Though we often record the occurrence of mortality and sickness within growing pig herds, we use this information in various ways. Often the methods that we use this information or record this information affects the outcomes of other indices such as average daily gain (ADG) and average daily feed intake (ADFI).

The level of sickness in a herd is often measured indirectly through the recording of mortality or culling due to diseases as well as decreased herd performance such as ADG. Additionally, clinical signs of disease such as coughing or diarrhea may be recorded or these clinical signs may also be measured at slaughter by assessing lesions such as pneumonia and rhinitis. All of these methods have their applications but are dependent upon a few requirements to be useful.

The first requirement in any recording system is that the record-keeping method be done consistently. This is performed relatively easily with concrete information such as the date and/or weight at which a pig dies. However, often it is difficult to rely on a consistent method of recording clinical disease. Different personnel have different sensitivities to signs such as the level of coughing or the severity of the lesions at necropsy. Even within personnel, often the ability to recognize diseases goes down with less time spent in the barn. In other words, it is less likely to recognize diseased pigs on the weekend. Many diseases only show clinical signs in the level of movement and/or attitude of the pigs and this relies on a sensitivity to these conditions.

Due to the lack of continuity of recorders and recording methods, it is often preferred to use concrete methods of recording disease, though these are often indirect measures. The information that we collect depends upon the purposes for collection. The purposes can include the prediction of number of pigs shipped and the timing thereof, the measurement of effects such as medication, vaccination, or different management methods, and simply the economic effects of disease. Overall, however, the ranking of availability of mortality and morbidity data usually is:

1. Occurrence and timing of deaths
2. Occurrence and timing of culls
3. Weights of mortality and culls
4. Movement of pigs to cull pens
5. Lesions at slaughter
6. Level of medication
7. Recording of respiratory signs
8. Recording of manure consistency
9. Daily feed intake
10. Daily water intake

A complicating factor is that diseases also differ in their prevalence within a herd. Certain diseases have a low level of involvement in the herd, but when they do occur, the effects can be quite severe. These may result in higher mortality rates but little effect upon barn level measurements like daily feed intake. Other diseases may have relatively mild effects but they affect the whole herd, so that the production effects can still be significant and daily feed intake may be affected.

If the grow/finish units are being run on an all-in:all-out basis, then the records should be performed on a regular, standardized basis. The information that should be recorded includes:

1. Mortality timing and weights

The purpose of recording this information is two-fold. The first is to characterize the pattern of mortality and start defining possible causes. The weight at time of death can be useful to differentiate short and long-acting diseases. Additionally, the mortality data is needed to accurately estimate the ADG, feed efficiency (FE) and feed conversions (FC) for the unit. Recording charts can be useful for this purpose.

2. Culling timing and weights

The purposes can be the same as for #1, but interpretation becomes difficult as the timing and level of culling varies. Nonetheless, it is important to record culls as it is needed to accurately define ADG, FE, and FC.

3. Slaughter checks

Though it is time-consuming to perform, the level of lesions at slaughter may be useful to determine disease patterns and the presence of problems. Again it must be performed in a standardized manner.

4. Medication use

This may be useful to explain the level of disease or the clinical signs seen, though it is difficult to interpret.

5. Feed use

Changes in feed use over time may reflect the outbreak of diseases such as viral diseases. Measurement is becoming simplified by using load cells under the feed-bins. It does not measure diseases which affect a small proportion of the pigs.

6. Changes in weight

Deviations from the expected growth curve can also be useful in showing the effects of disease as well as its occurrence. In-pen scales are being developed to make a chart easier to produce.

Take-Home Message