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Segregated Weaning and Disease Control Procedures

(87) The sow during her lifetime becomes strongly immune to most of the infectious diseases present in the herd in which she is kept. She passes on this immunity in the form of colostral antibodies to her piglets in the first few hours of life and later also in the form of milk antibodies.

In addition because she has developed such a strong immunity the sow has thrown off many of the infections that commonly affect younger growing pigs, such as Mycoplasma hyopneumoniae (causing enzootic pneumonia) and Actinobacillus pleuropneumoniae (causing necrotic pleuropneumonia). Two major factors are involved:

  1. The sow is not shedding many infectious pathogens, and
  2. The piglet is strongly protected against infection.

In the majority of cases piglets start becoming infected after they are weaned, when the milk antibodies have stopped and the colostrum antibodies are wearing off. They become infected from the older pigs in the first and second stage weaner accommodation and further infected when they enter the grower accommodation. Thus in herds in which respiratory infections are endemic the pigs only start to show clinical signs when they are 7-10 weeks old.

This important principal is now used to control or eliminate disease.


As so often happens when new procedures are developed a variety of different ill-defined terms are invented to describe them. So lets first list and then define the terms used for the procedures related to segregated weaning. (Fig.3-39).

What do these terms mean?

Medicated Early Weaning (MEW)

(See also chapter 4)

Pregnant sows are removed from the herd in small groups at about 110 days of pregnancy. (Fig.3-40). They are washed and medicated against whatever infections are to be eliminated. Farrowing is induced with prostaglandins at 113-114 days of age. The piglets are medicated from birth and weaned away to a separate clean site at 5-6 days of age. The sows may also be vaccinated against one or more infections in the herd before being moved to the farrowing accommodation.

Aim: To produce high health status breeding stock free from the infectious pathogens present in the herd of origin.

Effectiveness: This has been used successfully by breeding organisations on a large scale. It is comparable to primary SPF repopulation.

It is not a practicable procedure for commercial operations. It will only be effective if the source herd does not have active disease.

Modified Medicated Early Weaning (MMEW)

This is the same as MEW except that the sows are not removed to isolated farrowing accommodation but are allowed to farrow in the herd of origin the pigs being weaned away to a separate site at 5-10 days. (Fig.3-41). The age of weaning depends on the infectious pathogens that are to be eliminated.

Aim: The same as MEW but less all-embracing. The range of infectious pathogens to be eliminated is not quite so comprehensive. MMEW can also be used to move pigs from a diseased herd to a healthy herd.

Effectiveness: A well known veterinarian in the USA, Hank Harris studied the effectiveness of this procedure and produced pigs free from different infections, from herds in which they were endemic. (Fig.3-42 and 3-43). He found that different infections required different weaning ages and some need medication and / or vaccination of the sows and / or piglets. The development of three site and multi-site production systems were then developed by him.

These were developed for breeding organisations but have now been applied widely to commercial operations. Also the source herd must not have new infections. If it becomes infected with a new pathogen during the procedure the pathogen is likely to break through the system. Because of this, if it is used for moving pigs from a diseased herd to a healthy one, strict 4-8 week quarantine and testing has to be incorporated into the procedure.

Segregated early weaning (SEW)

This is the same as MEW but may be done without the use of medications.

Aim and Effectiveness: The same as MMEW.

Segregated weaning (SW)

This is the same as SEW except that the piglets are weaned away from the farm at a more conventional weaning age, say, 18-23 days.

Aim: When used routinely its purpose is to produce healthy slaughter pigs.

Effectiveness: Obviously this is not as comprehensively effective as MEW, MMEW or SEW but it is more practicable for commercial production and is the basis of three-site production and where combined with all-in all-out systems is highly effective in producing healthy high-performance weaners, growers and finishers.


This term (short for Isolated weaning ) has become much broader in its meaning and is now used to cover MMEW, SEW, SW and even sometimes three-site and multi-site production.

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