In the experiment testing efficiency of body tissue energy for milk production in lactating dairy cows, researchers studied how food intake affected milk production levels. In this experiment, six Holstein-Friesian dairy cows were chosen and then subjected to a calorimeter, in which two levels of metabolisable energy intake (MEI) were given during a total of nine days. In the first three days, the calorimeter maintained a normal level. For the last six days, the cows were subjected to lower levels of food intake through the calorimeter. The levels were reduced by 70 MJ per day. The explanatory variable is the amount of food intake by the calorimeter, with the two levels of food administered. The response variable is the amount of milk produced. The researchers, R.M. Kirkland, T. Yan, R.E. Agnew, and F.J. Gordon, all from Northern Ireland, wanted to know if cows would use body tissue to produce milk to accommodate the loss of nutrition. The six cows were chosen based on their size, lactation stage, and body fat storage. This does not follow the principles of experimental design because none of the six cows were chosen randomly, not even out of a group that met the needed criteria. The major finding in the experiment was that the six cows did not have a significant reduction after treatment in the milk production levels. This shows that cows may not have to have a great diet 100 percent of the time to be productive, although it is recommended.
