Intake rate during meals and meal duration for sheep in different hunger states, grazing grass or white clover swards

Meal patterns and rates of feed intake by grazing herbivores may be markedl y different from those found in housed ruminants and monogastrics. Cumulati ve intakes over the evening meal (satiety curves) were measured using group s of sheep (Ovis aries L.) grazing monocultures of white clover (Trifolium repens L., cv. Kent Wild White) and ryegrass (Lolium perenne L., cv. Parcou r). Intake was measured by weighing ewes before and after grazing, with an allowance for insensible weight loss, for each of six groups in sequence; w hen grazing clover after 15, 30, 45, 60, 75 or > 90 min and when grazing gr ass after 20, 40, 60, 80, 100 and > 120 min. In each case, the sixth group was allowed to graze until a break of at least 6 min had occurred, which wa s taken to be an inter-meal as opposed to an intra-meal interval. Measureme nts were made on both herbage species using non-fasted control animals and animals that had been fasted for 24 h prior to measuring intake. Regression s of cumulative fresh and dry matter (DM) intakes against minutes of eating (excluding intra-meal intervals), constrained to pass through the origin, were best described by linear rather than curvilinear relationships. This s howed that:intake rates were constant within a meal. However, as the meal p rogressed, the number of intra-meal intervals increased and if these interv als were included in eating time, then the relationships were curvilinear w ith intake rate decreasing with time since the onset of the meal. The non-f asted animals had shorter meals than fasted animals and animals grazing clo ver had shorter meals than those grazing grass. The application of these re sults to intake control mechanisms is discussed. ((C) 2001 Elsevier Science B.V. All rights reserved.