Digestion characteristics and growth of steers fed a corn-grain based supplement compared to a de-oiled rice bran plus cottonseed supplement with or without extrusion processing

This study evaluated ruminal digestion characteristics and performance of beef steers supplemented with either a conventional or co-product based feed, and the effects of extrusion of the co-product supplement. In experiment 1, a 3 × 3 Latin square design was used to evaluate ruminal digestion characteristics in cannulated beef steers fed hay plus (1) corn and cottonseed meal (71:29, w/w DM; CCSM); (2) de-oiled rice bran and whole cottonseed (62:38, w/w DM; DRCS) or; (3) extrusion processed DRCS supplement (EXT) with the de-oiled rice bran and cottonseed supplement being mixed before extrusion. Supplements were offered at 10 g/kg body weight (BW). Contrasts were used to evaluate differences between supplements, (1) CCSM versus the average of the DRCS and EXT and, (2) DRCS versus EXT. Neither supplement type nor processing affected predicted hay dry matter (DM) intake, supplement DM intake, or total DM intake, and supplement DM degradation rate in the rumen did not differ. However, rate of passage of the CCSM (58.4 g/kg/h) supplement was higher (P = 0.01) than the DRCS (44.1 g/kg/h) and EXT (45.3 g/kg/h) supplements. Passage rate also tended (P = 0.08) to be higher with EXT versus DRCS. Supplement type or processing did not affect hay DM degradation rate or passage rate (P > 0.10). Supplement type tended (P = 0.06) to change the ruminally degradable crude protein to ruminally degradable organic matter (OM) ratio (g/kg, RDP:RDOM) with CCSM supplement having a RDP:RDOM of 185 compared to 114 for DRCS and EXT. Supplement type or processing did not affect overall diet RDP:RDOM or total tract DM digestibility. Seventy-two crossbred beef steers were used in experiment 2. Hay DM intake tended (P = 0.07) to be higher for CCSM supplemented versus DRCS or EXT supplemented calves. Despite the tendency for higher hay intake of CCSM calves, ADG did not differ. De-oiled rice bran plus whole cottonseed can effectively replace corn plus cottonseed meal as a supplement for growing cattle fed low-quality hay, and extruding the de-oiled rice bran plus cottonseed supplement did not alter animal performance.