Manitoba Agriculture, Food and Rural Initiatives

Isolated Weaning Technology: Incorporation into the Canadian Code of Practice….Pigs

Terry Whiting
Epidemiology and Disease Control
Veterinary Services Branch, Manitoba Agriculture and Food

Abstract:

The Recommended Code of Practice for the care and handling of farm animals Pigs is due for revision in 2001. Isolated weaning techniques were not mentioned in the 1993 code but, have been widely adopted as of 2000. A committee has been working on an "Appendix" to the Code of Practice...Pigs. It is hoped the Appendix will address animal welfare aspects of iso-wean technology. This is the first time an "Appendix" has been developed. It is hoped that the Appendix can have wide circulation and industry discussion prior to it’s incorporation with corrections into the next draft of the Code of Practice…Pigs.

Introduction:

Animal friendly production is the goal of all producers. The most important cause of poor animal welfare in swine production is disease (Broom DM 1997). The way pigs are handled at weaning can eliminate infectious agents, enhance growth rate and increase the lean tissue mass of pigs at slaughter. Iso-wean is a complex pork production process that has been widely adopted in the last ten years in North America under a variety of names. IsoweanTM was once a trademark of Pig Improvement Corporation. Recently PIC has removed all trademark restrictions on the use of the term (Harris DL 1999). For the purposes of this paper iso-wean is defined as a process where:

1. newborn piglets receive sufficient high quality colostrum,
2. piglets are weaned from the sow at 14-19 days of age,
3. individuals achieve a weight of 4.5-5.5 kg at weaning,
4. weaned pigs are effectively isolated from the sow herd and held separate from all breeder and feeder (and feral) populations of swine of significantly different age and health status,
5. biosecurity measures are in place to minimize disease transmission into the isolated group.

The process was developed in commercial application with the intent to minimize the vertical transmission of certain diseases from the sow to the young piglets.

Modern Pork Production:

In conventional hog farming, as was most common through the ‘80’s, pigs are born, weaned at around 30 days of age and raised to market weight often in the same building. At market weight the pigs are carrying the same profile of swine pathogens as the sow herd. Iso-wean is designed as a non-surgical method of deriving specific pathogen free pigs from infected sows. Iso-wean also prevents the horizontal transmission of disease agents between pigs of different ages. Early isolated and age segregated pigs grow at least 10% faster than similar pigs maintained in a conventional herd, and require less medication during the growth phase (Dritz SS 1994, 1996). Maintaining a low pathogen load in the piglets at weaning and through the growth phase is better for animal welfare and improves productivity.

Inherent in iso-wean programs are all-in-all-out (AIAO) management strategies, disinfection of premises between production batches, strict biosecurity measures and only housing pigs of the same age together. Iso-wean also requires strict health management of the sow unit including careful acclimatization of gilts introduced to the herd (Rodibaugh MT 1998, Rajic A 1999, Heuser W 1999). Iso-wean pigs out-perform conventional pigs at the growing-finishing phase of production by reallocating the energy and protein normally used in body defense to enhanced growth. Part of this enhanced growth is due to clean pigs having an enhanced appetite. There is also evidence that pigs with a low antigen challenge during the growth phase develop a leaner, more desirable carcass than conventional pigs (Schinckel AP 1995, Williams NH 1997a,b,c). To realize the growth enhancement and leaner carcass the lack of stress inherent in the minimal-disease-state must be maintained throughout the growth period (Rodibaugh MT 1998).

Biologic Mechanism:

Over time, even sows in high health status units tend to become colonized by the common pathogens of swine. Moving high-health gilts onto these established premises requires a period of acclimatization for the naive replacement gilts. Mature sows and acclimatized gilts tend not to suffer disease or significant production loss due to the herd infection. These sow pools are often referred to as "stable" especially in relation to the porcine reproductive and respiratory syndrome (PRRS) (Heuser W 1999). Regular vaccination of the sow reduces the pathogen load in that sow and risk of shedding of infective agents, while increasing the colostrum quality and transfer of passive immunity to the piglets. Piglets receiving adequate colostrum are protected against colonization by specific pathogens up to a certain age. Weaning age is a factor in the success of iso-wean programs because the maternal immunity provided by the colostrum decreases at different rates for different infectious agents. The approximate age that the piglet loses maternal immunity, in well-managed systems, is summarized in Table 1. The actual age that bacterial colonization of the young pig takes place is variable in the field due to managerial differences in production.

