Proceedings of the 10th International Colloquium on Paratuberculosis

#225 Impact <strong>of</strong> Johne’s disease vaccines on a dairy herd
Zhao Lu, Ynte H Schukken, Rebecca L Smith, Yrjo T Grohn
College <strong>of</strong> Veterinary Medicine, Cornell University, USA
Aiming to reduce <strong>the</strong> prevalence <strong>of</strong> MAP infection, vaccination was applied as a control measure in some
dairy herds. However, as vaccines <strong>of</strong> Johne’s disease are imperfect and many effects are reported, including
reduction in susceptibility, infectiousness, shedding level, infectious period, and clinical cases. Quantitative
evaluation <strong>of</strong> <strong>the</strong> effectiveness <strong>of</strong> vaccines is, <strong>the</strong>refore, lacking. In this study, we developed a deterministic
vaccination model, with age structure including calves, heifers, and cows, to investigate <strong>the</strong> impact <strong>of</strong> imperfect
vaccines on <strong>the</strong> overall vaccine efficacy and <strong>the</strong> prevalence over time. Using <strong>the</strong> developed model, we derived
an analytical expression for <strong>the</strong> overall vaccine efficacy which may be used as a measure for comparing <strong>the</strong>
efficacy <strong>of</strong> various vaccines. In addition, we numerically compared <strong>the</strong> dynamics <strong>of</strong> prevalence in a 100% vaccinated
herd with a control herd.
#227 Association between cow reproduction and calf preweaning growth traits and Elisa s/p
ratio scores for paratuberculosis in a multi-breed herd <strong>of</strong> beef cattle
D. Owen Rae, Mauricio A Elzo, Shelly E Lanhart, F. Glenn Hembrey, Jerry G Wasdin, Danny J Driver
College <strong>of</strong> Veterinary Medicine, University <strong>of</strong> Florida, USA
MAP ELISA is used as a herd-screening tool that can detect approximately 50% <strong>of</strong> infected animals. Despite
low sensitivity, evidence suggests association between ELISA s/p ratio and cow and calf traits. The objective <strong>of</strong>
this study was to assess association between beef cow reproductive and weight traits, pre-weaned calf traits
and MAP ELISA sample to positive (s/p) score (0 = negative, 1 = suspect, 2 = weak-positive, and 3 = positive)
in a multi-breed herd <strong>of</strong> cows. Cows in <strong>the</strong> University research herd were tested by ELISA as part <strong>of</strong> <strong>the</strong>
annual herd monitoring and control program. Cows and calves in <strong>the</strong> herd were monitored for reproductive
and production traits according to <strong>the</strong> operating protocol <strong>of</strong> <strong>the</strong> unit. Records for <strong>the</strong> years 2002 - 2006 were
collated and summarized to evaluate study objectives. Cow data included: 624 measures <strong>of</strong> gestation length
(GL), 358 records <strong>of</strong> time to conception (TO), 605 calving intervals (CI), and 1240 measures <strong>of</strong> weight change
(from November to weaning, WC), from 502 cows. Calf data consisted <strong>of</strong> 956 birth weights (BWT), 923 weaning
weights (WWT), and 923 weaning weights adjusted to 205 d <strong>of</strong> age (WW205) from 956 calves. Traits were
analyzed individually using multi-breed mixed models. Fixed effects were year, age <strong>of</strong> cow, sex <strong>of</strong> calf, year ×
age <strong>of</strong> cow interaction (except WC), age <strong>of</strong> cow × sex <strong>of</strong> calf interaction (only for WC), ELISA score, and covariates
for breed fraction <strong>of</strong> sire and cow and heterosis <strong>of</strong> cow and calf. Random effects were sire (except for TO
and CI), dam, and residual. Estimates <strong>of</strong> differences between cows with non-zero and zero ELISA scores were
associated with lower cow fertility (longer TO), a lesser ability <strong>of</strong> cows to maintain weight (negative WC), lower
calf BWT, and lower calf weaning weight (WWT and WW205).
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