By William R. Fombelle, DVM
Carthage Veterinary Service, LTD
One of the most important yet often overlooked segments of the sow herd is the gilt-developer unit. Gilts are the lifeline of a sow herd, and their quality often predicts the future production of the entire herd. Future gilt production can be affected as early as weaning age, so it’s imperative these growing pigs receive daily attention and treatment if they’re to progress to their full potential.
Oftentimes, you can predict the sow herd’s productivity simply by walking through the gilt-developer unit. Farms with strong management will usually devote extra time and labor to their growing gilts. These producers understand the importance of gilts and pay great attention to their health and performance. Poorly managed farms are oftentimes behind in vaccination timelines and spend minimal time with their gilt developers.
Whether gilt-developer units are on the same site as the sow herd or an off-site unit, the basic approach to acclimation and vaccination are similar. The herd veterinarian should be up to speed with the herd’s history and the environmental pathogen load as well as the swine density and disease pressure in the area surrounding the farm.
There’s a common core of swine pathogens that can have a huge impact on a breeding herd’s reproductive productivity. These include porcine parvovirus, Erysipelothrix rhusiopathiae, Leptospira spp. and porcine circovirus type 2 (PCV2), and they are the basis for development of a herd’s vaccination and acclimation protocol.
There are also several pathogens that are flow dependent, such as porcine reproductive and respiratory syndrome virus (PRRSV), Mycoplasma hyopneumoniae or porcine epidemic diarrhea virus (PEDV). Each requires an in-depth protocol, even if they aren’t affecting the herd at the time. It’s very important we create a contingency plan for these diseases in case a disease introduction should occur.
Production systems vary and so will vaccination schedules, but generally, replacement gilts start receiving vaccines as soon as they are weaned off sows. They receive their first dose of PCV2 vaccine while they are still with the sow herd or very soon after they are delivered to the gilt-developer unit.
Once delivered, replacement gilts should be held under quarantine until sufficient time has elapsed to rule out transport contamination with PRRSV, PEDV and porcine delta coronavirus. Once the gilt group tests negative for these pathogens, they are moved into the gilt-developer unit’s general population.
Depending on a farm’s history and pathogen load, vaccination with an erysipelas vaccine at 6 to 8 weeks of age may be appropriate. E. rhusiopathiae can be a driver of growing-pig lameness and also a primary reproductive pathogen in swine. This Gram-positive bacterium can live in the environment for long periods of time and can be resistant to temperature change and common modes of disinfection. It can lead to fever, sepsis, cyanosis, “diamond skin disease” and vegetative endocarditis.
Influenza A virus vaccine is very commonly administered to breeding herds. Producers can work with their veterinarians to determine if a commercial vaccine will provide cross protection or if an autogenous vaccine is warranted. The veterinarian will take into account past strains of influenza that have affected the herd as well as pig density and other strains in the area around the farm.
As gilts continue to mature and near the age of boar exposure, growing gilts often receive a combination vaccine, which often includes parvovirus, Leptospira and erysipelas, usually beginning around 20 weeks of age. These vaccines are typically boostered 3 to 4 weeks later. A PCV2 booster vaccination is usually given around the same time.
Acclimation is simply planned exposure to certain pathogens that an animal will encounter as she flows through her productive life on the sow farm. In a perfect world, a gilt would be exposed to each individual pathogen at the perfect time to develop immunity before she leaves the gilt-developer unit and enters the breeding and gestation barn.
We all know, however, that a change in the flow of gilts or even herd closure can occur in an instant, most commonly when there’s a change in diseases affecting the sow herd.
Once gilts are vaccinated at 20 weeks of age, they can be acclimated to pathogens such as parvovirus, Leptospira and erysipelas. Farm teams collect and administer natural planned exposure to gilts to acclimate them to the environmental pathogens they’ll encounter when they leave the gilt-developer unit. This tissue is collected from placenta, mummified fetuses and stillborn piglets.
The goal of a successful gilt acclimation and vaccination plan is to achieve herd immunity in the gilt population against the pathogens that threaten their health and reproduction before they enter the breeding and gestation barn. Once gilts are bred, we don’t want anything to interrupt their pregnancy, whether it be infectious or non-infectious.
Since gilts are the building blocks of a sow herd’s productivity, achieving great gilt performance will give the sow herd the best shot at reaching high performance levels.