Feeding napier hay as supplement to sheep given poor quality natural pasture hay: effects of level of napier hay supplement and inclusion of urea in the basal diet on intake and digestibility

Three experiments were carried out using lambs to assess the effect of level of napier hay and urea supplements on the utilization of poor quality natural pasture (veld) hay. In all the experiments the lambs were given graded levels of napier hay as supplements to the basal diet of veld hay. In Experiment 1, the veld hay was not supplemented with urea; in Experiment 2, the veld hay was supplemented with 1% urea while in Experiment 3, the veld hay was supplemented with 1% or 2% urea. In all the experiments napier hay supplements increased total feed intake and in vivo digestibility of the diet (P < 0.05). High levels of napier supplementation tended to reduce the intake of veld hay below the level achieved on the unsupplemented control diet. However this decrease in veld hay intake was not as much as anticipated had the napier hay (corrected for its digestibility) simply replaced veld hay. Increasing the level of urea from 1 to 2% did not increase feed intake or digestibility or alter the pattern of substitution of veld hay by the napier. Across treatments, there was some evidence that the gain in the intake of veld hay resulting from napier supplementation was greater when urea was not added to the veld hay. In all the experiments, the increase in food intake was associated with an increase in faecal dry matter excretion suggesting that the increase in feed intake was facilitated by an increase in digesta passage rate. These results confirm that forage supplements are effective in increasing the utilization of poor quality forages and the response to the napier supplements was not entirely due to increasing nitrogen intake.