Natural Resources Institute Finland, Tietotie 2C, 31600, Jokioinen, Finland.
Universidade Federal de Viçosa, Departmento de Zootecnia, Avenida P.H. Rolfs, s/n°, 36570-900 Viçosa, MG, Brazil.
An Acad Bras Cienc. 2021 Feb 1;93(3):e20190487. doi: 10.1590/0001-3765202120190487. eCollection 2021.
Effects of protein supplementation, with and without starch supplementation, on nutritional performance and metabolic characteristics of cattle fed low- and medium-quality tropical forages were evaluated using 4 cannulated steers distributed according to a 4 × 4 Latin square. Experimental periods were divided into two subperiods. In the first subperiod, two animals received low-quality hay and two animals received medium-quality. Supplementation schemes were evaluated in the second subperiod: low-quality hay with protein (300 g of crude protein - CP/d); low-quality hay with protein (300 g CP/d) and starch (225 g/d); medium-quality hay with protein (300 g CP/d); and medium-quality hay with protein (300 g CP/d) and starch (225 g/d) supplementation. Without supplementation, medium-quality forage provided higher intake, digestibility, nitrogen balance (NB) and efficiency of nitrogen utilization (EFNU). Comparing subperiods, supply of supplements depressed medium-quality forage intake, but did not affect low-quality forage intake. Supplementation increased NB, EFNU and serum concentration of IGF1 in animals fed low-quality forage. Protein supplementation increases nitrogen retention in animals, an effect attributed mainly to anabolic stimuli. However, this effect is more prominent when animals are fed low-quality forages. No positive impact on animal metabolism was obtained with combination of supplemental protein and starch.
本研究采用 4 头安装有瘤胃瘘管的阉牛，采用 4×4 拉丁方设计，评估了添加或不添加淀粉的蛋白质补充对饲喂低、中质量热带牧草的牛的营养性能和代谢特性的影响。试验期分为两个亚期。在第一个亚期，2 头动物饲喂低质量干草，2 头动物饲喂中等质量干草。在第二个亚期评估了补充方案：低质量干草添加蛋白质（300 g 粗蛋白 - CP/天）；低质量干草添加蛋白质（300 g CP/天）和淀粉（225 g/d）；中等质量干草添加蛋白质（300 g CP/天）；以及中等质量干草添加蛋白质（300 g CP/天）和淀粉（225 g/d）。不添加补充剂时，中等质量的饲草提供了更高的采食量、消化率、氮平衡（NB）和氮利用效率（EFNU）。与亚期相比，补充剂的供应降低了中等质量饲草的采食量，但不影响低质量饲草的采食量。补充剂增加了低质量饲草采食动物的 NB、EFNU 和血清 IGF1 浓度。蛋白质补充剂增加了动物的氮保留，这种效果主要归因于合成代谢刺激。然而，当动物饲喂低质量饲草时，这种效果更为明显。添加蛋白质和淀粉的组合对动物代谢没有产生积极影响。
