Table 3.

Effects of weaning management and persistently infected bovine viral diarrhea virus (PI-BVDV) exposure on health of newly received beef calves

	Auction market		Preconditioned			Contrasts,1P =
Item	Control	PI-exposed	Control	PI-exposed	SEM	Management	Exposure	Interaction
No. pens2	14	14	12	11
Total BRD morbidity3, %	67.2	73.7	7.7	5.7	4.30	< 0.001	0.50	0.22
Treated once, %	33.1	30.2	3.2	0	4.00	< 0.001	0.40	0.96
Day of first treatment	3.0	2.7	2.5	0.9	1.47	0.23	0.33	0.49
Treated twice, %	26.0	25.9	1.1	0.6	3.78	< 0.001	0.94	0.95
Day of second treatment	7.3	6.2	4.0	2.6	1.65	0.007	0.30	0.92
Treated thrice, %	8.0	17.5	3.2	4.9	3.08	0.002	0.04	0.15
Day of third treatment	10.7	11.1	7.1	6.1	3.07	0.08	0.90	0.76
Relapse4, %	50.6	58.5	60.3	100	20.78	0.07	0.09	0.26
Chronically ill5, %	1.1b	7.6a	0.4b	0.3b	2.26	0.03	0.07	0.06
Antibiotic cost, $/calf	18.49	22.55	2.31	2.65	2.01	< 0.001	0.10	0.16

^a,bMeans within a row without a common superscript are different (P < 0.05).

¹Management = main effect of weaning management (auction market vs. preconditioned); Exposure = main effect of PI-BVDV exposure (control vs. PI-BVDV exposure); Interaction = management × exposure.

²Each pen consisted of 8 to 11 animals depending on block.

³Percentage of calves clinically diagnosed with bovine respiratory disease (BRD) and administered antibiotic 1 or more times.

⁴Relapse percentage calculated by dividing the number of calves within each experimental treatment treated with a second antibiotic by the total number of calves in each experimental treatment treated for BRD.

⁵Cattle were classified as chronically ill if 3 antibiotic treatments were administered and ADG ≤ 0.45 kg for the entire 42-d trial.