How to Improve Sow Reproductive Capacity? A Detailed Guide to Practical Breeding Methods
A sow's productive capacity is shown by the number of litters per year and the average number of weaned piglets per litter. The length of the sow's reproductive cycle determines the number of litters per year, while the number of live piglets born per litter and the pre-weaning mortality rate determine the number of weaned piglets per litter. Improving a sow's productive capacity mainly means improving the sow's reproductive cycle and the number of live weaned piglets.
Select Excellent Pig Breeds
In factory-style pig production, crossbred sows are mostly used as the dam of commercial pigs, because crossbred sows have heterosis in reproductive performance and at the same time meet the market demand for lean-type pigs. When selecting Landrace-Large White crossbred replacement gilts, the body should be straight or slightly sloping, and the abdomen relatively large and loose; sows with an overly contracted abdomen have poorer reproductive capacity. Teats should be neatly and evenly arranged, generally 7 pairs or more, plump, with no blind teats or accessory teats. The vulva should be moderate in size and drooping; sows with an upturned vulva generally have poorer reproductive performance and often show repeated returns to estrus or failure to conceive. A dam kept in normal condition, neither fat nor thin, has better reproductive performance, while sows with an excessively high lean meat percentage have poorer reproductive performance. In a three-way crossbreeding system, lean meat percentage is not required of the dam line.
Breed at the Right Time
Landrace-Large White or Landrace-Landrace replacement gilts are generally best bred when they reach a body weight of 110-115 kg; being above or below this weight affects litter size. The interval from obvious signs of estrus to ovulation in replacement gilts is generally 36-40 hours, and in multiparous sows 38-44 hours, with ovulation lasting an average of 2-7 hours. Therefore, mating once 8-12 hours after the start of estrus and re-mating after an interval of 12 hours can achieve very good results. For sows with indistinct estrus, a second re-mating is necessary. Sows generally come into estrus within 3-10 days after weaning, and pregnant sows must have their feed intake controlled; maintaining a moderate feed intake can increase their litter size.
Cull Breeds with Poor Reproductive Performance
Under normal production conditions, occasional sows remain in anestrus for a long time or return to estrus frequently; sows that do not respond to hormone-induced estrus and improved feeding management, or that return to estrus 3 times or more, should be culled in time. Sows generally have the highest litter size at parities 3-6, which declines by parities 9-10, and their mothering ability becomes noticeably poorer. Such sows should be culled in time. Sows with poor lactation performance or no milk after farrowing should be recorded, and if the same situation occurs again later, they should be culled.
Control Feed Intake
After a sow conceives, feed intake must be controlled: generally 1.6-1.8 kg per day within 30 days after conception, 2.1-2.3 kg per day from 30-60 days, 2.5-2.8 kg per day from 60-108 days, then gradually reduced over the last 7 days until it reaches 1.2 kg per day. For individual sows that are too thin or too fat, feed should be reduced appropriately; the standard body condition for a pregnant sow is moderately above average. Pregnant sows kept in large groups in the same pen should not be merged into other pens midway, to avoid stimulation such as crowding and fighting. Routine epidemic prevention and disinfection work should be done well, and internal and external parasites should be eliminated.