Induced circovirus immunity in sows through vaccination was pioneered by Merial only four years ago. The treatment has proved to boost performance, particularly sow fertility. There is also proven passive Porcine Circovirus Associated Disease (PCVD) immunity passed-on to litter members by vaccinated sows. But latest trials indicate that active piglet immunity through vaccination of weaners can offer even more.
Results of a large-scale trial of piglet PCV2 vaccination include a 6.8% increase in daily liveweight gain for treated pigs during the feeding period. Mortality for the vaccinated pigs was down by 7.4%
and there was also a significant reduction in ‘poor doers’ among the treated pigs in the trial.
With Lyon, France-based animal health company Merial the first to achieve EU (EMA) approval for both sow and piglet PCV2 vaccination, the time was ripe for announcement in July of the definitely upbeat results from a 1,100-piglet field trial run by Austria’s Pig Clinic at the Veterinary University of Vienna. Chosen by Prof Dr Mathias Ritzmann and his team was a 250-sow commercial unit. “This had a history of PMWS problems with a growing percentage of ‘poor-doers’ among the litters, growers and feeders,” explains Ritzmann.
“These are animals that are 25% below the average weight of their pen or group.”The mortality rate was also increasing steadily in the test herd. PCV2 infection was confirmed through histopathology, lymph node tests and lung tissue samples. The sows in the herd had not received PCVD vaccination. In total 1,105 piglets were randomly chosen from three successive farrowing groups and divided into treated or control groups. Treated group members received a one-shot vaccination of Merial Circovac (0.5 ml intramuscular) at three weeks of age. Control piglets received a placebo. A characteristic of this field trial was that treated and control pigs remained penned together. Weaning was at three weeks, growing period up to week 13 and then feeding through to slaughter at week 28.
This slaughter date is pretty late for some European countries but typical in the Austrian pig sector, according to Ritzmann.The first sign that piglet PCV2 vaccination was paying off was noted at the weighing half way through the feeding period (week 21) when the treated pigs proved to be returning a dlwg that averaged 64.8 g more than the control groups. The vaccinated pigs were at that time levelling at 584.8 g per day.
When the figures for the whole 15-week feeding period were examined, the treated pigs were still well ahead with an average daily liveweight gain of 651 g which was 41.4 g or 6.8% better than the control groups.
PCVD problems
Pigs performing well below average, the so-called ‘poor-doers’ are a sign everywhere of growing PCVD problems. Their presence in this Austrian farm was rapidly reduced in the treated groups with 14.72% around 25% below average liveweight. The control groups featured 19.87% poor-doers. Especially important, says Ritzmann, was the reduction in mortality amongst the animals that had been vaccinated against PCV2 as piglets. From week 13 to 21 (the main viraemia phase) mortality was reduced by 6% to just 2.53% in the treated groups. And the results from the whole feeding period improved on even this performance with a 7.4% reduction in mortality to an overall 4.01% deaths amongst the vaccinated pigs.
Another positive result from this PCV2 vaccination involved the reduction in viraemia and virus excretion in faeces. This was significantly reduced in general, but almost completely halted in one of the three age groups treated during the most active viremia phase from week 12 to 20.
“This does not mean that we can completely defeat PCVD in pig herds with vaccination,” cautions Ritzmann, who is director of the Vienna Pig Clinic.
He added that there is unfortunately no commercial pig farm anywhere in the world without some of the related diseases. This would probably remain the situation for decades ahead – possibly a good argument for adopting a piglet vaccination policy.
Vaccination for sows, piglets
Now that piglets as well as sows can be vaccinated against PCV2, what sort of strategy should be chosen for pig herds? Dr Ariane Schade from Merial’s large animal product management department pointed out that sow vaccination had already established itself through offering a good return-on-investment, principally through improvement in herd fertility and therefore general performance.
A field evaluation conducted on German farms indicated that sow vaccination on its own had reduced total piglet losses in the litter by 17% on average, by 63% for growers and by 52% during the feeding period.And of course the vaccinated sow passes on the antibodies she forms after vaccination to her litter members in her colostrum. As long as management at farrowing and suckling is good, cautioned Schade, this should transfer a good level of passive resistance to piglets.Results from commercial herds in the last four years have shown that losses are thus reduced right through to slaughter, with less disease and therefore reduced veterinary costs as well as higher daily liveweight gain and better feed conversion results.
But Schade reckoned there was a good financial argument for following the admittedly more expensive route of vaccinating the piglets as well as the sows where, for instance, barriers in some herds had developed preventing good passive resistance being transferred by the vaccinated sows. Such barriers could be caused by the presence of diseases other than PCV ones, preventing sufficient colostrum production and its uptake by litter members.
Sow vaccination
Sow vaccination also required certain lead-times before full effectiveness was clearly seen. Injecting the piglets as well encouraged active immunity and clearly reduced disease pressure in the feeding period, according to current results.
“The choice of vaccination plan depends on the individual farm,” concluded Schade. “On the bottom line a complete PCV2 protection packet is offered by vaccination of both sows and piglets with the best results then possible.”Particular situations where the double-barrelled approach would be desirable include large units with inherent management control challenges. This approach can also be cost-effective by offering health stability where a large herd is being further expanded. Another situation where piglet and sow vaccination could help: Where there are definite PCV2-caused fertility problems already present in the breeding herd.
Schade felt that this role of stabilising herd health and offering protection right down the line to slaughter has now been strengthened by the possibility of both sow and piglet PCV2 vaccinations.
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