A MODIFIED METHOD FOR DETERMINATION OF IN SITU RUMEN DEGRADATION OF FEEDSTUFFS

Abstract

In situ rumen dry matter (DM) and crude protein (CP) disappearance of various feed-stuffs was studied in Holstein cows. Comparisons of nylon bag size, method of containment within the rumen, and washing technique were made to develop a system which would reduce labor and improve precision among and within laboratories. Bags (7.0 × 11.0 cm) were suspended individually in the rumen by fishing line, or placed in a polyester mesh bag before being put in the rumen. No differences were observed between method of suspension in the rumen. The polyester mesh bag was then used to contain two nylon bag types (3.5 × 5.5 cm, 1-g sample (BT1); 7.0 × 11.0 cm; 5-g sample (BT2)) for incubation in the rumen. Small bags (BT1) were heat-sealed. Dry matter and CP disappearances from BT1 were lower than from BT2. These differences were attributed to washing technique as the larger bag (BT2) was washed more vigorously. A mechanical washing wheel was designed and built to reduce variability due to washing by hand. Bags washed by machine followed by hand washing had slightly higher DM and CP disappearances than bags washed by machine only; however, these differences did not significantly influence effective degradability. Feedstuffs were reincubated in small bags and large bags, and bags were mechanically washed. Dry matter and CP disappearance and effective rumen degradabilities of DM- and CP, assuming a constant rate of outflow, were not significantly different between bag types. Use of heat-sealed small bags (3.5 × 5.5 cm), containing 1-g samples incubated in the rumen within a polyester mesh bag, and a mechanical washer, provides a system for measuring in situ DM and CP disappearance from nylon bags which reduces labor input, can potentially improve consistency among and within laboratories, and facilitates high sample throughput. Key words: In situ, rumen, degradability, mechanical washer, Holstein cows