Table 1. Approximate age of loss of maternal immunity (Piglet colonization) For specific pathogens of production concern
 

Disease	Age days
Streptococcus suis	Near birth
Actinobacillus suis	<7
Haemophilus parasuis	<7
PRRS	1-9
Atrophic Rhinitis (Pasturella)	7-10
Mycoplasma hyopneumoniae	7-10
Swine influenza virus	14
Actinobacillus pleuropneumonia	16-18
Transmissible gastroenteritis	21
Swine dysentery	21

The sow to piglet (vertical) transmission of transmissible gastroenteritis virus (TGE), A. pleuropneumonia, M. hyopneumoniae, Serpulina hyodysenteriae, Bordetella bronchiseptica and toxigenic Pasturella, have been eliminated by iso-wean. Recently PRRS free pigs have been derived from infected sows using specific iso-wean practices (Rajic A 1999). Segregated weaning production can limit the need for antibiotics and grower pig vaccination for the control of respiratory disease (Dritz SS 1994). Although H. parasuis is not eliminated from the piglets by iso-wean at 15-16 days, clinical disease attributable to this organism seems to be greatly decreased by the implementation of iso-wean programs.

Although disease control and enhanced growth rates were the primary reason that iso-wean protocols were developed, iso-wean is often adopted when farms expand. Producers operating farrow to finish units can significantly expand their sow herd without a large capital investment and without hiring additional personnel by converting nursery and grow/finish facilities to farrowing rooms and gestation sow housing (Dewey C 1998).

Iso-weaning Pigs

In feral pigs or in outdoor farrowing of sows, piglets wean at 9-20 weeks of age by a combination of the sow presenting less often for nursing and the interest of the piglets decreasing. Under nutrition available in farming, sows reach peak lactation at 3-4 weeks after farrowing. Structured weaning requires changes in feed presentation to both the sow and the piglet. In Europe weaning pigs prior to 21 days of age is prohibited by regulation unless "the welfare or health of the dam or piglets would otherwise be adversely affected" (Broom DM 1997). The standard of the European regulation is met by iso-wean, as there are significant increases in the health and welfare of the young pig through the growth phase.

Isolation is often best accomplished by moving the pigs to another location as an off-site nursery or to a separate wean to finish operation. A whole technical language has developed to describe how various hog operations are organized by geographic and production-stage (Harris DL 1999). Many isolated weaning production systems are large, as piglets must be grouped together within about 5-7 days of age, and managed as AIAO. It may be necessary for private producers to participate in an integrated operation (contract weaner marketing and placement) to have an effective iso-wean system. To fill two 1000 head finishers, one for barrows and one for gilts per week you need a pool of 5000 sows.

The weaning process in any commercial production system requires changes to the environment of the pig. Weaning involves a sudden change in diet, loss of piglet-sow contact, movement to a new environment, and mixing with other pigs. Piglets react to weaning with increased activity, increased vocalization and tend to consume less feed than required for maintenance especially in the first 24 hours. The microscopic structure of the intestine of the piglet and the digestive enzyme profile change dramatically at weaning. These changes require feed components to be highly digestible and non-antigenic to the intestinal lining of the gut (Thacker PA 1999). To accomplish effective segregated weaning, several procedures must occur which require appropriate management (Table 2).

