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Studies show light and color can impact coccidiosis vaccine performance

Sometimes, nature really does know best. And in a modern hatchery vaccinating birds for coccidiosis, light and color can be important tools for maximizing distribution of vaccine oocysts and ensuring broad protection.

Since it was launched in late 1997, hatchery spray administration of Schering-Plough Animal Health's coccidiosis vaccine lines, Coccivac and Paracox, has proved to be a fast, inexpensive and effective way to immunize broilers, breeders and layers against coccidiosis.

Unlike other spray-administered vaccines that enter the birds' system, either through the eye or respiratory tract, coccidiosis vaccine must be ingested for an optimal intake and colonization of the intestinal tract. While the spray cabinet method is undoubtedly effective, understanding why it is effective "what stimulates the chicks to preen and ingest the vaccine they've sprayed with "is an extremely useful hatchery-management tool.

A series of three trials carried out at Texas A&M University provided some important insights, and shows that natural responses of chicks can be harnessed to ensure optimal uptake of spray cabinet-administered vaccine. The research¹ published in 2001, was supervised by Drs. Billy Hargis and David J. Caldwell, faculty members of the Departments of Poultry Science and Veterinary Pathobiology at the university.

Conducted under laboratory conditions, the first trial looked at the effect of manipulating sound, temperature and light. While changes in all three stimuli could be manipulated to increase preening behavior, changes in light levels, or photointensity, made the biggest impact.

Caldwell says the responses of the chicks were very much as expected, given what is known about their behavior.

Changing ambient sound levels from 83 dB before spraying to 56 dB at spraying and for 5 minutes following had the effect of increasing the amount of preening. So too did increasing the temperature from 20°C (68°F) before spraying to 35°C (95°F) during spraying and for 5 minutes after the vaccine had been applied.

Under commercial conditions, controlling levels of sound and temperature like this may not be practical. However, changing lighting conditions "an easier practice for most hatcheries "gave the most marked response.

Aviagen puts photointensity results into practice Aviagen's Dr. Stanley: Introduction of lighting to encourage vaccine uptake well worthwhile. 'The results have been positive.' Aviagen, a leading poultry breeder based in Huntsville, Alabama and Newbridge, Scotland, has successfully captured the benefits identified by Texas A&M University's preening behavior research in its coccidiosis vaccination program. The company, which supplies broiler breeder chicks to more than 85 countries worldwide, routinely vaccinates day-old chicks with Coccivac. Quick to see the advantages of the spray cabinet system, Aviagen introduced spray cabinets about 5 years ago "for the application of Coccivac-D. Dr. Bill Stanley, director of Quality Assurance for Aviagen, says the technology applied to coccidiosis vaccination fits well with the company's drive for system-wide standardization. Aviagen achieved ISO 9001 registration (the international standard for quality management systems) in June 2005. Stanley says the company successfully applied Texas A&M's findings to its own hatchery operations during February and March 2004, and the use of increased lighting has been established for about a year. "We haven't done any external trials to quantify the success of introducing increased lighting, but internally, the results have been positive," he says. "You can see an increase in preening activity under the intense lighting, which improves uptake and distribution of the coccidiosis vaccine." Applying the results from lab-based trials into a large-scale commercial operation took some working out, Stanley says, but ultimately the solution was fairly straightforward. "We developed a system of rollers in a series long enough to accommodate about 10 boxes of chicks at a time," he explains. "The rollers are on a slight decline, so the operator doesn't have to force them through. There are fluorescent lights over the rollers, and the chicks are exposed for about 6 minutes after they've been in the spray cabinet." Precise levels of photointensity aren't crucial, but as a general rule, the chicks would be exposed to about the same illumination found in a welllighted office "perhaps around 1,000 lux (93-foot candles). Stanley cautions: "Spreading the chick boxes out during the 6-minute period should be done in an area free of drafts to avoid chilling of chicks." Introducing fluorescent lighting to enhance preening and vaccine uptake has been a success for Aviagen, Stanley concludes. "The improved preening response, and improvements in vaccine uptake, have made the change well worthwhile for us."

In the first Texas A&M trial, photointensity was increased from 0 lux (complete darkness) to 1,243 lux (115.5- foot-candles) "about the same level as a mechanic's workshop or operating room "at the time of spraying. This lift in photointensity tripled or quadrupled preening events. The trial showed that a brief period of total darkness (less than 2.5 minutes) followed immediately by spray application in a strong light and maintained for a period afterward, can have very positive effects on preening behavior.

But conversely, putting chicks into dark conditions straight after spraying could have the reverse effect. In commercial hatcheries, where trays of chicks could be stacked straight after vaccine spraying, this is possible. This could lead to decreased preening activity and a consequent reduction in vaccine ingestion.

Other studies, conducted under commercial hatchery management conditions, have evaluated other photointensity regimes that could be implemented more easily in a day-to-day setting. Encouragingly, these trials have shown that it may not be necessary to put the chicks into total darkness prior to spraying.

This is consistent with the second Texas A&M University trial, in which chicks were taken from normal hatchery light levels of around 215 lux, exposed to a 15-second burst of intense light (3,226 lux) during spray vaccination, and then held in elevated light levels of 1,075 lux for a period postspraying. Preening activity was doubled in this trial.

Interestingly, this study also showed that if the 15-second period of intense light (created in the trial with portable halogen lights) was prolonged, the increased preening effect was lost. This was probably because the warming effect of the strong light made them sleepy, overwhelming the "wake-up" stimulus of the short burst of intense light.

Of course, day-old chicks aren't only responsive to light. Color plays a big part in their behavior, and the recommended practice of adding coloring agents to sprayed vaccine is well established. Not only does the color encourage preening, it also acts as a useful marker to confirm birds have been vaccinated.

Caldwell says a third Texas A&M trial looked at the impact of color on preening behavior. Colors throughout the spectrum, including fluorescents, were tried under a constant 990 lux before, during and after spraying.

The addition of colors under constant light levels stimulated a 2-fold to 3-fold increase in preening. Blues and greens showed the strongest effects, but the red used in the study (approved for use in Paracox-5 as Cochineal E120) was comparable, Caldwell says.

The light source (fluorescent versus incandescent) made no appreciable difference to the preening activity when different colors were being trialed.

Probably the most significant finding was that when coloring agents were added to the spray under conditions of increasing photointensity, it made no difference to the increase in preening behavior made possible by light alone.

That finding is a very important one for commercial hatcheries. It shows there is real flexibility when it comes to maximizing the uptake of coccidiosis vaccines applied using a spray cabinet:

"� Where use of coloring agents in spray cabinet vaccination is established as part of the routine, these trials show that the preening activity will be enhanced, even under constant lighting.

"� Where use of coloring agents is not practiced, then manipulation of photointensity alone can stimulate preening to a level even greater than that achieved through coloring agents.

"� Where a coloring agent is regularly used in combination with increased photointensity during and following spray cabinet vaccination, preening activity and vaccine intake are still enhanced.

Reference ¹ Journal of Applied Poultry Research. 2001; 10: 99-106, 107-111, 112-116.

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