Reasons Why Replacement Gilts Do Not Come Into Heat and Solutions

In pig farming, sows must be constantly replaced, that is, while culling sows that come into heat slowly, are old and weak, have poor milk production, or have reproductive disorders, high-quality purebred replacement gilts should be selected in time to supplement production. In fact, the so-called replacement gilt refers to a gilt kept for breeding from the piglet rearing stage until before the first mating. Now let us take a look at what to do when replacement gilts do not come into heat!

Causes of Replacement Gilts Not Coming Into Heat

1. Various stress reactions: For sows, too many stressors can lead to failure to come into heat. Common stressors such as the number of vaccinations and high temperatures can easily cause replacement gilts not to come into heat.

2. Herd disease causes: Herd diseases can also cause replacement gilts not to come into heat. Common diseases include porcine reproductive and respiratory syndrome, endometritis, and circovirus disease.

3. Nutritional imbalance: If the feed is deficient in protein and energy during the rearing period, replacement gilts are likely not to come into heat, and other nutritional imbalances can also affect replacement gilts.

4. Mistakes in feeding and management: Replacement gilts are suited to group housing in large pens. 4 to 6 per pen is more conducive to proper mounting behavior among the gilts that promotes estrus. Too few gilts leads to a lack of exercise, while too many makes the pen overcrowded and causes fighting.

What to Do When Replacement Gilts Do Not Come Into Heat?

1. Change pens: Move replacement gilts that are not coming into heat from their original pen to another pen. At the same time, they can also be grouped with parous sows of similar body size after weaning. When the parous sows come into heat and mount the replacement gilts, this stimulates the gilts to come into heat.

2. Increase exercise: Drive the replacement gilts that are not coming into heat up a hillside for a walk, or load them onto a truck to go out for a “spin”. After returning, sometimes the replacement gilts will come into heat.

3. Boar stimulation: When replacement gilts are around 180 days of age, let them come into contact with a boar. Puberty induction can greatly reduce the probability of replacement gilts not coming into heat. Generally, gilts that are not coming into heat are exposed to a boar 1 to 2 times per day, switching to a different boar every 2 to 3 days for estrus induction.

4. Hormone therapy: Hormone therapy can be used for replacement gilts that do not come into heat, using pregnant mare serum gonadotropin combined with human chorionic gonadotropin. Generally, it is used for at most three consecutive times. If the effect is not obvious, use should be discontinued.

5. Culling selection: A few replacement gilts have a beautiful body shape, but after trying various methods, they still disappoint. At this point, it is recommended to cull them, because some replacement gilts fail to come into heat due to defects in the pig itself.

Feeding and Management Techniques for Replacement Gilts

1. Isolation after introduction: After replacement gilts are introduced, they must not be mixed with the farm's own pigs immediately. On the premise that test results are normal, isolate them separately for about 1.5 months (at least 30 days), and mix them into the herd after basic vaccinations.

2. Feeding and management: Before replacement gilts reach 80 kg, ad libitum feeding can be used, but those that are too fat or too thin should be appropriately restricted or given more feed. When they reach 80 kg of body weight, restricted feeding should be used, strictly controlling body condition so as not to cause excessive fatness that affects normal estrus and mating.

3. Vaccination: Vaccination of replacement gilts is the key to achieving good results in future production. Vaccination varies among breeding stock suppliers, but the best method is to follow the procedures provided by the breeding stock supplier, which gives greater consistency.

4. Daily exercise: Before mating, replacement gilts must have enhanced exercise. Proper daily exercise can reduce the occurrence of limb diseases, improve appetite, and promote estrus.

5. Timely mating: Before mating replacement breeding pigs, the feeding and management staff should pay close attention to observing the time of their first estrus and keep detailed records for reference at the actual mating. The first estrus situation should also be recorded.

6. Mating methods: At present, mating methods mainly include natural mating and artificial insemination. Beginners in pig farming are best to first use natural mating, that is, driving replacement gilts with stable estrus and a boar with strong libido to the mating pen for mating.