摘要
Increasing nutrient utilization efficiency is an important component of enhancing the sustainability of beef cattle production. The objective of this experiment was to determine the association of glucose metabolism and insulin resistance with dry matter intake (DMI), average daily gain (ADG), gain:feed ratio (G:F), and residual feed intake (RFI). Steers (n = 54; initial body weight = 518 ± 27.0 kg) were subjected to an intravenous glucose tolerance test (IVGTT) where glucose was dosed through a jugular catheter and serial blood samples were collected. Three days after the last group’s IVGTT, steers began a 63-d DMI and ADG test. Body weight was measured on days 0, 1, 21, 42, 62, and 63, and DMI was measured using an Insentec Roughage Intake Control system (Hokofarm Group, Emmeloord, the Netherlands). To examine relationships between DMI, ADG, G:F, and RFI with IVGTT measurements, Pearson correlations were calculated using Proc Corr of SAS 9.4 (SAS Inst. Inc., Cary, NC). Additionally, cattle were classified based on DMI, ADG, RFI, and G:F, where the medium classification was set as mean ± 0.5 SD, the low classification was 0.5 SD from the mean. No associations between DMI and IVGTT parameters were observed, and no differences were detected when classifying cattle as having low, medium, or high DMI. Peak insulin concentration in response to the IVGTT tended to be correlated with ADG (r = 0.28; P = 0.07), indicating cattle with greater ADG tend to have a greater insulin release in response to glucose. Glucose nadir concentrations tended to be positively correlated with ADG (r = 0.26; P = 0.10). Additionally, the glucose nadir was greater in high-ADG steers (P = 0.003). The association of greater glucose nadir with high-ADG could indicate that high-ADG steers do not clear glucose as efficiently as low-ADG steers, potentially indicating increased insulin resistance. Further, RFI was not correlated with IVGTT measurements, but low RFI steers had a greater peak glucose concentration (P = 0.040) and tended to have a greater glucose area under the curve (P = 0.09). G:F was correlated with glucose area under the curve (r = 0.33; P = 0.050), glucose nadir (r = 0.35; P = 0.011), and insulin time to peak (r = 0.39; P = 0.010). These results indicate that glucose metabolism and insulin signaling are associated with growth and efficiency, but the molecular mechanisms that drive these effects need to be elucidated.
摘要译文
养分利用效率提高是增强牛奶生产可持续性的重要组成部分。该实验的目的是确定葡萄糖代谢和胰岛素抵抗与干物质摄入量（DMI），平均每日增益（ADG），增益：饲料比：F：F：F）和残留饲料摄入（RFI）的关联。对蒸汽（n = 54;初始体重= 518±27.0 kg）进行静脉内葡萄糖耐受性测试（IVGTT），其中通过颈椎导管给予葡萄糖，并收集了连续血样品。在最后一个组的IVGTT三天后，Steers开始了63-D DMI和ADG测试。在第0、1、21、42、62和63天测量体重，并使用Insentec粗糙摄入控制系统（Hokofarm Group，Emmeloord，荷兰）测量DMI。为了检查DMI，ADG，G：F和RFI与IVGTT测量之间的关系，使用SAS 9.4（SasInst。Inc.，Cary，NC）计算了Pearson相关性。另外，根据DMI，ADG，RFI和G：F分类牛，其中介质分类设置为平均值±0.5 SD，低分类为平均值为0.5 SD。未观察到DMI和IVGTT参数之间的关联，并且在将牛分类为低，培养基或高DMI时未检测到差异。响应于IVGTT的峰值胰岛素浓度倾向于与ADG相关（r = 0.28； P = 0.07），表明具有较大ADG的牛倾向于响应葡萄糖而具有更大的胰岛素释放。葡萄糖NADIR浓度倾向于与ADG正相关（r = 0.26； p = 0.10）。另外，高加速龙骨中的葡萄糖Nadir更大（p = 0.003）。较大的葡萄糖NADIR与高接ADG的关联可能表明高加速倾向不能像低ADG转向器那样有效地清除葡萄糖，这可能表明胰岛素抵抗增加。此外，RFI与IVGTT测量不相关，但是低RFI转向器的峰葡萄糖浓度更高（P = 0.040），并且在曲线下倾向于更大的葡萄糖面积（P = 0.09）。G：F与曲线下的葡萄糖面积相关（r = 0.33; p = 0.050），葡萄糖nadir（r = 0.35; p = 0.011）和胰岛素时间到峰值（r = 0.39; p = 0.010）。这些结果表明，葡萄糖代谢和胰岛素信号传导与生长和效率有关，但是驱动这些作用的分子机制需要阐明。