In this demonstration, we’re going to compare the results from GPS, and the results from the NASEM nutrient requirements for dairy cattle software program. There are important differences between the two programs. GPS models growth for four months, whereas the NASEM program will predict growth on a specific day, so we’ll need to make some adjustments to both programs to be able to do this comparison. We’ll use a very simple feeding program, only calf milk replacer and calf starter. No forage or silage or other feed ingredients. Let’s take a look at the liquid program. Now we are going to feed calves colostrum for the first day, transition milk thereafter, and then in 26/17 calf milk replacer, With this composition, the feeding program looks like this. We’re going to feed the colostrum for the first day for 5 liters, transition milk and colostrum on day 2. And then for the calf milk replacer, we’ll begin feeding on day 4 to 14 at 750g. To day 56 at 900 grams and then reduce the milk replacer to weaning on day 63. The grain program is quite simple. We’re going to use an 18% group protein, high starch calf starter. With this composition, the feeding program will simply be offering ad libitum between days three and Day 122. And as I mentioned, we’ll not offer any forage for the sake of this comparison. We set the calf up to begin at 42 kilos with a mature body weight of 700 kilos and a pre weaning average daily gain target of 800 grams per day. We’ll need to match these values with those that we enter into NASEM.

So here’s the NASEM program and we will begin by setting up the inputs and look at the animal description, we match the mature body weight, and we have looked at the age at 8 weeks of age and entered the body weight predicted by GPS. So we’re using an apples to apples comparison. Both programs are set to the temperature at 20°C and our production target like the set up for GPS, is set at 800 grams per day. The feeds in the ration will include a homemade calf starter, and a calf milk replacer, and I’ll explain a bit why I use a calf starter homemade in just a few moments. These will be the two ingredients that we use in the NASEM as well as in  the GPS setup. I’ve set the nutrient composition to be as close as possible between the two programs. Now there are slight differences. For example, with calf milk replacer as well as other calf related feeds. You’ll notice there’s no calculation of RUP or of the amino acids. And this is an important distinction I’ll explain in just a few moments. As closely as possible, I’ve set the nutrient composition for both the starter and the milk replacer to those of the values within GPS, so the ingredients are relatively similar, with a couple of exceptions.

1 is important, distinction is the composition of calf feeds Within the NASEM program. You’ll notice here for the milk replacer that we have no calculation of RUP, and the inclusion of no amino acids. The RUP fraction will be important as we calculate some of the values related to ME. OK, so for the the NASEM program, we’re going to predict growth on one day and so we’ll go to the ratio here and enter the values for the consumption of milk replacer and calf starter. You’ll note here the consumption of milk replacer .855 that’s taken directly from the GPS values. In the feeding program with GPS, we’re offering the calf 900 grams a day on a dry matter basis that calculates to 855. The 1.1678 intake of calf starter is the value from the GPS model. You’ll notice that it differs very slightly from the calculations. The estimate based on the NASEM model, which is 1.13. So basically we bet we have 1.12 versus 1.13. So within the NASEM model, we can do some quick calculations by refreshing the sidebar. NASEM will calculate the nutrient supply and requirements and calculate the energy allowable average daily gain, and the protein allowable average daily gain. As we can see here, approximately 1K per day. The amount of MP supplied is shown here, and the MP balance and the ME balance are calculated. There are some nutrient characteristics, protein, MP, NDF, etcetera that are reported by the NASEM model without the need for going to print the multiple reports. So how do these values compare with those from GPS?

Well, in order to do the calculations, we’ll go to the diagnostics screen and click on the supply calculations. This will bring up a new screen which is called nutrient requirements and supply. We’re going to look at day 56, so we’ll move down here and select day 56 and remember, net GPS does the calculations for every day, and we can look at those for every day. But we’re going to compare this one for day 56. I’ve clicked the checkbox here to look at the requirements for the target average daily gain, which is 0.8. Now, previously I looked at these values and knew the body weight was 81.93 predicted by GPS, so that was the value that I used within the NASEM model, so we could get these relatively similar. Now we’re feeding the same milk replacer, we’re feeding the same volume of calf starter. So essentially, if the calculations are reasonable, feeds should be quite similar, so we’ll move this up here to make it easy to see both on the screen. And I’ll bring the NASEM model in. We’ll look at just the sidebar for the moment, we can do a little bit of adjustments here and we should be able to see most of the values that we want to see between the GPS model and the NASEM model. So at the bottom line is that the energy allowable gain, which is the real calculation we want to look at for the NASEM model, was 1.01 for energy, allowable gain, the ME allowable gain calculated by by GPS is 0.99. There’s a slight difference between those two. The MP allowable gain was calculated at 1.04 kilos a day for MP allowable gain within the GPS model. It also is 1.04.

The slight difference between the ME allowable gain for GPS and the ME allowable gain for NASEM are based on a slight error in the calculations of the RUP contribution to fecal energy calculated by NASEM. So they’re slightly overestimating the ME values for their feeds, and that slightly increases the energy allowable gain that is calculated. The other nutrients and other calculations within the two models are very similar diet crude protein, 23.4 diet protein 23.42 MP, 1992 MP 1991 and so forth. So you can see that when we use the same switches so GPS calculates like NASEM, then, the values are basically the same. I hope this demonstration gives you some confidence that the GPS model is robust, sophisticated and predicts well. Well that will do it for this video, feel free to visit other parts of the GPS knowledge base to learn more about using the program.