Field trials on two continents show practical and economic benefits of E. coli vaccine in broilers
Presented at the XVIII Congress of the World Veterinary Poultry Association • 18-23 August 2013 • Nantes, France
Field studies on two continents have demonstrated that the modified-live vaccine Poulvac® E. coli reduces losses from Escherichia coli in broilers, even when the disease challenge is strong.
Poulvac E. coli, a “non-reactive vaccine,” has already contributed to a marked reduction in the incidence of peritonitis-related mortality in the US commercial layer industry, and challenge studies have demonstrated its benefits in broilers,1,2,3 said Kalen Cookson, DVM, MAM, a technical services veterinarian for Zoetis, Inc., in the US.
AT 40 DAYS OF AGE, VACCINATED BIRDS IN A NORTH AFRICAN TRIAL HAD LOWER TOTAL MORTALITY, BETTER BODYWEIGHTS AND A BETTER FEED-CONVERSION RATION COMPARED TO UNVACCINATED BIRDS.
Recently, field studies on multiple farms were conducted with the vaccine in the US and North Africa. “There were a variety of conditions on the farms, but one thing in common was a higher than normal E. coli disease challenge,” he said.
In the US trial, investigators administered the vaccine to more than 4 million broiler chicks at hatch. They compared performance to a control group of unvaccinated chicks hatched the previous week that were treated in ovo with the antibiotic gentamycin.
Chicks that received Poulvac E. coli and no gentamycin had a better adjusted feed conversion, lower mortality after week 1 and fewer condemnations compared to controls, yielding a US 0.51 cent (€ 0.39) advantage per pound (Table 1), Cookson reported.
Vaccinated chicks also had significantly less disease compared to controls, he said (Table 2).
In addition, broilers in the US trials that were vaccinated with Poulvac E. coli needed less antibiotic treatment and for a shorter duration of time (Figure 1).
North African trials
One of the field trials in North Africa involved two broiler houses, each with 8,000 birds, on the same farm with a history of high mortality due to E. coli. Investigators treated all birds with an antibiotic in ovo. Next, they vaccinated one of the houses with Poulvac E. coli at 3 days of age, and the other house served as a control and was treated with enrofloxacin for the first 3 days of life.
At 40 days of age, vaccinated birds had lower total mortality, better bodyweights and a better feed-conversion ratio compared to unvaccinated birds, Cookson reported (Table 3).
Zoetis researchers conducted another broiler field trial in North Africa with 18 paired-house sets on 15 different farms with a history of E. coli colibacillosis, but this time no preventive in ovo or in-feed antibiotics were administered.
Compared to controls, birds vaccinated with Poulvac E. coli had an overall better average daily gain and feed-conversion ratio, as well as fewer E. coli lesions. When antibiotic treatment was needed, it was necessary for a shorter duration, Cookson said (Table 4).
“The field trials showed that Poulvac E. coli can help reduce losses in broilers from pathogenic E. coli when measured by liveability, growth rate, feed conversion and less antibiotic use,” he said.
1 Cookson K, Davis S, et al. Cross protection study of a modified live E. coli vaccine against three heterologous APEC serotypes in commercial broiler chickens. In: Proceedings of the 58th Western Poultry Disease Conference; 2009 March; Sacramento, CA. p. 60-62.
2 Cookson K, Macklin K, et al. The efficacy of a novel live E. coli vaccine using a broiler skin challenge model. Abstract 1568. In: Proceedings of the 23rd World’s Poultry Congress; 2008 July; Brisbane, Australia.
3 Cookson K, Sasipreeyajan J, et al. Efficacy study of a live E. coli vaccine in broilers against three field isolates from Thailand. In: Proceedings of the 59th Western Poultry Disease Conference; 2010 April; Vancouver, BC, Canada. p. 70-72.