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Veterinarians present a visual guide to managing coccidiosis and plotting your success.

You've been successfully using ionophores to control coccidiosis, but lately performance in your broilers just doesn't seem as good as it used to be. You want to try switching to a new program, but can't decide whether to try a chemical-to-ionophore shuttle or a few rounds of coccidiosis vaccination.

How will you know what to expect with different programs? And how can you get the best coccidiosis control as well as optimum growth in birds? A new concept known as the Quadrants of Performance may be just what you need to understand and help predict the impact of various anticoccidial strategies on broiler performance.

"The Quadrants of Performance concept is a visual tool demonstrating the effects of anticoccidial control programs and a pathway for achieving improved outcome and cost effectiveness," says Dr. Charlie Broussard, director of global technical services for the Schering-Plough Animal Health Corporation's Poultry Business Unit.

Developed by coccidiosis specialists at Schering-Plough Animal Health, the concept is based on published and non-published work on oocyst cycling in chickens, as well as the company's extensive worldwide experience managing coccidiosis, the costly protozoan disease that threatens commercial poultry operations worldwide, he says.

Basic graph

The Quadrants of Performance concept starts with a basic graph that plots two major thresholds (Figure 1):

• Level of infection, illustrated by a horizontal line
• Age of infection, illustrated by a vertical line

"A coccidial challenge in Quadrants 2 or 4 is quite another matter," he says, "because these are times of rapid growth and a coccidial challenge can seriously impair the growth rate."

The worst-case scenario is a coccidial challenge during Quadrant 4, when the growth curve is strong. "You're to the right of the vertical threshold and above the horizontal threshold," Broussard says.

Not just a 'pass/fail' grade

Poultry veterinarian Dr. Linnea Newman, a consultant for Schering- Plough Animal Health, says the Quadrants concept encourages poultry integrators to examine how their current coccidiosis control program interacts with the broiler growth curve.

"As things are now, the industry thinks of coccidiosis control in terms of a simple pass/fail grade. Each week, feed conversion is assessed and a conclusion is made about whether the program is either working or not. This approach can lead to knee-jerk program changes when performance slips," she says.

The Quadrants concept goes beyond the simple "pass/fail" system. It considers when coccidiosis control has an effect on the growth curve. "You can have an overall passing grade on total coccidiosis control but could actually be leaving dollars on the table because your passing grade is really only a C+," she says.

In addition, the Quadrants concept encourages integrators to look at how performance in today's flock affects subsequent flocks and to aim for a solid grade "A" performance, Newman says.

Ionophore programs

As an example, Broussard cites experience with ionophores, which rely on oocyst "leakage" to stimulate the chicken's immune system against coccidial challenge. In situations where there is a high coccidial challenge as determined by the oocyst litter count and intestinal lesions, the peak challenge shifts with time to Quadrant 2, the same time when the growth curve and opportunity for maximal meat production is increasing. (See Figure 2.)

Continued use of ionophores can result in the selection of ionophore-tolerant coccidial strains, which make the anticoccidial program less effective. "Increased oocyst leakage can compromise the next flock through heavy carry-over of sporulated oocysts. Ionophore-tolerant coccidia strains may become hard to control, resulting in poor feed conversion and weight gain and increased production costs," he says.

Ionophores on farms with a low coccidial challenge result in slow development of coccidial immunity, Broussard says. Initially, results may be satisfactory if the coccidial challenge remains low but, with time, the peak challenge shifts to Quadrants 2, 3 and 4, resulting in ionophore-tolerant coccidial strains and a less effective anticoccidial program.

"Continuous oocyst leakage can slowly increase the number of oocysts carried over to future flocks, and it's not uncommon in these situations to see performance slowly deteriorate. You may not even realize it's happening but, eventually, production costs start creeping up as the peak oocyst challenge shifts to Quadrants 2, 3 and 4," he says.

Newman agrees and says, "High oocyst numbers at the end of one flock means that the next flock will have a bigger coccidiosis challenge and more resistant oocysts challenging the next coccidiosis control program.

