When it’s time to decide which corn-silage hybrids to plant, use neutral detergent fiber digestibility (NDFD) values to help you compare different hybrids. Karl Nestor, senior animal nutritionist with Mycogen Seeds, offers these tips:
1. Make sure the NDFD values were determined by the same lab method. Near-infrared spectroscopy (NIR) and in vitro — two lab measurements used to calculate NDFD — can give somewhat different values with the same sample.
2. Make comparisons at similar time points. The two most commonly reported time points are 30-hour and 48-hour NDFD. Samples will have different digestibility values at 30 hours versus 48 hours because of the extra 18 hours of digestion in the 48-hour test.
3. Look for at least a four- to five-unit difference in NDFD. Differences smaller than this could be a simple lab error or too small to show a difference in your cows’ performance.
4. Review multiple tests on a particular hybrid. The results of a hybrid that has been tested 20 times are usually more accurate than if it was tested only once or twice.
5. When comparing multiple hybrids, observe tests done in similar years. The NDFD of a hybrid can vary from year to year, with the exception of one that has many tests done over several years.