67 Association of Morbidity and Failure of Transfer of Passive Immunity in Beef-dairy Crossbred Calves

Abstract The objective of this prospective cohort study was to describe the prevalence of failure of transfer of passive immunity (FTPI) in beef-dairy crossbred calves, and its association with morbidity up to 30 d of life. A total of 393 one d old calves were enrolled upon arrival at a calf facility in Central Valley, California, from Jan-Mar 2021. Farm of origin, breed, sex, and weight were recorded at the day of arrival. Blood was collected at 24 ± 1 h post-arrival to evaluate total serum protein (TSP) and % Brix reading. Calves were classified as having FTPI if TSP < 5.2 g/dL, and brix < 8.2%. Farm personnel performed daily health evaluations and recorded diseases. Descriptive statistics, logistic regression, and survival analysis were conducted using SAS. Calves’ breeds were Angus × Holstein (AN × HO, 58%), Charolais × Jersey (CH × JE, 37%), and Angus × Jersey (AN × JE, 5%). Prevalence of FTPI was 36% (TSP) and 34% (brix). TSP and %Brix readings had a strong correlation (r = 0,99, P < 0.0001). Overall morbidity was 78% (70% had only diarrhea, 7% only respiratory disease and 23% both). The odds of disease up to 30 d was not associated with sex (female vs. male, OR = 0.77, 95% CI = 0.36–1.62), or breed (AN × HO vs. CH × JE, OR = 1.35, CI = 0.63–2.91; AN × JE not included in this analysis). FTPI was associated with greater odds of disease (OR = 2.91, CI = 1.19–7.09, P = 0.01). There was a tendency for association between FTPI and the hazard of disease up to 30 d (HR = 1.43, CI = 0.96–2.10, P = 0.07). Therefore, FTPI may predispose beef-dairy crossbred calves to diarrhea and respiratory disease up to 30 d of life.