Table 2. Procedures inherent in Iso-wean programs

Process	Stage	Management Control Point
Early Weaning	Sow	mid-lactation for the sow, mastitis,
	Piglet	Nutritional needs of piglets, Source of Protein
	Piglet	Small piglets at weaning (<5kg)
	Piglet	Drive to Standardize, cross fostering, split weaning
	Piglet	Residual nursing behavior
Geographic movement (at least 2km)	Piglet	Transportation of small piglets
Change to solid food	Piglet	Delay in feed acceptance
Intensive sow management	Sow	Vaccination, nutrition, re-breeding

In development of pig behavior, piglet activity changes from being ‘silent and still’ appropriate for the birth nest, to a pattern of increased interaction with the sow and siblings from day one to ten. Outdoor piglets can find and follow the sow at about ten days of age. In outdoor systems the sow isolates herself at farrowing and will re-locate the family herd at about day 8. The sow and litter joins the family unit of females at about ten days post farrowing (Broom DM 1997). Scientific studies agree that the frequency and severity of belly nosing and feed refusal increase as the age at weaning decreases, but there is no clear demarcation (Dybkjaer L 1992, Broom DM 1997, Worbec EK 1999). In Canada the most popular age of iso-weaning is around 16 days. This time coincides with the age of self-directed mixing with other litters in feral or outdoor raised piglets.

Weaning at seven days can result in initially inactive piglets, which tend to develop an increase in belly-nosing behaviour directed at pen mates. Inactivity and belly-nosing is greatly decreased by weaning at fourteen days (Worbec EK 1999). Belly-nosing has been interpreted as redirected suckling and exploratory behaviour in the absence of a sow (Dybkjaer L 1992). Worbec demonstrated that 14-day weaned pigs belly-nosed more than 21-day weaned pigs, however, pigs weaned and mixed at 16 days have less aggressive encounters with pigs from other litters than when weaned at four weeks (Roberts S 1998). Work is currently ongoing to investigate the motivation behind belly-nosing.

The uterus of the sow takes approximately 14 days to recover from the effects of pregnancy, to a state where another pregnancy is possible (Britt JH 1997). Shorter lactation periods are associated with slower return to estrus, reduced farrowing rates and decreased subsequent liter size, especially in first parity (Dritz SS 1994). Most sows return to estrus around 24 days post farrowing whether weaned at 14 or 21 days. Reducing lactation length from 30 to 17 days does not however, decrease nor increase the number of pigs per sow per year (Xue JL 1993). Iso-weaning does not impair the overall annual or lifetime reproductive performance of the sow.

The drive to produce a weekly crop of sized matched weaned piglets can result in an increase of cross fostering of piglets in iso-wean systems. Extensive cross fostering (more than once in a piglets nursing period) has been shown to be detrimental to piglet welfare resulting in increased piglet fighting and injury (Robert S 1998) and a decrease in weaning weight (Straw BE 1998). Straw demonstrated that extensive cross fostering decreases piglet variability by slowing down the faster growing piglets. Cross fostering can improve piglet welfare if properly managed. Modern lines of lean sows tend to be prolific and some sows will have have more than 10 "good" piglets born alive. Using cross fostering litters to keep litter size balanced to sow nursing ability by fostering once at 24 hours old has shown to be effective and increases animal welfare as it increases piglet survival (Roberts RS 1998). Split weaning, where the larger piglets in a litter are weaned earlier and placed in piggy barrels in close proximity to the sow has also shown promise to decrease variability in piglet size at weaning. Vocalization by the sow may be an important clue to eat in piglets less than 16 days old (Hyrcak L. personal communication).

Transportation alone does not appear to be an immediate cause for concern in well-run iso-wean systems. Sixteen-day old piglets have the necessary agility and social behaviour to chase and load on trailers and reasonable ability to respond to small changes in temperature. Iso-weaned piglets do not eat for the first 24 hours post weaning (Thacker PA 1999), leaving reasonable times for assembly and transport. Transport stress can become a concern when there is significant delay in movement of the piglets after weaning. In commercial production, there is often serious competition for farrowing and animal holding space and other causes of unanticipated pig-flow interruption. In the export of iso-wean piglets to the USA there is always the risk of delay in movement. In a production system with competition for resources, smooth animal weaning and placement becomes a serious management responsibility.

