Vaccination to Control Coccidiosis in Cage and Floor-reared Layer Pullets11 October 2016
Coccidiosis vaccination for layer pullets has become more common, whether the birds are raised in cages, aviary systems or on the floor, writes Linnea Newman, DVM.
Commercial layer operations with low challenge may be able to manage with anticoccidial medication in the feed, allowing gradual exposure to wild Eimeria strains. But many operations have experienced resistance with repetitive use and the result is loss of body weight uniformity, peaks in morbidity or mortality and coccidiosis outbreaks late in the pullet phase or even in young layers.
Vaccination has been a successful method of coccidiosis control in broiler breeder replacements for decades, but layer pullets present different challenges. Application, management of environmental humidity and access to faeces to ensure recycling of Eimeria oocysts are important areas of focus.
Hatchery spray, feed spray, "wet feed" (diluted vaccine mixed with feed and immediately fed to birds) and drinking water application have all been successfully used, depending upon local management conditions.
A water circulation system must be in place to vaccinate pullets via drinking water to ensure that the heavy oocysts stay suspended. The vaccine is a low dose of oocysts, designed to initiate a life cycle in the birds with minimal intestinal damage.
Birds that are missed in the initial application will be subject to wild strain infection or to ingestion of a higher dose of oocysts shed by their hatch-mates when the first vaccinal life cycle has completed and the next generation of oocysts are shed into the environment. Therefore, uniformity of the initial application is crucial.
Development of immunity requires the flock to ingest the oocysts that are shed following the initial vaccination life cycle, and again following subsequent life cycles until four or five life cycles have been completed in the flock. Eimeria necatrix and Eimeria brunetti are deadly species that require significantly longer exposure to ensure complete immunity.
Recycling of oocysts requires re-ingestion of oocysts from the faecal material. Flocks in cages present a unique challenge, and some coccidiosis vaccines specifically state on the label that they should only be used in floor-reared birds.
Successful vaccination in cages requires using some kind of durable paper on the cage floor for at least 16 days, and preferably for 21 to 28 days. Feed is spread on the papers for the first seven to ten days to encourage picking up both feed and Eimeria oocysts.
When pullets are started in central tiers and then moved to upper and lower tiers as they grow, the papers are split into two in each cage. As pullets are moved up or down, half of the paper is moved to the new cages to maintain access to oocysts.
In aviary systems, as pullets move to the floor, the papers can be moved to the floor with them. Floor-reared pullets may start in a more confined floor area to ensure sufficient bird density to have uniform exposure to shedding oocysts.
Due to variability of management and local environmental conditions, each system should be evaluated as an individual case, with critical attention to detail in the program design.
Eimeria oocysts require heat and humidity to "sporulate" and become infective. Without humidity, the Eimeria life cycle stops or stutters, resulting in uneven coverage and uneven development of immunity.
Environmental relative humidity of 60 per cent is strongly recommended. When faeces, litter or papers are very dry at five weeks of age, it is an indicator that the flock could have problems later on when they are moved to the layer site and they become exposed to flies and faeces. Work with a knowledgeable technician to develop farm-specific strategies to enhance oocyst exposure and critical humidity levels.
Pullet vaccination can be monitored by faecal oocyst counts at three-day intervals beginning at day 14. The counts provide a map of vaccine recycling and they can be used to measure the effects of environmental modification.
Coccidiosis vaccination in pullets requires attention to encourage Eimeria recycling. Partial dosing of vaccine or use of anticoccidial medication in the feed or water post-vaccination can hurt immunity development....more MSD Animal Health Articles