(1) In this study, suckler beef calves had greater odds of bovine respiratory disease (BRD), navel infection, and joint infection/lameness during the first 6 months of life than dairy calves. (2) From birth to 6 months of age suckler beef calves had greater rates of navel infection, but decreased rates of diarrhoea compared to dairy calves.(3) Optimal test cut-offs for classification of morbidity and mortality outcomes in suckler beef calves ranged from 12 to 18 ZST units. Optimal test cut-offs for classification of morbidity and growth outcomes in dairy calves was 19 ZST units

Failure of passive transfer (FPT) of immunity occurs when the calf does not absorb sufficient colostral immunoglobulin (Ig) in the immediate post-natal period.More research is needed to validate FPT test cut-off values, based on their relationships with key health and performance outcome measures, such as morbidity, mortality and growth.

Data were obtained from two studies: 1) a longitudinal study on herd-level factors associated with the health and survival of calves on Irish farms and 2), a longitudinal study on individual calf-level risk factors for morbidity in spring-born calves. The herd-level study was conducted between July 1, 2014–December 31, 2015 and the calf-level study was conducted between January 1–December 31, 2016.

The performance of passive immunity tests for classification of failure of passive transfer (FPT) risk, based on their relationships with calf health and performance was evaluated.

The methods used to recruit farmers may have introduced a selection bias; farmers were primarily recruited through KT activities and participation in the study was voluntary. One can speculate that individuals who attend KT events and engage advisory services may be more progressive farmers and more likely to implement best management practices. Misclassification of disease status could have occurred for some calves. Obtaining accurate calf health information based on farmer diagnoses and recording is a challenge. The age of calves at blood sample collection may be a potential concern. The upper age limit for blood sampling was 21 days of age because on many farms in Ireland, especially suckler beef farms, only a small number of calves are born within a 1 week period. It is likely, however, that the extended sampling age range may have resulted in the passive immunity test results for some of the older calves at blood sample collection being under-estimated.

Three lessons can be learned from this research:

1. Pre-calving and colostrum management practices implemented on commercial farms largely determine passive transfer. 

2. There is large variation in colostrum quality between individual cows and by farm.

3. Several management practices and animal factors, including the timing and amount of colostrum fed, colostrum feeding method, time spent in the maternity area, breed, twin birth, dystocia, dam parity and health status, and herd size are known to be associated with the acquisition of passive immunity in calves.

Testing calves for FPT is an important step in monitoring the successfulness of colostrum management programmesand resolving on-going calf health problems