Kennedy K M, Kuhla B
Research Institute for Farm Animal Biology (FBN), Institute of Nutritional Physiology "Oskar Kellner," Wilhelm-Stahl-Allee 2, Dummerstorf, 18196, Germany.
Research Institute for Farm Animal Biology (FBN), Institute of Nutritional Physiology "Oskar Kellner," Wilhelm-Stahl-Allee 2, Dummerstorf, 18196, Germany.
J Dairy Sci. 2023 Apr;106(4):2933-2947. doi: 10.3168/jds.2022-22330. Epub 2023 Feb 22.
Understanding nutrient utilization and partitioning is essential for advancing the efficiency of dairy cattle. Our objective was to determine if dairy cows exposed to a 24-h fasting period differ in heat production (HP) and macronutrient oxidation at different stages of lactation. Twelve primiparous, lactating German Holstein dairy cows were used in a longitudinal study design spanning from 2013 to 2014. Dairy cows were housed in respiration chambers during 3 stages of the lactation cycle: early (mean ± SD; 28.8 ± 6.42 d), mid- (89.4 ± 4.52 d), and late (293 ± 7.76 d) lactation. Individual CO, O, and CH gas exchanges were measured every 6 min for two 24-h periods, an ad libitum period and fasting period (RES). Blood was sampled at the start and end of the RES period. Gas measurements were used to calculate HP, net carbohydrate oxidation (COX), and net fat oxidation (FOX). Measurements were corrected with metabolic BW (kg of BW; cBW). The RES period for each stage of lactation was further subdivided into the start (RES) and end (RES) by averaging the first and last 2 h of the RES period. The net change was calculated as RES - RES. All energy variables differed among lactation stage within the RES period except for HP/cBW. As expected, COX, COX/cBW, COX/HP, HP, and HP/cBW, were greater at the RES compared with RES, whereas FOX, FOX/cBW, and FOX/HP were greater at the RES except for FOX and FOX/cBW during mid lactation, which was only a tendency for a difference. The net change for COX, COX/cBW, HP, HP/cBW, and FOX/cBW did not differ among stages of lactation. Despite detecting a tendency for a difference among stage of lactation for FOX, pairwise analysis revealed no differences. Plasma triglyceride, urea, and nonesterified fatty acid concentrations were greater at RES than RES. The net change for plasma glucose, urea, β-hydroxybutyrate, and nonesterified fatty acid concentrations were greater in early than late lactation. Our results demonstrate that despite differences in absolute measurements of energy variables and plasma metabolites, the change in whole-body macronutrient oxidation and HP as cows' transition from a fed-like state to a starvation-like state during a 24-h fasting period is consistent throughout lactation.
了解营养物质的利用和分配对于提高奶牛生产效率至关重要。我们的目标是确定经历24小时禁食期的奶牛在泌乳不同阶段的产热（HP）和常量营养素氧化是否存在差异。在2013年至2014年的纵向研究设计中，使用了12头初产泌乳德国荷斯坦奶牛。在泌乳周期的三个阶段，奶牛被安置在呼吸室内：泌乳早期（平均值±标准差；28.8±6.42天）、中期（89.4±4.52天）和晚期（293±7.76天）。在两个24小时时间段内，每6分钟测量一次个体的CO、O和CH气体交换，一个自由采食期和禁食期（RES）。在RES期开始和结束时采集血液样本。气体测量用于计算HP、净碳水化合物氧化（COX）和净脂肪氧化（FOX）。测量值用代谢体重（体重千克数；cBW）进行校正。泌乳各阶段的RES期通过平均RES期的前2小时和后2小时进一步细分为开始（RES）和结束（RES）。净变化计算为RES - RES。除HP/cBW外，RES期内所有能量变量在泌乳阶段之间均存在差异。正如预期的那样，与RES相比，RES时的COX、COX/cBW、COX/HP、HP和HP/cBW更高，而除泌乳中期的FOX和FOX/cBW外，RES时的FOX、FOX/cBW和FOX/HP更高，只是存在差异的趋势。COX、COX/cBW、HP、HP/cBW和FOX/cBW的净变化在泌乳阶段之间没有差异。尽管检测到FOX在泌乳阶段之间存在差异的趋势，但成对分析显示没有差异。RES时血浆甘油三酯、尿素和非酯化脂肪酸浓度高于RES。血浆葡萄糖、尿素、β-羟基丁酸和非酯化脂肪酸浓度的净变化在泌乳早期大于晚期。我们的结果表明，尽管能量变量和血浆代谢物的绝对测量值存在差异，但在24小时禁食期内，随着奶牛从进食状态转变为饥饿状态，全身常量营养素氧化和HP的变化在整个泌乳期是一致的。
