Doreau M, Martin-Rosset W, Barlet J P
Reprod Nutr Dev (1980). 1981;21(1):1-17.
Twenty-one circadian blood sample profiles were made in heavy brood mares during pregnancy, lactation or the dry, non-pregnant period. The mares were fed forage-rich diets containing different levels of energy and nitrogen (table 1). Each profile consisted of 7 samples taken at 8 a.m., 11 a.m., 3 p.m., 7 p.m., 11 p.m., 4 a.m. and 8 a.m. The animals were fed at 8:30 a.m. The eleven plasma components evaluated were glucose, non-esterified fatty acids, beta-hydroxybutyrate, acetate, alanine, insulin (energy metabolites), urea, total protein (nitrogen metabolites), calcium, inorganic phosphorus and magnesium (mineral metabolites). Profile results are shown in table 2 and figure 1. Glucose, insulin and alanine increased and non-esterified fatty acids, acetate and beta-hydroxybutyrate decreased during the prandial period (between 8 a.m. and 11 a.m.). The glucose and insulin peaks were short, while the other components returned slowly to preprandial values. Acetate and beta-hydroxybutyrate were maximal during the night, while urea increased moderately during the prandial period. Protein concentration did not vary. The effect of feeding on minerals was moderate: there was a slight increase in calcium and magnesium and a decrease in phosphorus. The following differences were related to diet or physiological state (figs. 2, 3, 4): --higher glucose and insulin peaks when concentrate intake was high; --lower circadian variation of non-esterified fatty acids, beta-hydroxybutyrate and acetate in dry, non-pregnant, well-fed mares; --higher acetate levels with a high-forage diet; --more rapid alanine decrease during late pregnancy than in early lactation; --higher circadian variations in minerals during lactation than during pregnancy. The prandial variations of the following factors were significantly correlated (table 3): --glucose and insulin, --acetate and beta-hydroxybutyrate, --beta-hydroxybutyrate and non-esterified fatty acids, --acetate and non-esterified fatty acids. The origin of these variations is discussed. Two factors intervened: 1) exogenous production Very rapid digestion of the concentrate induced an increase in glucose (and thus in insulin) and alanine. The volatile fatty acids produced in the hindgut caused nocturnal peaks of acetate and beta-hydroxybutyrate; 2) a lipogenic phase (which began after mean meal intake) alternating with a lipolytic phase, providing constant coverage of the energy needs. This explains the large post-prandial decreases in non-esterified fatty acids, acetate and beta-hydroxybutyrate.
在妊娠、泌乳或非妊娠空怀期，对21匹高产母马进行了24小时血液样本采集。母马采食富含不同能量和氮水平的草料日粮（表1）。每次采样包括在上午8点、11点、下午3点、7点、晚上11点、凌晨4点和上午8点采集的7份样本。动物于上午8:30喂食。所评估的11种血浆成分包括葡萄糖、非酯化脂肪酸、β-羟丁酸、乙酸盐、丙氨酸、胰岛素（能量代谢产物）、尿素、总蛋白（氮代谢产物）、钙、无机磷和镁（矿物质代谢产物）。采样结果见表2和图1。在进食期间（上午8点至11点），葡萄糖、胰岛素和丙氨酸增加，而非酯化脂肪酸、乙酸盐和β-羟丁酸减少。葡萄糖和胰岛素峰值短暂，而其他成分则缓慢恢复到进食前水平。乙酸盐和β-羟丁酸在夜间达到最高水平，而尿素在进食期间适度增加。蛋白质浓度没有变化。进食对矿物质的影响适中：钙和镁略有增加，磷减少。以下差异与日粮或生理状态有关（图2、3、4）：——精料摄入量高时，葡萄糖和胰岛素峰值更高；——非妊娠空怀、采食良好的母马，非酯化脂肪酸、β-羟丁酸和乙酸盐的昼夜变化较小；——高草料日粮时乙酸盐水平更高；——妊娠后期丙氨酸的减少速度比泌乳早期更快；——泌乳期矿物质的昼夜变化比妊娠期更大。以下因素的进食期变化显著相关（表3）：——葡萄糖和胰岛素；——乙酸盐和β-羟丁酸；——β-羟丁酸和非酯化脂肪酸；——乙酸盐和非酯化脂肪酸。讨论了这些变化的来源。有两个因素起作用：1）外源性产生 精料的快速消化导致葡萄糖（进而胰岛素）和丙氨酸增加。后肠产生的挥发性脂肪酸导致乙酸盐和β-羟丁酸的夜间峰值；2）脂肪生成期（在平均进食后开始）与脂肪分解期交替，以持续满足能量需求。这解释了进食后非酯化脂肪酸、乙酸盐和β-羟丁酸的大幅减少。
