Napier or groundnut hay as supplements in diets of sheep consuming poor quality natural pasture-hay 2. Effect on intake and rumen digesta kinetics

Abstract

Three experiments, each of a 5 × 5 Latin square design, were carried out using sheep to assess the effect of supplementing poor quality natural pasture (veld) hay with graded levels of napier or groundnut hay on feed intake, rumen fermentation, digesta pool size and passage rate. In experiment 1, napier hay was fed at 0 g day −1 , 100 g day −1 , 200 g day −1 , 300 g day −1 or ad libitum. In experiment 2 the same levels of feeding were used with groundnut hay, while in experiment 3, napier and groundnut hay were each fed at 0 g day −1 , 150 g day −1 or 300 g day −1 to enable a direct comparison of the two supplemental forages. All the forages used were chopped to a particle size of about 1 cm prior to feeding. The veld hay was supplemented with 1% urea and was always offered ad libitum. The forage supplements were fed separately. In all the experiments, the forage supplements increased total feed intake, digestibility and concentration of ammonia and volatile fatty acids in the rumen. Incubation of veld hay in the rumen of sheep given napier and groundnut hay as supplements or as sole feeds, showed no effect on degradation pattern including rate of degradation. Rumen digesta pool size was not altered, but fractional outflow rate was increased by supplementation. The increase in feed intake was therefore largely facilitated by an increase in digesta passage rate.