de Oliveira Franco Marcia, Detmann Edenio, de Campos Valadares Filho Sebastião, Batista Erick Darlisson, de Almeida Rufino Luana Marta, Barbosa Marcília Medrado, Lopes Alexandre Ribeiro
Department of Animal Science, Universidade Federal de Viçosa, Viçosa, MG 36570-000, Brazil.
Asian-Australas J Anim Sci. 2017 Jun;30(6):797-803. doi: 10.5713/ajas.16.0629. Epub 2016 Oct 28.
Effects of nitrogen supplementation associated with different levels of starch on voluntary intake, digestibility, and rumen and metabolic characteristics of cattle fed low-quality tropical forage ( hay, 7.4% crude protein, CP) were evaluated using ruminal and abomasal cannulated steers.
Five European×Zebu young bulls (186 kg body weight, BW) were distributed according to a 5×5 Latin square. The following treatments were evaluated: control, supplementation with 300 g CP/d (0:1), supplementation with 300 g starch/d and 300 g CP/d (1:1), supplementation with 600 g starch/d and 300 g CP/d (2:1), and supplementation with 900 g starch/d and 300 g CP/d (3:1). A mixture of nitrogenous compounds provided 1/3 from true protein (casein) and 2/3 from non-protein nitrogen (mixture of urea and ammonium sulphate, 9:1) was used as the nitrogen supplement. In order to supply energy a unique source of corn starch was used.
Supplements increased (p<0.05) dry matter intake, but did not affect (p>0.05) forage intake. There was a cubic effect (p<0.05) of starch on voluntary intake. This was attributed to the highest forage intake (g/kg BW) when using the 2:1 starch:CP ratio. Supplements increased (p<0.05) organic matter (OM) digestibility, but did not affect (p>0.05) neutral detergent fibre corrected for ash and protein (NDFap) digestibility. There was a positive linear effect (p<0.05) of the amount of starch supplemented on OM digestibility. Total NDFap digestibility was not affected (p>0.05) by the amount of supplemental starch. Ruminal ammonia nitrogen concentrations were higher (p<0.05) in supplemented animals, however, a negative linear effect (p<0.05) of amount of starch was observed. Supplements increased (p<0.05) the nitrogen balance (NB) and efficiency of nitrogen utilization. These effects were attributed to increased body anabolism, supported by higher (p<0.05) serum concentration of insulin-like growth factor 1. Increasing the amount of starch tended (p<0.06) to linearly increase the NB. In spite of this, there was a highest NB value for the 2:1 starch:CP ratio amongst the treatments with supplementation.
Nitrogen supplementation in cattle fed low-quality tropical forage increases nitrogen retention in the animal's body. An additional supply of starch increases nitrogen retention by increasing energy availability for both rumen and animal metabolism.
使用瘤胃和真胃插管的公牛，评估补充氮并搭配不同水平淀粉对采食低质量热带牧草（干草，粗蛋白含量7.4%）的牛的采食量、消化率、瘤胃及代谢特性的影响。
五头欧洲×瘤牛杂交的年轻公牛（体重186千克）按5×5拉丁方设计进行分配。评估了以下处理：对照组、每天补充300克粗蛋白（0:1）、每天补充300克淀粉和300克粗蛋白（1:1）、每天补充600克淀粉和300克粗蛋白（2:1）、每天补充900克淀粉和300克粗蛋白（3:1）。含氮化合物混合物中，三分之一来自真蛋白（酪蛋白），三分之二来自非蛋白氮（尿素和硫酸铵混合物，9:1），用作氮补充剂。为提供能量，使用单一来源的玉米淀粉。
补充剂增加了（p<0.05）干物质采食量，但未影响（p>0.05）牧草采食量。淀粉对采食量有立方效应（p<0.05）。这归因于使用2:1淀粉:粗蛋白比例时牧草采食量最高（克/千克体重）。补充剂增加了（p<0.05）有机物（OM）消化率，但未影响（p>0.05）校正灰分和蛋白质后的中性洗涤纤维（NDFap）消化率。补充淀粉量对OM消化率有正线性效应（p<0.05）。补充淀粉量对总NDFap消化率无影响（p>0.05）。补充组动物的瘤胃氨氮浓度较高（p<0.05），然而，观察到淀粉量有负线性效应（p<0.05）。补充剂增加了（p<0.05）氮平衡（NB）和氮利用效率。这些影响归因于机体合成代谢增加，这由较高的（p<0.05）胰岛素样生长因子1血清浓度支持。增加淀粉量倾向于（p<0.06）使NB呈线性增加。尽管如此，在补充处理中，2:1淀粉:粗蛋白比例的NB值最高。
给采食低质量热带牧草的牛补充氮可增加动物体内的氮保留。额外补充淀粉通过增加瘤胃和动物代谢的能量供应来增加氮保留。
