The Influence of Varied Cellulose and Nitrogen Levels upon Ration Digestibility and Nitrogen Balance of Lambs Fed Semipurified Rations

Abstract

Lambs were fed semipurified rations containing one of three levels of cellulose (21.4, 31.4 or 41.6%) and one of three nitrogen levels (1.65, 2.05 or 2.45%). Cellulose and nitrogen levels were varied by substituting a purified source of cellulose and protein for cornstarch. Increasing the cellulose levels significantly and linearly increased cellulose and ether extract digestibility; decreased the digestibility of organic matter, nitrogen-free extract and reduced percentage of total digestible nutrients, and was without significant effect upon the apparent nitrogen digestibility. Increasing nitrogen levels significantly and quadratically influenced the digestibility of organic matter, cellulose, nitrogen-free extract, nitrogen and the percentage of total digestible nutrients. The digestibility of nitrogen was not further increased by increasing ration nitrogen from 2.05 to 2.45%; the digestibility of the other nutrients in rations containing 2% of nitrogen was significantly higher than in rations containing either 1.65 or 2.45% of nitrogen. The influence of cellulose upon the digestibility of organic matter in semipurified rations was shown to be due both to its diluting effect (upon easily digestible components) and to its depressive effect upon the digestibility of non-cellulose organic matter. This depressive effect is approximately one-fourth that reported for natural type rations. This is interpreted as supporting the “envelopment” concept of depressed nutrient digestibilities with increasing cellulose concentration. Increased cellulose levels significantly increased daily urinary nitrogen and decreased daily nitrogen balances.