Wean-to-finish (W-F) has hit the pork industry by storm. The production system costs a little more to implement, but it's a lot less hassle.

Now producers want answers to questions about such things as utility costs and performance paybacks.

Birth Of A New System The introduction of W-F technology has led to production changes and new challenges.

Instead of designing nurseries for 6-8 groups/year and finishers for 2.7 turns annually, W-F units can handle 2.1 turns/year.

Instead of the traditional one nursery and two grow-finish barns, we now worry about matching W-F facilities at 2.1 turns/year with finishers at 2.7 turns/year and a whole host of other questions.

Why Wean-To-Finish? There are few tasks more detested than cleaning and disinfecting between groups of pigs. With all-in, all-out (AIAO), producers use high pressure washers to clean barns between pig groups to reduce risk of disease transfer. This is time consuming and messy.

Moving and mixing nursery pigs is stressful. Research suggests that even if pen integrity is maintained, each move through production costs a day of growth. Transporting pigs is costly. In three-site

production systems, moving pigs between nursery and finisher sites costs $1/pig or more.

All those drawbacks make W-F attractive.

In some cases, producers will absorb the slightly higher production costs of W-F in exchange for less power washing and pig moving.

A New Type Of Production The first reported W-F facilities were constructed in southeast Iowa by Oakville Feed and Grain. These facilities were traditional grow-finish units modified with partial woven wire flooring. Weaned pigs were held on the woven wire. Curtains were dropped to contain the heat in a smaller area of the facility. Later, the gates were removed and the pigs had access to both woven wire and concrete slat flooring.

Joe Connor, DVM, Carthage, IL, adapted the system by using a partial plastic nursery floor, the rest concrete slats. This adaptation is still used, but most producers use only concrete slats, with or without mats, for 1-3 weeks postweaning.

Challenges And Opportunities A major challenge of W-F systems is being an expert in nursery management for two weeks after placement, and then a grow-finish expert for the remaining 24 weeks. In larger systems, personnel are assigned the sole task of assisting during the critical two-week period after weaning.

An argument against W-F is the high cost of heating a facility in cold climates. Producers address this challenge by tightening up their facilities, restricting ventilation and using zone heating.

Many producers have adopted W-F because it simplifies pig flow and recordkeeping.

For performance, producers report daily gains of 1.4-1.45 lb./day with a feed:gain ratio of 2.6-2.7. Some report 1.5 lb./day gains and 2.4 feed conversions. These figures are remarkable when you consider 1997 PigChamp data suggests a national average of 1.34 lb./day gains and 2.9 feed:gain from 12.4 lb. to 243 lb.

University Of Nebraska Research There are no published research results comparing W-F performance to conventional nursery-to-finisher performance. The University of Nebraska is completing a trial sponsored by Alpharma Inc. and the National Pork Board that addresses some common questions asked by producers and their advisers.

This research is investigating the impact of three weaned pig management systems on performance from wean-to-slaughter weights. The systems under investigation include:

* Single-fill, W-F. Pigs are weaned into fully slotted finishing pens stocked at 7.5 sq. ft./pig from wean-to-slaughter.

* Double-stock (DS), W-F. Pigs are weaned into fully slotted finishing pens at twice the density of W-F (3.75 sq. ft./pig). Eight weeks after weaning, the pigs are divided into two groups, one group remaining in the original pen and the other moved to another pen in the same barn. Pigs are grown to slaughter at 7.5 sq. ft./pig.

* Nursery moved to finisher (NF). Pigs are weaned into a mechanically ventilated nursery with woven wire floors and stocked at 3.75 sq. ft./pig. Eight weeks after weaning, they are relocated to the same finisher as W-F and DS and grown to slaughter at 7.5 sq. ft./pig.

The university finishing facility used in this research is a 5-year-old, double wide, naturally ventilated, fully slotted facility with 8 x 14-ft. pens. The concrete slats are 7 in. wide with a 1-in. slot.

There are 15 pigs/pen for the W-F and NF treatments and 30 pigs/pen for the DS. There is a two-hole W-F feeder and one bowl drinker/15 pigs.

Heat lamps are used for supplemental heat for the W-F and DS treatments. Comfort mats were used in all trials. Pigs were floor fed three times/day for the first week after weaning. A commercial nursery diet was fed; diets were switched based on a feed budget.

Temperatures in the nursery were kept at 84-86 degrees F the week after weaning and were programmed to decline 3-4 degrees per week thereafter until 70 degrees F was reached. However, two of the three trials began in April and by mid-May outside air temperatures prevented the planned-for decline in temperature. Air temperature in the finishing facility was maintained at 73-76 degrees F with heat lamps used for supplemental heat as needed. They were generally removed after 3-4 weeks.

Pigs were weaned at 17 days of age and transported to the research unit at weaning. In trials 1 and 2, the pigs were purchased from a source 100 miles away. In trial 3, pigs were from a source 70 miles away. Trials were started in April and October in an attempt to pair up heating seasons and limit effects of season.

Two trials are completed and the third will be completed by the time readers receive this Blueprint.

In trials 1 and 2, veterinarians diagnosed gut edema 2-4 weeks postweaning. It was most severe in the W-F and DS treatments. In trial 1, only the W-F and DS treatments received medication. In trial 2, all pigs were medicated.

Pigs in trials 1 and 2 had many health challenges due to problems linked to Porcine Reproductive and Respiratory Syndrome (PRRS).

The reduction in performance for DS vs. W-F is probably related to group size. There is good evidence that increasing group size decreases daily feed intake and daily gain. However, the reduction in individual pig performance doesn't outweigh the overall improvement in pig weight gain per unit of floor space, a critical factor when assessing the economics of W-F strategies.

In spite of the health problems noted for trials 1 and 2 and the differential treatment of gut edema, W-F pigs outperformed DS and NF pigs during the nursery phase (Table 1). The response appears to be a feed intake response, resulting in faster daily gain, with no difference in feed conversion. Even though temperatures in our nursery were set low to reduce heat stress, feed intake was lower for the NF groups.

Table 2 offers a look at W-F PigChamp production data and nursery, grower and finisher performance.

Summary A lot of work remains for researchers. If we can determine why the increase in feed intake has been observed, it may be possible to apply that knowledge to conventional nurseries. It may be that W-F removes an unknown obstacle to feed intake that we have unconsciously built into many current production systems. It's clear from the results to date that the newly weaned pig can adapt to a variety of housing systems and perform well beyond our expectations. The challenge ahead is to resolve any obstacles to pig growth as housing technology evolves.