Validation of the cannulated pig model for determining intestinal nutrient disappearance in cattle

Abstract

The mobile nylon bag technique was used to determine the potential of cannulated pigs to model intestinal dry matter (DM) and crude protein (CP) digestibility of ruminal undegradable residues (RUDR) of various feed samples in cattle. A total of 11 feeds (six protein supplements and five forages) varying in rumen degradability were utilized: canola meal (regular vs. heated); soybean meal (regular vs. heated); distillers’ grains (regular vs. heated ); alfalfa hay (regular vs. dehydrated alfalfa pellets); barley silage (regular vs. heated); and barley straw. Ruminal undegradable residues of each feedstuff were placed into eight polyester bags and inserted into the duodenum of two cannulated Hereford steers (644 ± 14 kg). Another eight bags for each RUDR sample were randomly allocated to six crossbred gilts (Camborough 15 line female × Canabred sire; 50 ± 1.2 kg body weight) and inserted into the pigs’ duodenum via duodenal cannulas. Bags were recovered in the feces from both the cattle and pigs. Regression analysis was used to relate intestinal DM and CP digestibility obtained in pigs with those obtained in steers. Intercepts not different from zero were forced through the zero intercept to obtain a measure of bias and loss of precision resulting from forcing the zero intercept. The non-zero regression equations relating steer estimates to those obtained from pigs were -3.17 + 0.95 X [r2 = 0.98, residual standard deviation (RSD) = 3.84] and 0.35 + 0.96 X (r2 = 0.98, RSD = 6.16) for DM and CP disappearance, respectively. Forcing the non-zero intercept resulted in pigs over predicting intestinal DM disappearance in cattle by 10.6% with a RSD of 4.30. Using the pig model, intestinal CP disappearance of cattle was over predicted by 3.1% with a RSD of 5.85. It was concluded that pigs can be used to model intestinal DM and CP disappearance of ruminal undegraded feed residues in cattle. Key words: Cattle, pigs, mobile nylon bag technique, intestinal nutrient availability