Management, timing of coccidiosis challenge improves feed utilization

Looking for an edge on competitors, integrators have long sought ways to improve feed efficiency. But with feed prices continuing to soar, making the most of rations is not simply a competitive edge — it’s a matter of business survival.

Besides tweaking feed formulations, integrators are realizing there are other ways to get the most from feed.

“It’s easy to put an energy value on a nutritive factor, such as corn, soybean or starch,” said Dr. Robert Teeter, a poultry nutrition researcher at Oklahoma State University, “but other factors, especially energy expenditure, along with many other factors, are also crucial” (see Figure 1).

In fact, he said, the amount of heat energy birds expend in their daily activities may be even more important than the actual nutrient value of their diets. Keeping such energy loss to a minimum is vital. Teeter said, “A calorie not expended as heat is money in your pocket.”

In lab experiments he conducted, Teeter found that feed-conversion rates for birds raised on the same ration and to the same weights can vary from 1.63 to 2.11, depending on differences in bird behavior that can be manipulated by management changes.

For that reason, Teeter and colleagues developed highly sensitive ways to measure what they call “effective caloric value,” or ECV, which is the relative loss of energy — and potential growth — associated with various changes in management that affect bird activity. These include changes in lighting, temperature, ventilation, stocking density and the method by which water is delivered.

“Activity regulation offers integrators an avenue for a competitive edge, if they recognize those opportunities and take advantage of them,” Teeter said.

Pellets can increase feed value

For example, simply pelleting feed instead of feeding mash can reduce bird activity associated with eating and, thereby, significantly increase the effective value of feed calories by about 187 kcal/kg of diet, he said. Research by Teeter and others has shown that improvements gained by pelleting are greatest in the latter part of the growth cycle, when birds are consuming the most feed.

Lighting programs, too, can be used to increase the ECV of feed, Teeter explained. In one series of studies, he compared the effects on ECV of two lighting programs: 23 hours light/1 hour dark compared to 12 hours dark/12 hours light.

Birds in the 23/1 lighting environment consumed about 3,250 kcal/kg to reach market weight, while birds in the 12/12 environment used only 3,100 kcal/kg to attain the same weight — a savings of 150 kcal.

As Teeter pointed out, instead of increasing the caloric density of the diet to improve FCR, a grower could choose to use reduced periods of lighting to get the same level of performance.

Similar kinds of performance gains can be attained by manipulating the ambient temperature in which birds are raised, Teeter said.

Controlling the timing of coccidiosis challenge

One of the most significant improvements in ECV can be gained by effectively controlling the timing of coccidiosis challenge, he continued.

While it is true that optimal performance would be achieved in an environment completely free of coccidia, it’s unrealistic to expect such conditions in the field, given the limitations of currently available anticoccidials. So for years, integrators have been accepting low-level coccidiosis and its associated loss in FCR as a normal part of using ionophores to grow broilers.

However, the impact on ECV of even low-level coccidiosis can vary dramatically depending on the age at which challenge occurs, Teeter said.

In a series of studies, the researcher and his group challenged birds at various points in their life cycle with an orally administered solution containing three common species of Eimeria, the parasite that causes coccidiosis. After challenge, Teeter monitored the birds closely, recording changes in factors such as heat production, live weight, retained energy and composition of excreta. After 6 days, the birds were necropsied and their coccidial lesions scored.

Compared with controls that received no coccidial challenge, the birds with coccidial lesions scored lower in live weight and average daily gain, and had poorer FCR. As the size of lesions increased, so did the negative effects on growth and feed conversion.

But what was most significant, Teeter emphasized, was that late in life even minor coccidial lesions exacted a significant toll. “In the grower-finisher phases, the consequence of lesions was markedly elevated, and the closer we got to the end of the growth curve, the more significant the consequences,” he said.

Real-world significance

The findings have important real-world significance. In birds grown on a 48-day schedule, for example, about half the total consumption of food occurs during the final 2 weeks, he said. If birds are stressed with coccidiosis lesions during that time, it reduces appetite, elevates maintenance costs, increases malabsorption of nutrients and, therefore, cuts into the ECV of feeds. “Unfortunately, though, birds [with coccidial lesions] don’t reduce their appetites to the complete degree that would eliminate feed loss; they continue to eat and continue to consume profits,” he said.

In contrast, his and other studies have shown that early exposure to coccidiosis — such as occurs in birds vaccinated at 1 day of age against coccidiosis — has only a minor negative effect on those same variables. Birds have sufficient time after early challenge to make up for lost performance resulting from exposure, whereas later the consequences are much greater, he said.

Like other management decisions, such as lighting and temperature changes or pelleting versus mashed feeds, the timing of coccidial challenge is a crucial variable that can be manipulated to advantage, and it should be considered in formulating any management strategy, he stressed.

“It’s very important to understand the effects of coccidiosis challenge and to avoid these lesions, especially late in the growth cycle, since they significantly reduce flock profitability,” Teeter said.

Dr. Robert Teeter

Figure 1: The impact on effective caloric value of even low-level coccidiosis can vary dramatically, depending on the age at which challenge occurs.