Vetech Laboratories Inc., 131 Malcolm Road, Guelph, Ontario, Canada N1K 1A8

Published in: Journal of Applied Poultry Research. 2004. 13(2): 360-363.

Summary

Coccidiosis continues to affect caged layers worldwide despite keeping them on wire all their productive lives. Coccidiosis in caged layers, diagnosed either in clinical or sub-clinical forms, has one feature in common, unpredictability. Until recently, despite the use of vaccine, coccidiosis remained problematic, particularly at the beginning of lay, likely related to the low protective immunity for a lack of vehicle for recycling. An approach for using paper plates, both for vaccination as well as recycling is described. Caged layers that were vaccinated once with gel-puck coccidiosis vaccine laid at over 90% continuously for over 24 weeks with little or no problem of coccidiosis.

Description of Problem

Coccidiosis, a common challenge for birds reared on litter, does not seem to be controlled by the use of wire cages and continues to affect layers worldwide mostly during rearing and early egg production. This is in contrast to the concept that the problem of coccidiosis has been essentially eliminated from the layer operation when pullets were started on wire from day one and kept on wire through to the end of the laying cycle [1].

In Canada, commercial layer operations have been suffering the consequences of coccidiosis more often now than in the recent past [2]. The reasons are not yet clear, but it has been attributed to the increasing numbers of pullets per cage and the use of the manure belt system [3]. In Brazil, outbreaks of coccidiosis became noticeable in caged layers after layer companies changed from the traditional system, where droppings fall onto the house floor, to the manure belt system [4]. The spreading of oocysts through the manure belts seems self-evident. However, it’s still uncertain as to how these oocysts initially infect birds during rearing and early egg production.

Coccidiosis in pullets raised in cages, although mostly sub-clinical, appeared to be unpredictable both in terms of timing and severity. In fact, some of these sub-clinical infections are noticed only because of increases in morbidity and mortality caused by secondary agents such as Clostridium. (Necrotic Enteritis) [2].

Control programs for coccidiosis in the egg industry are variable, however, data from the U.S. show that all pullets have some type of anticoccidial program [5]. Anticoccidial drugs are used for the majority of birds raised on the floor, but less so in cage-reared pullets. Only slightly more than half of caged pullets have some type of anti-coccidial program (Table 1).

Coccidiosis in layers (floor or cage reared) has been increasingly reported shortly after the hens start to lay, particularly around 23 to 24 weeks of age [6]. A reduction of egg production for several weeks is not uncommon. There are several explanations for the outbreak of coccidiosis in this period, but it is commonly agreed that low immunity is most likely the cause [1,2,3,7]. It is difficult for birds raised on wire to develop protective immunity due to few opportunities to contact sporulated oocysts for recycling.

Early floor-reared layer pullets receiving anticoccidials have been suggested to rely on “leakage” of oocysts to generate protective immune response. Generally, anticoccidials are withdrawn long before birds come into lay, therefore the immunity acquired through “leakage” is likely to be incapable of protecting hens through the production period [7]. Besides, there is no set idea on the size of “leakage”, nor what size of challenge is needed during the rearing period to extend the immunity into egg production. Often, answers to this question do not become clear until the birds start production. This uncertainty led caged layer producers to adopt the use of vaccine to reduce the risk of coccidiosis especially during the production period.

In the past, the use of coccidiosis vaccines in caged birds met with limited success because of poor recycling. Recycling, or repeated exposures to oocysts, is necessary for establishing protective immunity [8]. Some producers adopted double vaccination during the rearing to replace recycling, but this practice is deemed expensive.

Our objective was to summarize attempts in the past few years to encourage recycling and to describe an encouraging approach that lead to little or no coccidiosis problem.

Field Reports

Before the present approach of encouraging recycling, several other approaches were also tried, including covering the cage floor with newspaper for up to 4 weeks; trying several types of corrugated paper products; vaccinating birds at two different ages, but all with limited success. Seemingly, the newspaper approach encouraged too much recycling resulting in some coccidiosis breaks. Corrugated paper products could not withstand scratching and mostly disintegrated within a life cycle of coccidia or 7 days and, therefore, were unsuitable for promoting recycling. A ratio of about 4 paper plates/cage was attempted but with some coccidiosis breaks around 3 to 4 weeks of age, not unlike the results seen when cage floors were covered with newspaper. The first successful attempt with the paper plate approach was noted in 1999 to 2000. Two flocks of about 42,500 day-old layers each were vaccinated once with 1 gel-puck on one 15 cm (diameter) or 6” round paper plate (Figure 1) at ratio of about 50 birds/puck with the following results (Table 2). Egg production per hen housed appeared to be better than expected in either strain of layers by at least 10 eggs with no problem of coccidiosis throughout rearing and production. Since then, 2 flocks per year, or 6 additional flocks, have been vaccinated at the same farm with similar results with little or no problem of coccidiosis.

FIGURE 1. Gel-delivered vaccine and paper plate used for layers.

Brooding cage (60 x 90 cm): 46 birds/cage from 0 to 4 wk.

There was a lapse of over 3 years before a close examination of this approach was made. This was due, in part, to problems that arose from trying other approaches, i.e.: newspaper to cover cages and others, and partly because there was no clear evidence of cause and effect on coccidiosis tied in with the performance of caged layers.

Here, we were provided a clearer evidence of cause and effect on coccidiosis and caged layer performance. This particular farm, of about 75,000 birds, broke with coccidiosis in previous non-vaccinated flock. The flock experienced a significant overall reduction in the number of eggs per hen housed together with increased mortality. The drop in egg production continued and extended to 8 weeks before recovering (Figure 2). Overall, this flock peaked at over 90% egg production for only a brief

6 weeks. The present flock on this farm was vaccinated against coccidiosis with gel-puck on paper plates at a ratio of 50 chicks/plate at day old. Birds were given other vaccinations common to the egg layers and were fed a diet with 18.5% protein for laying hens. The paper plates stayed in place for about 2 weeks or until they were shredded by the birds. Performance to 47 wk shows egg production of over 90% from 23 wk to 47 wk (Figure 2), with a total mortality of 1.4% and a total egg production of 175.1 eggs per hen housed.

Conclusion and Application

1. This report describes a method of vaccinating cage-reared layers with coccidiosis vaccine in gel pucks on 15 cm paper plates at a ratio about 50 chicks/per plate. The paper plates were placed at 1 day of age and remained for about 2 wk in cages to promote recycling.

2. Egg layers vaccinated with this method had little or no problem with coccidiosis. To date, all caged layers so treated consistently produced more eggs than expected, showing that this method of vaccination effectively controlled the adverse effects of coccidiosis in caged layers.

References

Available upon request from: immucox@vetechinc.com