Abstract #W17

# W17
A novel objective chute score interacts with monensin to affect growth of receiving cattle.
Kelsey A. Bruno*1, Eric S. Vanzant1, Alex W. Altman1, Monoj Kudupoje1, Kyle R. McLeod1, 1University of Kentucky, Lexington, KY.

Temperamental animals often have lower gains associated with reduced intake and/or efficiency. Temperament is ill defined. Thus, different temperament measures may relate differently to production traits. Also, hepatic oxidation theory (HOT) suggests that propionate can exacerbate intake depression in stressed cattle. To examine relationships between diet, temperament, growth, and health, 160 crossbred steers were used in a 56-d RCBD experiment with a 2 × 2 x 2 factorial treatment structure. The experimental unit was pen (5 pens/treatment). Steers were pen fed a corn silage-based diet with or without monensin, ad lib. Temperament treatments (assigned on d −7) were exit velocity (EV; slow vs. fast) and objective chute score (OCS; low vs. high), a novel temperament measure, the CV of weights collected at 5 Hz for 10 s while an animal’s head was restrained in a chute. Both were measured on d −7, 1, 14, 28, 55, and 56. Subjective chute scores (SCS) were measured on d −7 and d 56 by 4–5 observers. Jugular blood samples were analyzed for antibody response to leptospirosis vaccine. There was a positive correlation between SCS and OCS (P < 0.01; R2 = 0.38) and SCS was moderately repeatable among observers (Krippendorff’s α = 0.58 to 0.67). Treatment x day effects (P < 0.10) for EV and OCS indicated that initial measures may be better proxies of growth than average measures. There were no interactions between EV and OCS (P ≥ 0.24) and no interactions between treatments (P ≥ 0.12) on intake (%BW). Monensin decreased intake (P < 0.01) without effect of temperament. Thus, our hypothesis regarding HOT was not supported. Gains, antibody titer, and gain:feed responses to monensin depended on OCS (P < 0.10) but not (P > 0.34) EV. Gain was reduced (P < 0.10) by monensin with low, but not high OCS and gain:feed was increased (P < 0.10) and titer response decreased (P < 0.10) by monensin on high, but not low OCS. Gain and intake tended (P < 0.15) to be reduced in fast, compared with slow EV steers. Results provide novel indications that certain temperament measures can interact with dietary manipulation to influence animal performance.

Key Words: temperament, growth, monensin