Research Unit Nutritional Physiology Oskar Kellner, Leibniz Institute for Farm Animal Biology (FBN), Wilhelm-Stahl-Allee 2, 18196 Dummerstorf, Germany.
J Dairy Sci. 2013 Feb;96(2):971-80. doi: 10.3168/jds.2012-5727. Epub 2012 Dec 6.
In addition to plasma metabolites and hormones participating as humoral signals in the control of feed intake, oxidative metabolic processes in peripheral organs also generate signals to terminate feeding. Although the degree of oxidation over longer periods is relatively constant, recent work suggests that the periprandial pattern of fuel oxidation is involved in regulating feeding behavior in the bovine. However, the association between periprandial oxidative metabolism and feed intake of dairy cows has not yet been studied. Therefore, the aim of this study was to elucidate possible associations existing between single feed intake events and whole-body net fat and net carbohydrate oxidation as well as their relation to plasma metabolite concentrations. To this end, 4 late-lactating cows equipped with jugular catheters were kept in respiratory chambers with continuous and simultaneous recording of gas exchange and feed intake. Animals were fed ad libitum (AL) for 24h and then feed restricted (RE) to 50% of the previous AL intake for a further 24h. Blood samples were collected hourly to analyze β-hydroxybutyrate (BHBA), glucose, nonesterified fatty acids (NEFA), insulin, and acylated ghrelin concentrations. Cross-correlation analysis revealed an offset ranging between 30 and 42 min between the maximum of a feed intake event and the lowest level of postprandial net fat oxidation (FOX(net)) and the maximum level of postprandial net carbohydrate oxidation (COX(net)), respectively. During the AL period, FOX(net) did not increase above -0.2g/min, whereas COX(net) did not decrease below 6g/min before the start of the next feed intake event. A strong inverse cross-correlation was obtained between COX(net) and plasma glucose concentration. Direct cross-correlations were observed between COXnet and insulin, between heat production and BHBA, between insulin and glucose, and between BHBA and ghrelin. We found no cross-correlation between FOX(net) and NEFA. During RE, FOX(net) increased with an exponential slope, exceeded the threshold of -0.2g/min as indicated by increasing plasma NEFA concentrations, and approached a maximum rate of 0.1g/min, whereas COX(net) decayed in an exponential manner, approaching a minimal COX(net) rate of about 2.5 g/min in all cows. Our novel findings suggest that, in late-lactating cows, postprandial increases in metabolic oxidative processes seem to signal suppression of feed intake, whereas preprandially an accelerated FOX(net) rate and a decelerated COX(net) rate initiate feed intake.
除了血浆代谢物和激素作为体液信号参与采食调控外，外周组织的氧化代谢过程也会产生终止采食的信号。虽然在较长时间内的氧化程度相对稳定，但最近的研究表明，围饲期间的燃料氧化模式与奶牛的采食行为有关。然而，奶牛围饲期间的氧化代谢与采食量之间的关系尚未得到研究。因此，本研究旨在阐明单次采食事件与全身净脂肪和净碳水化合物氧化之间可能存在的关联，以及它们与血浆代谢物浓度的关系。为此，我们对 4 头泌乳后期奶牛进行了研究，这些奶牛均配备了颈静脉导管，在呼吸室中连续同步记录气体交换和采食量。动物进行自由采食（AL）24 小时，然后进行采食限制（RE）至之前 AL 采食量的 50%，再持续 24 小时。每小时采集血液样本以分析 β-羟丁酸（BHBA）、葡萄糖、非酯化脂肪酸（NEFA）、胰岛素和酰化 ghrelin 浓度。互相关分析显示，采食事件的最大时间与餐后净脂肪氧化（FOX(net)）和餐后净碳水化合物氧化（COX(net)）的最低水平之间存在 30-42 分钟的偏移。在 AL 期间，FOX(net) 不会增加到 -0.2g/min 以上，而 COX(net) 不会在开始下一次采食事件之前降低到 6g/min 以下。COX(net) 与血浆葡萄糖浓度之间存在强烈的负交叉相关。还观察到 COXnet 与胰岛素、产热与 BHBA、胰岛素与葡萄糖以及 BHBA 与 ghrelin 之间的直接交叉相关。我们没有发现 FOX(net) 与 NEFA 之间的交叉相关。在 RE 期间，FOX(net) 呈指数增长，随着血浆 NEFA 浓度的增加超过 -0.2g/min 的阈值，并且接近 0.1g/min 的最大速率，而 COX(net) 呈指数衰减，接近所有奶牛的最小 COX(net) 速率约为 2.5g/min。我们的新发现表明，在泌乳后期奶牛中，餐后氧化代谢过程的增加似乎会发出抑制采食的信号，而在采食前，加速 FOX(net) 速率和减速 COX(net) 速率会引发采食。
