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Late coccidiosis challenge has ‘profound’ impact on profits

Acoccidiosis challenge late in the production cycle has a profound, negative effect on energy utilization, flock performance and profitability — even when coccidial gut lesions are minor, indicates expansive research by a US nutritionist.

“I have never conducted a nutrition study with the order of magnitude that this study revealed about the impact of intestinal health on energy utilization,” Dr. Robert Teeter, of Oklahoma State University, said during a talk on the economic impact of subclinical coccidiosis in broilers.

His findings, which are being borne out in the field (see article, page 21), show that when broilers experience a coccidiosis challenge late in the production cycle, they use up more energy and need more feed compared to birds challenged with coccidiosis early in the production cycle. The result is increased malabsorption, reduced effective caloric value and an elevated maintenance cost, Teeter said.

The researcher and his team measured the effect of coccidial lesions on energy utilization, also known as the “calorific cost,” with the aid of indirect calorimetry chambers. His lab at the university has 60 of the chambers — the largest set for small animals anywhere in the world. The chambers enable measurement of values such as oxygen consumption and carbon dioxide production in real time as birds are exposed to various stressors such as coccidiosis.

Teeter also uses an X-ray densitometer (DEXA) unit to noninvasively scan birds and quantify protein, fat, water, ash and energy content. “[This technology] gives us a very complete picture of what’s happening with growth and performance,” explained the nutritionist, whose work is in part sponsored by Intervet/Schering-Plough Animal Health.

Gross lesions in the experiments are evaluated with the widely accepted Johnson-Reid Lesion Evaluation Score, where ranges from zero, indicating no intestinal lesions, to 4, the most severe lesions.

Study with Cobb broilers

Teeter’s most recent experiment involved 936 Cobb male broilers raised to 48 days of age. The birds came from a variety of coccidiosis-control programs, so they had varying degrees of immunity to coccidiosis.

At weekly intervals, groups of the birds were moved for 6 days to the metabolic chambers and were challenged with an oral dose of Eimeria acervulina, E. maxima or E. tenella, three coccidial species known to wreak havoc in poultry complexes; some birds received sterile water and provided a control.

The composition of the birds — the protein, fat, water, ash and energy content — was measured before and after chamber placement with the aid of the DEXA unit. Teeter assessed bird performance and metabolism to create a broad performance-lesion score. He also measured the effects of lesion scores on calorie expenditure (calorific cost) and contrasted the effects of early versus late lesion scores on performance and dietary caloric-density cost.

Overall, performance declined as lesion scores went up. For instance, in birds with a higher lesion score, metabolizable energy (ME) declined. For 800-gram (1.76-pound) birds, ME consumption declined about 25% with a lesion score of 2, and in older, 3,000- gram (6.61-pound) birds, it fell 30%.

The heavier, older bird challenged with coccidiosis “gets hit really hard, comparatively speaking, in weight gain, feed efficiency and so forth,” Teeter said, adding that “not only does the younger bird have less of a physiological and metabolic impact, it also has more time available for compensatory gain.”

Average daily gain decreased about 1.5% of bodyweight in grams for each increase in the coccidiosis score, Teeter continued. At the end of the 6-day period in the metabolic chambers, average daily gain fell 40% in the 800-gram (1.76-pound) birds with a lesion score of 2, and in the 3,000-gram (6.61-pound) birds with a lesion score of 2, there was no gain at all (see Figure 1).

“Gain was eliminated for these birds, so depending on how many of them you have in your population in the field, it’s going to have a very marked influence on performance,” he said.

These findings indicate that a 2,000-gram (4.4-pound) bird with a lesion score of 1 is going to be gaining 30 grams (0.06 pound) less per day; if it has a lesion score of 2, it will gain 60 grams (0.13 pound) less per day, he said.

Effect on feed efficiency

The effects of coccidial lesions on feed efficiency were similarly negative. Each increase in the coccidiosis lesion score was associated with a decrease in feed efficiency of 0.0084% of bodyweight. Put another way, the feed-conversion ratio increased from 2.0 to 3.02 in a 2,000-gram (4.4-pound) bird.

With the aid of an energy model that predicts ME consumption and by looking at kilocalories — which is 1,000-gram calories — lost in excreta, Teeter also determined that the 800-gram (1.76-pound) birds were losing almost 31 kcals of extra energy a day if they had a coccidial lesion score of only 2. Older, 3,000-gram (6.61-pound) birds were consuming a little over 650 kcals of energy a day, indicating a good appetite, but there were many more malabsorbed calories — almost 84.

So there’s a very, very high loss from malabsorbed calories, and this just demonstrates the importance of intestinal health in a growing broiler,” Teeter said. “Those intestines have to indeed be healthy for these birds to be able to extract those calories appropriately.”

If producers want to achieve a bodyweight of about 2,500 grams (5.51 pounds), it’s going to take about 39 days and an ME consumption just shy of 14,000 kcals in an ideal production environment. However, when stresses such as coccidiosis present, they steal energy. The bird responds by either eating more feed to compensate or by diverting calories away from what it consumed, in which case it gains less weight. “You’d have to purchase extra feed for the bird to utilize with no return on investment in the form of body tissue to market,” Teeter explained.

He emphasized that in addition to coccidiosis, management factors affect energy expenditure in broilers. Lighting, for instance, reduces bird heat production about 24%; a properly administered lighting program increases the effective caloric value, or the caloric density of the diet, while a poorly managed lighting system steals energy from broilers.

Pellet quality likewise affects dietary caloric density. Compared to a mash, feeding 100% pellets results in an additional 187 kcals of energy, or less energy expended. “The more birds rest, the less time they spend eating, the more efficient they are at eating and the less energy they expend on activity,” Teeter said.

Based on the massive amount of data produced by his study, the researcher concluded that lesions resulting from a coccidiosis challenge are associated with significant energy and performance costs. The consequences of these lesions are markedly elevated during the growerfinisher phases versus the starter phase of production.

An early coccidiosis challenge, as occurs with coccidiosis vaccination administered at 1 day of age, has a minor negative effect on feed consumption, average daily gain, live-weight yield, feed conversion, maintenance energy costs and malabsorption. When the same stress presents late in the growth curve, as occurs with in-feed anticoccidials, there is a major negative impact on all of these factors, Teeter said, noting that, “You especially want to consider malabsorption in that mix.”

“When coccidiosis challenge occurs during the final 2 weeks of the growth cycle, even minor lesions can significantly reduce flock profitability,” he added.

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