NASCalf Demo – Scours
Hello, and welcome to this NASCalf demonstration. In this video, we’ll look at how calf scours are modeled in NASCalf and how they affect predicted growth. Let’s get started.
Scours are a common challenge in young calves and can significantly impact performance by reducing growth. However, most growth models do not account for scours because there is limited research quantifying how diarrhea affects digestibility, intake, and nutrient utilization. During development of NASCalf, we reviewed available literature and on-farm data. While we observed changes in intake, digestibility, and average daily gain, the data were not sufficient to reliably adjust all parameters. As a result, the model simplifies this process by adjusting average daily gain (ADG) only, without directly modifying dry matter intake.
To use the scours feature, go to the Farm and Calf Information screen. Here, you can select a scour score from 0 to 3:
0 = no scours, 1 = mild, 2 = moderate, and 3 = severe.
You can also choose the day scours begin, with a default of 7 days.
Each score reduces ADG for a defined period:
- Score 1: ADG reduced to 80% of normal for 7 days
- Score 2: ADG reduced to 70% of normal for 14 days
- Score 3: ADG reduced to 60% of normal for 21 days
These adjustments are based on observed on-farm performance rather than precise biological equations.
When we apply these scores, we see relatively small effects with mild scours, but more noticeable impacts as severity increases. For example, moderate scours reduce body weight at two months and slightly decrease overall growth. Severe scours result in larger losses—on the order of several kilograms by two months of age. These results are consistent with what we typically observe under field conditions.
You can also adjust the timing of scours. While most cases occur around 7 to 10 days of age, later events—such as coccidiosis—can be modeled by selecting a later start day.
On the Scientific page, NASCalf also estimates the economic impact of scours. This is based on research showing that each day of illness reduces future milk production. The model converts that loss into an economic value using milk price assumptions. While this approach is simplified, it provides a practical estimate of the long-term cost of calf health challenges.
In summary, the scours feature in NASCalf is designed to reflect real-world impacts using a simple, practical approach. It allows you to explore how different levels and timing of scours affect growth and economics, even when detailed biological data are limited.
Thanks for watching, and be sure to explore other NASCalf Knowledge Base videos to get the most out of the program.
