The problem with gilts is that they have to be gilts before they can be sows. However, their impact on overall farm productivity should not be underestimated. Depending on the life cycle and the replacement rate, gilts can comprise 25% of all farrowings on the farm.
A common argument among experts in the field of swine reproduction is whether to mate gilts for the first time based on their age or their weight. The answer to that question is actually “both.”
A gilt that reaches a predetermined age of 30 weeks that experiences health challenges and produces low average daily gain may be no more ready to mate for optimal lifetime performance than an extraordinarily fast-growing gilt that reaches 300 lb. by 20 weeks of age.
The gilt that attains both a minimum weight and a minimum age will usually make the most pigs for the least cost over her lifetime. But a major health challenge can delay the age at first mating.
Do the Vet to Vet
Veterinarian-to-veterinarian health consultations help assure the health compatibility of the source herd with the receiving herd, coordination of vaccinations and management priorities for the specific genotype.
After shipment has been approved, there is still a health risk due to common pathogens that may be encountered due to transportation stress.
This risk of disease exposure can occur during transport or just prior to shipment.
Consequently, new breeding stock should never be placed into the breeding herd until they have cleared a predetermined isolation period.
Isolation, Acclimation
Be sure to isolate and acclimate all incoming gilts to protect the health of the source herd and the animals being introduced. Following basic guidelines reduces disease risk and preserves the genetic potential of the new stock.
Acclimation allows the new breeding animals to build an immune system comparable to that of the destination herd. Although the destination herd may not be showing clinical symptoms of disease, the new animals may exhibit clinical symptoms as they mount an immune response.
Immunization against diseases within the recipient herd will help the newly introduced animals withstand this insult. The acclimation period allows time to closely monitor immune responses, establishes health commonality between the new animals and the destination herd, and allows for maturation and boar exposure of the new gilts.
Case Study No. 1
A weaned pig producer had been purchasing select-age gilts from the same multiplier farm for several years, but decided to change sources to capture more genetic potential.
The producer had become complacent with the isolation and acclimation procedures practiced on his farm.
Because he had experienced so few problems, instead of the planned 30-day isolation period, coupled with routine testing prior to entry, the immediate need for gilts to fill a breeding group dictated that he move a load of gilts directly into the breeding barn.
Unfortunately, the gilts were not vaccinated with the Lawsonia intracellularis (porcine proliferative enteritis or ileitis) vaccine, and 10% of the group experienced a severe Proliferative Hemorrhagic Enteropathy (PHE), which is the acute and bloody form of ileitis. Before intervention with appropriate antibiotics could be instituted, the producer lost 5% of the group of gilts and an additional 5-10% were severely compromised, making it necessary to extend their age at first mating.
Had this pork producer gone to the trouble of requesting a vet-to-vet consultation, he would likely have discovered that the new source of gilts were not protected with the Lawsonia intracellularis vaccine. The source herd initiated vaccine on future groups of gilts and the issue was resolved.
Case Study No. 2
A 2,500-sow farm raised internally produced replacement gilts. They normally mated the gilts on the second estrus period at about 30 weeks of age. This process provided an adequate number of inexpensive replacements, the owners were satisfied with the level of production and their herd veterinarian was pleased with the reduction in health risk the internal multiplication offered.
All seemed fine until this sow operation experienced a moderate case of porcine circovirus-associated disease (PCVAD) in the replacement gilts, which increased mortality substantially and slowed average growth rates.
Consequently, the lower weight gain led to an extended age at first mating, which created a large hole in their weekly breeding groups.
Fortunately, the farm was able to purchase enough commercial circovirus vaccine to cover all their replacement gilt needs and in a matter of months they were again able to meet breeding targets and return performance to normal.
