Precipitation and forage growth: Hay quality considerations

Adele Harty
SDSU Extension Cow/Calf Field Specialist

The weather-related opportunities and challenges that 2019 has presented are forcing farmers and ranchers to alter “normal” management decisions. The precipitation and forage growth that the state has experienced this year is something most have never seen and may never see again, but with the additional rainfall, comes variation in forage quality. SDSU Extension encourages producers to test hay and forage crops every year, but if this is not a normal practice for you, this will be the year to start. The information gained from the forage tests will help make the best management decisions regarding cattle nutrition and finances.

Multiple factors affect forage quality in a “normal year” including stage of maturity, leafiness, color, foreign matter and odor and condition. This year, there are additional factors that will affect hay quality, with rain being a major player. In western South Dakota, it has been extremely challenging to get hay into a bale before it gets rained on in the windrow. Hay that has not been rained on may be rather scare and as a result fetch a premium price if it is sold.

The weather has affected the normal growth of these forages. It is amazing that in the middle of August, the countryside is still green. The forages are still growing, even though they have headed out. With the moisture and cooler temperatures, plants continued to grow while they matured. The grasses and legumes are leafy and have good color to them. Because this is out of the normal, there is some question as to the quality of forages this year. There are many bales dotting hay fields, but quality may be lower than expected due to the abnormal growing conditions.

When the growing conditions are coupled with the fact that a lot of hay has been rained on, that can reduce quality even more. When hay is rained on in the windrow, there are a few things that happen to decrease quality and the overall value of the hay. Timing of this rain can have varying impacts. If rain occurs shortly after harvest and moisture levels in the hay remain above 30%, the plant continues to respire, which results in carbohydrate losses in the hay and decreased energy levels. If hay is close to baling, or more dry when it receives rainfall, leaching of carbohydrates can occur. The drier the hay when it is rained on, the more susceptible it is to leaching.

If leaching occurs, there is a loss in dry matter and carbohydrates causing an increase in fiber which results in decreased digestibility and energy value of the forage. This can be costly with the dry matter loss, but also the decreased energy levels can result in increased need for supplemental feeds, depending on how severe the decrease and what quality the hay was prior to harvest. The third thing to consider with hay that has been rained on in the windrow is additional leaf loss. This additional loss can occur in a couple ways, with one being hard rain shattering the leaves and the other being additional loss due to additional raking. Leaf loss is a bigger concern with legume hay than grass hay, but can be a problem with both. The leaf loss can be extremely variable, but remember that every time a windrow is turned to help promote drying after rainfall, more leaf loss occurs. Depending on the amount of leaf loss, there may be a significant drop in protein levels.

Without collecting a representative sample and testing hay, there is no way to know how much quality has been affected by the abnormal growing conditions and hay being rained on in the windrow or simply not being able to get the hay put up in a timely manner. SDSU Extension has hay probes available for check-out to make this process a bit easier. We are also available to help with interpreting the results and determining how best to use the feed. For more information on hay quality, contact Adele Harty at 605-394-1722 or another SDSU Extension cow/calf field specialist or beef specialist.