Prediction of the voluntary intake of low quality roughages by sheep from chemical composition and ruminal degradation characteristics

Abstract

AbstractSix cereal straws and two traditional hays were used to study the relationship between voluntary dry matter (DM) intake and chemical composition and ruminal degradation characteristics. The voluntary DM intake was measured during 60 days using Barbarin adult ewes given food individually in four groups of six animals. The forages were offered to the ewes twice daily and were supplemented with 10 g DM of soya-bean meal per kg M0·75 per day and 30 g per ewe per day of a commercial mixture of minerals and vitamins. The chemical composition and the leaf/stem (L/S) ratio of the forages were determined. Their ruminal degradation characteristics were measured by using the nylon bag technique according to the exponential model Dg = a + b (1 – e−ct). Crude protein contents of straws ranged from 22 to 35 g/kg DM and that of hays from 35 to 57 g/kg DM. The corresponding values of L/S ratio varied from 0·68 to 0·88. The voluntary DM intake was highly variable and the hays were ingested at greater amounts than the straws, although their degradable (b) and their rate of digestion (c) were not significantly different (P > 0·05).Significant relationships were established between voluntary DM intake and the neutral-detergent fibre (R2 = −0·72; P < 0·001), acid-detergent fibre (R2 = −0·75; P < 0·001) and a values (R2 = 0·83; P < 0·001). The precision of the prediction was significantly improved using ruminal degradation characteristics (Syx = 4·42) compared with the chemical composition (Syx = 5·60).