C. Infectious Bronchitis (IB)

The mean results of the 58 groups tested (508 assays) are shown in Figure 3.25. The regression line is based on the M41 HI test results in birds over 20 weeks of age. The small number of 793B variant and Elisa results have been added. The results are very similar to those in broiler parents. Once again it appears that the 793B variant may be involved in a significant proportion. About half of the groups tested had GMT's over 4.