Technical University of Munich, Chair of Animal Nutrition, Liesel-Beckmann-Straße 2, 85354 Freising, Germany; Bavarian State Research Center for Agriculture, Institute for Animal Nutrition and Feed Management, Prof.-Duerrwaechter-Platz 3, 85586 Poing/Grub, Germany.
Technical University of Munich, Chair of Animal Nutrition, Liesel-Beckmann-Straße 2, 85354 Freising, Germany.
Animal. 2021 Nov;15(11):100366. doi: 10.1016/j.animal.2021.100366. Epub 2021 Oct 1.
The objective of this study was to evaluate the effect of supplementing a CP-reduced diet with rumen-protected methionine on growth performance of Fleckvieh bulls. A total of 69 bulls (367 ± 25 kg BW) were assigned to three feeding groups (n = 23 per group). The control (CON) diet contained 13.7% CP and 2.11 g methionine/kg diet (both DM basis) and was set as positive control. The diet reduced in CP (nitrogen) (RED) diet as negative control and the experimental RED + rumen-protected methionine (MET) diet were characterised by deficient CP concentrations (both 9.04% CP). The RED + MET diet differed from the RED diet in methionine concentration (2.54 g/kg DM vs. 1.56 g/kg DM, respectively) due to supplementation of rumen-protected methionine. Rumen-protected lysine was added to both RED and RED + MET at 2.7 g/kg DM to ensure a sufficient lysine supply relative to total and metabolisable protein intake. Metabolisable energy (ME) and nutrient composition were similar for CON, RED, and RED + MET. Bulls were fed for 105 days (d) on average. Individual feed intake was recorded daily; individual BW was recorded at the beginning of the experiment, once per month, and directly before slaughter. At slaughter, blood samples were collected and carcass traits were assessed. Reduction in dietary CP concentration reduced feed intake, and in combination with lower dietary CP concentration, daily intake of CP for RED and RED + MET was lower compared with CON (P < 0.01). Daily ME intake was reduced in RED and RED + MET compared with CON (P < 0.01). Consequently growth performance and carcass weights were reduced (both P < 0.01) in both RED and RED + MET compared with CON. Supplemental rumen-protected methionine was reflected in increased serum methionine concentration in RED + MET (P < 0.05) as compared to RED but it did not affect growth performance, carcass traits and serum amino acid (AA) concentrations, except for lysine which was reduced (P < 0.01) compared to CON and RED. In conclusion, bulls fed RED or RED + MET diets were exposed to a ruminal CP deficit and subsequently a deficit of prececal digestible protein, but methionine did not appear to be the first-limiting essential AA for growth under the respective experimental conditions.
本研究旨在评估在降低 CP 的日粮中添加保护性蛋氨酸对弗莱维赫公牛生长性能的影响。共有 69 头公牛（367±25kgBW）被分为三组（每组 23 头）。对照组（CON）日粮含有 13.7%CP 和 2.11g 蛋氨酸/kg 日粮（均为 DM 基础），作为阳性对照。降低 CP（氮）（RED）日粮作为阴性对照，实验 RED+保护性蛋氨酸（MET）日粮的 CP 浓度不足（均为 9.04%CP）。由于添加了保护性蛋氨酸，RED+MET 日粮的蛋氨酸浓度（2.54g/kgDM）与 RED 日粮（1.56g/kgDM）不同。两种 RED 日粮和 RED+MET 日粮均添加了 2.7g/kgDM 的保护性赖氨酸，以确保相对于总可消化蛋白和代谢蛋白摄入量，赖氨酸供应充足。CON、RED 和 RED+MET 的可代谢能（ME）和营养成分相似。公牛平均饲养 105 天（d）。每天记录个体采食量；实验开始时、每月一次和屠宰前直接记录个体 BW。屠宰时采集血样，评估胴体性状。降低日粮 CP 浓度减少了采食量，并且与 RED 和 RED+MET 相比，日粮 CP 每日摄入量较低（P<0.01）。与 CON 相比，RED 和 RED+MET 的 ME 日摄入量降低（P<0.01）。因此，与 CON 相比，RED 和 RED+MET 的生长性能和胴体重降低（均 P<0.01）。添加保护性蛋氨酸导致 RED+MET 血清蛋氨酸浓度增加（P<0.05），但与 RED 相比，生长性能、胴体性状和血清氨基酸（AA）浓度不受影响，除了赖氨酸，其浓度降低（P<0.01），与 CON 和 RED 相比。综上所述，饲喂 RED 或 RED+MET 日粮的公牛暴露于瘤胃 CP 缺乏，随后出现可消化蛋白的前腔缺失，但在各自的实验条件下，蛋氨酸似乎不是生长的第一限制必需 AA。
