A MODIFIED NYLON BAG TECHNIQUE FOR DETERMINING APPARENT DIGESTIBILITIES OF PROTEIN IN FEEDSTUFFS FOR PIGS

Abstract

A method for measuring protein digestibility of small feed samples was developed with growing pigs fitted with a single cannula in the duodenum. Feed was ground through a 0.8-mm mesh screen and 1-g samples were enclosed in 25 × 40-mm monofilament nylon bags (50-μm mesh). Following pre-digestion in vitro to simulate gastric digestion (0.01 N HCI; pepsin 1 g/L; 2.5 h), the bags were inserted into the small intestine via the duodenal cannula, recovered in feces within 48 h, frozen, lyophilized and analyzed for protein. Apparent protein digestibility of soybean meal and meat-and-bone meal were 88.1 and 80.9%, respectively, compared with 90.0 and 79.1, respectively, determined conventionally. Protein digestibility (nylon bag vs. conventional technique) for three barley samples were 63.2 vs. 65.2%, 62.8 vs. 67.6% and 62.3 vs. 67.5%. The pigs were fed a 16% crude protein grower diet during the nylon bag studies. Preliminary studies showed no recovery of nylon bags in feces, unless the pig was starved for 1 day, when these were administered via a gastric cannula. The nylon bag technique, when samples are inserted via the duodenal cannula, appears to be a promising approach for rapid determination of protein digestibilities in small samples of feedstuffs. Key words: Nylon bag, digestibility, protein, cannula, pigs