Good colostrum management wins yet again.
Windeyer and Others ("Factors associated with morbidity, mortality and growth of dairy calves up to 3 months of age" Prev. Vet. Med. 113(2):231-240 February, 2014) used blood serum total protein values from 2,874 calves from 19 dairies in Minnesota and Ontario to assess the degree of passive immunity transfer. In general these were well-managed calf enterprises averaging close to 2 pounds a day gain in first two months.
Among the six factors associated with risk of being treated for bovine respiratory disease (BRD) was failure of passive transfer of immunity. "A cut-point of 5.7g/dl was the most predictive of BRD before 5 weeks of age." Colostrum wins yet again if it is of good quality, fed ASAP and in great enough volume.
Two other risk factors for BRD that caught my attention were the herd -level of incidence of BRD [Is there a lot of it going around?] and season of the year [Fall and Spring weather can be tough on calves].