Originally, medicated early weaning was developed to replace total repopulation of sow herds.

The development of the medicated early weaning process (MEW) and spin-offs, such as modified medicated early weaning (MMEW) and segregated early weaning (SEW), was originally designed for disease elimination. It was thought that rather than starting clean sow herds and pig systems with Caesarean-derived pigs, early weaning coupled with medication programs could produce similar results. It would cost less, take less time and still retain the genetic resources of the parent herd.

Breeding stock producers primarily used the concept to eliminate disease or produce healthier breeding stock.

Thomas Alexander, DVM, first developed the MEW technique in the 1970s for establishing new breeding herds from existing farrow-to-finish herds. The MEW process featured several procedures designed to reduce potential disease spread from sows to piglets:

- Use of small groups of older sows from closed breeding herds;

- Removal to isolated farrowing facilities during late gestation;

- Medication of sows before farrowing and during lactation;

- Induced, attended farrowings to ensure piglets received colostrum and antibiotics immediately;

- Medication of piglets throughout the suckling period and early nursery stage; and,

- Weaning only the biggest, healthiest pigs at 5 days of age or less to an isolated nursery.

During the mid- to late-1980s, D. L. (Hank) Harris, DVM, refined the MEW concept into what he called MMEW. He hypothesized that it could be applied routinely on a large scale for commercial pig production.

The key concept was that disease transmission could be reduced or eliminated provided pigs removed from the sow herd were still protected by passive maternal immunity and not exposed to older, diseased pigs.

A goal was to successfully commingle large numbers of farms' offspring.

Early Successes Most of the early projects involved intensive sow medication and vaccination programs, intensive piglet injections (often daily) prior to weaning and extensive medication programs involving injectable, water-soluble and feed-grade antibiotics to pigs upon arrival at the off-site location. That nearly eliminated major pathogens in pigs 10-15 days of age.

Most early breeding stock examples and the MEW research studies were done with only the biggest, strongest piglets that had surely received colostrum to assure success. Colostrum-deprived or deficient piglets were excluded for fear they could be disease carriers. These high-risk pigs were almost never studied.

Still, many early successes with breeding stock companies and commercial systems fueled some of the massive expansion in large-scale confinement systems.

Concerns and Doubt Today, many doubt the performance and results of these early weaning systems. There have been far more health challenges than predicted. Some things we've learned:

1. The sow was less forgiving than we anticipated. Weaning younger than 17 days very often plays a significant role in unacceptable reductions in wean-to-first service interval, farrowing rate and total born.

The uterus often does not have enough time to fully recover if litters are weaned before 17 days of age.

2. Compliance with strict maximum age limitations (often 16-21 days) and minimum weight requirements (often 7-8 lb.) is very difficult to adhere to. This is especially true as new genetics boost litter sizes.

If lightweight pigs were backward, crossfostered and kept until they were big enough, all-in, all-out (AIAO), by room, was compromised. The result could be more disease problems in farrowing and grow-finish.

Lightweight pigs in the nursery became problem pigs with much higher death loss. They required expensive feeds and more intensive management (sorting, extra heat lamps and mats, gruel or hand feeding).

3. Depopulation became a technique of the past. It was too costly and time-consuming. Multi-site systems made segregating the pigs easy to do.

In reality, multi-site systems have far fewer depopulations because disease outbreaks are typically much shorter than on farrow-to-finish farms often forced to depopulate.

Typically, six to eight weeks after a break of Mycoplasmal pneumonia, swine influenza virus (SIV) or porcine reproductive and respiratory syndrome (PRRS), health can appear extremely good in a multi-site system. The producer is often unwilling to depopulate when performance is going so well, despite the potential for similar disease flare-ups down the road. If this sow herd was part of a commingled, farrow-to-finish system, it often becomes the source of infectious organisms to nursery/grow-finish pigs.

4. There were false expectations that early work showing success with MEW and SEW would carry over into field conditions.

5. Labor became hard to find. As the industry grew and required more labor, the U.S. economy experienced record growth in the mid-late 1990s. Labor shortages resulted in more instances of poor piglet care the first day (getting every pig a dose of colostrum); poor farrowing house management practices and not following MMEW steps.

