Table 1.

Summary of study activities and the number of calves

	PI3V challenge study		BRSV challenge study
	Day in the study	Calves (n)	Day in the study	Calves (n)
Calves received into facility, aged 0–3 days, and blood sampled for serology	D0–D7	21	D0–D7	15
Enrolment and selection (health, weight)	D0–D3	21	D0–D2	15
Randomisation and separation of MDA+ control animals to avoid cross contamination from vaccinal virus	D0–D1	21	D0–D1	15
Vaccination and blood sampling (animals are 10±3 days old)	D0	21	D0	15
Control animals moved back in the same air space as vaccinates	D21	20	D21	15
(Regular serological evaluation every two weeks post vaccination)
Challenge	D92	17	D84	15
(Postchallenge monitoring—clinical signs and nasal swabs—and daily for 14 days)
End of study	D106	17	D98	15

BRSV, bovine respiratory syncytial virus; MDA, maternally derived antibodies; PI3V, parainfluenza type 3 virus.