Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Animal Science


Two trials were conducted to determine the total aromatic amino acids (TAAA) and phenylalanine (L-PHE) requirement for pregnant swine. In trial one, twelve Yorkshire x Landrace (Y x L) gravid gilts and in trial two six Y x L gravid gilts were assigned to 6 x 6 Latin-square experiments from d 40 to d 100 of gestation. A basal 12% protein diet of dextrose, corn starch, dried whey, L-glutamic acid, solka floc, soybean oil, amino acids, minerals and vitamins was fed at a rate of 1.82 kg/d. In trial one, the basal diet (.13% L-PHE plus L-TYR) was supplemented with L-PHE to provide 2.37 (basal), 4.19, 6.00, 7.83, 9.65, and 11.47 grams/day (g/d) TAAA. In trial two, the basal diet was supplemented with 6.00 g/d L-TYR and 1.46 (basal), 2.27, 3.27, 4.20, 5.10, and 6.00 g/d L-PHE. Each treatment diet was fed within each of six 10-d periods. In trial one, urine nitrogen (N) excretion decreased, while daily (N) retention increased (lin. P < .01, quad. P < .05) with increasing levels of TAAA intake to a breakpoint of .43% and .42% or 7.38 and 7.64 g/d TAAA, respectively. Fasting and postfed plasma urine N concentrations decreased (lin. and quad. P < .01) to a breakpoint of .37% and .34% or 6.73 and 6.19 g/d, respectively. Urine urea decreased (lin. P < .01) with increasing dietary TAAA to 9.65 g/d or .53% intake. Plasma L-PHE and L-TYR increased (lin. P < .01) as dietary total TAAA intake increased. In trial two, maximum N retention and minimum urine N excretion (lin. P < .05) occurred when 5.10 g/d L-PHE (.28% of diet) were consumed. Plasma urea N did not change significantly, however, the lowest level occurred at an intake of 2.73 g/d L-PHE (.15% of diet). Urine N responded (quartic, P < .05) to increasing levels of L-PHE with minimum excretion occurring when 4.2 g/d L-PHE (.23% of diet) were consumed. As L-PHE intake increased plasma L-PHE concentrations postfed increased (lin. P < .01) and 3.27 g/d L-PHE (.18% of diet) increased postfed concentrations equal to fasted concentrations. Fasting levels of L-TYR increased (lin. P < .05; cubic, P < .01) with increasing levels of L-PHE intake while postfed concentration did not change. Considering the criteria evaluated in trial 1 and adjusting for diets containing natural feedstuffs, .41% or 7.44 g/d TAAA seems to meet the dietary requirement for pregnancy. Response criteria in trial 2 suggest a minimal L-PHE intake of .24% or 4.35 g/d.



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James Curtis Trew



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42 pages