27 September 1996


Gilts are the fuel which feeds the farms productivity, and correct feeding, integration and supply management are vital, writes specialist pig vet John Carr

PLANNING the monthly purchase of gilts to maintain the pool, holds the key to maximising output. Too few gilts ready to serve before the next gilt delivery could mean an empty farrowing crate and 10 fewer pigs sold.

Also the decision to buy in extra gilts is often left until a service batch is taken into the farrowing house and the empty crates are apparent. Because sows remain in the farrowing house for five weeks – and gilts are not served until they have been on the farm for 10 weeks – there is no time to buy in the exact number of extra gilts to replenish the gilt pool. So most producers, run a larger gilt pool than necessary to cover a high number of drop- outs.

But, this can lead to too many gilts in season in any one week, adding pressure on the farrowing house at the end of the gestation and incurring feed, bedding and labour costs.

To manage the gilt pool more effectively, gilts should be ordered when a service batch reaches week 10 of gestation, 10 weeks before this batch will be served again. This means as the correct number of gilts are taken from the pool, there will be the exact number of gilts ordered to sustain the pool.

To do this accurate records must be used to keep track of drop-outs from each service batch.

One method to help plan gilt purchases is to make use of the service C-sum provided by many computer programmes (see table).

Gilt cycling should also be regulated. Gilts bought in on a monthly contract at the same weight should join different service weeks.

If they are all the same age/weight they could begin cycling in the same week. That is one of the commonest reasons for excessive numbers of breeding females being present in the farrowing house. So, purchase gilts in small enough groups or at different weights. For example 75kg, 85kg and 95kg to encourage a spread of cycles.

When gilts arrive, pen them in groups of four to eight and isolate them from the recipient herd in buildings as far as possible from the main pig buildings.

Provide each gilt with at least 1sq m (10sq ft) and ensure floors are not slippery and bedded with straw.

Two weeks after arrival – if the herd does not have a history of swine dysentery – introduce dung and bedding materials from the rest of the herd to introduce gilts to disease and build up immunity. However, this should not be sourced from the farrowing house.

At four weeks after arrival, allow contact with cull sows or finishing pigs (maximum of 10 gilts to one pig) and formulate a vaccination programme with a vet.

Six weeks post-arrival, feed ad lib on dry sow rations until mating and expose to a mature boar for about 15min daily. This must be supervised, and gilts should not receive constant boar exposure which could reduce the intensity of oestrus. From this time onward check gilts twice daily to detect the second heat. Record the onset of heat and put gilts to the boars as soon as they will stand and reintroduce them again 24 hours later. Again matings should be supervised. Once gilts have been served move them to an in-pig area to keep stress down and improve the chances of successful implantation and restrict feed levels.

Feed levels offered throughout the introduction period should provide a growth rate from delivery of 500-600g a day of lean tissue.

To achieve this feed 2-2.5 kg of a standard grower or high density finisher diet with 14.0-14.5MJ DE/kg from the time gilts reach 100kg. This should be continued until 14 days pre-mating.

Feed intakes during the last two weeks before mating should be increased to provide a flush of eggs at service. Offer feed ad lib or increase previous feed levels by 0.5kg to 0.75kg a head a day.

A standard dry sow/gestation diet of 12.5-13.5MJ DE/kg. To ensure intakes are kept high always allow 0.35m (1ft) of trough space a gilt and ensure plenty of clean water is available with a flow rate of 1.5-2 litres/min, ideally into a bowl or trough. &#42


Targets at 1st service:

&#8226 210 days old.

&#8226 Over 120kg body weight.

&#8226 Back fat at P2 over 20mm.


Using a farm which practises a six-week gilt introduction programme with gilts served at second heat nine-10 weeks post-arrival as an example.

Five weeks are spent in the farrowing house, which is managed on an all-in all-out basis, so 10 sows are needed every week to fill all farrowing crates.

Each service week a target 12 sows are served to provide 10 sows to fill the farrowing house and allowing for two drop-outs.

The table shows that 12 sows are served in a batch in service week one, gestation week one. As the gestation period continues the number remaining in the batch is written onto the C-sum sheet each week. In gestation week three, one sow from service week one drops out. The group now contains 11 sows and the figure is marked in red. Therefore, at gestation week 10 it is already known that one gilt will have to be drawn from the gilt pool to bring this batch back to 12 after they leave the farrowing house.

Two sows then return in batches from service week two and three so a further four gilts will be required. At the end of the first month (service week four) only 10 sows and gilts are served. By gestation week four only eight sows remain in the group and a further four gilts will be drawn from the pool after farrowing.

Service week four signifies the end of the month and time to order gilts to replenish the gilt pool. By adding up the number of extra gilts needed from each service week the correct number can be ordered in time to sustain the gilt pool exactly.

Provide housing with:

&#8226 Ambient temperature 18C-22C.

&#8226 Ammonia levels below 20ppm.

&#8226 Ventilation: minimum 16m/hour maximum 100/hour.

As sows progress through pregnancy in their service groups diligent recording of drop-outs allows earlier planning of gilt replacement needs.

To sustain the gilt pool at a constant level it is vital to discuss gilt needs with your local breeding company representative and plan well ahead to minimise costs.