Effect of selective consumption on voluntary intake and digestibility of sorghum (Sorghum bicolor L. Moench) stover, cowpea (Vigna unguiculata L. Walp.) and groundnut (Arachis hypogaea L.) haulms by sheep

Abstract

Three experiments with 12 animals each, were conducted to measure the effect of selective consumption on intake of organic matter (IOM), crude protein (CP) content and digestibility of ingested organic matter (DOM), and intake of digestible organic matter (IDOM) of sorghum (Sorghum bicolor L. Moench), stover (SS), cowpea (Vigna unguiculata Walp.) (CH) haulms and groundnut (Arachis hypogaea L.) haulms (GH) by sheep. On organic matter (OM) basis, SS contained 70.6% stems, 15.5% leaf sheaths, 6.5% leaf blades, 6.0% leaf central nerves and 1.4% ears; CH contained 64.2% stems and 35.8% leaves, and GH 50.1% stems and 49.9% leaves. Forages were not chopped and a wide range of feeding levels (amount of offered organic matter, OOM) was applied. The lowest and highest OOM (g kg ˇ0.75 per day) were: 30‐110 for SS, 37‐189 for CH and 30‐194 for GH. Maximum IOM values (estimated by non-linear regression analysis) were 47.3, 85.9 and 81.6 g kg ˇ0.75 per day for SS, CH and GH, respectively. Selective consumption of leaves caused significant increases in the CP content of ingested OM for CH and GH, and increased DOM for SS and CH. The amount of digestible OM for production (IDOM — maintenance requirements) per unit of feed OM offered (value for animal production (VAP)) was used as the criterion for optimum feeding levels. For CH and GH, the maximum value (VAPmax) (0.32 and 0.26, respectively) was reached at feeding levels of 96 and 91 g OM kg ˇ0.75 per day, respectively. At these levels of OOM, 80 and 84% of the offered OM was eaten. Corresponding IDOM values were 54.3 and 48.0 g kg ˇ0.75 per day. In the case of SS, a very high feeding level