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Objective Movement of Calf-Fed Holstein Steers Fed in Confinement
The objective of this study was to determine the impact of zilpaterol hydrochloride (ZH) on movement behavior of calf-fed Holstein steers fed in confinement. The experimental design was a randomized complete block, with a 2 x 11 factorial treatment arrangement of ZH supplementation 0 or 20 d by 11 slaughter dates (254, 282, 310, 338, 366, 394, 422, 450, 478, 506, and 534 days on feed). Steers were fed in 28 d periods; d 1 to 4 included no ZH supplementation, d 5 to 24 included ZH (8.33 mg/kg dietary DM) supplementation, and d 25-28 allowed for withdrawal. Animal movement was monitored during each 28 d using IceQube pedometers (IceRobotics, Edinburgh, Scotland, UK), which recorded standing time (mm:ss), lying time (mm:ss), number of steps taken, and number of lying bouts continuously during the 28 d study period. Data collection began at 1200 h on d 1 to remove variation from movement caused by processing the animals at approximately 700 h; data collection ended on d 28 at 2400 h. Data were analyzed as repeated measures using a compound symmetry covariance structure via the GLIMMIX procedure of SAS. Treatment means were generated using the LSMEANS option and separated when significant with the PDIFF option that was adjusted with the Bonferroni correction to reduce the probability of a type-I error α = 0.05. Treatment x days on feed interactions occurred (P < 0.01) for each outcome variable; they were likely the cause of small sample size per slaughter group and are not likely to be biologically repeatable. No difference (P > 0.05) was observed between ZH supplementation treatment groups in the quantity of minutes spent standing (0 d ZH=565; 20 d ZH=557), minutes spent lying (0 d ZH=875; 20 d ZH=883), or number of steps taken per 24 h day (0 d ZH=1602; 20 d ZH=1637). However, the number of lying bouts was different (P< 0.01) between treatment groups; cattle supplemented ZH exhibited 10.7 lying bouts whereas those not supplemented ZH had 11.9 bouts. These results indicate similar objective movement between calf-fed Holstein steers supplemented ZH for 0 or 20 d.
Keywords: zilpaterol hydrochloride, Movement, Pedometers.