Energy expenditure of splanchnic tissues and hindlimbs in growing lambs fed frozen rye-grass: effects of barley supplementation and changes between 2.5 and 7 months of age

Abstract

In order to study the effects of barley supplementation (Exp. 1), six lambs of 40 kg of body weight were fed on either rye-grass or rye-grass supplemented with barley according to a tripli- cate Latin Square design at an estimated level of 1.5 and 2.0 fold the maintenance energy require- ments. In order to study the effects of age (Exp. 2), 3, 6 and 5 lambs aged 2.5, 4 and 7 months old respectively were used. They were fed with rye-grass only at estimated levels of 1.8, 1.7 and 1.5 fold the maintenance energy requirements. All animals were equipped with chronic blood catheters in the mesenteric artery, portal, hepatic and external iliac veins and with ultrasonic blood flow probes around the portal vein and the external iliac artery. In Experiment 1, portal blood flows increased by 11.5% with supplementation (P < 0.05) while iliac blood flow tended to increase by 15% (NS). Con- sequently, O2 consumption increased by 20% (P < 0.03), 35% (P < 0.08) and 19% (NS) in the portal drained viscera, liver and hindlimb, respectively, with barley supplementation. In Experiment 2, por- tal blood flow, expressed on a metabolic body weight basis, decreased by 17% from 2.5 to 4 months of age and did not change from 4 to 7 months (P < 0.004). Iliac blood flow did not increase significantly between 2.5 and 7 months of age due to large inter-individual variability. No significant effect of age was noted on portal drained viscera and liver energy expenditure expressed on a metabolic body weight basis, while the hindlimb energy expenditure tended to increase (NS). It was concluded that in supplementing ryegrass with barley, the increment in splanchnic and carcass energy expenditure ac- counted for 30 and 26% of the increment of ME intake in finishing lambs and experimental results on organ and tissue energy expenditure obtained in ruminant lambs below 7 months of age may be applied to growing and finishing lambs.