PSXII-28 Effect of corn type and tylosin inclusion on performance and liver function in feedlot heifers

Abstract

Abstract The objective was to compare the effect of corn type and tylosin inclusion on heifer growth performance, liver function, and carcass characteristics. Angus and Simmental × Angus heifers (n = 120; 188 ± 2.6 kg) were blocked by initial body weight (BW) and alloted to 8 pens. Pens were randomly assigned on d 0 to either be fed tylosin (T+) or no tylosin (T-). Heifers were adapted to the finishing diets utilizing a common adaptation proccess over 35 d. On d 36, pens were then assigned to a high moisture corn-based diet (HMC) or a dry-rolled corn-based diet (DRC) to achieve a 2 × 2 factorial design. Body weight was recorded and blood was collected on d 0, 35, and approximately every 28 d following. Rumen fluid and fecal grab samples were collected on a subset (n = 48) every 56 d. Treatment did not affect BW (P ≥ 0.14) or overall average daily gain (P ≥ 0.65) throughout the trial. No differences (P ≥ 0.21) were observed in overall dry matter intake. There was a diet × tylosin inclusion effect (P = 0.02) for estimated starch digestibility to be greatest for HMC/T+ heifers. On d 252, HMC heifers had greater (P = 0.03) ruminal pH before feeding compared to DRC. Heifers fed DRC/T- had the greatest (P = 0.01) blood urea nitrogen concentrations of all treatments. Aspertate aminotransferase was greater in T+ heifers compared with T- (P < 0.01). Heifers fed HMC had a larger (P = 0.04) longissimus muscle area than heifers fed DRC. Heifers fed HMC T+ had the most (P = 0.04) desireable yield grade. Although corn type and tylosin inclusion did not affect growth performance, corn type may affect starch digestibility, ruminal pH and blood markers of liver function.