The Amino Acid Requirements of Swine: I. Tryptophan

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Abstract
A diet inadequate in tryptophan was established by modifying the diet of Heinemanu (1946). It was composed of hydrolyzed fish protein (26.1%), dextrose (30.2%), dextrin (25%), lard (11%), minerals (5.2%), celluflour (2%), and liver extract (0.5%). Water-soluble vitamins were added as listed by Heinemann, except that thiamin chloride was fed at a level of 0.4 mg./kg. of live wt./pig daily. Each pig was fed 1,500 I.U. of vit. A, 200 I.U. of vit. D, 50 mg. of a-toco-pherol, and 2 mg. of vit. K daily. The hydrolyzed protein was treated to remove most of the tryptophan. dl-Trypto-phan was added to the control diet (group A) at a level of 0.4% of the total ration. Four [male][male] and 4 [female] [female] were paired for the exptl. study. They were fed twice daily. The controls (group A, 4 pigs) receiving the purified ration plus 0.4% dl-tryptophan, had an avg. daily gain of 1.42 lbs. for 28 days. They had glossy smooth hair coats. At 28 days they were removed from the expt., and they averaged 96 lbs. in wt. Group B (4 pigs) on the deficient diet lost 2.13 lbs./pig after 1 week, while those receiving 0.4% dl-tryptophan gained an avg. of 8.9 lbs. in the first wk. Two pigs after 21 days lost an avg. of 5.5 lbs., and had symptoms of inanition. Addition of dl-tryptophan produced a growth rate of 1.47 lbs./pig daily for the next 19 days of the expt. The gloss returned to their hair coat. The other 2 pigs were held on the deficient diet for 14 days, after which 0.4% dl-tryptophan was added. Before addition, the pigs lost 3.5 lbs. in 14 days; after addition, there was an avg. gain of 1.06 lbs. daily for 26 days. Their appearance improved markedly. Tryptophan is an indispensable amino acid for growing pigs.