Gilt Health and Performance
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NADIS disease bulletins are written specifically for farmers, to increase awareness of prevalent conditions and promote disease prevention and control, in order to benefit animal health and welfare. Farmers are advised to discuss their individual farm circumstances with their veterinary surgeon.
March 2005
By Mark White BVSc DPM MRCVS
Gilt Health and Performance
Individual lifetime production for the sow depends upon a wide range of factors including genetic make up, nutrition, housing etc. Furthermore, it is a common feature that herds with very high levels of output (more than 24 pigs reared per sow per year) tend to have high replacement rates and, as such, performance of the gilt and younger sow is critical.
To achieve a good start and obtain litters from gilts that do not drag down herd output, it has long been established that gilts must be big enough and old enough when served to ensure sexual maturity and body condition that is conducive to lifetime production. Often quoted standards are a minimum of 210 days of age, at a minimum of 125kg with a P2 backfat level of at least 20mm. The latter, in particular, can be difficult to achieve. With a wide variation of breed types and crosses now used, specific figures are needed for each type of animal and these should be obtained from either the breeder supplier or the veterinary advisor. For instance, pure bred grandparents, which have had something of a revival in recent years, will need to be older (up to 240 days old) whereas parent crosses containing Chinese breeds may be successfully bred slightly younger.
Over-riding all these managemental considerations is the health of the gilt prior to breeding and there is considerable argument as to what is the best requirement of an incoming animal. For instance, is it better to bring in an animal that is positive for a specific disease (e.g. PMWS) following earlier challenge or is it better to bring in as healthy an animal as possible and acclimatise it before service? Whilst the answer to such questions must be decided on an individual basis in conjunction with advisers, it is as well to consider the dynamics of disease and infection and what effect that may have on both the individual gilt and the whole herd.
A number of key features need highlighting:-
1) Empirical observation (and to a lesser extent, research data) suggest that any serious systemic disease challenge to a gilt at or around puberty can have a long term and even permanent adverse effect on reproductive capacity. For instance, a serious challenge with Actino pleuropneumonia will stop the gilt cycling or limit ovulation rates in those which do cycle. Some producers will remember the early 1990’s when Blue Ear Disease (PRRS) first started and the infected gilts, which introduced disease onto the farm, that never performed to expected standards.
2) In more recent times, observations suggest that damage done much earlier in life (e.g. 20-40kg range) can have a damaging effect on future breeding. It is unclear whether this is a result of a direct effect on the ovaries and reproductive system or whether it is a more general effect on the body as a whole.
3) In the ideal world, gilts should arrive on farm immune to the diseases that it is known that they will meet. This can only be achieved by exposure – either to the disease itself risking lasting damage – or by vaccination prior to entry in an otherwise naïve healthy animal.
4) If the animal has been exposed to infection prior to delivery, the timing is important. If it happens early in life and does not cause lasting damage, then the chances are that by the time the gilt is sold onto the recipient farm, the infection will have passed and, therefore, will be no problem.
5) However, if the animal is recently challenged prior to supply, it is likely that it will be excreting infectious organisms at the time of delivery, risking de-stabilising the recipient farm, particularly if it is introduced directly rather than through quarantine.
6) Alternatively, the gilt may enter the customer farm unchallenged and naïve. If challenged immediately with a high level of exposure, there is a danger:-
a) That the gilt will suffer damage that may impact on her future breeding ability
b) That the gilt will act as a generator of the causative organism and excrete them into the environment and de-stabilise the rest of the herd.
If not challenged immediately, the gilt may progress through the herd only to breakdown with disease later in life.
As readers will see, there is no ideal plan to follow but the following rules of thumb should help in the decision process:-
1) Establish which major diseases are present in your own herd.
2) Establish via veterinary liaison that the intended supply farm does not have any serious disease not present on your own farm.
3) Liaison is needed to establish pre-delivery vaccination schedules.
4) If the supply farm is positive for any disease present on your own unit, establish via your veterinary surgeon that the actual level/severity of the disease on the supply farm is low i.e. young pigs only receive a mild challenge.
5) If incoming gilts are naïve to some diseases they will meet, controlled challenge is necessary after arrival – do not have them next to the hospital!
6) Where acclimatisation is needed, it should occur in isolation to prevent de-stabilisation of the main herd.
Copyright © NADIS 2005
While every effort is made to ensure that the content of this forecast is accurate at the time of publication, NADIS cannot accept responsibility for errors or omissions. All information is general and will need to be adapted in the light of individual farm circumstances in consultation with your veterinary surgeon
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