Nutricorp, Araras, SP 13601-000, Brazil.
Faculdade de Medicina Veterinária e Zootecnia, Universidade Estadual Paulista (UNESP), Botucatu, SP 18618-000, Brazil.
J Anim Sci. 2022 Jul 1;100(7). doi: 10.1093/jas/skac182.
This experiment evaluated the effects of advancing days on feed (DOF) on insulin resistance (IR) of finishing Bos indicus bulls offered a high-concentrate diet. On day 0, 100 Bos indicus Nellore bulls were housed in 12 feedlot pens (8 or 9 bulls/pen) for a 108-d feeding period, in a manner that all pens had an equivalent BW at the beginning of the finishing period. Bulls received the same diets throughout the 108-d feeding period. Diets were corn-based (38% starch) and were offered in amounts to ensure ad libitum intake. Individual shrunk BW was obtained on days 0 and 108 after 16 h of feed and water withdrawal, whereas unshrunk BW was recorded on days 19 and 60 for average daily gain (ADG) calculation. From days 0 to 108, feed intake and feed efficiency (FE) were calculated from each pen. Blood samples were collected on days 0, 60, and 108 to assess serum concentrations of haptoglobin, cortisol, glucose, and non-esterified fatty acids (NEFA), and insulin. Glucose, NEFA, and insulin concentrations were used to determine revised quantitative insulin sensitivity check index (RQUICKI), so that lower RQUICKI values indicate a greater IR of the herd. Pen was used as the experimental unit. Overall, DMI increased as DOF also increased (R2 = 0.71), being greater from days 19 to 60 and 60 to 108 vs. 0 to 19 (P < 0.0001), but did not differ between days 19 to 60 and 60 to 108 (P = 0.79). Conversely, ADG and FE linearly decreased as DOF increased from days 0 to 108 (P < 0.0001; R2 = 0.68 and 0.79, respectively). Log-transformed RQUICKI decreased as DOF increased up to 108 (P < 0.0001; r = -0.61). Similarly, serum concentrations of haptoglobin and cortisol increased as RQUICKI increased (P < 0.0001; r = 0.43 and 0.67, respectively). In summary, insulin resistance, per RQUICKI, increased and performance reduced in feedlot bulls with the advance of days on feed. Moreover, inflammatory markers were also positively associated with insulin resistance, suggesting that inflammation might be involved with the incidence of insulin resistance.
本实验评估了高浓度日粮育肥期长天数对印度瘤牛公牛胰岛素抵抗（IR）的影响。在第 0 天，100 头印度瘤牛公牛被安置在 12 个饲养栏中（每栏 8 或 9 头公牛），进行为期 108 天的饲养期，每个饲养栏在育肥期开始时具有相同的初始体重。在 108 天的饲养期间，公牛都接受相同的日粮。日粮以玉米为基础（38%淀粉），并提供足够的饲料以确保自由采食。在禁食和禁水 16 小时后，于第 0 天和第 108 天测量个体收缩体重（shrunk BW），于第 19 天和第 60 天测量未收缩体重（unshrunk BW）以计算平均日增重（ADG）。从第 0 天到第 108 天，根据每个饲养栏计算采食量和饲料效率（FE）。在第 0 天、第 60 天和第 108 天采集血液样本，以评估血清中结合珠蛋白、皮质醇、葡萄糖和非酯化脂肪酸（NEFA）以及胰岛素的浓度。使用葡萄糖、NEFA 和胰岛素浓度来确定修正后的定量胰岛素敏感性检查指数（RQUICKI），较低的 RQUICKI 值表明群体的胰岛素抵抗更大。饲养栏用作实验单位。总的来说，随着天数的增加，DMI 也增加（R2 = 0.71），从第 19 天到第 60 天和第 60 天到第 108 天之间的增加比从第 0 天到第 19 天之间的增加更大（P < 0.0001），但第 19 天到第 60 天之间和第 60 天到第 108 天之间没有差异（P = 0.79）。相反，随着天数从第 0 天增加到第 108 天，ADG 和 FE 呈线性下降（P < 0.0001；R2 分别为 0.68 和 0.79）。随着天数的增加，RQUICKI 的对数呈线性下降（P < 0.0001；r = -0.61）。同样，随着 RQUICKI 的增加，结合珠蛋白和皮质醇的血清浓度也增加（P < 0.0001；r = 0.43 和 0.67）。总之，随着天数的增加，育肥期印度瘤牛公牛的胰岛素抵抗增加，性能降低。此外，炎症标志物也与胰岛素抵抗呈正相关，表明炎症可能与胰岛素抵抗的发生有关。
