The effect of stage of maturity in sheep upon intake and digestion of roughage diets

Abstract

In two experiments, weaner (15-17 kg liveweight) and mature (40-45 kg) Merino wethers were fed ad libitum on three chopped hays of varying quality. Measurements were made of intake and digestion of organic matter (OM) and cell wall content (CWC), retention time of a digesta marker, and the particle size distribution of CWC recovered in the faeces. When offered subterranean clover hay (OM digestibility 70 %) the weaners consumed 19 % more OM (g/kg0.75) than did the mature wethers, but the digestibilities of OM and CWC were similar for each age group. Possible reasons for this variation in intake are discussed. Intake and digestion of OM and CWC were similar for both groups given the two poorer hay diets (OMD, 56 and 46 %), but several weaners could not be sustained for long periods on the poorer of the two diets. Implications for young sheep grazing dry pastures are discussed.