NASCalf Demo
In this brief demonstration, I’ll give you an overview of the program’s capabilities and show how it can be used to better understand the assumptions behind the NASEM model. We’ll also see how the model can be used to predict growth of young dairy calves and evaluate the implications of different feeding and management decisions. Let’s get started.
I’ll assume you’ve already installed the program. We’ll begin on the Performance page, which you can access by clicking the Performance tab in the lower left-hand corner of the screen. This page displays the growth predictions for animals fed the default diet.
In the upper right-hand corner, you’ll see a chart showing intakes of liquid, grain, and forage, along with changes in body weight from day zero through four months of age. In the upper left, there are two charts summarizing body weight at 0–2 months, 2–4 months, and 0–4 months, as well as the calculated average daily gain for those same periods.
In the center left portion of the screen, we see information on weaning age and the age at which calves double their birth body weight. Along the bottom of the Performance screen are several key performance indicators, including feed cost, feed efficiency, and intakes of liquid and dry feeds.
Let’s now evaluate the inputs that drive these results, starting with the animal. Click on the Farm and Calf tab in the menu bar at the upper left of the screen. Here, we can adjust the birth body weight and mature body weight of the animal, along with several prediction parameters, including target average daily gain before and after weaning. There are additional parameters available here as well, but we won’t cover them in this short demo. Once the animal parameters are set, click OK and move on to the dietary inputs.
Dietary information is entered in three sections: liquid, grain, and forage. We’ll start with the liquid feeding program by clicking the appropriate menu item. This opens the liquid feeding grid, where we can define both the feeding program and the nutrient composition. We’ll begin with the feeding program.
The grid consists of rows representing the feeds being offered and columns showing feed name, cost, and feeding periods. Each feeding period includes a begin day, an end day, and the number of grams fed during that period. Each period represents a step or change in the feeding program, and NASCalf allows up to 20 feeding changes per simulation.
For example, during day one—period one—we feed 5,000 grams, or 5 liters, of colostrum during the first 24 hours. Period two begins on day two and ends on day three, during which the calf receives 1 liter of colostrum and 4 liters of transition milk. In period three, colostrum and transition milk are discontinued, and milk replacer powder is introduced. Period four runs from day four through day fourteen, during which the calf receives 750 grams of milk replacer powder. Subsequent periods adjust both the amount fed and the timing, with the final period corresponding to weaning.
A couple of important points to remember – liquid feeds are entered in milliliters, so 4 liters of whole milk would be entered as 4,000 grams or milliliters. Milk replacer powder is entered as grams on an as-fed basis. After entering the feeding program, click OK to close the grid.
From the menu bar, click the Composition tab to adjust the nutrient composition of the liquid feeds. These values are entered on a 100% dry matter basis. NASCalf includes a built-in calculator—right-click within a cell to convert values from as-fed to 100% dry matter. After making any necessary changes, click OK to close the nutrient composition grid.
We’ll now repeat this process for the grain program. In this example, two dry feeds are offered: a calf starter and a calf grower. The grid shows the feed name, cost per ton, and the feeding period, defined by the first and last day each feed is offered. Here, the starter is fed from day three through day 56, and the grower from day 57 through day 122, which is the end of the simulation.
The final column specifies the maximum amount that can be consumed per calf per day, entered on an as-fed basis. For example, if we want to limit intake to 3 kilograms per day, we enter 3, and the program will prevent intake from exceeding that level. Nutrient composition for grain feeds is adjusted in the same way as for liquids, again on a 100% dry matter basis.
Finally, we’ll look at forages. In this example, calves are offered a single forage—sorghum hay—although NASCalf allows up to six forages in a simulation. As with grains, we specify the cost per ton on an as-fed basis and the days on which the forage is offered. Here, forage feeding begins on day 45 and continues through day 122.
We can also set a maximum forage intake. In this case, it’s set to 9 kilograms, which effectively represents ad libitum intake, since expected intakes are much lower. It’s important not to enter zero in this field, as that would indicate the forage is not offered at all.
The final column represents the percentage of total dry matter intake that comes from forage. For example, in a dry TMR with 5% forage and 95% concentrate, we would enter 5%. When forage is offered ad libitum, we must estimate this value. Research suggests calves typically consume 5–10% of their dry matter intake as forage, so in this example we assume an average of 8%. This is a simplification, as actual forage intake can vary widely in practice.
Once the animal and feed information are entered, we can evaluate the results. In this simulation, the calf begins at 42 kilograms on day zero and reaches 152 kilograms at four months of age. Predicted average daily gain is 1.74 kilograms per day during the first two months, just over 1 kilogram per day during the second two months, and approximately 900 grams per day overall.
Total feed cost for the simulation is just over 300 U.S. dollars. Liquid intake totals 61 kilograms, while dry feed intake—including both grain and forage—is approximately 229 kilograms. The program calculates an overall feed efficiency of 37.7%, and the cost per kilogram of body weight gain in this scenario is $2.77.
One particularly important calculated value is the age at which calves reach 15 kilograms of cumulative NFC intake. Research published in the Journal of Dairy Science indicates this is the point at which calves are truly ready to be weaned. In this simulation, that threshold is reached at 63 days of age. This value is shown in the upper-right graph and in the second gauge on the center-left of the Performance screen. Although the actual weaning age is 78 days, the model suggests physiological readiness occurs earlier, at around day 63. The simulation also indicates that calves double their birth body weight at approximately 58 days of age, which aligns well with common industry recommendations.
There is much more information available in NASCalf to evaluate feeding programs relative to growth and farm goals. The Diagnostics tab provides detailed daily outputs, including protein and energy responses. The Minerals tabs summarize macro- and micro-mineral supply and requirements, while the Amino Acid tab presents hypothetical amino acid requirements and supply for young calves. For additional demonstrations and deeper dives into the model, please visit the NASCalf Knowledge Base.
Thanks for watching, and we hope to see you again soon.