Pork producers used to select replacement gilts from their own herds. They farrowed two or four times a year to match up with favorable weather conditions.
Because of this timing, few females were less than 12-13 months of age at first farrowing. Gilts were expected to farrow and wean no more than seven to eight pigs.
Today's finishing hogs are expected to weigh 250 lb. by 165 days. With genetic selection, appropriate facilities, few health challenges and proper nutrition, gilts can weigh 250 lb. by 150 days of age. This animal is big enough to breed but is physiologically immature. This new gilt is bred much earlier and has been genetically selected to farrow and wean a large litter of large pigs.
Case Study No. 1
Poor genetics, health and carcass quality led a producer to depopulate and repopulate his herd. His new gilts were known to be prolific and productive.
Due to limited space, lost production (downtime) and cost, the animals were mated shortly after arrival. Gilts were bred in groups to batch farrow every 28 days. They farrowed large litters and nursed well.
Shortly after weaning, several sows were found down in their pens. They responded very poorly to treatment with antibiotics and pain relievers. The problem persisted for three groups before veterinary intervention was requested. By this time, nearly 40% of the weaned sows were down, not yet in heat, sold or dead.
The diet was examined and found to be very adequate for lactation. However, average daily feed intake was low. Total calories, protein and mineral levels were too low due to low consumption. It also was discovered that the females in the herd that had returned to heat or were not bred until at least the third heat were not affected. Autopsies on two downer sows revealed hip and/or pelvic fractures with muscle damage in the large muscle masses of the leg (ham). Close observation of recently weaned females showed better-conditioned animals attempting to mount smaller, thinner animals. This was suspected to have caused the damage.
To solve this problem, more attention was given to individual feeding of lactating sows. Litters were split-weaned, with the biggest two or three pigs removed five days before weaning the rest of the litter. At weaning, sows remained in the farrowing crate for two days for full feeding.
These procedures greatly reduced the fallout rate of sows. The producer noticed there were few thin sows. Better attention to nutrient uptake stopped the fractures. The result was improved sow longevity.
Case Study No. 2
A breeding stock supplier called regarding high replacement rate on one of two farms supplied by the same source farm.
Farm A was 600 sows. Bred sows were grouped outdoors and had a 3% mortality rate. Farm B sows were confined in crates and some in pens. This farm was also about 600 sows, but space was tight so gilts were bred on first heat after arrival. Mortality rate was 12%.
Our investigation uncovered several reasons for what was occurring. Gilts were 240-260 lb. at arrival for both farms. Farm A placed gilts in a spacious, bedded shelter with access to a self feeder and a gilt development ration. Gilts were exposed to cull sows and feedback during the first month, but they weren't bred for 60 days or at least until the third heat cycle.
Even though Farm A gilts were housed outdoors in groups, special care paid big dividends in performance and in returning animals to full production. Average parity is nearly 4.2, quite old by most standards.
However, lifetime production is approaching 40 pigs/sow. Annual replacement rate is under 30%. With fewer gilts coming into the herd, health remains stable.
In contrast, Farm B was greatly concerned about genetic and nutrition suppliers. Records revealed about half of the mortality was in parity 2 sows or younger. Gilts were being rushed into the herd and potentially ruined.
In response, new gilts for Farm B were taken to an off-site location, fed a better diet, aged one more heat cycle and given plenty of space.
On the farm, it was found that the feed drops were not accurately measuring feed. Sows were really getting 4.5 lb. instead of 5 lb. This 10% reduction over a prolonged period was reducing lifetime productivity. These changes, plus more attention to animal care, have cut mortality in half to 6%. Replacement rate is well below 50%, where it had been more than 60%.
Plan Sow Longevity
Reducing sow attrition or increasing sow longevity has no down side. Having sows live longer and stay productive should be economically rewarding in nearly all cases.
Keep sows longer - as long as they are productive. To accomplish this requires a plan and the discipline and commitment to follow through with it.