Division 1 Sampling frame
United Kingdom
A minimum number of pigs, kept during at least the preceding three months in the Member State, shall be ad random sampled in accordance with Table 1.
Table 1
Minimum sample size
| Based on an infinite population (> 100 000 per year), an estimated prevalence of 50 %, a confidence level of 95 % and a accuracy of 2, 3, 4 and 5 % respectively. | |
| Number of pigs present in the population | Minimum sample sizef1 |
|---|---|
| > 20 000 000 | 2 400 |
| 10 to 20 000 000 | 1 067 |
| 2 to 10 000 000 | 600 |
| < 2 000 000 | 384 |
Member States shall take a 10 % extra number of samples, to be analyzed in case some samples would be excluded from the study for various reasons.
Samplings shall be stratified by month to ensure to cover the different seasons.
Sampling shall be stratified by slaughterhouses that participate and proportional to slaughterhouse capacity. Each Member State shall rank all slaughterhouses according to their fattening pigs throughput in the previous year. Thus, each Member State shall identify those plants that accounted for at least 80 % of all slaughtered fattening pigs.
The total number of pigs and carcases to be sampled in each of the slaughterhouses included in the study shall be estimated by multiplying the sample size (e.g. 2 400) by the proportion of fattening pigs processed in the previous year. For example, if one slaughterhouse accounted for 25 % of fattening pigs slaughtered in the selected slaughterhouses (those representing at least 80 % of all fattening pigs slaughtered in the Member State), then (2 400 × 0,25) 600 pigs shall be sampled. These shall be evenly divided so that 50 pigs were sampled in every month, for 12 months. A further example is shown in Table 2.
Naturally, if a slaughterhouse is no longer in production, if a new facility has been opened or there is predicted to be a significant change in plant throughput during the survey, then the estimated throughput shall be adjusted accordingly.
Table 2
Weighing of slaughterhouses for the purpose of allocating the number of fattening pigs to be sampled from each slaughterhouse; calculation of sampled animals per slaughterhouse
| This number should represent at least 80 % of slaughtered fattening pigs in a Member State. | ||||
| Slaughterhouse ID | Number of fattening pigs processed previous year | Percent of total slaughter included in the study | Number of samples per slaughterhouse | Samples per month(/12) |
|---|---|---|---|---|
| AXD | 88 000 | 17,6 | 0,176 × 2 400 = 422,4 | 422,4:12 = 36 |
| SVH | 25 000 | 5,0 | ||
| TPB | 75 000 | 15,0 | ||
| MLG | 100 000 | 20,0 | ||
| GHT | 212 000 | 42,4 | ||
| Total | 500 000f2 | 100,0 | ||
For each slaughterhouse each month, a number between 1 and 31 shall be selected at random. If the randomly selected number is a slaughtering day, for that month, then that day is selected for sampling. If not, then a new number is selected randomly. This process is performed once a month and repeated so many times as there are samples to be collected at the slaughterhouse. For example, in the slaughterhouse AXD the process shall be repeated at least 36 times to select at least 36 working days randomly. Naturally, it might be more than one carcase to be sampled on the same day.
As the number of animals slaughtered on a specific day may vary enormously, the random selection of the individual animal shall take place at the slaughterhouse at the day randomly selected for sampling. The given day, the total number of animals is known, and the personnel of the slaughterhouse shall then randomly select a carcase or carcases using the randomisation sheet which has been provided to them and which has been generated using a maximum that exceeds the highest possible number of fattening pigs slaughtered on any given day in any slaughterhouse in the Member State.
A randomisation table may then look as shown in Table 3.
Table 3
Randomisation table
| i.e. the fifth carcase to be processed on the 19th day of that month should be sampled for the survey. | ||
| Slaughterhouse | Day of the month | Identity of carcasef3 |
|---|---|---|
| AXD | 19 | 5 |
| 4 | 2 | |
| 12 | 124 | |
| 12 | 2 | |
| 8 | 59 | |
The following animals shall be excluded from the baseline study:
-
animals with a live weight of less than 50 kg or more than 170 kg,
-
animals that have undergone emergency slaughter,
-
any carcase that is totally condemned.
Annotations
Footnotes
- f1
-
Based on an infinite population (> 100 000 per year), an estimated prevalence of 50 %, a confidence level of 95 % and a accuracy of 2, 3, 4 and 5 % respectively.
- f2
-
This number should represent at least 80 % of slaughtered fattening pigs in a Member State.
- f3
-
i.e. the fifth carcase to be processed on the 19th day of that month should be sampled for the survey.