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Asian-Australas J Anim Sci > Accepted Articles
DOI: https://doi.org/10.5713/ajas.19.0498    [Accepted] Published online November 1, 2019.
Administration of encapsulated L-tryptophan improves duodenal starch digestion and increases gastrointestinal hormones secretions in beef cattle
Sang-Bum Lee1  , Kyung-Won Lee2  , Tao Wang3  , Jae-Sung Lee1,*  , U-Suk Jung1  , Jalil Ghassemi Nejad4  , Young-Kyoon Oh5  , Youl-Chang Baek5  , Kyoung Hoon Kim6  , Hong-Gu Lee1,4,* 
1Department of Animal Science and Technology, Sanghuh College of Life Sciences, Konkuk University, Seoul 05029, Korea
2Life Science Technology, Inc., Seoul 06134, Korea
3Department of Animal Nutrition and Feed Science, College of Animal Science and Technology, Jilin Agricultural University, Jilin 130118, China
4Team of an Educational Program for Specialists in Global Animal Science, Brain Korea 21 Plus Project, Sanghuh College of Life Sciences, Konkuk University, Seoul 05029, Korea
5Department of Nutrition and Physiology, National Institute of Animal Science, RDA, JeonJu 55365, Korea
6Graduate School of International Agricultural Technology, Pyeongchang Campus, Seoul National University, Pyeongchang 25354, Korea
Correspondence:  Jae-Sung Lee, Tel: +821058804153, Fax: +82-33-242-4540, Email: jalil@kangwon.ac.kr
Hong-Gu Lee, Tel: +821058804153, Fax: +82-33-242-4540, Email: jalil@kangwon.ac.kr
Received: 17 June 2019   • Revised: 23 August 2019   • Accepted: 17 June 2019
This study investigated the effects of oral administration of rumen-protected L-tryptophan (RPL-T) on duodenal starch digestion and gastrointestinal hormones (GIH) secretions using Hanwoo beef steers as the animal models.
Four steers (423 ± 24 kg) fitted with ruminal and duodenal cannulas were employed in a crossover design replicated twice. Treatments were control (basal diet) and RPL-T (basal diet+191.1 mg/kg BW) group. Blood and duodenal samples were collected to measure serum GIH levels and pancreatic α-amylase activity at day 0, 1, 3, and 5 (-30, 30, 90, 150, and 210 min) of the study. Samples from each segment of the gastrointestinal tract were collected via ruminal and duodenal cannulas and were used to determine soluble protein and the starch digestion rate at days 6 (-30, 180, 360, and 540 min) and 8 (-30, 90, 270, and 450 min) of the experiment.
No significant difference in ruminal pH, NH3-N, and total VFA including the levels of acetate, propionate, butyrate, isobutyrate, valerate, isovalerate, and the acetate-to-propionate ratio was observed between groups (p>0.05). Crude protein uptake was higher and feces starch content was lower in RPL-T group than the control group (p<0.05). The D-glucose contents of feces in RPL-T group decreased at day 5 compared to those in the control group (p<0.05), however, no change was found at day 0, 1, or 3 compared to the control group (p>0.05). Serum cholecystokinin (CCK), Melatonin (MEL), duodenal pancreatic α-amylase activity, and starch digestion were significantly higher in RPL-T group than the control group (p<0.05).
Taken together, oral administration of RPL-T at the rate of 191.1 mg/kg BW consistently increased CCK concentration, pancreatic α-amylase activity in duodenal fluids, and starch digestion rate in the small intestine and thus found to be beneficial.
Keywords: α-Amylase; Cholecystokinin; L-tryptophan; Monogastric; Polygastric Model; Protein
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