Effects of forage inclusion and cattle breed on apparent digestibility and ruminal pH of steers fed a whole shelled corn-based diet

Objectives were to evaluate the effects of cattle breed, Holstein or Angus, and forage inclusion on total tract digestibility and ruminal pH in cattle fed a whole shelled corn-based diet. Six Holstein and six Angus steers were assigned to a 2 × 3 factorial arrangement of treatments. Factors included breed, Holstein or Angus, and forage inclusion at 0%, 8%, or 16% forage (dry matter [DM] basis). Steers were fed in a replicated 3 × 3 Latin square, split-plot design. Each period consisted of 14 d diet adaptation followed by 7 d of sample collection. Data were analyzed using the MIXED procedures in SAS (v9.4 SAS Inst. Inc., Cary, NC). Repeated measures were used to analyze changes in ruminal pH over time. There was no interaction of breed × diet (P ≥ 0.19) on dry matter intake (DMI) or digestibility; however, Holstein steers had greater (P = 0.03) DMI than Angus steers. Despite the impact of breed on intake, there was no effect (P ≥ 0.33) of breed on diet digestibility. Digestibility of DM increased (linear; P < 0.01) as forage was removed from the diet, but there were no differences (P ≥ 0.32) in Neutral Detergent Fiber (NDF) and starch digestibility. However, due to the change in diet, NDF intake digested on a grams per day basis increased (P ≤ 0.01) and starch intake digested (g/d) decreased (P = 0.01) as forage inclusion increased. There was a tendency for breed × diet interaction (P = 0.08) on ruminal pH. Holstein steers fed 8% or 16% forage had greater ruminal pH than Holstein steers fed 0% forage; but, ruminal pH of Angus steers was not altered by diet.