Table 5.

Effects of feeding ractopamine hydrochloride on temperament and mobility of Holstein steers

	Dose				P-value		Duration				P-value
Item	0	300	400	SEM	Linear	Quadratic	28	35	42	SEM	Linear	Quadratic
Pens	13	13	13				13	13	13
Steers	237	239	241				238	239	240
Chute temperament1
Day 02	1.68	1.61	1.51	0.09	0.11	0.52	1.60	1.61	1.51	0.09	0.35	0.09
Final3	1.65	1.57	1.62	0.25	0.55	0.45	1.64	1.54	1.66	0.25	0.88	0.10
Chute exit4
Day 0	1.79	1.58	1.50	0.12	<0.001	0.95	1.67	1.47	1.74	0.12	0.51	<0.001
Final5	1.39	1.26	1.21	0.20	0.02	0.55	1.25	1.25	1.35	0.20	0.14	0.45
Pens	8	8	8				8	8	8
Steers	137	135	138				137	136	136
Stride length6, cm
Day 0	40.8	41.4	41.7	0.03	0.37	0.76	43.3	40.4	40.6	0.30	0.02	0.31
Final	43.1	44.9	47.4	0.02	<0.001	0.96	43.2	47.9	44.9	0.20	0.37	0.02
Mobility7
Day 0	1.17	1.13	1.14	0.06	0.45	0.67	1.16	1.13	1.15	0.06	0.79	0.66
Final	1.18	1.17	1.16	0.04	0.67	0.93	1.14	1.24	1.13	0.04	0.88	0.04
Harvest mobility8	1.32	1.39	1.37	0.06	0.19	0.45	1.32	1.41	1.35	0.06	0.53	0.11

¹Steers were observed in a squeeze chute for 15 s after their head was caught, by one blinded, trained observer. The 1 to 4 point scoring system was adapted from Grandin (1995): 1 = calm, no movement; 2 = restless shifting; 3 = head throwing, squirming and occasionally shaking the squeeze chute; 4 = violently and continually shaking the squeeze chute.

²Respective duration ractopamine hydrochloride feeding day 0.

³Last day of ractopamine hydrochloride feeding.

⁴Steers were observed as steers left the squeeze chute by one trained individual. The 1 to 4 point scoring system was adapted from Grandin (1995): 1 = normal walk; 2 = trot or fast walk; 3 = run or sprint; 4 = leap or jump.

⁵Last day of ractopamine hydrochloride feeding. d 0 chute exit score was used as a covariate in the model (P = 0.01).

⁶Steers were observed for individual stride length while moving approximately 4 m from the squeeze chute by measuring the distance between the furthest back rear foot to the back of the forward rear foot when both hooves were in contact with the dirt surface.

⁷Steers were evaluated for individual mobility while moving approximately 30 ft from exiting the squeeze chute. The 1 to 4 point scoring system was adapted from Lily Edwards-Callaway, JBS: 1 = normal, fluid, even rhythm, and weight bearing on all 4 feet; 2 = slightly hesitant and stiff, shuffles feet, but still moves with the herd; 3 = obviously still and sore footed, reluctant to move, cannot keep up with the herd; 4 = extremely reluctant to move, animal refused to move when encouraged by a handler; any steps are short and very unsteady.

⁸Harvest mobility scores were observed at packing plant as steers were moved into harvest facility.