Have you ever considered the level of detail that goes into a research project, whether it involves 24 pigs or 2400 pigs? In reality, the number of pigs doesn’t impact the detail, just that with more pigs, the complexity of the detail can sometimes be almost overwhelming.
I mention this today since I spent considerable time in the past month designing a large wean-finish trial involving over 2000 pigs. Pigs were ear tagged at the sow farms and individually weighed prior to weaning. With the ear tag, we recorded the birth mother, along with other information. Yesterday, our research site received 50% of these pigs, with the remaining pigs coming Monday morning.
I know many readers of this blog would think that for many wean-finish trials, it should be sufficient to just gate-cut 27 pigs into every test pen and then randomly assign treatments and begin the experiment. However, in reality that doesn’t work.
At SVC Research, every pig that enters our facility is ear tagged and individually weighed. We then allocate pigs such that every pen of pigs has the same variation in weight (all experimental units are the same), rather than relying on the chance that every pen is the same. In some trials, we have other criteria that must be controlled for.
This means that yesterday, every one of the 1200 newly weaned pigs that arrived was hand carried to their pen based on their ear tag number. There were approximately 600 barrows and 600 gilts delivered, meaning we placed pigs into 22 pens in each room. While the pens are on each side of the central aisle and at one end of the barn, many pigs had to be carried over 110 ft to their pen. Do this 27 times for each pen and you begin to see the magnitude of the labor effort.
The reason for individually tagging pigs is not only for assignment to pens, but pigs are individually weighed at 2 points later during their growth to slaughter. By having an ear tag in the pig, we can track how the experimental treatments impact variation in weight gain, etc. Tagging pigs also means we can identify whether a pig is in the right pen throughout the experiment.
I mention this effort to highlight the effort involved in starting a research trial on a commercial scale. Having large populations of pigs involved in an experiment has the advantage of increasing the statistical power of an experiment (odds of learning whether a difference between treatments really exists, even at a small difference level). It has the disadvantage of complexity when it comes time to actually put the pigs on-test. Mistakes get made when you carry that many pigs and it often takes many more hours of effort to sort out these errors.