Early D M, Provenza F D
Department of Rangeland Resources, Utah State University, Logan 84322-5230, USA.
J Anim Sci. 1998 Mar;76(3):728-34. doi: 10.2527/1998.763728x.
We addressed two questions involving food preference. First, we determined how a food's flavor and nutritional characteristics affected preference. In three trials, we offered lambs isonitrogenous foods differing in energy (trial 1, 90% TDN; trial 2, 100% TDN; trial 3, 110% TDN); each food was offered in apple and maple flavors. We hypothesized that preference for apple- or maple-flavored food would decrease with increasing duration of exposure (1, 2, or 4 d), and we speculated that the change in preference would intensify when food contained inadequate or excessive levels of energy. After eating food in one flavor, lambs preferred the alternative flavor, even after only a 1-d exposure, and preference for the alternative flavor was greater when the food had inadequate or excessive energy (P < .05). The second experiment determined whether eating a food with rapidly or slowly digestible sources of energy in the morning affected lambs' food preferences in the evening. We speculated that lambs fed rapidly digestible food in the morning may prefer a slowly digestible food in the afternoon because slowly digestible food better maintains nutrient status throughout the night or because preference for the rapidly digestible food decreases after exposure in the morning. We offered lambs isonitrogenous and isocaloric foods, that differed in rates of digestion, in apple and maple flavors. Lambs fed rapidly digestible food in the morning preferred slowly digestible food in the alternative flavor in the evening. However, lambs fed slowly digestible food in either flavor in the morning preferred slowly digestible food in both flavors in the evening (P < .05). These results show that lambs' preferences change as a result of food ingestion, and the degree of change in preference depends on the nutritional characteristics of the food. These findings further suggest food intake might be increased by providing a variety of foods to livestock on rangelands, pastures, or in confinement.
我们研究了两个与食物偏好有关的问题。首先，我们确定了食物的风味和营养特性如何影响偏好。在三项试验中，我们给羔羊提供了能量不同但含氮量相同的食物（试验1，90%总可消化养分；试验2，100%总可消化养分；试验3，110%总可消化养分）；每种食物都有苹果味和枫糖味。我们假设，随着接触时间的增加（1天、2天或4天），对苹果味或枫糖味食物的偏好会降低，并且我们推测，当食物能量水平不足或过高时，偏好的变化会加剧。在食用了一种风味的食物后，羔羊更喜欢另一种风味，即使只接触了1天，并且当食物能量不足或过高时，对另一种风味的偏好更强（P < 0.05）。第二项实验确定了早上食用能量消化速度快或慢的食物是否会影响羔羊晚上的食物偏好。我们推测，早上喂食易消化食物的羔羊下午可能更喜欢难消化的食物，因为难消化的食物能在整个晚上更好地维持营养状态，或者因为早上接触易消化食物后对其偏好会降低。我们给羔羊提供了含氮量和热量相同但消化速度不同的苹果味和枫糖味食物。早上喂食易消化食物的羔羊晚上更喜欢另一种风味的难消化食物。然而，早上喂食任何一种风味难消化食物的羔羊晚上都更喜欢两种风味的难消化食物（P < 0.05）。这些结果表明，羔羊的偏好会因食物摄入而改变，偏好变化的程度取决于食物的营养特性。这些发现进一步表明，通过在牧场、草地或圈养环境中为家畜提供多种食物，可能会增加采食量。
