Attention to developing gilts can reward you well in the farrowing house.
Gilts give you plenty of reasons to question whether they are worth much extra effort. They are hard to breed; farrow fewer pigs than sows; require special housing, feeding, handling; close observation; and may bring in disease.
But since gilts make up at least 25 percent of the breeding herd, it pays to remember that their performance has a profound effect on your operation’s profits.
“It makes good business sense to use practices that help maximize your gilts’ productivity, promote long life and profitable performance,” stresses Monte McCaw, veterinarian and member of the Pig Health and Management Group at North Carolina State University.
To have a stream of replacement gilts that perform well in your breeding herd, McCaw recommends a program to develop gilts that:
1. Are fertile.
2. Produce adequate milk for good pig growth.
3. Are able to hold up during lactation.
4. Are healthy – which means they won’t introduce a new disease or be susceptible to any already present.
To ensure your gilt program helps you reach each of those goals, McCaw highlights the following steps and considerations.
After selecting gilts (weighing about 210 pounds), feed a lactation diet with elevated levels of protein, lysine, calcium, phosphorous and trace minerals to develop strong bones.
For 10 to 14 days before breeding, increase daily feed by 50 percent to 100 percent to improve ovulation rate and the number of pigs born alive. This can add as much as one pig per litter.
Following this flushing and mating period, limit-feed gilts for 21 days. Then full-feed to build body weight and encourage early estrus, maximum ova shed and longevity in the sow herd.
Keep in mind that the first estrus is affected by genetics. Crossbreds may cycle 20 days earlier than purebreds. There are additional variations between purebreds, for example: Landrace and Large White breeds cycle younger than Yorkshires or Durocs.
If gilts are brought onto the farm, delay breeding until the second estrus, because of stress and reduced energy level due to hauling and adjusting to the new herd.
Environment and Housing
A developing gilt’s environment influences its sexual maturity. Gilts raised indoors take longer to mature than ones reared outdoors. Of course outdoor rearing may not be feasible in your operation.
Gilts raised in groups of 10 to 30, indoors or out, reach puberty sooner than ones crated individually or in a pen of just three or four gilts. Also, when groups involve 50 or more gilts, conception rates decline.
Compared with gilts reared in groups of 10 to 30, those kept in individual crates have nearly twice as many silent heats and irregular cycles.
At 10 to 12 months of age, tethered gilts have significantly greater incidence of immature reproductive tracts than pen-reared ones.
Density in gilt developer pens appears to have no effect on age of puberty. However, overcrowding increases injury risk from fighting – 12 square feet is adequate.
Do not expose gilts to mature boars until they reach puberty.
Environmental temperatures affect gilts’ in terms of development and fertility.
For example, housed at 90°F, only 30 percent of gilts in a research test reached puberty by 230 pounds. Compare that with a 90 percent rate when gilts were housed in temperatures not exceeding 75°F in facilities.
Excessively high temperatures after mating and during early gestation increase embryo mortality and reduce the number of pigs born alive.
Gilts housed under drafty conditions – or individually in damp conditons – need more feed to maintain growth rate and body condition that maximizes fertility at mating time.
Ventilation is important to remove ammonia gas that can delay puberty.
Properly timed boar exposure promotes early gilt development and visible estrus, up to 40 days sooner. This greatly reduces feed and housing costs.
Early puberty lets you wait and breed a gilt on her second or third estrus, which can add one more pig per litter born alive. Gilts that are quick to show estrus usually return to heat promptly and also have high conception rates.
Do not start boar exposure until a gilt reaches 160 pounds or she will be less
responsive at puberty. Use mature boars that are at least 10 months old. Rotating boars encourages cycling and mating.
Each day, take a gilt from her pen to a boar’s pen and allow physical contact for 5 to 15 minutes. Fenceline contact is not enough. The rest of the time, keep the gilt away from boar contact and scent.
Robust body condition is not only important when a gilt enters the breeding herd, but also through gestation and first lactation. Without it she likely won’t cycle or conceive, and will need to be culled by the second parity. This is particularly true with heavy-milkers and gilts with large first litters.
A good growth target is for the gilt to gain 100 pounds from breeding to farrowing.
Make sure gestation and lactation rations supply high levels of amino acids and energy, as well as appropriate amounts of calcium and phosphorous.
After the first week of lactation, feed the gilt all she will eat. And, to maximize milk production and minimize weight loss, consider feeding her three or four times a day.
With a replacement gilt, health means she should neither bring in a new disease nor be susceptible to any diseases already present in your sow herd. Make sure that purchased gilts are tested before you receive delivery.
Work with your veterinarian to implement an isolation program of testing, vaccination, exposure or feedback.
While gilts (and new boars) are in isolation, closely observe them daily for any abnormal signs: coughs, diarrhea, lack of appetite, depression, reluctance to move, rough hair coat, off-color feces, pale skin or gums, rapid breathing.
If anyone in your operation detects questionable symptoms, consult with your veterinarian. If a disease is the problem, sell the animal(s). Then thoroughly clean and disinfect your isolation unit before bringing in any new animals.
To make the isolation period more efficient, expose each gilt to a boar daily. Observe and record estrus to expedite the process once the gilt enters the breeding herd.
n Before moving new gilts into your herd, re-test them to cross-check that they have been successfully acclimatized to existing diseases in your herd.
Always keep in mind:
1. Lactation is half of a sow’s purpose in the herd
2. The number of functional teats controls the number of pigs weaned.
For those reasons, consistently select and keep only gilts with well-spaced and well-formed teats.
Sound like a lot of work? Sure, but you’ve already invested a lot of money on the health and genetics of your replacement gilts whether you buy them or produce them. Adding these management steps to ensure that a gilt has a long and productive life in the breeding herd is simply smart business.