Determination of the digestibility of neutral- and acid-detergent fiber of rough and succulent feeds using an improved method in vitro

Abstract

Goal. To study the digestibility of structural carbohydrates of rough and succulent feeds using an enzyme complex identical to the enzymes of the animal body in vitro. Methods. The content of neutral-detergent fiber (NDF) was determined by the method of hydrolysis of feed in a neutral detergent, and the content of acid-detergent fiber (ADF) was determined using an acid detergent. The digestibility of NDF and ADF of feeds was determined by the method of fermentation under optimal conditions in vitro using an enzyme complex consisting of cellulase, α-amylase, and protease. The results of the study of feed digestibility were compared with similar results obtained using the in vivo method. Results. The mass fraction of crude fiber in hay, silage and green mass samples determined following the methodological requirements of DSTU 8844:2019 was lower than the mass fraction of NDC in the same feeds. Thus, in corn silage, this indicator was almost 1.7 times lower, and in awnless hay — more than half lower, despite the fact that they included the same carbohydrate fractions, hemicellulose, cellulose, and lignin. The values of the content of ADF and crude fiber are quite close, but ADF, according to the methodological characteristics, included only cellulose and lignin. The lowest NDF digestibility coefficient was in hay harvested from awnless hay in the earing phase, and the highest was in lucerne hay harvested in the budding-flowering phase. Almost similar data on digestibility coefficients were obtained in «in vivo» experiments on ruminants: the difference between the values was within the error range. The difference between the digestibility coefficients of the ADF of the indicated feeds was somewhat greater. If the digestibility coefficients of the ADF in silage and green mass of corn were quite close, then in wheatgrass concentrate the digestibility coefficient of the ADF in in vitro conditions was 21.42%, and in in vivo conditions — 18.00%. A similar result was obtained regarding the digestibility coefficient of the ADF of the awnless stokolos (Bromus L.) hay — 20.95 and 17.73%. In lucerne hay in the budding–beginning of the flowering phase, the digestibility coefficients of the ADF in «in vitro»and «in vivo» experiments were almost at the same level and within the error range — 41.45 and 40.62%. Conclusions. The proposed method for determining the digestibility of neutral- and acid-detergent fiber of rough and succulent feeds in vitro allowed determining the digestibility coefficients of these organic substances in the body of farm animals with high accuracy and mobility.