How to Improve Sow Reproductive Capacity? A Detailed Guide to Practical Breeding Methods
Production capacity is expressed as the number of litters per year and the average number of weaned piglets per litter. The length of the sow reproductive cycle determines the number of litters per year, while the number of live piglets per litter and the pre-weaning mortality rate determine the number of weaned piglets per litter. Improving sow production capacity mainly involves improving the sow reproductive cycle and the number of weaned live piglets.
In commercial-scale farming operations, crossbred sows are mostly used as the maternal line for market 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-Yorkshire (Large White) replacement gilts, the body shape should be straight or slightly sloping, and the abdomen should be relatively large and loose; sows with an excessively contracted abdomen have poorer reproductive capacity. Teats should be neatly and evenly arranged, generally 7 pairs or more, full and plump, with no blind teats or accessory teats. The vulva should be moderate in size and pendulous; sows with an upturned vulva generally have poorer reproductive performance and often show returns to estrus or failure to conceive. A sow 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 maternal line.
Landrace-Yorkshire or Landrace-Chester White replacement gilts are generally best mated when they reach a body weight of 110-115 kg; being above or below this weight affects litter size. The interval from the appearance of obvious estrus signs 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 for the first time 8-12 hours after the onset of estrus and repeating the mating 12 hours later can achieve very good results. For sows with inconspicuous estrus, it is necessary to carry out a second repeat mating. Sows generally come into estrus within 3-10 days after weaning. After pregnancy, sows must have their feed intake controlled; maintaining a moderate feeding level can increase the number of piglets per litter.
Under normal production conditions, if individual sows do not come into estrus for a long time or return to estrus frequently, and drug-induced estrus and improved feeding management are ineffective, or if a sow returns to estrus 3 times or more, she should be culled in a timely manner. Sows generally have the highest litter size at parities 3-6, which declines by parities 9-10, and their mothering ability clearly becomes poorer. Such sows should be culled promptly. 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.
After a sow becomes pregnant, feed quantity must be controlled. Generally, within 30 days after pregnancy, feed 1.6-1.8 kg per day; from 30-60 days, feed 2.1-2.3 kg per day; from 60-108 days, feed 2.5-2.8 kg per day; and gradually reduce it 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 appropriately reduced. The standard body condition for a pregnant sow is slightly above moderate. Pregnant sows housed together in large pens should not be merged into different 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.