Post-mortem surveys carried out to investigate high levels of piglet mortality have shown that over 30% of the piglets that die have no milk in their stomachs.

The baby piglet is usually born in a fairly precarious state with limited energy reserves and with no acquired immunity. It undergoes a marked drop in environmental temperature from 39ºC (102ºF) often down to as low as 18ºC (65ºF). It has no fat insulation, very little hair and poor thermo-regulating mechanisms. It is therefore very sensitive to temperature changes and is heavily dependant on a high environmental temperature to maintain its own body temperature. It has a disparity in size to the sow of approximately 1:200, which is rather an unbalanced situation to be presented with at birth.

It therefore has to satisfy three very important requirements.

1. The intake of antibodies from the colostrum, in particular IgG (immunoglobulin G) and IgA (immunoglobulin A). Without these it will die, having no protective mechanisms against the environmental organisms.
2. It must conserve heat to be able to utilise its scant energy resources to compete with litter mates and gain access to a teat.
3. It requires an immediate digestible source of energy (i.e. sows milk).

Clinical abnormalities of the piglet at birth.

• Low birth weight – immature
• Hypoglycaemic – low blood sugar
• Anoxic – short of oxygen
• Defective – e.g. splay leg, cleft palate
• Anaemic
• Diseased e.g. PRRS, E. coli.
• Traumatised

Fostering the piglet implies removing it from its own natural mother to another sow so that it is able to gain access to a teat, suckle and thereby survive. There are a number of reasons why it is necessary to carry this out.

Reasons for fostering

Too many piglets Some herds have the luxury of having too many pigs born alive and these surplus pigs if they are to survive must be given a new dam. The fostering of such pigs is a vital component of increasing output and when we see records of herds weaning 11 piglets per sow farrowed, invariably they are fostering to create new litter groups.

Variable birth weight The mortality within any litter group is dependent in part upon the variation in birth weights. The greater the variations, then the higher the mortality in those piglets of low birth weight.

Fostering pigs at birth between sows is an important procedure in reducing piglet mortality.

Weak or poor viability piglets As with small pigs, poor viable weak piglets are likely to die if left unattended. The grouping of eight or ten of these together onto a sow with good teat access is a part of efficient farrowing house management and increases the survivability of these piglets by some 80%.

Mastitis or diseases in the sow These may result in little milk being available. It may be necessary to foster the whole litter onto other good milking sows.

Savaging This is common in intensive environments. Occasionally if a gilt or sow does not respond to sedation it is necessary to foster the whole litter.

Delayed weaning Pigs that are held back from weaning because they are small or unthrifty are often moved to a foster sow. Be careful not to move sick pigs back to younger ones. The ideal is to have separate small farrowing rooms for such procedures. Foster sows should not be moved to the next room where sows are due to farrow (see "culled sows" below).

Starved piglets These are often seen at 3 to 5 days of age because one or more quarters of the udder have stopped producing adequate milk.

Death of a sow at farrowing Occasionally this occurs and it is necessary to foster the complete litter. This can also arise if an emergency hysterectomy is carried out on the sow due to farrowing difficulties.

The rules of fostering

If fostering is to be successful then there are certain ground rules which should be followed closely.

Timing The ideal time to foster a pig is as soon as it is born or within six hours and this is the procedure often adopted to even up numbers across litters and birth weights when a number of sows are farrowing at the same time. Provided piglets are moved within this period onto another sow that is at a similar stage then there are no problems with incompatibility or intake of colostrum. The second time period is when surplus pigs are being collected together to make a fresh litter. In this case they should not be moved from the sow until at least 6 to 8 hours after farrowing, when they have had a minimum four 40 minute periods of uninhibited access to the teat. This is to ensure maximum colostrum intake because the fostered pigs are going to be moved forward to a sow that will be suckling a litter approximately 4 to 5 days of age and there will be no colostrum.

This age factor is important if the establishment of a new litter is to be successful. Furthermore it is essential that only the biggest pigs are fostered forward to make up a fresh litter.

Procedures

1. Mix the sow's own litter and the foster one in the creep and hold there for approximately 30 minutes.
2. Move the sow's 5-day-old litter forward to a sow suckling a litter of 10 days of age and repeat the mixing process. This acclimatisation is a valuable technique because it allows the piglets to inter-mingle and make the foster litter much more acceptable to the sow.
3. Repeat 2 and the 10 day old litter is moved to a sow suckling at 15 days of age.
4. The 15 day old litter is weaned early and there is no loss in non-productive days or increase in lactation length..
5. Fostering can also be carried out with poor piglets between one and seven days of age. It is important to identify these pigs early because they tend to lose their suckling reflex and die. Again the technique is similar. Find a sow that is suckling a litter 5 to 7 days of age, moving her litter forward and foster on the poor pigs. For disease control purposes isolated farrowing pens are best used.
6. Give such piglets a 0.5ml injection of long-acting oxytetracycline at the time of movement because they are disadvantaged and susceptible to infections.

Selection of the sow and management The success of fostering, particularly whole litters, depends on the numbers of days the foster sow has been suckling and keeping the age disparity between the foster litter and the sow's own litter to within 4 to 6 days. Always select a docile sow with a good teat profile, particularly if a litter of poor viable pigs are collected together. The gilt or second parity animals are best.

The sows udder Look carefully at the foster sows udder and the quality of the piglets that are suckling. For example, if there are ten good pigs suckling then that sow will receive ten foster pigs. However, if there are only eight good suckling and two poor pigs then do not expect ten pigs to survive. Only foster eight.

Availability of water Whenever a litter is fostered always make sure there is clean, fresh water available for the piglets. In some cases the sow may be reluctant and slow to accept the fostered litter and piglets quickly become dehydrated.

The movement of foster pigs Wherever possible always foster within farrowing houses, or into a farrowing house with older pigs. It is bad policy to move piglets back into younger age groups due to the risk of spreading disease.

Culled sows It is a useful technique to have a number of farrowing crates set aside so that sows due for culling can be used for extra suckling. By removing them out of the mainstream of the farrowing houses they do not interfere with the important all-in all-out procedures.

If you have a litter size of a least 10.5 born alive and are only weaning nine pigs per sow, I suggest you read this section again and look at the advantages that can be gained from fostering.