caa a22 4500 388063262 CHVBK 20180307125127.0 cr unu---uuuuu 161130e199807 xx s 000 0 eng 10.1017/S0007114598001822 doi S0007114598001822 pii (NATIONALLICENCE)cambridge-10.1017/S0007114598001822 Uptake of acetylated peptides from the small intestine in sheep and their nutritive value in rats [Elektronische Daten] Acetylation is a potential method for protecting dietary peptides from degradation by rumen micro-organisms. As a first step in determining the nutritive value of acetylated peptides, their disappearance in the small intestine of sheep and their ability to support growth in a rat bioassay were measured. 15N-labelled peptides were prepared from lucerne which had been grown with 15N-labelled (NH4)2 SO4 in the absence of Rhizobium. Peptides were prepared by enzymic hydrolysis of the extracted protein. Two peptide preparations were made using different proteinase mixtures. These mixtures contained peptides with an average molecular weight of 559 and 522 Da. They were treated with acetic anhydride, which resulted in 85 and 88% modification respectively, and their uptake from the small intestine was determined by injecting 1 g of untreated or acetylated peptides in a Cr-EDTA solution into the jejunum of two sheep fitted with jejunal catheters and ileal cannulas. Ileal digesta were collected and analysed for Cr and 15N. The uptake of dialanine (Ala2) and N-acetyl-Ala2 were compared in a similar way. The disappearance of 15N from lucerne peptides was high (88 and 93% respectively) and this was not affected significantly by acetylation (86 and 87%). Corresponding values for Ala2 and N-acetyl-Ala2 were both 96%, as measured by HPLC. It was therefore concluded that acetylation did not affect the uptake of peptides from the small intestine in sheep. Two feeding trials were carried out with rats. The first trial was carried out with a protein-free diet to which was added 10% lactalbumin or 5% lactalbumin and then a mixture of methionine-free amino acids, either alone or supplemented with Met, Gly-Met or acetylated Gly-Met. The rats grew equally well on all sources of Met, but failed to grow significantly on the mixture of Met-free amino acids. In the second trial the diet contained casein as 5·9% of the basal diet. Additional casein, pancreatic casein hydrolysate (peptides) and acetylated pancreatic casein hydrolysate (acetylated peptides) were compared as sources of amino acids, at inclusion rates of 100 g/kg final diet. Feed intake was similar with casein and peptides treatments, but was depressed by 23% with acetylated peptides. Live weight gain was 15 and 75% lower with the peptides and acetylated peptides diets respectively. Addition of lysine, arginine or histidine did not restore feed intake or weight gain of rats receiving acetylated peptides, but feed intake was restored immediately when peptides replaced acetylated peptides. When intake was restricted to 9 g/d and acetylated casein hydrolysate replaced half of the protein in the diet, rats gained weight less rapidly (1·44 v: 1·09 g/d) and retained less N, such that only 0·36 of the acetylated peptide-N was calculated to remain available to the animal. This N retention compared with 0·70 for unmodified casein. Thus, the rat bioassay indicated that certain specific peptides may well be of high nutritive value following acetylation, but that there may be problems of inappetance and inefficient utilization with acetylated peptide mixtures. Copyright © The Nutrition Society 1998 Acetylated peptides nationallicence Small intestine nationallicence Nutritive value nationallicence Sheep nationallicence Rat nationallicence Wallace R. J. Rowett Research Institute, Bucksburn, Aberdeen AB21 9SB, UK Min W. K. Rowett Research Institute, Bucksburn, Aberdeen AB21 9SB, UK Witt M. W. Rowett Research Institute, Bucksburn, Aberdeen AB21 9SB, UK Grant G. Rowett Research Institute, Bucksburn, Aberdeen AB21 9SB, UK MacRae J. C. Rowett Research Institute, Bucksburn, Aberdeen AB21 9SB, UK Maeng W. J. Kon-Kuk University, Seoul, South Korea Newbold C. J. Rowett Research Institute, Bucksburn, Aberdeen AB21 9SB, UK Rode L. M. Agriculture Canada Research Station, Lethbridge, Alberta T1J 4B1, Canada British Journal of Nutrition Cambridge University Press 80/1(1998-07), 101-108 0007-1145 80:1<101 1998 80 BJN https://doi.org/10.1017/S0007114598001822 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1017/S0007114598001822 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Wallace R. J. Rowett Research Institute, Bucksburn, Aberdeen AB21 9SB, UK NATIONALLICENCE 700 1- Min W. K. Rowett Research Institute, Bucksburn, Aberdeen AB21 9SB, UK NATIONALLICENCE 700 1- Witt M. W. Rowett Research Institute, Bucksburn, Aberdeen AB21 9SB, UK NATIONALLICENCE 700 1- Grant G. Rowett Research Institute, Bucksburn, Aberdeen AB21 9SB, UK NATIONALLICENCE 700 1- MacRae J. C. Rowett Research Institute, Bucksburn, Aberdeen AB21 9SB, UK NATIONALLICENCE 700 1- Maeng W. J. Kon-Kuk University, Seoul, South Korea NATIONALLICENCE 700 1- Newbold C. J. Rowett Research Institute, Bucksburn, Aberdeen AB21 9SB, UK NATIONALLICENCE 700 1- Rode L. M. Agriculture Canada Research Station, Lethbridge, Alberta T1J 4B1, Canada NATIONALLICENCE 773 0- British Journal of Nutrition Cambridge University Press 80/1(1998-07), 101-108 0007-1145 80:1<101 1998 80 BJN CC0 http://creativecommons.org/publicdomain/zero/1.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-cambridge