PREDICTION OF THE VOLUNTARY INTAKE OF LOW-QUALITY ROUGHAGES BY SHEEP FROM CHEMICAL-COMPOSITION AND RUMINAL DEGRADATION CHARACTERISTICS

Six cereal straws and two traditional hays were used to study the rela tionship between voluntary dry matter (DM) intake and chemical composi tion and ruminal degradation characteristics. The voluntary DM intake was measured during 60 days using Barbarin adult ewes given food indiv idually 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 M(0.75) per day and 30 g per ewe per day of a commercial mixtu re of minerals and vitamins. The chemical composition and the leaf/ste m (LIS) ratio of forages were determined. Their ruminal degradation ch aracteristics were measured by using the nylon bag technique according to the exponenfini model Dg = a + b (1 - e(-ct)). Crude protein conte nts 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 voltintauy DM intake was highly variable and the hays w ere ingested at greater amounts than the straws, although their degrad able (b) and their rate of digestion (c) were not significantly differ ent (P > 0 . 05). Significant relationships were established between v oluntary DM intake and the neutral-detergent fibre (R(2) = -0 . 72; P < 0 . 001), acid-detergent fibre (R(2) = -0 . 75; P < 0 . 001) and a v alues (R(2) = 0 . 83; P < 0 . 001). The precision of the prediction wa s significantly improved using ruminal degradation characteristics (S- yx = 4 . 42)compared with the chemical composition (S-yx = 5 . 60).