Scott LL, Provenza FD
Department of Rangeland Resources, Utah State University 84322-5230, Logan, UT, USA
Appl Anim Behav Sci. 2000 Jul 1;68(4):293-305. doi: 10.1016/s0168-1591(00)00096-4.
Ruminants eat a variety of foods from different locations in the environment. While water, cover, social interactions, and predators are all likely to influence choice of foraging location, differences in macronutrient content among forages may also cause ruminants to forage in different locations even during a meal. We hypothesized that lambs forage at locations containing foods that complement their basal diet and meet their nutritional needs. Based on this hypothesis, we predicted that lambs (n=12) fed a basal diet low in protein and high in energy would forage where a high-protein food (Food P) was located, and that lambs (n=12) fed a basal diet low in energy and high in protein would forage where a high-energy food (Food E) was located. Food P was a ground mixture of blood meal (50%), grape pomace (30%), and alfalfa (20%) that contained 47% crude protein (CP) and 2.211 Mcal/kg digestible energy (DE). Food E was a ground mixture of cornstarch (50%), grape pomace (30%), and rolled barley (20%) that contained 6% CP and 3.07 Mcal/kg DE. Food P provided 212 g CP/Mcal DE, whereas Food E provided 20 g CP/Mcal DE. Lambs growing at a moderate rate require 179 g CP and 3.95 Mcal DE. During Trial 1, we determined if lambs foraged to correct a nutrient imbalance, and if they preferred a variety of foods (Foods P and E) to only one food at a location (Food P or E). During Trial 2, we determined if nutrient-imbalanced lambs foraged in the location with the food that corrected the imbalance when the location of the foods changed daily. During Trial 3, lambs were offered familiar foods (Foods P and E) at the location furthest - and novel foods (wheat and soybean meal) at the location nearest - the shelter of their pen. During all three trials, lambs foraged most at the location with the food that contained the highest concentration of the macronutrient lacking in their basal diet, but they always ate some of both foods. Lambs did not feed exclusively at the location with a variety of foods (P and E). Rather, they fed at the location nearest the shelter that contained the macronutrient lacking in their diet. As availability of the food with the needed macronutrient declined in one location, lambs moved to the nearest location that had food with the needed macronutrient. When food that complemented their basal diet was moved to a different location, lambs foraged in the new location. Collectively, these results show that lambs challenged by imbalances in energy or protein selected foods and foraging locations that complemented the nutrient content of their macronutrient imbalanced basal diets.
反刍动物会食用来自环境中不同地点的各种食物。虽然水、遮蔽物、社交互动和捕食者都可能影响觅食地点的选择，但即使在同一餐中，不同草料间的宏量营养素含量差异也可能导致反刍动物在不同地点觅食。我们假设羔羊会在含有能补充其基础日粮并满足其营养需求的食物的地点觅食。基于这一假设，我们预测，喂食低蛋白、高能量基础日粮的羔羊（n = 12）会在高蛋白食物（食物P）所在的地点觅食，而喂食低能量、高蛋白基础日粮的羔羊（n = 12）会在高能量食物（食物E）所在的地点觅食。食物P是由血粉（50%）、葡萄渣（30%）和苜蓿（20%）混合而成的地面饲料，含有47%的粗蛋白（CP）和2.211兆卡/千克的可消化能量（DE）。食物E是由玉米淀粉（50%）、葡萄渣（30%）和轧制大麦（20%）混合而成的地面饲料，含有6%的CP和3.07兆卡/千克的DE。食物P每兆卡DE提供212克CP，而食物E每兆卡DE提供20克CP。以中等速度生长的羔羊需要179克CP和3.95兆卡DE。在试验1中，我们确定羔羊是否通过觅食来纠正营养失衡，以及它们是否更喜欢多种食物（食物P和E），而不是某一地点的单一食物（食物P或E）。在试验2中，我们确定当食物的位置每天变化时，营养失衡的羔羊是否会在能纠正失衡的食物所在的位置觅食。在试验3中，在离羊栏遮蔽物最远的位置给羔羊提供熟悉的食物（食物P和E），在离遮蔽物最近的位置给它们提供新食物（小麦和豆粕）。在所有这三项试验中，羔羊大多在含有其基础日粮中缺乏的宏量营养素浓度最高的食物所在的位置觅食，但它们两种食物都会吃一些。羔羊并非只在有多种食物（P和E）的位置进食。相反，它们在离遮蔽物最近且含有其日粮中缺乏的宏量营养素的位置进食。当一个位置中含有所需宏量营养素的食物供应减少时，羔羊会转移到最近的有所需宏量营养素食物的位置。当补充其基础日粮的食物被转移到不同位置时，羔羊会在新位置觅食。总体而言，这些结果表明，受到能量或蛋白质失衡挑战的羔羊会选择能补充其宏量营养素失衡基础日粮营养成分的食物和觅食地点。
