Kovar J L, Lewis A J, Radke T R, Miller P S
Department of Animal Science, University of Nebraska, Lincoln 68583-0908.
J Anim Sci. 1993 Aug;71(8):2133-9. doi: 10.2527/1993.7182133x.
The bioavailability of threonine in solvent-extracted soybean meal for 10- to 20-kg pigs was determined using the slope-ratio method. In Exp. 1, the assay range was determined by feeding six diets to 144 pigs. The basal diet (.40% threonine) contained corn, soybean meal, and corn gluten meal. Five additional diets were formulated by supplementing the basal diet with .05 to .25% crystalline L-threonine in .05% increments. Weight gain, gain/feed, and plasma concentrations of threonine and urea responded quadratically (P < .05) to increasing dietary threonine. Breakpoints ranged from .51 to .54% dietary threonine. Experiment 2 consisted of seven trials in which a total of 239 pigs were used in a randomized complete block design. Pigs were penned individually and had ad libitum access to feed and water during the 21-d experiment. The same basal diet that was used in Exp. 1 was supplemented with .018, .053, or .070% threonine from either L-threonine or soybean meal. The weight gains of the pigs were partitioned to yield the response due to the supplemental threonine ingested. Multiple regression was performed on partitioned weight gain vs supplemental threonine intake, and the assay was tested for validity. The regression lines for L-threonine and soybean meal were linear (P < .05) and the intercepts were not significantly different (P > .10). The slope ratio for soybean meal:L-threonine was .80. Although the difference between the soybean meal and L-threonine slopes was not significant (P > .23), the best estimate of the bioavailability of threonine in soybean meal relative to that of L-threonine was 80%.
采用斜率比法测定了溶剂萃取豆粕中苏氨酸对10至20千克仔猪的生物利用率。在试验1中，通过给144头猪饲喂六种日粮来确定测定范围。基础日粮（苏氨酸含量为0.40%）包含玉米、豆粕和玉米蛋白粉。通过在基础日粮中以0.05%的增量补充0.05%至0.25%的结晶L-苏氨酸来配制另外五种日粮。随着日粮苏氨酸含量的增加，体重增加、增重/采食量以及苏氨酸和尿素的血浆浓度呈二次曲线反应（P < 0.05）。日粮苏氨酸的断点范围为0.51%至0.54%。试验2由七次试验组成，共239头猪采用随机完全区组设计。在为期21天的试验中，猪单独饲养，自由采食和饮水。试验1中使用的相同基础日粮补充了来自L-苏氨酸或豆粕的0.018%、0.053%或0.070%的苏氨酸。对猪的体重增加进行划分，以得出因摄入补充苏氨酸而产生的反应。对划分后的体重增加与补充苏氨酸摄入量进行多元回归，并对测定方法进行有效性测试。L-苏氨酸和豆粕的回归线呈线性（P < 0.05），截距无显著差异（P > 0.10）。豆粕与L-苏氨酸的斜率比为0.80。尽管豆粕和L-苏氨酸斜率之间的差异不显著（P > 0.23），但相对于L-苏氨酸，豆粕中苏氨酸生物利用率的最佳估计值为80%。