6. Diseases changed. The diseases of the '70s and '80s - such as swine dysentery, Actinobacillus pleuropneumonia, atrophic rhinitis and chronic Mycoplasmal pneumonia - are gone or have been greatly reduced by early weaning multi-site systems.

In their place are PRRS and SIV. These diseases are equally difficult to control. PRRS lacks good vaccines and basic knowledge for long-term, predictable control.

Vaccines seem to help with SIV but are costly and labor-intensive for large systems. In hog-dense areas, SIV still circulates site to site.

PRRS and SIV have seemingly adapted very well to the early weaning systems and don't seem to have any age-specific weaning time for elimination; these diseases are very fickle.

7. Training and health perceptions. There has been much use of contract nurseries, finishers and wean-to-finish barns. This rapid expansion has brought many new hires. Personnel training has not been as extensive or as good as it should have been.

The perception was high-health pigs coming to the nursery or finisher would require very little effort to raise. Problems occurred. Barns were not adequately pre-warmed, and computerized ventilation systems weren't properly managed. Walking barns, early detection and sort-down of diseased pigs fell short.

8. Commingling affects health status. We knew we couldn't commingle feeder pigs (40-60 lb.). With MMEW, many thought they could commingle pigs of almost any health status. We learned we can't. Management failures:

- Not kicking "dirty" farms out fast enough or long enough in commingled systems.

- Medicating or vaccinating specific sow herds that picked up diseases that were different from other sow herds in the system, or vaccinating entire systems when a couple of the sow herds became infected.

- Depopulating for a continuing disease threat on a specific sow farm. These failures often resulted in prolonged poor performance in an early weaned system.

9. Barn utilization changed. Ten to 20 years ago, producers sold a pen of pigs and replaced it with a new pen of pigs. Very rarely did they have empty pig spaces.

Now, attempts to go AIAO often lead to inefficient barn utilization. At times, 15% of the available pig spaces in a system will be empty from topping out finishers. This problem is compounded by differences in growth rate between barrows and gilts and the new packer grids with a narrow range of acceptable pigs qualifying for maximum premiums, penalizing the heavies.

10. Transportation is a concern. Early weaned systems mean many pigs on the road. Problems will arise.

The Future Early weaning systems still hold many advantages such as: disease control and elimination, specialized labor, reducing the risk of long-term, economically devastating disease and reducing or eliminating the need for periodic depopulation/repopulation.

Early weaning systems also allow commingling an adequate number of single-age pigs weekly to fill nursery or finishing sites that can be cost effective and run AIAO by site.

AIAO by site advantages were glaringly apparent in recent PRV outbreaks. These infected nursery or finishing sites were just naturally depopulated as part of their scheduled flow, thus removing PRV without any undue difficulties or additional costs. This has allowed for the large-scale use of contracting with significant leverage and geographic specialization.

Pig growth rates have improved with early weaning systems. But, the use of better genetics - particularly through AI and more phase feeding, split-sex feeding and AIAO have been factors, too.

Summary It's time researchers, swine veterinary consultants and producers return to the original early weaning programs and review why they worked. They must adjust their systems to obtain similar results. For example:

- Sow vaccination programs;

- Medication programs for sows and piglets (injectable and feedgrade);

- Weaning age to balance health, medication cost and sow performance;

- Nursery receiving medication and environmental programs; and,

- Which pigs meet the standards to be allowed "into the system."

The industry will have to develop procedures and protocols, genetics and nutrition to increase average birth weights, consistency of birth weights, lactation or milk output and weaning weights and decrease weight separation at weaning.

The industry and producers must develop ways to handle lightweight pigs such as alternative, continuous grow-out systems, selling lightweight pigs and alternative feeding methods (such as milk feeding) to enable these pigs to catch up.

For herds with inconsistent sow performance, review the following guidelines for managing the early weaned female.

- Conduct a thorough retrospective analysis of your production records. Identify the lowest practical lactation length and try not to deviate from it at weaning.

- Reduce the range of lactation lengths at weaning to a range compatible with satisfactory reproductive performance for your operation (i.e. 14-16 days versus 12-18 days).

- Focus on maximizing feed intake during lactation and reducing heat stress.

- Identify sub-populations of females such as parity-1 females or females with poor lactation feed intake and extend lactation.

- Carefully weigh the benefits of early weaning against the cost of reduced sow performance before phasing out a traditional weaning system.