Our aim with this study was to evaluate the consumption, performance, quantitative characteristics of carcasses, biochemical profile, plasma levels of ghrelin and leptin, expression of the receptor for ghrelin (GHS-R1a) in the hypothalamus and duodenum, and the number of goblet cells in the duodenum of calves subjected to milk volume restriction and supplemented with 2-hydroxy-4-(methylthio)butanoic acid (HMTBa). We used 21 Holstein mixed-breed calves, aged between 3 and 15 d with an average weight of 36.8 kg, and housed in pens with troughs for hay, concentrate, and water. The study included two consecutive experimental periods (first period [P1] and second period [P2]) of 21 d each, with 7 d of adaptation to the diet and facilities. The calves were distributed in a completely randomized design in three treatments with seven repetitions. 1) Control: 6 liters of milk/d during P1 and 6 liters of milk/day during P2; 2) RES (milk restriction): 3 liters of milk/day during P1 and 6 liters of milk/day during P2; and 3) RES + HMTBa: 3 liters of milk/day during P1 and 6 liters of milk/day during P2 + 3.3 g of HMTBa/day in both periods. HMTBa was supplied in milk, and the amount of concentrated ration and hay provided and leftovers were recorded daily to estimate dry matter (DM) and crude protein consumption. Mean daily weight gain (DWG), final weight (FW), and feed conversion (FC) were obtained at the beginning and at the end of each 21-d period. Plasma concentrations of ghrelin and leptin, triglycerides, total protein, urea, lactate, creatinine, alkaline phosphatase, and cholesterol were measured for P1 and P2 at the end of each 21-d period. At the end of P2, animals were slaughtered; sections of the duodenum were collected to evaluate the expression of GHS-R1a and quantity of goblet cells; hypothalamus was used to evaluate the expression of GHS-R1a; rumen was used to evaluate the thickness of epithelium and keratin and the density, height, and width of ruminal papillae. In P1, total DM consumption, FW, DWG, glucose, and triglycerides were lower in the RES and RES + HMTBa groups (P < 0.001). In P2, there was an improvement in the FC of the RES + HMTBa group (compared with Control and RES groups) and a lower urea concentration in the RES group (compared with Control and RES + HMTBa groups) (P < 0.001). No differences were observed among groups regarding hormonal concentrations, histological parameters, and GHS-R1a expression in the duodenum and hypothalamus. Therefore, milk restriction combined with HMTBa supplementation promoted greater compensatory gain by a mechanism independent of changes in GHS-R1a expression and hormone levels of ghrelin and leptin.

中文翻译：

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与补充 2-羟基-4-(甲硫基)丁酸相关的牛奶限制的小牛 (Bos taurus) 的性能和血清参数

我们本研究的目的是评估胴体的消耗、性能、定量特征、生化特征、生长素释放肽和瘦素的血浆水平、下丘脑和十二指肠中生长素释放肽受体 (GHS-R1a) 的表达以及高脚杯的数量小牛十二指肠中的细胞受到牛奶体积限制并补充了 2-羟基-4-(甲硫基)丁酸 (HMTBa)。我们使用了 21 头荷斯坦混种小牛，年龄在 3 到 15 天之间，平均体重 36.8 公斤，圈养在带有干草、浓缩物和水槽的围栏中。该研究包括两个连续的实验期（第一期 [P1] 和第二期 [P2]），每期 21 天，其中 7 天适应饮食和设施。小牛以完全随机的设计分布在三个处理中，重复七次。1）控制：P1期间6升牛奶/天，P2期间6升牛奶/天；2) RES（限奶）：P1 期间每天 3 升牛奶，P2 期间每天 6 升牛奶；3) RES + HMTBa：P1 期间每天 3 升牛奶，P2 期间每天 6 升牛奶 + 两个期间每天 3.3 克 HMTBa。HMTBa 以牛奶的形式提供，每天记录提供的浓缩日粮和干草的数量以及剩余物的数量，以估计干物质 (DM) 和粗蛋白消耗量。在每个 21 天期间的开始和结束时获得平均日增重 (DWG)、最终体重 (FW) 和饲料转化率 (FC)。在每个 21 天结束时测量 P1 和 P2 的血浆中生长素释放肽和瘦素、甘油三酯、总蛋白、尿素、乳酸、肌酐、碱性磷酸酶和胆固醇的浓度。P2结束时，动物被宰杀；取十二指肠切片，评价GHS-R1a的表达和杯状细胞的数量；下丘脑用于评估GHS-R1a的表达；瘤胃用于评估上皮和角蛋白的厚度以及瘤胃乳头的密度、高度和宽度。在 P1 中，RES 和 RES + HMTBa 组的 DM 总消耗量、FW、DWG、葡萄糖和甘油三酯较低（P < 0.001）。在 P2 中，RES + HMTBa 组的 FC 有所改善（与对照组和 RES 组相比），RES 组的尿素浓度较低（与对照组和 RES + HMTBa 组相比）（P < 0.001）。在十二指肠和下丘脑中的激素浓度、组织学参数和 GHS-R1a 表达方面，各组之间没有观察到差异。所以，