37 Supplemented with Yucca Schidigera Extract to Feedlot Cattle Consuming Diets with or Without Monensin

Abstract

Abstract This experiment compared performance and physiological responses of feedlot cattle receiving a saponin containing feed ingredient manufactured from purified extract of Yucca schidigera [Micro-Aid (MA); DPI Global, Porterville, CA] which replaced or was fed in conjunction with feed-grade antimicrobials. Yearling, Angus-influenced steers (n = 20) arrived at the experimental feedlot on d -19 and a shrunk body weight (BW; 309 ± 4 kg) was immediately recorded. Steers were ranked by BW and allocated to 4 groups of 30 steers each. Groups were housed in of 4 drylot pens equipped with GrowSafe automated feeding systems (4 bunks/pen) during the experiment (d -15 to 69). On d 0 groups were randomly assigned to receive a total mixed ration containing: monensin and tylosin (RT; 360 mg/steer daily from Rumensin and 90 mg/steer daily from Tylan; Elanco Animal Health, Greenfield, IN) and/or 4 g/steer daily of MA in a 2 × 2 factorial arrangement of treatments. During the experimental period non-supplemented (CON) steers received a total mixed ration containing no additives. Individual feed intake was recorded daily, and steer BW was recorded every 28 d and before slaughter. Steers were slaughtered according to BW and slaughter groups were balanced by treatments (36 steers on d 120, 36 steers on d 146, and 48 steers on d 174). Carcass traits were recorded upon slaughter. On d 55 eight rumen-cannulated heifers were housed with yearling steers (1 pair/pen). Pairs rotated among groups every 21 d, resulting in a 4 × 4 Latin Square design (n = 8 per treatment) with a 5-day washout between rotations. Rumen fluid was collected from pairs on d 55, 75, 90,110, 125, 145, 160, and 180 (beginning and end of each 21-day rotation) and pH was recorded immediately after collection. No RT × MA treatment interactions were detected (P > 0.10). Feed intake was decreased (P < 0.01) in steers receiving RT, whereas feed efficiency was greater (P = 0.02) in steers receiving RT. Carcass variables including hot carcass weight, backfat thickness, Longissimus muscle area, marbling, yield grade, and percent of carcasses grading choice or better did not differ among treatments (P ≥ 0.17). Rumen fluid pH was greater (P = 0.04) in steers receiving RT. Steers receiving MA had greater (P = 0.03) rumen fluid pH and decreased (P = 0.04) rumen fluid viscosity. Collectively, supplementing feedlot cattle with Yucca schidigera extract improved rumen pH and viscosity, but failed to impact performance or carcass measures in feedlot cattle.