摘要
The objective of this experiment was to examine the effect of milk replacer (MR) feeding rate (FR) and frequency (FF) on glucose metabolism before and after weaning during summer and winter in the subtropical climate of the southeastern United States. Holstein calves (n = 48/season) were enrolled at 8 d of age (DOA) in the summer (June to August, body weight = 40.6 ± 0.7 kg) and winter (November to January, body weight = 41.9 ± 0.8 kg). In each season, calves were randomly assigned to 1 of 4 treatments in a 2 × 2 factorial arrangement including 2 FR [0.65 (low) or 0.76 kg of solids/d (high) of a 26% CP and 17% fat MR] and 2 FF [2× (0700 and 1600 h) or 3× (0700, 1600, and 2200 h)]. Calves were managed similarly and housed in polyethylene hutches bedded with sand. Milk replacer (12.5%) was fed based on treatments until 42 DOA when FR was reduced by half and offered 1×/d (0700 h) for 7 d. Plasma was collected weekly at 1400 h for analyses of glucose and insulin concentrations in all calves. Pre- and postprandial glucose and insulin concentrations of a subset of calves (n = 10/treatment per season) were measured on 20 DOA. A subset of calves (n = 8/treatment per season) was subjected to an intravenous glucose tolerance test (GTT) on 27 and 57 DOA and insulin challenge on 28 and 58 DOA at 1030 h. Average ambient temperature was 26.1 ± 2.2°C in summer and 12.9 ± 5.4°C in winter. During the preweaning period in both seasons, feeding high increased plasma glucose concentrations compared with low, and increasing FF reduced basal insulin concentrations. Compared with 2×, feeding 3× did not affect postprandial glucose but lowered insulin in the summer, whereas in the winter, increased glucose from 30 to 180 min but lowered insulin from 240 to 420 min after MR feeding. Following GTT before weaning in both seasons, 3× reduced insulin increment and area under the curve compared with 2× without affecting glucose disposal. After weaning, treatment did not affect glucose disposal or insulin responses after GTT during winter, but calves fed 3× had faster glucose disposal and stronger insulin responses than 2× during summer. In both summer and winter, preweaned calves fed 3× had greater decrement and area under the curve of plasma glucose after insulin challenge, suggesting enhanced peripheral tissue insulin response compared with 2×. This effect persisted after weaning only during summer. Increasing FR had no effect on metabolic responses in both seasons. In conclusion, increasing MR FF from 2 to 3 times per day reduced insulin secretion but enhanced insulin response on peripheral tissues of preweaned calves regardless of season.
摘要译文
该实验的目的是在夏季和冬季在美国东南部的夏季和冬季进行断奶之前和之后，检查牛奶替代品（MR）喂养率（FR）和频率（FF）对葡萄糖代谢的影响。夏季（6月至8月，体重= 40.6±0.7公斤）荷斯坦牛犊（N = 48 /季节）均为8岁（DOA）（DOA），冬季（11月至1月，体重= 41.9±0.8千克） 。在每个季节中，小腿被随机分配到2×2因子装置中的4个处理中的1个，包括2 fr [0.65（低）或0.76千克固体/ d（高）的26％CP和17％脂肪MR]和2 FF [2×（0700和1600小时）或3×（0700,1600和2200小时）]。犊牛类似地进行管理，并在与沙子的聚乙烯Hutches床上铺有。牛奶替代品（12.5％）基于治疗喂养，直至42 doA在FR减少一半时，提供1×/ D（0700小时）7天。每周收集血浆，在1400小时内收集，以分析所有犊牛的葡萄糖和胰岛素浓度。在20 doa上测量犊牛群（每季节N = 10 /治疗）的前后葡萄糖和胰岛素浓度。在27和57个DOA和胰岛素攻击的静脉内葡萄糖耐量试验（GTT）和胰岛素攻击在1030小时的静脉内葡萄糖耐受试验（GTT）的静脉内葡萄糖耐量试验（GTT）。夏季平均环境温度为26.1±2.2°C，冬季12.9±5.4°C。在两种季节的预制期间，喂养高增加的血浆葡萄糖浓度与低，增加了FF降低的基础胰岛素浓度。与2倍相比，喂养3×不会影响黄昏葡萄糖，但夏季胰岛素降低，而在冬季，在MR喂养后，从30〜420分钟降低胰岛素。在两种季节断奶之前GTT之后，3次减少胰岛素增量和曲线下的面积与2×而不影响葡萄糖处理。断奶后，治疗不影响冬季GTT后的葡萄糖处理或胰岛素反应，但饲喂3次的小牛在夏季期间葡萄糖处理更快，胰岛素响应比2×更强。在夏季和冬季，喂养3×的预期小牛在胰岛素攻击后的血浆葡萄糖曲线下具有更大的衰减和面积，表明与2×相比增强的外周组织胰岛素反应。在夏季时，这种效果仍然存在。增加的FR对两个季节的代谢反应没有影响。总之，每天2至3次增加FF至3次降低胰岛素分泌，但无论季节如何，预期犊牛外周组织的胰岛素反应都会增强。
Ruth M. Orellana Rivas[1];Thalyane Rodrigues[1];Jordana da Silveira E. Sousa[1];Victor H. L. R. Melo[1];Jing Gao[1];Diego Ferreira de Araújo[1];Juliana Goncalves de Souza[1];Thiago N. Marins[1];Pedro Melendez[2][3];John K. Bernard[1];Sha Tao[1]. Effect of milk replacer feeding rate and frequency of preweaning dairy calves in the southeastern United States: Glucose metabolism[J]. Journal of Dairy Science, 2022,105(2): 1170-1185