COMPARATIVE DIETARY PREFERENCES, NUTRIENT UTILIZATION, AND RUMEN FUNCTION IN SHEEP AND GOATS RECEIVING FORAGE DIETS (RUMINANT)

Dietary preferences, nutrient utilization, and rumen function were compared between grazing sheep and goats. Marginal land, which included 60% open fields and 40% wooded areas was grazed by esophageally fistulated sheep and goats. Among more than 50 plant species available only 23 were detected in the animal diets, and only 8 made significant contributions. Goats exhibited a greater preference for shrubs and trees than sheep. Legumes contributed up to 29% and 5% of the sheep and goat diets, respectively. Nitrogen content of the diet ranged from 1.47% to 2.53% and in vitro digestibility from 44% to 53%; both were generally higher for sheep than for goats. Using internal and external indicators, two year mean organic matter intake and digestibility values were 58.1 g/W kg ('.75) and 60.1% for sheep and 45.9 g/W kg('.75) and 58.4% for goats. The ratio technique gave higher digestibility values than those derived from in vitro digestion. Digestibilities determined with acid insoluble ash were more closely related to the in vitro technique than lignin and insoluble silica.;Because minimal overlap in dietary preference exists between sheep and goats, mixed species pastures can be optimally managed by cograzing these animals. No inherently superior digestive ability exists between these animal species.;High and low quality timothy hays were fed to rumencannulated sheep and goats at either 75% or 95% of previously measured ad libitum intake. Digestibility of dry matter, crude protein, NDF and ADF were higher for high quality hay but did not differ between the two animal species. Using fecal concentration curves of Cr-EDTA and ytterbium, a mathematical model was used to describe turnover rate from the reticulo-rumen (3.6 and 3.5 %/hr for sheep and goats, respectively), cecum and proximal colon (8.0 and 8.4 %/hr) and transit time (16.1 and 24.2 hr). Mean values of rumen fluid pH, ammonia (mg/100 ml), osmolality (mOsm/1), total VFA (mg/100 ml), rumen fluid volume (1), dilution rate (%/hour) and outflow rate (1/d) were 6.69, 7.48, 230.4, 72.7, 10.5, 6.42 and 16.09 for sheep, respectively. Respective values for goats were 6.61, 7.99, 238.9, 63.3, 8.22, 6.15 and 12.31.