In the late 1980s and into the 1990s, there was a movement within the swine industry to move to segregated early weaning and multi-site production. This system was known by a variety of names such as Isowean, medicated early weaning, modified medicated early weaning and segregated early weaning.

The primary advantage of each of these methods was to lower disease prevalence in nursery and finishing pigs. This was accomplished by removing the piglets from the sow while the piglets still retained sufficient maternal antibodies to keep them from becoming infected with pathogens carried by their dams.

Early Weaning Successes

Early studies encompassing these methods were attempted on a wide range of pathogens. Successful disease elimination was achieved with Actinobacillus pleuropneumonia (APP), Mycoplasmal pneumonia, Pasteurella multocida Type D, Transmissible gastroenteritis (TGE), pseudorabies (PRV) and Streptococcus suis.

For more information on how these disease elimination processes work, producers may wish to review Alexander, T.J. (1980) “Medicated early weaning to obtain pigs free from pathogens endemic in the herd of origin,” Veterinary Record, 106:114-119.

However, producers should first seek to understand their own herd's health status when considering whether to increase weaning age.

For example, research trials and field experience indicate that weaning pigs at 16 days of age or less is successful in eliminating APP serotypes 1, 2, 5 and 7. Raising the weaning age in a sow herd with endemic APP will more than likely allow disease transmission to the piglets. The cost of repetitive APP episodes may outweigh the increased value of weaning weight and age.

Even though early weaning can be quite successful in achieving disease elimination, the level of management is intensive. Expensive diets, supplemental heat, and higher mortality and morbidity all add to the costs of this process.

Early weaning also gained momentum because the pork industry rationalized that since the farrowing space is the most expensive space in the production system, the shorter lactation length would increase farrowing crate turns and lower facility costs/weaned pig.

This was accomplished with 16-17 crate turns/year being achieved by many herds, thus dramatically reducing facility costs/weaned pig.

Effect on Nursery and Wean-to-Finish Performance

Numerous studies indicate that heavier pigs at entry perform better in the wean-to-finish or nursery phase.

More recent data indicates that the age at which pigs are weaned is a major factor contributing to performance in the nursery and finishing stages of pig production.

A general rule of thumb is that a piglet will gain ½ lb. every day it remains on the sow over 15 days. Figure 1 is a chart of weaning age compared to weaning weight on a large farm in western Illinois. Note how the trend line for weaning weight is nicely correlated with weaning age.

For additional information, producers may refer to Harris, D.L., “Multi-site pig production,” Iowa State University Press, Ames, IA, (2000).

Weaning Age Comparisons

Researchers at Kansas State University (KSU) conducted a study comparing pigs weaned at 12, 15, 18 and 21 days of age. Figure 2 shows the average daily gain of those groups. They found an increase of 107 g./day (0.235 lb./day) in average daily gain from weaning to finish in pigs weaned at 21 days, compared to pigs weaned at 12 days.

In addition to improvements in average daily gain, the KSU researchers also found that weaning pigs older led to lower mortality (Figure 3 on page 8), increased weight sold/pig weaned and decreased cost/100 lb. of pigs sold.

For more information, producers should refer to Main, R.G., “Increasing weaning age improves pig performance in a multi-site production system,” Journal of Animal Science, 82:1499-1507.

Move to Later Weaning

As more research is being publicized on the influence of weaning weight and weaning age on performance of pigs in the nursery and finishing, there is an accelerated trend toward increasing weaning age.

Producers should remember that weaning age averages are important, but weaning age ranges are critical. A herd with a 16-day weaning age average will have a range of 12-19 days because of bump weaning and split weaning practices.

Bump weaning is a common method of providing a nurse sow for fallback pigs. A litter of excellent pigs is weaned 5-7 days younger and their dam used to suckle a litter of pigs 7-10 days of age, freeing a sow to suckle fallbacks that are 3-7 days of age. Split weaning is the early weaning of the 2-3 heaviest pigs in a litter three-plus days before the remaining litter is weaned. This allows the remaining pigs to gain weight more rapidly.

Weaned pig demand for contracts has moved recently from a range of 14-21 days of age, to a higher range of 16-26 days of age.

Effect of Lactation Length on Reproductive Performance

In addition to the improvement in growth performance of (later) weaned pigs, there is a beneficial effect on sow reproductive performance as well.

Longer lactation length gives the sow's uterus more time to involute (heal) following farrowing.

Assuming excellent lactation feed consumption, there is an increase in the number of eggs ovulated, which can translate into larger numbers of live born piglets in subsequent parities.

Longer lactation length also decreases the wean-to-service interval and increases the conception rate, resulting in fewer non-productive sow days. Our data suggests for each one-day increase in lactation length, there will be a 0.05-0.1 increase in live born and a 0.5% increase in farrowing rate in subsequent litters.

Consider the Costs

Economics of the decision to add lactation length include a review of space and inventory. The space is simply a function of high-cost farrowing ($2,500-plus/crate space) vs. nursery space. When evaluated on the basis of square feet, adding farrowing space becomes more economical (Table 1). A sow and 10 piglets require 5 × 7 ft. of farrowing crate space. The sow needs 2 × 7 ft., leaving 21 sq. ft. for the piglets. A litter of 10 weaned pigs has 2.1 sq. ft. of space/pig. Assuming a farrowing crate cost of $2,500/crate or $71/sq. ft., and a nursery space of $130/pig space, pigs in the nursery are generally stocked at 3 sq. ft./pig, or $43.33/sq. ft.

