Responses of milk protein,arterial AA concentration,and mammary AA metabolism to graded abomasal casein infusion in lactating goats |
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| Institution: | 1. College of Science, Northwest A&F University, Yangling, Shaanxi 712100, PR China;2. Department of Physics, Pukyong National University, Busan 608-737, Republic of Korea;3. Department of Chemistry, University of Massachusetts Amherst, 710 North Pleasant Street, Amherst, MA 01003, United States;1. Department of Chemical and Materials Engineering, University of Idaho, Moscow ID 83844, USA;2. Department of Materials Science and Engineering, University of North Texas, Denton, TX 76203, USA;1. The State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, No. 1295 Dingxi Road, Shanghai 200050, China;2. University of Chinese Academy of Sciences, No. 19A Yuquan Road, Beijing 100049, China;1. China Aviation Lithium Battery Co. Ltd., Luoyang 471003, China;2. School of Chemistry and Chemical Engineering, Jiangsu Key Laboratory of Green Synthetic Chemistry for Functional Materials, Jiangsu Normal University, Xuzhou 221116, China;3. College of Chemistry and Molecular Science, Wuhan University, Wuhan 430072, China;1. Key Laboratory of Analytical Science and Technology of Hebei Province, College of Chemistry and Environmental Science, Hebei University, Baoding 071002, PR China;2. College of Science, Agriculture University of Hebei, Baoding 071000, PR China |
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| Abstract: | It has been generally assumed in postruminal protein or AA infusion studies that casein or AA mixtures mimicking the essential AA (EAA) composition of milk approach ‘ideal protein’ status, but the differences in postabsorptive metabolism of individual EAA may bring the assumption into question. Graded amounts of caseinate sodium were abomasally infused into lactating goats, and concentrations in the plasma of carotid, mammary uptakes and utilization efficiencies of amino acids were monitored in the present study. The results indicated that arterial concentrations of all the amino acids, except for Arg were increased with the increase of caseinate sodium infused (P < 0.05). The increments in plasma concentration differed with individual EAA. Concentrations of Ile, Leu, and Lys increased about two-folds, and that of Met, Thr, Phe, and His increased 58.33, 32.5, 29.87, and 61.66%, respectively, when data of the 99 g/day and the control treatment was compared. Mammary extraction efficiencies of Arg, Thr, Lys, Leu, and Phe increased with graded casein infusion (P < 0.05), while those of the other EAA were not significantly changed (P > 0.05). Mammary extraction efficiencies of individual non-essential amino acids (NEAA) varied greatly, and ranged from 9.18 to 33.89% in the control treatment. Except for Pro, mammary extraction efficiency of NEAA increased with graded casein infusion. Mammary uptake to milk output ratios (U/O) of sequestered AA was generally increased with the increase of casein infused, but that of Thr, His, and Ala was not insignificantly changed (P > 0.05). Compared with the data of previous researchers, the U/O of Thr recorded in the present study was much lower (<0.42). We speculate that Thr may be extracted in forms other than FAA (such as peptide bond AA) by the mammary under conditions of the present study. Consistent with the results of other authors, mammary uptake of Arg was two times more than milk output even in the control treatment, which suggests that there may be a requirement of Arg other than milk protein synthesis in the mammary. |
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