Preparing for Winter Feeding

With record breaking heat and extreme drought conditions, making plans and preparations for winter feeding needs for your herd is as important as ever. We are estimating a 60% reduction in average hay production this year due to the drought. With less hay available for the winter, many producers will have to supplement with feed and winter forages. It’s important to have your hay tested to determine the nutrient content and see where and how much you will need to supplement with in order to continue to meet the nutritional requirements of your herd while maintaining body condition scores. We have a probe available for checkout in both the St. Landry and Evangeline offices. A routine analysis by the LSU Forage Lab cost $15 per sample. Usually about four core samples will fill a quart size bag.

Understanding the Forage Sample Analysis Report

A routine forage sample analysis includes important nutritional components such as dry matter content, crude protein, total digestible nutrients, fiber (acid detergent and neutral detergent), relative forage quality, dry matter intake, and mineral concentration.

The forage analysis will have 2 columns, as received and dried sample basis. When interpreting a forage analysis report for developing a supplemental feeding strategy, all interpretation is based on the dried sample basis column, as this is your sample with the moisture removed. Moisture levels may vary across samples, so comparing forages on a 100% dry matter basis allows for a more equal comparison among forage types.

All values on the analysis are reported as percentages. The first item you’ll see is dry matter content. Samples are weighed as received, then dried out at 135° F for 72 hours. The sample is then weighed again now that all the moisture has been removed. The different between dry matter content as received and dried sample basis is your moisture content. With the high humidity levels we are faced with in Louisiana, we tend to have a higher moisture content in our hay than what is considered ideal. A goal of 85% dry matter is preferred for hay, while 40-60% dry matter is acceptable for baleage.

Next is Crude Protein, shown as CP. Crude protein is the total nitrogen in a forage sample multiplied by a 6.25 correction factor. Protein is important for growth, milk production, and muscle development. A lactating cow needs a diet containing 11% CP on a daily basis during the first 60 days after calving. During mid-to-late lactation, CP needs decrease to 9%. A dry, pregnant cow has the lowest CP needs (7%) until the last 60 days before calving when nutrient needs begin to increase again. While the crude protein value is important, energy value and intake of forages is more important.

Energy value is shown on the forage analysis as Total Digestible Nutrient, or TDN. TDN is calculated based on ADF(Acid Detergent Fiber) and CP. Typically, the greater the value, the more energy-dense the forage is considered. Low-quality hay is generally 45 to 52% TDN. Mid-quality hay is generally 52% to 58% TDN, and high-quality hay is greater than or equal to 58% TDN. A dry cow requires a minimum of 48% TDN, and a lactating cow needs a diet that is at least 60% TDN per day.

Dry Matter Intake, shown as DMI, is calculated based on ADF, NDF(Neutral Detergent Fiber), and CP. It is expressed as a percentage of live body weight of the animal and varies depending on the quality of the forage. Ideally, you want this number to be higher than 2%, about 2.2-2.5. DMI is correlated with the amount of NDF in the forage: as NDF increases, intake decreases.

Neutral Detergent Fiber, shown as NDF, is the residue or insoluble fraction left after boiling a feed sample in neutral detergent solution. The NDF contains plant cell wall components except for some pectins. The NDF is considered a close estimate of the total fiber constituents of feedstuffs since it measures cellulose, hemicellulose, lignin, silica, tannins and cutins. As previously stated, NDF is negatively correlated to intake, so high NDF values in your dried sample basis will lead to lower DMI.

Acid Detergent Fiber, shown as ADF, is the residue remaining after boiling a forage sample in acid detergent solution. The fibrous component represents the least digestible fiber portion of forage. This highly indigestible part of forage includes lignin, cellulose, silica and insoluble forms of nitrogen but not hemicellulose. Forages with higher ADF are lower in digestible energy than forages with lower ADF, which means that as the ADF level increases, digestible energy levels decrease.