PARTNER FEATURE ▶▶▶
Combating Spotty Liver Disease naturally
The egg industry is increasingly moving towards cage-free production systems. While these systems may improve animal welfare, they pose a higher risk for certain diseases, especially Spotty Liver Disease. Plant-based nutritional solutions offer the capability to support layer performance when faced with Spotty Liver Disease.
BY ANJA PASTOR, PHYTOBIOTICS FUTTERZUSATZSTOFFE GMBH, ROBERT MOORE, RMIT UNIVERSITY AND PETER SCOTT, SCOLEXIA.
I
140 160 180 200
100 120
20 40 60 80
0 NC
* p < 0.05 ** p < 0.01
34 ▶ POULTRY WORLD | No. 8, 2021 PC IQs
n recent decades, Spotty Liver Disease (SLD) in laying hens was a problem seen mainly in Australia and the UK. Over the last few years, its presence has also been confirmed in North America, Central America (Costa Rica),
and Europe. Although the disease was described as early as in 1954, its aetiology was only determined in 2015: a novel Campylobacter that was isolated from infected laying hens in the UK. In 2016, Australian researchers were able to isolate the same pathogen from a flock with SLD, that was named Campylobacter hepaticus. C. hepaticus is a gram-negative, S-shaped bacterium with single bipolar flagellae.
Figure 1 - Levels of IL-8, a pro-inflammatory cytokine, in blood of laying hens challenged with Campylobacter hepaticus – either without addition of a feed additive (PC), or with plant-derived IQs (IQs), compared to non-infected hens (NC).
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Mainly in free-range systems SLD mainly occurs in extensively free-range flocks but has also been observed occasionally in barn and even cage sys- tems, as well as in breeder stocks. As the bacterium is found in the gastrointestinal tract and viable bacteria can be isolat- ed from the faeces of infected animals, a faecal-oral infection route is most likely. The disease is characterised by increased mortality (up to 10%) and reduced laying performance (up to 25%). The livers of affected birds show multiple, 1-2 mm long grey/white le- sions. The occurrence of 1 mm red haemorrhagic lesions has also been described but their presence is more sporadic. It usually affects birds with a good body condition, exhibiting a brief period of depression. Dead birds with post-mortem signs of SLD are found without any prior clinical signs of dis- ease. Outbreaks are often observed within the period of peak lay (most commonly from weeks 22 to 30), while range access and husbandry stressors, such as interruptions to the feeding routine, seem to further promote the disease.
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Zoonotic risk of Campylobacter? While whole genome analysis showed that C. hepaticus is very closely related to Campylobacter jejuni and Campylo- bacter coli, which are known zoonotic campylobacters, there is no current epidemiological evidence that C. hepaticus, despite its clinical presence in chickens for many decades, is zoonotic. Tetracycline is the first-choice antibiotic to treat Campylobacter spp. infections in chickens, although Phung and others (2020) already reported resistance to tetracycline. Macrolides are the antibiotics of first choice for human infections with Campylobacter species. Therefore, in animals they are the second choice of antibiotics to treat Campylo bacter infections to minimise the risk of resistance developing. Although vaccines are in development, no formulation is commercially available yet. C. hepaticus DNA has been found in wild birds and rats, underlining the importance of biosecurity to minimise the risk of a C. hepaticus infection. Feed additives are also being widely trialled to evaluate their potential efficacy in affected flocks. A blend of plant- derived isoquinoline alkaloids (IQs) was tested in laying hens orally challenged with C. hepaticus.
IL8 concentration (pg/ml)
PHOTO: MICHEL VELDERMAN
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