Dynamics of digestion in cattle, sheep, goats and deer

Four experiments were conducted to study factors affecting digestibility of forages in cattle, sheep, goats and white-tailed deer. In a series of digestion trials (Exp. 1), the dry matter digestibility of a moderately high fiber diet was greater in cattle than in deer. Digestibilities of the diet in sheep and goats were intermediate and not different from either extreme. In a second series of trials (Exp. 2), relative organic matter digestibilities were for goats more than sheep more than deer. However, in Exp. 2, intake in goats was very low and digestibility appeared to be positively related to retention time and inversely related to turnover rate. Results of three trials (Exp. 3) suggested that rate of digestion was related more to diet than to the animal species consuming the diet. In grazing animals (Exp. 4), goats digested a smaller percentage of consumed material than either cows or sheep during three of four seasons even though diets were of similar in vitro digestibility. This difference was related to a faster turnover and shorter retention time in goats. These data support the concept that there are species differences in gastrointestinal dynamics which may be which may be important determinants of adaptability to grazing conditions.