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Journal Paper Article Abstract

Bioavailability of Tryptophan in Soybean Meal for
10-kg Pigs Using Slope-Ratio Assay

Olayiwola Adeola
Department of Animal Sciences
Purdue University, West Lafayette, IN 47907

ABSTRACT: A basal diet formulated to contain 1.1 (analyzed to contain 1.03) g of tryptophan/kg, but adequate in all other amino acids, was supplemented with .2, .4, or .6 g tryptophan/kg from L-tryptophan, or .2 or .4 g tryptophan/kg from soybean meal. Each of the six diets was fed for 28 d to six barrows and six gilts (individually penned) with an average initial weight of 9.8 kg. Dietary supplemental tryptophan from either L-tryptophan or soybean meal increased (P < .05) daily weight gain, feed intake, and gain:feed ratio. Plasma concentrations of tryptophan increased and urea decreased with increasing dietary L-tryptophan supplementation (P <. 05). Common-intercept, multiple linear regressions in slope-ratio methodology were performed using non-partitioned and partitioned daily weight gain, gain:feed ratio, or plasma tryptophan:urea ratio as dependent variables and supplemental tryptophan level (g/kg), daily total tryptophan intake (g/d), or daily supplemental tryptophan intake (g/d) as independent variables. For each of the three dependent variables, estimates of tryptophan bioavailability were > 100% when daily supplemental tryptophan intake was used as the independent variable. Estimates of TRP bioavailability based on non-partitioned ADG were 90, 99 and 110% when supplemental TRP level, daily total TRP intake and daily supplemental TRP intake were used as the independent variables, respectively.

Key Words: Soybean Oilmeal, Tryptophan, Bioavailability, Pigs, Plasma Urea, Plasma Amino Acids

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