIONS OF MAIZE SILAGE AND RED-CLOVER HAY FOR RUMINANTS, USING ADULT SHEEP AS A MODEL

Four combinations of maize silage and artificially dried red clover we re fed consecutively to adult wether sheep ad libitum and at a level d esigned to maintain liveweight. On a dry matter (DM) basis, the diets contained silage and clover at ratios 1 : 0, 2 : 1, 1 : 2, and 0 : 1. A fifth diet contained maize silage plus urea (as 1% of the silage DM) . Energy, nitrogen (N), and carbon balances were measured at both feed ing levels and while fasting. The maize silage contained 11 g N and 41 1 g cell wall organic matter/kg DM; corresponding values for red clove r hay were 37 and 290 g. Energy and protein metabolisms were monitored on the 5 diets and were related to dietary N content. Feed intake and digestibility increased with the proportion of clover in the diet and , hence, with increasing dietary N content. Energy losses from methane and heat production did not differ among diets, whereas urine energy losses were smallest, and therefore, efficiencies of utilisation of me tabolisable energy (ME) greatest, on the silage-only and silage + urea diets. Greater urinary N losses on the diets of 1 : 2 silage : clover and clover-only led to lower N balances at the same apparently digest ed N intake on these 2 diets. There were positive associative effects between the silage and clover for voluntary feed consumption; digestib ilities of energy, N, and cell wall organic matter; and energy and N b alances. A ratio of ME to digestible energy of 0.81 underestimated the content of ME in silage by 0.5 MJ/kg DM, yet overestimated it in clov er by 0.4 MJ/kg DM. The ME value of the silage + urea diet (11.6 MJ/kg DM) was one of the highest reported in sheep for maize silage using i ndirect calorimetry.