Effects of season of birth, breed and age of dam on litter and pig performance traits

In Tennessee there is wide variation in the practices followed by swine producers with reference to the breed and age of the breeding animals used in their herds. Some swine producers use gilts almost exclusively, whereas others depend largely on mature sows. On most Tennessee farms, both gilts and mature sows are used to produce pigs, but the number of gilts or sows a farmer keeps varies from farm to farm. There is no definite plan used by many swine raisers in maintaining their herds of breeding sows, and there may be wide variation in the breeding of sows and gilts on the same farm from year to year.

It is the practice of some farmers to use only one breed of gilts, breeding them to farrow their first and only litter when they are about 1 year old. When the litters are weaned, the gilts are marketed. To produce next year's pigs, gilts are selected in the fall from the spring pigs on hand. Many sows are sold for slaughter before they reach their peak performance.

One of the major elements contributing to profits in the swine enterprise is the size of litters sows and gilts produce. It requires on the average the gross returns from about six pigs to pay the cost of carrying the sow. The total cost of carrying a sow in the breeding herd remains practically constant whether she produces 2 or 10 pigs. With larger litters less feed is required to produce 100 pounds of marketable pork.

A sow's value in the herd is determined largely by the number and quality of pigs farrowed and raised. Performance in these traits is influenced by age and breeding of the sow and other genetic and environmental factors.

Therefore, the swine producer who does not take advantage of all means available to maximize litter size, growth rate and efficiency may be robbing himself of extra profit.