In many pig farms, sows take a long time to come into heat after weaning. Repeated unsuccessful breeding and recurring returns to heat mean that every day a sow remains open adds to the losses. Many people rely solely on estrus-inducing drugs or switch vaccines, but the problem keeps coming back. In fact, the root cause is not the medication; it is that the critical weaning stage has not been properly managed.
Follow this field-tested standardized program for weaned sows, and the post-weaning estrus rate will remain consistently above 90%, reducing non-productive days, improving the conception rate, and protecting the pig farm’s most important profits.
I. Core Management Objectives
Maintain body condition during stable lactation and strictly control weight loss and body condition decline.
The weaning-to-estrus rate is consistently above 90%
Shorten the interval between weaning and mating to improve ovulation and conception rates.
Reduce mastitis and endometritis, and reduce sow culling
Two. Feeding standards for late lactation
After farrowing, sows have free access to feed for 7 days and are guaranteed an adequate supply of drinking water throughout the full 24 hours of the day.
During the summer heat, add feed during the cooler morning and evening hours, and use wet feed to increase feed intake. Increase feed for lean pigs to improve their body condition, and limit feed for fat pigs to prevent them from becoming overfat.
Use lactation-specific feed throughout, with a reasonable crude fiber ratio to prevent constipation. Do not change feed during lactation to avoid stress-related milk reduction and intestinal disorders.
Add Breeding Multivitamins and Astragalus Polysaccharide to the daily feed mix to stabilize lactation function, reduce substantial weight loss, and lower the likelihood of anestrus after weaning.
The ideal backfat standard at weaning: 16-18 millimeters.
Backfat thickness below 14 millimeters delays estrus and reduces litter size.
Backfat is greater than 20 mm, follicle development is poor, and breeding is difficult.
Three. Key points for weaning operations
Gradually reduce feed for 24 hours before weaning, with water available throughout.
For fattening pigs and sows with high milk production, reduce feed or withhold it on the day of weaning.
Thin pigs and severely emaciated sows should be fed small amounts that day to maintain body condition.
It is strictly forbidden to restrict feed 3-5 days before weaning, as this will result in poor piglet growth and more diarrhea, while also damaging the sow’s reproductive system.
Standard procedure on the day of weaning
1. Transfer the piglets first, then keep the sows resting undisturbed in their original pens for 24 hours before moving them to another group to reduce stress.
2. Record weaning weight, parity, and body condition; establish a farm register.
3. Check each udder and address mastitis promptly
Four. Common parameters for non-pregnant sows
1. Backfat reference for each breed
Plus-series pig 15-16mm
American-style pig 13 to 17 mm
Danish pig 12 to 15 mm
General body condition score 2.5-3.5 points
Keep weight loss during lactation within 10%; it will not affect estrus or mating. If weight loss exceeds 20%, delayed estrus, reduced ovulation, and decreased production capacity may occur.
2. Short-term enhanced feeding promotes ovulation
Begin flushing sows 3-4 days after weaning, feeding 3-4 kilograms of complete feed per day, together with reproductive health care.
Providing premium feed to replacement gilts 11-14 days before breeding yields the best results in improving ovulation.
3. Abnormal Physical Condition Conditioning
Allow thin sows to eat high-energy, high-protein feed freely, and breed them again once their backfat has recovered to more than 12 millimeters.
For overweight sows, reduce concentrate feed and provide 5 to 7 kilograms of fresh green fodder daily, or supplement with 200 grams of glucose to regulate body condition.
Five. Environmental requirements for the empty sow house
1. Temperature standard
Minimum temperature for a slatted-floor barn: 20℃
The minimum temperature for bedding barns is 15℃
Below 10℃, sows basically stop coming into heat
Above 23℃, estrus quality and mating rate decrease significantly
2. Ventilation standards
Winter minimum 16 cubic meters/hour
Summer maximum 100 cubic meters/hour
Effectively reduces ammonia and reproductive stress
3. Lighting standards
Daily light exposure for 14-16 hours, at an intensity of no less than 100 lux, promotes follicular development.
VI. Attracting and Group Management
Stimulate sows in heat with boar exposure 2 times daily, for 15-20 minutes each time. Farms without boars can use boar scent agent as a substitute.
Each pen houses 4-5 head. Animals are grouped by strength, and pheromones from outside the group are used to induce synchronized estrus throughout the pen, making it easier to monitor estrus centrally.
Engage in moderate exercise by moving the sows daily to help overcome anestrus and promote ovulation.
Seven. Management of anestrus and culling
Not in estrus 10 days after weaning; intensify estrus stimulation, exercise, and health conditioning.
For sows with persistent corpora lutea, administer altrenogest for 18 consecutive days, then synchronize estrus with hormones after discontinuation.
Treat mastitis and endometritis with lincomycin. In herds with subclinical health issues and frequent subclinical inflammation, use tylvalosin for whole-herd control to reduce repeat estrus and anestrus.
If a sow remains in anestrus for more than 20 days after weaning, cull her directly to save the cost of unproductive feeding.
Internal and external parasite control must be completed during the non-pregnant period. Thoroughly wash, disinfect, and dry the housing to safeguard reproductive health.
Eight. Estrus detection and breeding
Breeding must be assessed comprehensively based on three criteria.
1. Standing reflex: With the boar present, press on the sow’s back; she stands still and accepts mounting.
2. Vulvar condition: deep red and wrinkled, swelling has subsided, soft to the touch
3. Cervical mucus condition: thick and cloudy, with strands that can be stretched 0.5 centimeters, indicates the optimal time.
Best practice: Perform the first insemination 12-24 hours after the standing reflex appears, then repeat once at an interval of 12 hours, so the sperm are waiting for the eggs. The optimal time to breed Beijing Black pigs is 36-48 hours after the standing reflex.
Conclusion
Low sow estrus rates are mostly caused by insufficient estrus stimulation.
Implementing this standardized weaning management can reliably improve the farm’s estrus rate and number of piglets born. For farms without boars or where sows show no obvious signs of estrus, use boar scent attractant directly to assist with inducing estrus. This is a low-cost way to address the difficulty of inducing estrus and reduce losses from non-pregnant sows.