Diet sample collection by esophageal fistula and rumen evacuation techniques

Abstract

Two trials were conducted to compare diet samples collected in the evacuated rumen or through the esophageal fistula. Hypotheses tested were (1) rumen evacuation would not decrease selectivity, (2) being in the rumen during collection would not alter the sample, and (3) both techniques accurately estimated nutritional characteristics of the feed offered. Five steers bifistulated at the esophagus and rumen were used in a grazing and a stall trial. Three collection techniques were used in each trial: rumen collection after evacuation (RC), esophageal collection with the rumen evacuated (ECRE), and esophageal collection with the rumen full (ECRF). Comparison of RC and ECRE assessed the influence of being in the rumen, and ECRE vs ECRF tested selectivity. Hay was sampled before feeding in the stall trial to test hypothesis 3. All samples were analyzed for organic matter (OM), nitrogen (N), neutral detergent fiber (NDF), acid detergent fiber (ADF), acid detergent lignin (ADL), hemicellulose, and cellulose. In the grazing trial, collection technique affected only ADL (P = 0.05), with ECRE depressed compared to ECRF. Organic matter, N, ADL, and hemicellulose responded (P < 0.05) during the stall trial as follows. Salivary ash contamination depressed OM (P = 0.03) in all collected masticate compared to the feed offered. Rumen collection elevated N (P = 0.04), but esophageal samples and feed were equal. Hemicellulose was depressed slightly (P = 0.01) in all collected masticate. Both techniques elevated ADL (P = 0.001), with RC having a greater effect than ECRF. Both collection techniques should provide satisfactory results in grazing trials if precautions are taken. Comparison across techniques appears appropriate if caution is exercised, particularly concerning N and ADL.