Salinas-Chavira Jaime, Carvalho Pedro H V, Latack Brooke C, Ferraz Marcos V C, Montano Martin, Zinn Richard A
Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Tamaulipas. Km-5 Carretera Victoria-Mante, Cd. Victoria, Tam. 87000, Mexico.
Department of Animal Science, University of California, Holtville, CA 92250, USA.
Transl Anim Sci. 2024 Jan 8;8:txae003. doi: 10.1093/tas/txae003. eCollection 2024.
The objective was to examine the effects of metabolizable protein (MP) and ruminal-protected methionine supplementation on growth performance of Holstein steer calves during the initial feedlot growing phase (112 d). One hundred eighty Holstein steer calves (122 ± 7 kg) were blocked by weight and assigned to 30 pens (6 steers per pen). Five treatments were applied: 1) control, a diet based on steam-flaked corn containing urea and dry distillers grains plus solubles as supplemental N sources with no amino acid addition; 2) control diet plus blood meal supplementation; 3) diet from treatment 2, with 0.064% Smartamine M (70% methionine; Adisseo, Alpharetta, GA) supplementation; 4) diet from treatment 2 with 0.096% Smartamine M supplementation; 5) diet from treatment 2 with 0.128% Smartamine M supplementation. All diets were formulated to exceed the estimated MP requirements. The estimated metabolizable lysine, as well as methionine, was deficient in the control diet. Blood meal was added to the control diet to meet estimated lysine requirements (diet 2), the other diets had increasing concentrations of supplemental methionine. Supplemental MP enhanced (10%, < 0.02) interim and overall 112-d average daily gain (ADG). Additional effects of supplemental methionine on ADG were not appreciable ( > 0.10). Supplemental MP did not affect ( > 0.10) dry matter intake (DMI) during the first 56-d period; however, it tended to increase ( = 0.08) DMI during the subsequent 56-d period. Overall, supplemental MP or methionine had no appreciable effect (P > 0.10) on DMI. Supplemental MP improved ( < 0.01) gain efficiency and estimated dietary net energy (NE) values during the initial 56-d period (11 and 7%, respectively) and overall (7 and 4%, respectively). Supplemental MP did not affect ( > 0.10) gain efficiency during the second 56-d period, although it tended to enhance ( = 0.08) estimated dietary NE. Supplemental methionine did not appreciably affect ( > 0.10) gain efficiency or estimated dietary NE. Therefore, adding MP to cover the estimated limiting amino acid supply in diets may enhance the gain efficiency and dietary energetics of growing Holstein calves. However, amino acid addition supplementation beyond the requirements may not produce extra productive performance of steer calves.
本研究旨在探讨在育肥牛初始育肥阶段（112天），可代谢蛋白质（MP）和瘤胃保护蛋氨酸补充剂对荷斯坦公牛犊生长性能的影响。180头荷斯坦公牛犊（体重122±7千克）按体重进行分组，分配到30个围栏（每个围栏6头公牛犊）。采用了五种处理方式：1）对照组，以蒸汽压片玉米为基础的日粮，含有尿素和干酒糟及其可溶物作为补充氮源，不添加氨基酸；2）对照组日粮加血粉补充剂；3）处理2的日粮，添加0.064%的Smartamine M（70%蛋氨酸；安迪苏公司，美国佐治亚州阿尔法利塔）；4）处理2的日粮，添加0.096%的Smartamine M；5）处理2的日粮，添加0.128%的Smartamine M。所有日粮的配方均超过估计的MP需求量。对照组日粮中估计的可代谢赖氨酸和蛋氨酸均不足。在对照组日粮中添加血粉以满足估计的赖氨酸需求量（日粮2），其他日粮中补充蛋氨酸的浓度逐渐增加。补充MP提高了（10%，P<0.02）中期和112天的总体平均日增重（ADG）。补充蛋氨酸对ADG的额外影响不显著（P>0.10）。补充MP在前56天期间对干物质采食量（DMI）没有影响（P>0.10）；然而，在随后的56天期间，它有增加DMI的趋势（P=0.08）。总体而言，补充MP或蛋氨酸对DMI没有显著影响（P>0.10）。补充MP提高了（P<0.01）初始56天期间（分别提高11%和7%）以及总体（分别提高7%和4%）的增重效率和估计日粮净能（NE）值。补充MP在第二个56天期间对增重效率没有影响（P>0.10），尽管它有提高（P=0.08）估计日粮NE的趋势。补充蛋氨酸对增重效率或估计日粮NE没有显著影响（P>0.10）。因此，在日粮中添加MP以满足估计的限制性氨基酸供应，可能会提高生长中的荷斯坦犊牛的增重效率和日粮能量学。然而，超过需求量添加氨基酸补充剂可能不会使公牛犊产生额外的生产性能。
