Studies on the diet of grazing animal. III. The effect of pasture species and pasture structure on the herbage intake of sheep

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Abstract
The digestible organic matter intake (DOMI) of 35-kg year-old Merino wethers was studied on seven pasture types. For each pasture type a range of pasture conditions was used. Relations between DOMI and in vitro diet digestibility (D), total dry matter per acre (TDM), green dry matter per acre (GDM), mean leaf length of green herbage (LL), and number of leaves per unit area (LN) were investigated by multiple regression analyses. In general where there was a limited range of TDM, this variable and D were the major contributors to variation in DOMI. This pattern was associated with a low GDM/TDM ratio, and ability to select herbage high in D was important. Over a wider range of TDM, D was replaced by GDM or LL as a major contributor to variation in DOMI. Variations in this general pattern are discussed. Not only is the DOMI of grazing sheep influenced to different degrees by different pasture characteristics in different situations but the relations differ for different classes of sheep. Analysis of simple relations between DOMI and TDM shows different asymptotes on one pasture type for different classes of sheep.