Availability of amino acids for 10- to 20-kilogram pigs: lysine and threonine in soybean meal.

ABSTRACT

The availabilities of lysine and threonine in soybean meal for 10- to 20-kg pigs were determined in two experiments using slope-ratio methodology. In the first experiment, a basal diet formulated to contain 6 g of lysine/kg, but adequate in all other amino acids, was supplemented with 1, 2, or 3 g of lysine/kg from either soybean meal or L-lysine-HCl. Each of the seven diets was available on an ad libitum basis to six individually penned pigs (barrowsgilts, 11) from an initial weight of 9.9 kg until they reached a live weight of 20.8 kg. Daily feed intake was similar among diets. Common-intercept multiple linear regression of daily live weight gain and gainfeed ratio on dietary lysine level indicate slope ratios (soybean meallysine.HCl) of .85 and .88, respectively. In Exp. 2, a basal diet formulated to contain 4 g of threonine/kg was supplemented with .65, 1.30, 1.95, or 2.60 g of threonine/kg from either soybean meal or L-threonine. Each of the nine diets was available on an ad libitum basis to six individually penned pigs (barrowsgilts, 11) from 9.9 to 21.0 kg live weight. As in Exp. 1, daily feed intake was similar among the nine diets. The slope ratios (soybean mealL-threonine) from common-intercept multiple regression analyses were .73 and .78 for daily weight gain and gainfeed ratio, respectively. Thus, the availabilities of lysine and threonine in soybean meal for young pigs were estimated to be 85 to 88% and 73 to 78%, respectively.