Coccidiosis Control Strategies Utilising Vaccination13 September 2016
Coccidiosis vaccination has become a significant control strategy for broiler integrators, reaching 25 per cent of all broilers placed in the US (2015), according to estimates by MSD Animal Health. Linnea Newman, DVM, reports.
How is vaccination being used? There are three major strategies: vaccine as a sustainable year-round programme, vaccine in rotation with anticoccidials, and a vaccine-anticoccidial hybrid shuttle programme.
An important concept to understand when exploring these programmes is ‘carry-over’ – the carry-over of coccidial oocysts from one broiler flock to the next, with or without clean-out and disinfection. It is caused when broiler flocks are slaughtered during active subclinical coccidiosis.
Since active subclinical infections occur with a peak between 24 and 42 days of age, small bird integrations that slaughter between 30 and 36 days are most affected.
Strategy 1 – Sustainable year-round vaccination programme
Until now, this programme has been employed largely by organic producers, but integrators producing conventionally raised birds have committed multiple complexes to this practice during the past year as the interest in antibiotic-free production has increased in the US.
The vaccine is used in flock after flock with continued success. Producers have used the programme continuously for 6+ years, and continue to perform at industry parity. Without the late oocyst shedding typical of anticoccidial programmes, the overall cocci challenge on the farm declines with time.
Strategy 2 – Vaccine in rotation with anticoccidials
Rotation is the most common use of vaccine. Vaccine is used for at least three sequential flock cycles during a production year, followed by rotation to an anticoccidial programme for two to three cycles, then returning again to vaccine.
Anticoccidial rotation is predominantly used during winter or wet months. This strategy maintains sensitivity of the farm Eimeria population to the anticoccidials, helping those anticoccidials to work at their best during the peak coccidiosis challenge season.
In this programme, coccidiosis challenge tends to build up through the successive anticoccidial flocks, with significant subclinical coccidiosis and oocyst shedding in the 24-42 day period at the end of winter or rainy season. This high carry-over oocyst burden puts pressure on the first vaccination cycle each year.
Strategy 3 – Hybrid vaccine-anticoccidial shuttle
This is a sustainable programme that can be used year-round or in rotation. Vaccine is administered at the hatchery and the starter feed is unmedicated to enable the vaccine to recycle and to begin to develop immunity.
A ‘leaky’ anticoccidial – either low-dose ionophore or zoalene – is added to the grower or finisher feed. Ideally, the anticoccidial medication is not added to the diet until the process of building immunity is complete (about 21-25 days of age). Thus, a sensitive vaccine is always introduced at the beginning of a flock, enabling the shuttle anticoccidial to be effective.
The building of immunity and shedding of oocysts is usually a bell-shaped curve. The anticoccidial cuts the back half of the bell-curve off, enabling birds to recover faster and, according to users, perform better.
All three strategies for the use of coccidiosis vaccine require an understanding of how the Eimeria population dynamics of one flock will affect the subsequent flocks. Management adjustments to encourage consistent vaccination response make sustainable coccidiosis control achievable....more MSD Animal Health Articles