Demo Large Volumes

Hello, and welcome to this Colostrum Monte Carlo Knowledge Base video. In this demonstration, we’re going to look at how feeding large amounts of colostrum—and therefore large amounts of IgG—can affect the apparent efficiency of IgG absorption and the resulting serum IgG concentration.

For this demonstration, we’re using the base exponential equation to calculate apparent efficiency of absorption, or AEA, as shown in the graph on the right.

You’ll notice that the equation includes a negative coefficient multiplied by CIgGI100. This represents cumulative IgG intake, expressed per 100 grams of IgG consumed. As cumulative IgG intake increases, the predicted efficiency of absorption decreases. In the base equation, each additional 100 grams of cumulative IgG intake reduces predicted AEA by about 5 percentage points before the effect of age is applied.

Importantly, cumulative IgG intake carries forward from one feeding to the next. Therefore, IgG consumed in the first feeding affects the predicted efficiency of absorption in the second feeding, and IgG consumed in both the first and second feedings affects the third.

Let’s look at how this works. First, I’m going to set a random seed so that our results will be identical each time we run the simulation. I’ll also set the number of feedings to three.

We’ll begin with a single feeding of 6 liters of colostrum at 2 hours of age. Obviously, 6 liters would be an unusually large first feeding, but it provides a useful example for this demonstration.

Colostral IgG concentration is set at approximately 68 grams per liter. When we run the simulation, total IgG intake is just over 400 grams. Predicted serum IgG concentration is approximately 25 grams per liter, and the apparent efficiency of absorption for that first feeding is about 23 percent.

Now let’s go back and distribute the same amount of colostrum over two feedings. Instead of feeding all 6 liters at once, we’ll feed 4 liters at 2 hours of age and another 2 liters at 12 hours. Total colostrum intake and total IgG intake remain essentially the same.

When we run the simulation again, total IgG intake is still just over 400 grams, but predicted serum IgG increases to approximately 28 grams per liter. The efficiency of absorption for the first feeding is approximately 29 percent, while the second feeding is approximately 16 percent.

Now we’ll make one more change.

This time, we’ll divide the 6 liters into three 2-liter feedings, given at 2, 8, and 16 hours of age.

Again, total colostrum intake and total IgG intake are essentially unchanged. But notice what happens to the efficiency of absorption. AEA for the first feeding increases to more than 34 percent. The second feeding is approximately 23 percent, and the third is approximately 13 percent. Predicted serum IgG remains around 28 grams per liter.

These examples illustrate an important feature of the CMC model. Feeding a very large amount of IgG early in life can reduce the predicted efficiency with which that IgG is absorbed. Dividing the same total amount of colostrum among multiple feedings can improve the efficiency of the earlier feedings, although this must be balanced against the continuing decline in absorption associated with increasing calf age.

This also illustrates why simply assuming that more colostrum at the first feeding will always produce a proportional increase in serum IgG may not be appropriate. CMC allows us to explore the interaction between the amount of IgG consumed, the timing of each feeding, and the changing efficiency of absorption.

That will do it for this demonstration. Be sure to visit the other CMC Knowledge Base articles and videos to learn how to get the most out of the program. Thanks for watching.