PSVII-1 - Effect of the Sequence of Feeding Forage and Concentrate-based Diets on Dry Matter Intake and Average Daily Gain of Growing Angus Bulls

Abstract: The objective of this experiment was to determine the effects of diet type and sequence on average daily gain (ADG) and feed intake (DMI) in Angus bulls. Diets were concentrate (CONC; 58% dry-rolled corn, 18% Sweet Bran, 9% prairie hay, 5% alfalfa hay, and 10% supplement) and forage (FOR; 60% prairie hay, 30% alfalfa hay, and 10% supplement). Angus bulls (n=19; initial BW = 293 ± 10.3 kg) were placed in individual pens and assigned to receive FOR followed by CONC (FC; n=9) or CONC followed by FOR (CF; n=10). Cattle were transitioned to the respective diets over 21 days and acclimated to the treatment diet for 10 days. Each period was 56 days. BW was measured on consecutive days at the beginning and end and every 14 days during each period. Data were analyzed using a mixed model (SAS 9.4) including the fixed effects of diet, sequence, and the interaction. Diet was treated as a repeated measure. Pearson correlations were also performed within the treatment groups. There was a sequence × diet interaction (P < 0.01) for DMI, indicating that the difference in diet DMI was smaller when cattle consumed CONC before FOR. The correlation of diet DMI was only significant in the FC group (r = 0.72; P = 0.03). There was a sequence x diet interaction (P = 0.02) for ADG, indicating that while ADG was greater during CONC feeding, the difference between the diets was greater for the FC sequence. The ADG:DMI ratio was greater for CONC (P < 0.01) but was not affected by sequence (P = 0.96). These data indicate that estimates for DMI and ADG on forage or concentrate diets do not depend strongly on the sequence of feeding the diets, but the correlation of DMI and ADG between the two diets does.