摘要
The objective of this experiment was to assess a new method to determine the bioavailability (BA) of rumen-protected (RP)His, RPLys and RPMet products by determining rumen escape (RE) and fecal excretion of undigested AA from RPAA. Eight lactating Holstein cows (79 ± 21 days in milk, 53.0 ± 7.0 kg/d milk yield), four of which rumen-cannulated, were used in a replicated 4 × 4 Latin square design experiment with four, 26-day experimental periods and a preceding 22-day background (BG) period. Four combinations of nine commercial and experimental RPAA (HisA, HisB, LysA, LysB, LysC, MetA, MetB, MetC, MetD) were fed daily to supply 20, 25, and 35 g/day of digestible (d)His, dLys and dMet, respectively. The following treatment combinations were used: (1) HisALysAMetA, (2) HisBLysBMetB, (3) LysCMetC and (4) LysCMetD. Spot sampling of feces was performed during the BG period to establish basal levels of AA in feces. Total fecal collection and blood sampling were performed during the last three days of each experimental period. Rumen escape fraction of each RPAA product was determined in situ and was greater for HisA (0.90) than for HisB (0.64), ranged from 0.33 to 0.85 (SEM = 0.017) for RPLys and from 0.53 to 0.95 (SEM = 0.017) for RPMet. Apparent post-ruminal digestibility of AA from RPAA was calculated as [(RE of AA, g/day – BG corrected fecal AA output, g/day) ÷ RE of AA, g/day]. Digestibility was similar between the two RPHis products (0.85 and 0.90). Apparent post-ruminal digestibility of Lys from RPLys products varied from 0.30 to 0.79 and digestibility for RPMet varied from 0.85 to 0.96. Bioavailability was calculated as: (RE, g/g × AA digestibility, g/g) × 100 and was greater for HisA compared with HisB (76.1 and 57.9 % respectively), varied from 9.63 (LysC) to 67.0 % (LysA) for the RPLys and was lowest for MetC (49.3 %) and greatest for MetD (91.9 %) among the RPMet products. Plasma His concentration was greater for HisA than for HisB and plasma Met concentration was greater for MetD compared with the other three RPMet products, reflecting estimated BA of the RPAA products. In contrast, plasma Lys concentration did not differ among RPLys products. This study showed that a method using fecal AA output in combination with RE of RPAA can reveal differences in BA between RPAA products. This is a first step in establishing the fecal AA excretion technique for determination of BA of RPAA and warrants further validation.
摘要译文
本实验的目的是评估一种新的测定瘤胃保护的（RP）His，RPLys和RPMet产品的生物利用度（BA）的方法，方法是确定RPAA中未消化的氨基酸的瘤胃逸出量（RE）和粪便排泄。在重复的4×4拉丁方设计实验中使用了8头泌乳荷斯坦奶牛（奶牛79±21天，产奶量53.0±7.0 kg / d），其中四只瘤胃经空心包装，有四个，26天的实验时间，前22天的背景（BG）期间。每天饲喂九种商业和实验RPAA的四种组合（HisA，HisB，LysA，LysB，LysC，MetA，MetB，MetC，MetD），以每天提供20、25和35 g的可消化（d）His，dLys和dMet，分别。使用以下治疗组合：（1）HisALysAMetA，（2）HisBLysBMetB，（3）LysCMetC和（4）LysCMetD。在BG期间对粪便进行现场采样，以建立粪便中AA的基础水平。在每个实验期的最后三天进行全部粪便收集和血液采样。每个RPAA产品的瘤胃逸出率均在原位测定，对于HisA（0.90）大于HisB（0.64），RPLys的范围为0.33至0.85（SEM = 0.017），RPMet的范围为0.53至0.95（SEM = 0.017） 。 RPAA中氨基酸的瘤胃后消化率的计算公式为[（AA的RE，克/天– BG校正后的粪AA的产量，g /天）÷AA的RE，克/天]。两种RPHis产物的消化率相似（0.85和0.90）。 RPLys产品的Lys的瘤胃后表观消化率从0.30到0.79不等，RPMet的消化率从0.85到0.96不等。生物利用度的计算公式为：（RE，g / g×AA消化率，g / g）×100，HisA高于HisB（分别为76.1和57.9％），HisA的生物利用度从9.63（LysC）到67.0％（LysA）变化RPMy产品中RPLys最低，MetC最低（49.3％），MetD最高（91.9％）。与其他三种RPMet产品相比，HisA的血浆His浓度高于HisB，MetD的血浆Met浓度较高，这反映了RPAA产品的估计BA。相反，RPLys产品之间的血浆Lys浓度没有差异。这项研究表明，将粪便AA输出与RPAA的RE结合使用的方法可以揭示RPAA产品之间的BA差异。这是建立用于确定RPAA BA的粪便AA排泄技术的第一步，值得进一步验证。
S.E.Räisänen[a];C.M.M.R.Martins[a][b];K.Nedelkov[a][c];J.Oh[a][d];M.T.Harper[a];A.Melgar[a];X.Chen[a][e];C.Parys[f];R.A.Patton[g];M.Miura[h];A.N.Hristov[a]. Bioavailability of rumen-protected methionine, lysine and histidine assessed by fecal amino acid excretion[J]. Animal Feed Science and Technology, 2020,268