First published in The Ranger, vet Matt Balfour discusses the implications of extending lay or flock health, with a focus on maintaining disease protection as birds move beyond traditional production limits.
The layer industry has made significant progress in recent years in extending the laying cycle of hens to 100 weeks and beyond. This is an excellent news story for the sector. Longer production cycles improve bird welfare, enhance farm profitability and contribute to a lower carbon footprint per dozen eggs produced.
However, extended lay does not come without challenges. If we expect birds to perform well to 100 weeks, we must invest in them appropriately from the start.
Achieving longevity in lay begins in rear. Key areas of focus include:
- Rearing pullets to achieve optimal frame size and uniformity
- Implementing a comprehensive vaccination programme to maximise disease protection
- Considering appropriate feed additives during lay to support gut health and immunity
- Maintaining robust parasite control throughout lay
- Where possible, boosting vaccine protection during lay
Long-lived flocks place prolonged demands on the immune system. Therefore, disease prevention strategies that were adequate for 72-80 week cycles may require reassessment when targeting 100+ weeks.
Salmonella Protection into Late Lay
One particular issue in extended lay systems has been the duration of protection provided by currently available live Salmonella vaccines. Traditionally, three doses administered during rear have formed the backbone of Salmonella control programmes. However, these programmes do not carry datasheet protection claims extending into late lay.
We know that vaccine protection is influenced by several factors, including:
- Environmental challenge pressure
- The bird’s immune competence
- Presence of co-infections
- Quality and consistency of vaccine administration
Importantly, vaccine-derived immunity does not cease abruptly – it declines gradually over time. Nevertheless, as flocks are now kept significantly longer, maintaining adequate protection through late lay has become increasingly important.
Avipro Salmonella Duo – New In-Lay Claim
A major development in Salmonella control has recently been achieved with the licensing of an in-lay dose of Avipro Salmonella Duo. Elanco has received authorisation for a fourth dose to be administered during lay (in both layers and breeders) at 50 weeks of age (+/- 1 week). Importantly, this fourth dose carries zero egg withdrawal.
With this updated programme (assuming vaccination at 50 weeks):
- Protection against Salmonella Enteritidis (SE) is extended to 100 weeks
- Protection against Salmonella Typhimurium (ST) is extended to 94 weeks
This effectively covers the production period of most long-lived flocks and represents a significant advancement for the industry.
It is important to note that the enhanced protection claim applies only where birds have already received three doses of Avipro Salmonella Duo during rear. For example, there is no claim where birds have received three doses of a competitor vaccine followed by one dose of Avipro Duo.
Producers should bear in mind that:
- Doses of 1-3 of Avipro Duo (given in rear) still carry a 21-day egg withdrawal period
- Only the fourth dose administered in lay has zero egg withdrawal
- BEIC require that the person administering the vaccine must be appropriately trained and able to provide evidence of training if requested at audit. Additionally, there must be a SOP in place and full administration records must be kept, including:
- Date of administration
- Vaccine batch number
- Administrator’s name
- Volume of stock solution
- In-line doser settings
- The quantity and batch number of chlorine scavenging product used
It is worth mentioning that the Avipro Duo vaccine strain should not grow on MSRV media. Therefore, the likelihood of a vaccine-strain positive Salmonella at routine sampling following in-lay vaccination is extremely low. However, best practice would be to wait at least 7 days after vaccination before sampling.
Summary
As the industry continues its transition towards longer-lived birds, maintaining robust disease control throughout the extended production cycle is critical.
The authorisation of a fourth in-lay dose of Avipro Salmonella Duo represents a major step forward in Salmonella control. It helps address concerns about waning immunity in late lay and will go a long way towards preventing any resurgence of Salmonella cases as flocks move beyond traditional production limits.