Evaluation of the Technique of Acid Detergent Insoluble Protein Determination

Abstract

Vegetable cell wall components are commonly present in animal feeds, and are able to be used by ruminant animals. However, some of these have little digestibility or may not be digestible, taking up a big space in their gastrointestinal tract, which can affect their nutrition and performance. The cell wall is chemically composed of cellulose, hemicelluloses, pectin, lignin, and minor parts of proteins and tannins. Thus, several studies have been performed aiming at practical techniques for measuring the concentration of such structural substances. The aim of the present study was to test whether the method of separation of cell wall components using detergents [1] in a sequential way could interfere with the value of acid detergent insoluble nitrogen (ADIN). The analysis was conducted for neutral detergent fiber (NDF), acid detergent fiber (ADF) and sequentially and non-sequentially, according to USDA Agriculture (method 379) [2]. Eight feeds were tested: Brachiaria hay ( Brachiaria sp.), barley hay ( Hordeum vulgare L.), Cratylia hay ( Cratylia argentea ), sunflower silage ( Helianthus annuus ), millet silage ( Pennisetum typhoides ), maize silage ( Zea mays L.), ground and rehydrated, pequi fruit peels ( Caryocar brasiliense Camb), and Tifton 85 hay ( Cynodon sp.). Samples were ground in a Wiliey-type mill and went through a 1-mm sieve; then, they were analyzed through the ADF techniques sequentially and non-sequentially from NDF. The product of these steps was studied for the acid detergent insoluble protein (ADIP). The significant difference was seen in the determination of ADIP between the two methods for five feeds, while three feeds did not show any difference (P < 0.05). Due to our findings, we conclude that it is reasonable to determine ADIP for ADF non-sequentially from NDF.