Another cost in extending lactation length is the increase in inventory. A 1,200-sow herd would normally farrow 8.05 sows each day. In order to increase lactation days, and still maintain weekly breeding targets, the herd inventory must be increased. A 4% increase in inventory is necessary to add six days over average lactation length, from 16 days to 22 days (Table 2).

The real cost, then, of extending lactation length is what the 4% increase in sow inventory adds to the overall cost of production.

Cost of production is allocated to “weaned pig cost.” A 4% increase in weaned pig cost over a current cost of $30/weaned pig is then $1.20/pig. The added cost must be returned through increased production to maintain the same breakeven on the weaned pig.

A 4% reduction in inventory can be made up with an increase of one pig/sow/year (p/s/y) in productivity (Table 3A, page 11).

However, a 4% decrease in inventory does not provide the same results as adding more farrowing space with a 4% increase in inventory (Table 3B, page 11). The table shows that a 4% decrease in inventory with the same number of farrowing crates will only add one additional day/lactation.

Producers often ask to drop sow inventory in order to increase piglet output. This model would work if sow productivity was “exponential” in improvement. The reality is that sow herd improvement will not likely compensate for the need to decrease sow inventory. Decreased sow herd inventory will result in fewer pigs being produced, and thus, higher weaned pig cost. As inventory decreases, the age of the piglet does not increase rapidly enough to make up for the drop in sow numbers. These production figures show:

  • A 4% decrease in inventory only added one day to lactation length.

  • In order to add six days to lactation length, a 20% decrease of inventory is required, or more farrowing crates must be added.

A 20% decrease in inventory drops a 1,200-sow herd to 960 sows. In order for 960 sows to wean 30,000 pigs/year (25 p/s/y on 1,200 sows), the producer would need the remaining 960 sows to achieve 32.5 p/s/y.

Table 1. Economics of Extending Lactation Length
Space Square Feet Cost
Farrowing Crate 35 sq. ft. (3.5 sq. ft./pig) $200/pig space
Nursery 3 sq. ft./pig $200/pig space
Finisher 7.5 sq. ft./pig $180/pig space
Wean to Finish 7.5 sq. ft./pig $200/pig space
Table 2. Increased Sow Inventory to Extend Lactation Length
Lactation Length Increase in Sow Inventory Percent Inventory Increase
16 days 0 0
18 days Add 16.1 days 1.34
20 days Add 32.2 days 2.68
22 days Add 48.3 days 4.02
1,200 sows × 2.45 litters/sow/year = 8.05 litters/day Cost: 4% increase × $30/weaned pig cost = $1.20/pig

Add Crates to Extend Weaning Age

Therefore, instead of looking at reducing the sow herd inventory in order to achieve an older weaned pig, producers need to look at adding farrowing crates.

With weekly farrowing groups, producers need to consider their total farrowing crate capacity, divided by their weekly farrowing target, in order to understand the number of weekly groups housed in farrowing at any one time. The formula our production system is currently using is four weekly groups in farrowing in order to achieve an average of 22 days of lactation.

In this example, a 1,200-sow farm would require 224 farrowing crates to achieve 22 days of average lactation.

The Danish Perspective

A very popular speaker at the 2004 Carthage Veterinary Service, Ltd. Swine Conference was Hasse Paulsen, a veterinarian from Denmark. Paulsen works with several farms in Denmark that are producing over 30 p/s/y.

Some of these management differences are causing U.S. producers to rethink some of their production practices, especially concerning weaning age and lactation length.

Table 3. Decrease in Sow Inventory
A. Pigs Per Sow Per Year
4% decrease in inventory on 1,200 sows = inventory of 1,152 sows
1,200 sows @ 22 pigs/sow/year = 1,152 sows @ 23 pigs/sow/year
1,200 sows @ 23 pigs/sow/year = 1,152 sows @ 24/pigs/sow/year
1,200 sows @ 24 pigs/sow/year = 1,152 sows @ 25/pigs/sow/year
B. Litters Per Sow Per Year
1,200 sows with 192 farrowing crates at 2.45 litters/sow/year = 56.5 weanings/week = 23.7 total farrowing crate days/group.
192 crates divided by 56.5 crates/week = 3.39 groups. A new “group” farrows every seven days, therefore, 56.5 = 23.7 days for the space.
1,152 sows with 192 farrowing crates at 2.45 litters/sow/year = 54.3 weanings/week = 24.7 total farrowing crate days/group.
192 crates divided by 54.3 crates/week = 3.54 groups. A new “group” farrows every seven days, therefore, 54.3 = 24.7 days for the space.

Evidence from these Danish farms would suggest that a key to lifetime performance of sows is a challenging period for gilts. Farms in Denmark routinely have gilts raise 13 pigs for 21 days, when the piglets are weaned. The gilts are then given 11-13, one-week-old piglets to raise for an additional 14 days. This results in a 35-day average lactation period for gilts. The Danish farms' average lactation length is 21 days for parity 2-plus sows.

Danish producers also differ from U.S. producers in that gilts are not bred before 8 months of age and at a minimum weight of 300-350 lb.

Summary

The industry is moving toward a higher piglet weaning age. This is producing a heavier weaning weight and improved throughput from improved average daily gain, litter size and farrowing rate, and most importantly, a higher level of profitability.

Producers should study this change in consultation with their swine veterinarian to evaluate the cost benefit.