"If I have 10% resistant oocysts, and I carry over 100 oocysts, it means that I have a grand total of 10 resistant oocysts in my house. If I have the same 10% resistant oocysts and I carry over 100,000 oocysts per gram of litter to the next flock, I have 10,000 resistant oocysts per gram of litter. That's a big challenge to the next program and contributes to program failures."

Chemical and ionophore programs

The course of events is similar with chemical-to-ionophore programs, Broussard says. When anticoccidial chemicals are used in the starter feed, oocyst shedding is pushed to Quadrant 2, that critical growth period. Ionophore leakage may allow the number of chemical-resistant coccidia to grow. High numbers of residual oocysts challenge the efficacy of the ionophore starter in the next rotation.

With chemical-to-chemical programs, the situation changes somewhat. Initially, chemical anticoccidials appear to be very effective. They shut down oocyst shedding in the house and reduce peak coccidial challenge to very low levels during Quadrant 1. But drug resistance can build up fast and shift the peak oocyst challenge to Quadrant 3, due to a quick selection of strains that are resistant to chemical anticoccidials.

"Initially, we see dramatic improvement in performance after switching from straight ionophore programs to a chemical-to-chemical program," Broussard says. "But then drug resistance appears after one or two growouts, and clinical coccidiosis results. Flock performance is compromised and production costs rise."

"We have learned that if you're in Quadrant 2, 3 or 4, performance may be suffering either slightly or severely, and changes need to be made," he says.

Coccidiosis vaccination

Experience in the field with coccidiosis vaccines such as Paracox-5, which initiates life-long immunity against coccidiosis in chickens, has shown that vaccination results in an early, mild predictable pattern of reaction in Quadrant 1, before the fastest growth spurt kicks in, Broussard says. (See Figure 3.)

Coccidiosis vaccination can be used exclusively for coccidiosis control or integrated into other anticoccidial programs. Research shows that Paracox vaccines seed houses with drug-sensitive oocysts, increasing coccidial sensitivity to ionophores and chemical anticoccidials, he says.

"Either way, vaccination can help producers raise flocks that have the ability to realize their full genetic potential, as shown in the Quadrants of Performance," Broussard says.

Intestinal health

Performance in vaccinated birds can be improved, Broussard continues, with management and nutrition. Toward this end, Schering-Plough Animal Health has developed the IDEA concept, a novel nutritional plan for vaccinated birds. It promotes good nutrition early in life when the digestive and immune systems are developed and coccidial challenge is low. The result, he says, is healthy gut development in birds that depend on immunity rather than drugs.

"Resistance to intestinal disease is better and so is performance for the rest of the bird's life," Broussard says. When coccidial replication in vaccinated birds reaches it peak, the IDEA concept encourages the use of a highly digestible diet to further maximize intestinal integrity.

"Improved digestibility reduces damage to the enterocytes and reduces the availability of nutrients for bacterial growth," he says.

With intestinal immunity established, vaccinated birds can express their maximum potential for growth and feed efficiency. IDEA is also economical because it enables feed cost savings, Broussard adds.

Conclusion

Says Newman: "The best overall control program induces early immunity that creates low oocyst numbers at the end of the flock and minimal carryover to the next flock. Low oocyst numbers means less total challenge on new chicks in the next flock and less potential for developing a significant population of resistant oocysts for future flocks."

Early immunity, Newman notes, also creates in-house "down time" - no coccidiosis activity, just as though the house was empty "from 25 days of age on. "It's like getting an extra free week or two of layout time in terms of coccidiosis control," she says.

Broussard says, "As the saying goes, 'knowledge is power', and the Quadrants of Performance concept gives us more knowledge. It provides a thorough understanding of each anticoccidial rotational cycle and its impact on subsequent rotational cycles, making it an innovative and valuable tool that can help poultry integrators assemble highly effective annual anticoccidial control programs with the few remaining approved products left on the market today."

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