The general European opinion is summarized in a recent review of swine production. By far the most important single cause of poor animal welfare identified is disease. The report, however goes on to say "In well operated ISO/SE weaning systems there is little evidence to suggest that animal health is greatly improved. More research is clearly necessary in this area especially if method of production becomes a future trade issue" (Broom DM 1997). In iso-wean applications in North America, where geographic separation of production sites is possible, there is evidence that the increased health status acquired by iso-wean, a direct welfare benefit to the pig, can be maintained through the feeder stages. The production experience in Canada and the US does not support the opinion of the European Scientific Veterinary Committee, if applied to North America.

Response to Public Concern:

Current "Codes of Practice" are a printed set of standards generally recognized by the participants in the practice as both do-able and appropriate. Codes of Practice have been developed to cover such diversity as the practice of law, medicine, construction, engineering and the protection of the environment. Although a "Code" is not a legal obligation as a directly enforceable regulation under an Act; the Codes of Practice are often recognized by the court as the "standard of a reasonable man" (British Common Law). A requirement in the development of an honest code of practice is to represent all concerns fairly and in a transparent manner.

Canadian Farming Codes of Practice:

In 1980 the Canadian Federation of Humane Societies began coordinating the process of developing codes of practice for all farmed livestock. A Code Review Committee is made up of representatives from farm groups, animal welfare groups, veterinarians, animal scientists, federal and provincial governments, related agricultural sectors and interested individuals.

The Canadian Agricultural Research Council (CARC) was established in 1974 as a non-profit organization and incorporated in 1985. It was created to advise the National Agricultural Coordinating system (originally established in 1932) on the state and needs of national programs for agricultural research and development. In 1994, CARC's mandate was augmented to be directly responsible for the coordination of research and development as well as technology transfer. In 1995, CARC accepted the lead, in cooperation with the Canadian Federation of Humane Societies, in updating and developing codes of practice for the care and handling of farm animals. Canadian swine producers have been very pro-active in support of the Code movement both in dealing with environmental concerns and animal care. Canada is highly respected internationally for its animal care codes of practice.

Discussion:

The number of pigs weaned per sow per year, is a valuable financial measure of production. Initially it was thought that iso-wean would significantly increase the pigs weaned per sow per year. This index of production has not improved nearly as fast as the pigs weaned per crate per year (a measure of facility utilization), when iso-weaning is implemented. The pig specific production benefits of iso-wean are a faster growing feeder pig and leaner carcass at slaughter. A high score on both of these indices are consistent with a pig having lived a stress free life.

I suspect the failure to effectively adopt iso-wean in Europe is that early attempts did not work. Failure may have been because of the inability to achieve nursery and feeder isolation due to the land carrying density of the swine producing belts of Belgium-Holland-Germany combined with the limits on unit production size in the regulated European agricultural industry (restrictions on integration). The EU also prohibited iso-wean by law at about the same time essential piglet nutritional research was being completed in the USA. Successful implementation of iso-wean has been made possible only with the greatly increased understanding of the nutritional and palatability needs of the young pig. Meeting those needs has required the development of specific products such as spray dried porcine plasma (Hanson JA 1993).

In support of new production systems in agriculture there is a need to demonstrate with sound scientific research that the system does not have a detrimental effect on the welfare of the animals. To describe and recommend humane management practices, as the Code of Practice intends to do, it is important to document that the welfare benefits gained by the high health standard of the pigs in iso-wean systems contributes significantly to their well being. The Code is an attempt to indicate specifically, practice A is recommended because it results in welfare benefit B. Humane animal production is everybody’s concern and everyone from producers to scientists working in agriculture are working towards the best possible specific management practices.

Acknowledgement:

I would like to thank Dr. E. Hyrcak, Willomeade Professional Services, for her insight, review and valuable comments during the preparation of this paper.

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