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United States Department of Agriculture

Agricultural Research Service


item Kerr, Brian
item Moran Jr, E
item Kidd, M

Submitted to: Journal of Applied Poultry Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/8/2005
Publication Date: 6/1/2005
Citation: Kerr, B.J., Moran Jr, E.T., Kidd, M.T. 2005. Effect of supplementary tryptophan prior to marketing on carcass quality in broilers. Journal of Applied Poultry Research. 14:306-314.

Interpretive Summary: Tryptophan is typically supplied in the diet with intact proteins at levels required for maximum animal growth and muscle development. When supplemental trytophan is supplied in the diet above that required for protein synthesis, it has been shown to alter brain tryptophan levels which subsequently influence the synthesis of serotonin, an inhibitory neurotransmitter in the central nervous system. In domestic animals, therapeutic functions of tryptophan include reducing feed intake, modifying aggression, suppressing hysteria, and inhibiting the response to stress. In poultry production and marketing there are potentially high levels of stress as birds are caught from growing houses and placed into transport crates, transported in these crates to processing facilities, shackled on processing chains, and handled in the processing plant. Suppression of the stress response may be beneficial in terms of animal welfare and meat quality. Experiments were conducted to determine the effect of short-term supplementation of tryptophan on behavioral and physiological responses, and meat quality indices of broilers prior to handling and processing. Data from these experiments reported that supplemental tryptophan, whether in an intubated tablet, added to the water supply, or in the final withdrawal feed was insufficient to have any meaningful effect on broiler carcass defects. Research results described in this report provides nutritionists at universities, feed companies, allied industries, and broiler production facilities information showing that short periods of high dietary levels of tryptophan have little effect on the carcass quality of broilers in response to catching or processing handling.

Technical Abstract: Three experiments were conducted to examine the effect of supplemental Trp on carcass quality of broilers. The first experiment utilized 49 d old broilers, crop intubated with two tablets containing 500 mg Trp compared to birds not crop intubated, with processing occurring 14 hr after intubation. For the second experiment, broilers were taken off feed on d 49, weighed, and allotted to either normal drinking water or offered a Trp-saturated solution containing 5 g of Trp per 1000 ml of water, for 4 hours in pens during feed withdrawal until cooping for 14 hours prior to processing. In the third experiment, a withdrawal feed was formulated with standard or high dietary Trp (2X requirement, 0.33% versus 0.18%) and fed to broilers from 46 to 49 d of age. Our results suggest that supplemental Trp, whether in an intubated tablet, water, or final feed was insufficient to have any meaningful effect on broiler carcass defects. Supplementation of Trp in the water did reduce water consumption compared to birds offered the control water (42.1 ml vs. 88.9 ml, respectively). Consequently, until the level and length of Trp supplementation can be determined to alleviate contradictory findings and inconsistent results reported in the literature, determination of the genuine effects of supplemental Trp on behavior modification and carcass quality improvements in broilers are speculative at this time.

Last Modified: 10/19/2017
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