Management of high-lean hogs as replacement gilts

Purdue University 1996 Swine Research Report. It is a current accepted trend in the swine industry to produce a leaner, faster growing animal. Consumers as well as producers want lean pork. As hog producers convert genetics and manage their existing genetics to achieve a lean animal, they are presented with a problem. There is not an established system or method of raising high lean growth gilts as replacements. Research is being conducted on this problem.


Seventy-four high health, high lean gain gilts arrived at the Purdue Animal Sciences Research Center on October 19 at 165 days of age with an average weight of 240 lbs. Upon arrival, they were housed in open-front units. The gilts were ad-libitum fed to November 15; at this point, they had consumed approximately 7 lbs/day of a .80% lysine corn-soybean meal diet and had grown to an average weight of 297 lbs. The gilts were then fed 5 lbs/day of a .75% lysine diet. The gilts were vaccinated for PRRS on November 17 and vaccinated twice with Farrowsure-B.


The gilts were daily exposed to a boar and observed for signs of estrus. The gilts were not synchronized by relocation and boar exposure. Instead, the gilts cycled erratically the first 60 days after arrival. The average age of first observed estrus for the gilts was 188.7 days. On December 5, 14 gilts had not been detected in estrus and were injected with PG-600. Breeding was conducted from November 27 to December 17. The gilts were either bred upon first noticeable estrus, second observed estrus, third observed estrus, or they were induced for estrus with PG-600.


After breeding, gilts were fed 5 lbs/day of a .75% lysine gestation diet. By January 23, they averaged 382 lbs. Of the 14 gilts injected with PG-600, 12 cycled and were bred, with a 73% conception, 8.7 pigs/litter, and 7.3 pigs weaned/litter. The high lean gain gilts had an average of 9.5 pigs born alive/litter and 8.21 pigs weaned/litter. Four of the gilts had small litter sizes (1, 3, 3, and 4 pigs born alive). The Purdue herd gilts and sows averaged 10.1 pigs/litter and 8.1 pigs weaned/litter. The high lean gain gilts averaged 422 lbs and .79 inches of backfat at farrowing, and 407 lbs at weaning.


The high lean gain gilts continued to grow rapidly to heavier weights than average gilts. They were larger when they started cycling, and it was difficult to get them synchronized. They were heavier at first farrowing and had some unexplained small litter sizes. High lean gain gilts cannot be treated like average gilts, as they will be heavier at first estrus and farrowing, and have a larger mature size.


Additional research is required into the management and nutritional needs of high lean gain gilts as replacement females.