Villalba J J, Provenza F D, Hall J O, Peterson C
Department of Forest, Range and Wildlife Sciences, Utah State University, Logan 84322-5230, USA.
J Anim Sci. 2006 Aug;84(8):2213-23. doi: 10.2527/jas.2005-634.
We hypothesized that lambs discriminate the postingestive effects of P and associate those effects with feed flavor to modify feed choices. Three predictions were tested based on this hypothesis: 1) lambs will modify preference for arbitrary flavors eaten during intraruminal infusions of NaH2PO4, 2) changes in preferences are more specific than changes in osmotic load induced by salts of Na; and 3) preference for P is inversely related to the concentration of inorganic P in blood. Thirty lambs were depleted of P by the offer of a P-deficient diet, allocated to 3 groups (10 lambs/group), and conditioned during 3 periods as follows: During conditioning period 1, lambs in each of 3 groups ate a poorly nutritious feed (grape pomace), flavored differently for each group, while water was infused into the rumen. During conditioning periods 2 and 3, lambs again ate grape pomace, with 2 new flavors now paired with infusion of an aqueous solution (126 mmol) of NaCl (conditioning period 2) or NaH2PO4 (conditioning period 3), rather than with water. After conditioning, all lambs were offered a choice of the 3 flavors during preference tests immediately after conditioning (period 1) and every 3 wk thereafter (periods 2, 3, and 4). During period 1, when serum inorganic P levels were greatest, lambs preferred flavors paired with water > NaCl > NaH2PO4 (P < 0.05). During periods 2 and 3, as inorganic P concentrations decreased in serum, lambs preferred flavors paired with NaH2PO4 > NaCl (period 2, P = 0.10; period 3, P = 0.05). Lambs preferred flavors paired with water > NaH2PO4 in period 2 (P < 0.001), but those differences disappeared in periods 3 and 4 (P > 0.05). During period 4, lambs preferred flavors paired with NaCl > NaH2PO4 (P < 0.10). The estimate of the slope for the linear relationship between intake of flavors paired with NaH2PO4 and serum inorganic P was negative (P < 0.0001), whereas estimates of the slopes for the relationships between intake of flavors paired with NaCl or water and serum inorganic P were not different from 0. Thus, preference for P was inversely related to the concentration of serum inorganic P. Our results suggest lambs discriminated among the postingestive effects of NaH2PO4, NaCl, and water and associated those effects with specific flavors. Lambs avoided flavors paired with NaH2PO4 during periods of P replenishment, and they increased preference for those flavors during periods of P need.
我们假设羔羊能够辨别磷的食后效应，并将这些效应与饲料风味联系起来，从而改变饲料选择。基于这一假设，我们测试了三个预测：1）羔羊会改变对瘤胃内注入磷酸二氢钠期间所吃任意风味的偏好；2）偏好变化比钠的盐类所引起的渗透负荷变化更具特异性；3）对磷的偏好与血液中无机磷的浓度呈负相关。30只羔羊通过提供低磷日粮使其缺磷，分为3组（每组10只羔羊），并在3个阶段进行如下条件训练：在条件训练期1，3组中的每组羔羊都吃一种营养较差的饲料（葡萄渣），每组的风味不同，同时向瘤胃内注入水。在条件训练期2和3，羔羊再次吃葡萄渣，此时两种新风味分别与氯化钠水溶液（126 mmol，条件训练期2）或磷酸二氢钠水溶液（条件训练期3）注入配对，而不是与水配对。条件训练后，在条件训练后立即（阶段1）以及此后每3周（阶段2、3和4）的偏好测试中，所有羔羊都可以选择这3种风味。在阶段1，当血清无机磷水平最高时，羔羊对与水配对的风味的偏好 > 氯化钠 > 磷酸二氢钠（P < 0.05）。在阶段2和3，随着血清中无机磷浓度的降低，羔羊对与磷酸二氢钠配对的风味的偏好 > 氯化钠（阶段2，P = 0.10；阶段3，P = 0.05）。在阶段2，羔羊对与水配对的风味的偏好 > 磷酸二氢钠（P < 0.001），但在阶段3和4这些差异消失了（P > 0.05）。在阶段4，羔羊对与氯化钠配对的风味的偏好 > 磷酸二氢钠（P < 0.10）。与磷酸二氢钠配对的风味摄入量与血清无机磷之间线性关系的斜率估计为负（P < 0.0001），而与氯化钠或水配对的风味摄入量与血清无机磷之间关系的斜率估计与0无差异。因此，对磷的偏好与血清无机磷浓度呈负相关。我们的结果表明，羔羊能够区分磷酸二氢钠、氯化钠和水的食后效应，并将这些效应与特定风味联系起来。在磷补充期间，羔羊避免选择与磷酸二氢钠配对的风味，而在需要磷的期间，它们对这些风味的偏好增加。
