Some factors associated with the difference in nutritive value of artificially dried red clover and perennial ryegrass for sheep

Abstract

1. Three sheep fitted with duodenal re-entrant cannulas and three with large rumen fistulas were given red clover, perennial ryegrass and a 2:1 (w/w) mixture of grass and clover in two Latin square arrangements. Measurements were made of voluntary intake, digestibility, flow of nutrients into the duodenum and the flow of Cr-EDTA marker through the reticulo-rumen.2. Organic matter (OM) digestibility was similar for the three feeds but the voluntary intake decreased in the order mixture > red clover > perennial ryegrass. There was an increase in the rate of marker flow from the rumen and a decrease in retention time of the same order. Rumen volume did not change significantly.3. There was a reduction in the mean particle size of rumen contents in the order perennial ryegrass > clover > mixture. The in vitro digestibility of particles decreased with size; the reduction being more rapid for clover than perennial ryegrass.4. The proportion of ingested digestible OM appearing at the duodenum increased from 18.4% to 26.7% to 30.0% for perennial ryegrass, clover and the mixture respectively.5. A higher proportion of digestible cellulose and hemicellulose disappeared over the stomach for the perennial ryegrass feed compared to the clover and the mixture but over 96% of water soluble carbohydrates and starch disappeared over the stomach for all three feeds.6. The apparent digestibility of nitrogen was similar for all three feeds but the proportion of undigested feed N appearing at the duodenum was calculated to be greater by a factor of 1.71 and 2.52 for clover and mixture feeds compared to grass.7. It was concluded that the higher nutritive value of red clover compared to perennial ryegrass was due to an increased rate of flow of nutrients througth the reticulo-rumen and an increase in the proportion of digestible OM digested post ruminally.