Chemical composition and porcine in vitro disappearance of heat-pretreated and multi-enzyme-supplemented soybean hulls

Abstract

Soybean hulls are poorly digested by pigs. Heat-pretreatment or the use of fiber-degrading enzyme supplementation of soybean hulls can potentially improve the digestibility of soybean hulls. Thus, study was conducted to determine the effects of heat pretreating (at 160 °C and 70 psi for 20 min) and supplementing soybean hulls with the multienzyme product, Superzyme-OM (Canadian Bio-Systems, Alberta, Calgary, AB, Canada), which was in liquid form in was dosed at 3 mg/g of sample, which supplied 5100 U of cellulase, 3300 U of pectinase, 720 U of mannanase, 90 U of galactanase, 3600 U of xylanase, 1080 U of glucanase, 4500 U of amylase, and 360 U of protease per kilogram of feedstuff on porcine in vitro nutrient disappearance. The samples were subjected to in vitro enzymatic hydrolysis using pepsin and pancreatin. The samples were incubated in a buffer solution with fresh pig feces as inocula for 72 h to measure gas production. Concentration of volatile fatty acids (VFA) per gram of dry matter (DM) of samples was measured in fermented solutions. On a DM basis, untreated and pretreated soybean hulls contained 10.4 and 10.6 % crude protein. Heat pretreatment reduced total non-starch polysaccharides content of soybean hulls from 71.5 to 64.2%. Heat pretreatment and multi-enzyme supplementation did not interact on coefficient of in vitro disappearance of dry matter (IVDDM). Heat pretreatment increased (P < 0.01) the coefficient of IVDDM of soybean hulls by a mean of 45.5 % whereas multi-enzyme supplementation tended to increase (P = 0.055) the coefficient of IVDDM of soybean hulls by 3%. Heat pretreatment and multi-enzyme interacted (P < 0.05) on fractional rate of degradation and half time such that the fraction rate of degradation for soybean hulls increased (P < 0.01) and the half time for soybean hulls decreased (P < 0.05) when both heat-pretreated and multi-enzyme supplemented. Cumulative gas volume for heat-pretreated soybean hulls at 8, 12, 18, 24, 36, and 48 h after the commencement of incubation was greater (P < 0.01) than that of untreated soybean hulls. Heat pretreatment of soybean hulls increased (P < 0.05) the VFA production per gram of DM of feedstuff. In conclusion, heat-pretreatment and multi-enzyme supplementation increased IVDDM of soybean hulls, implying that the heat pretreatment used in the current study can be used to enhance the nutrient utilization of soybean hulls for pigs.