Egg Industry - December 2008

are most susceptible to the effects of challenge from transfer extending to onset of lay.

Monitoring—Serology is a practical way to ensure that flocks are im-

pullet program. Once baselines are established, low titers suggest improper vaccination or high titers indicate field challenge. In general, a live program should yield ELISA geometric mean

FIGURE 2. TYPICAL MG PLATE POSITIVE REACTIONS AFTER AN MG BACTERIN ADMINISTERED BY
INJECTION AT 12 WEEKS OF AGE.
If the vaccination program is adequate to the level of challenge, there should be no
drop in production concurrent with a rise in titer.

munized—not just vaccinated. Flocks should be sampled just prior to housing to measure their response to the

titers (GMT) between 2,500-4,000 ELISA prior to housing. A combination live-killed program generally

should result in titers of 5,000 to 8,000 ELISA units, approximately three to four weeks after the killed injection.

Figure 1 shows how inadequate administration of vaccine (birds with dye on feathers receive only a partial dose) can influence serology. Titers should be monitored at 15-week to 20-week intervals during production.

Shortly after housing, IBV titers typically spike from exposure to the resident virus on the farm. The levels then gradually decline as circulating immunity wanes. If IBV is suspected as being responsible for lowered production or egg quality issues, SPF cockerels can be placed as sentinels together with newly housed flocks.

One week after placement, sentinels are sacrificed and tracheal and lung tissue is submitted for attempts at virus isolation or PCR assay to confirm the presence of RNA fragments characteristic of IBV. Blood samples can be collected from remaining sentinels two and three weeks after transfer for serologic assay using the strain specific hemagglutination technique. If virus

D oes your marketing pla n provide rea son enough to TRa \SS aUR SR[PR and invest i n Cage F ree?

We have millions of reasons w hy you should.

While producers such as yourself, and our competition, are trying to understand the

c hallenges involved in designing, building and converting houses into

A lternative Layers, we’ve been doing it. In fact, there are MILLIONS of Big Dutchman Alternative Layers globally. Let our Production Specialists, full-time personnel that understand production management requirements, show you how using our extensive p roduct line can help you to get off the fence.