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首页> 美国卫生研究院文献>Journal of Animal Science >Dietary protein reduction on microbial protein amino acids digestibility and body retention in beef cattle. I. Digestibility sites and ruminal synthesis estimated by purine bases and 15N as markers
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Dietary protein reduction on microbial protein amino acids digestibility and body retention in beef cattle. I. Digestibility sites and ruminal synthesis estimated by purine bases and 15N as markers

机译：饮食中的蛋白质减少会影响肉牛的微生物蛋白质氨基酸消化率和身体滞留率。一以嘌呤碱基和15N为标记物估计的消化部位和瘤胃合成

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The objectives of this study were to evaluate the effect of reducing dietary CP contents on 1) total and partial nutrient digestion and nitrogen balance and 2) on microbial crude protein (>MCP) synthesis and true MCP digestibility in the small intestine obtained with 15N and purine bases (>PB) in beef cattle. Eight bulls (4 Nellore and 4 Crossbred Angus × Nellore) cannulated in the rumen and ileum were distributed in duplicated 4 × 4 Latin squares. The diets consisted of increasing CP contents: 100, 120, or 140 g CP/kg DM offered ad libitum, and restricted intake (>RI) diet with 120 g CP/kg DM. The experiment lasted four 17-d periods, with 10 d for adaptation to diets and another 7 for data collection. Omasal digesta flow was obtained using Co-EDTA and indigestible NDF (>iNDF) as markers, and to estimate ileal digesta flow only iNDF was used. From days 11 to 17 of each experimental period, ruminal infusions of Co-EDTA (5.0 g/d) and 15N (7.03 g of ammonium sulfate enriched with 10% of 15N atoms) were performed. There was no effect of CP contents (linear effect, P = 0.55 and quadratic effect, P = 0.11) on ruminal OM digestibility. Intake of CP linearly increased (P < 0.01) with greater dietary CP. The NH3-N (P < 0.01) and urinary N excretion (P < 0.01) increased in response to dietary CP, whereas retained N increased linearly (P = 0.03). Liquid-associated bacteria (>LAB) in the omasum had greater N content (P < 0.05) in relation to the particle-associated bacteria (>PAB). There was no difference between LAB and PAB (P = 0.12) for 15N:14N ratio. The 15N:14N ratio was greater (P < 0.01) in RI animals in relation to those fed at voluntary intake. Microbial CP had a quadratic tendency (P = 0.09) in response to CP increase. Microbial efficiency (expressed in relation to apparent ruminally degradable OM and true ruminally degradable OM) had a quadratic tendency (P = 0.07 and P = 0.08, respectively) to CP increasing and was numerically greatest at 120 g CP/kg DM. The adjusted equations for estimating true intestinal digestibility of MCP (Y1) and total CP (Y2) were, respectively, as follows: Y1 =−-16.724(SEM = 40.06) + 0.86X(SEM = 0.05) and Y2 = −43.81(SEM = 49.19) + 0.75X(SEM = 0.05). It was concluded that diets with 120 g/kg of CP optimize the microbial synthesis and efficiency and ruminal ash and protein NDF digestibility, resulting in a better use of N compounds in the rumen. The PB technique can be used as an alternative to the 15N to estimate microbial synthesis.
机译：这项研究的目的是评估降低饮食中CP含量对1）全面和部分营养物消化和氮平衡以及2）对微生物粗蛋白（> MCP ）合成和真实MCP消化率的影响。在牛中以 15 N和嘌呤碱（> PB ）获得的小肠。在瘤胃和回肠中插管的八头公牛（4头Nellore和4头杂种Angus×Nellore）分布在重复的4×4拉丁方格中。饮食包括增加CP含量：随意提供100、120或140 g CP / kg DM，以及以120 g CP / kg DM限制饮食（> RI ）。实验持续了四个17天的时间，其中10天用于适应饮食，另外7天用于数据收集。使用Co-EDTA和不易消化的NDF（> iNDF ）作为标记物获得了Omasal消化道流量，并且仅使用iNDF来估计回肠消化道流量。在每个实验阶段的第11至17天，瘤胃中注入Co-EDTA（5.0 g / d）和 15 N（7.03 g硫酸铵，其中富含10％的 15 N个原子）。 CP含量对瘤胃OM消化率没有影响（线性效应，P = 0.55，二次效应，P = 0.11）。饮食中CP含量越高，CP的摄入量线性增加（P <0.01）。 NH3-N（P <0.01）和尿中N的排泄（P <0.01）随日粮CP的增加而增加，而保留的N呈线性增加（P = 0.03）。相对于与颗粒物相关的细菌（> PAB ），与气味相关的液体相关细菌（> LAB ）的氮含量更高（P <0.05）。对于 15 N： 14 N比率，LAB和PAB之间没有差异（P = 0.12）。 RI动物中 15 N： 14 N的比例相对于自愿喂养的动物更大（P <0.01）。响应于CP的增加，微生物CP呈二次趋势（P = 0.09）。微生物效率（相对于表观瘤胃可降解的OM和真正瘤胃可降解的OM表示）具有CP的二次趋势（分别为P = 0.07和P = 0.08），并且在120 g CP / kg DM时数值最大。估算MCP（Y1）和总CP（Y2）的真实肠消化率的调整方程分别为：Y1 =-16.724（SEM = 40.06）+ 0.86X（SEM = 0.05）和Y2 = -43.81（扫描电镜= 49.19）+ 0.75倍（扫描电镜= 0.05）。结论是，日粮中CP含量为120 g / kg时，可优化微生物的合成和效率，并提高瘤胃灰分和蛋白质NDF的消化率，从而在瘤胃中更好地利用N化合物。 PB技术可以替代 15 N来估算微生物的合成。

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