One of the most frequently asked questions by producers is, "How do I handle the health of my gilt pool?"
Purchased gilts and the much-misunderstood PRRS (Porcine Reproductive and Respiratory Syndrome) have complicated the health stability of the gilt pool.
It seems like a lot of our time as swine veterinarians is spent designing farm-specific isolation, acclimation and gilt pool health programs.
Sadly, many farms don't properly work gilts into the breeding herd.
When PRRS became a serious issue, cutting corners on gilt health, isolation and acclimation started costing in production and consequently profit.
The concept "cool down" had to be dealt with. Allowing time after exposure to on-farm disease, with extra time for gilts to "cool down" and stop shedding, was forgotten. Having time to blood test, vaccinate, provide feedback, and live animal exposure was a new mental and physical facility dilemma.
All of these issues lead to periodic reproductive failure in the existing sow herd. The larger the farms, the longer it takes to reach farm targets.
Unfortunately, many farms didn't return to their previous production levels. They continued to experience a 10% reduction in farrowing rate. Something had to be done to stabilize health of incoming gilts and stop the flood of virus and bacteria pressuring the sow herd's immune status.
Case Study During a routine herd visit, a client said he had six to eight abortions during the last week. This farrow-to-finish, single-site farm was on a weekly farrowing schedule. The producer was doubling his sow herd. A lot of gilts were being introduced to the farm in a short time. Delivery of these gilts always seemed to be late and the producer was in the "I need to breed them right away" mode. A set of gilts were brought directly into the breeding barn the week before.
We suspected PRRS as the cause of the problem. However, to confuse the issue, the farm was also experiencing a swine influenza virus (SIV) break.
The producer chose not to do diagnostic work but preferred to mass vaccinate the sow herd. We chose to use the new killed PRRS vaccine and SIV vaccine. All sows were vaccinated and repeat vaccinated in two to three weeks. The problem quieted down.
The discussion at the next herd visit turned to prevention. What could we do to prevent stressing herd immunity each time gilts were introduced into the breeding herd?
I asked to do a "Swine Genetic Health Survey" on the gilt supply farm. The survey is a two page questionnaire we use to collect health information.
With permission, I contacted the veterinarian of the gilt farm. He was very helpful and up front about the pig health of the multiplier. We found the multiplier was PRRS positive and SIV negative. The blood test results during routine serology told us the gilts were becoming infected with PRRS late in the finisher. By the time the gilts hit my client's breeding barn, they were still shedding a lot of PRRS virus into his sow herd.
Even though his sow herd was serologically (blood test) positive to PRRS virus, some of the pregnant sows didn't have enough immunity to ward off the PRRS virus that the gilts were bringing with them into the sow herd. So some of the sows aborted or ended up as not-in-pig sows.
The question then was how to stop PRRS virus invading this herd. That's where gilt isolation, acclimation and "cool down" became important. We chose to bring three months worth of varying age gilts to the farm at one time. Housing was in outside lots some distance from the rest of the complex. The different age groups were housed in separate pens next to each other. We blood tested them upon arrival and found varying levels of exposure to PRRS with the older gilts showing higher test (ELISA) titers.
All gilts were vaccinated with two doses of killed PRRS vaccine and two doses of SIV vaccine. Recently aborted sows or open gilts (one or two) were placed in each pen, exposing the newly purchased gilts to the farm's PRRS strain. The exposure animals were left in the pens for two weeks.
At that point, we started the "cool down" portion of the system. The breeding gilts became infected and started to shed. Acclimation was really the key post exposure to allow gilts to "cool down" before entry into the sow herd.
The good news is that the farm stabilized and reproduction returned to normal. Increased costs were for vaccine, feed and environment. Decreased cost was out-of-pocket expense for the junior gilts.
Organizing and scheduling gilt deliveries is always the challenge to this system but well worth it. The farm is running well now.
Conclusion Know your own herd health profile as well as the farm where you purchase breeding stock. Remember, their herd health can change just like yours can. Isolation, acclimation and "cool down" are imperative. Time is the key.
Your veterinarian needs to be the important resource person in the development of your farm-specific system.