Cornell University Cooperative Extension
Hay harvest has been in full swing this week and crops have continued to advance in maturity. Orchardgrass and bluegrass were in early heading stage and both grass and legumes grew rapidly. Grass fields have passed the target NDF and we recommend harvest of grass core acres as quickly as possible. We predict alfalfa fields will be at target NDF by early next week. Alfalfa/grass mixtures at target NDF and we would recommend harvest of these fields as quickly as possible. The return to more seasonable temperatures contributed to rapid growth of both grasses and legumes, both putting on 6 or 7 inches of growth this week. Fiber accumulation made up for slow changes the past couple weeks, advancing on average 2 percentage points per day last week. Once grasses reach 60 NDF the NDF goes up more slowly, but digestibility continues to decline rapidly.
NDF digestibility decreased by 4 points and alfalfa decreased by 7 points, on average. This is typical as legumes are generally lower in digestibility than grasses. In general, NDF digestibility results this week are still in a good range, but will continue a steep decline as plants continue to mature. Second cutting was growing fast on several of the fields harvested last week. For fields harvested this week, plan for a high quality second harvest of equal quantity in about 30 days. Remember for grasses leave a 4 inch stubble height to preserve plant energy reserves and promote a rapid regrowth. This also helps reduce the potential for bringing soil into the forage, raising ash content and predisposing for improper fertilization. Pest Alert: We are hearing reports from other parts of the state of armyworm feeding. No disasters at this point, but a warning to keep an eagle eye and try and catch any infestations before large losses happen.
Bottom Line: All hay crops are at or past optimum quality, Harvest as quickly as practical. Table 1 has each sample location, listed by Town and elevation, and lists the species sampled, average height, and neutral detergent fiber (aNDFom). We recommend grasses be harvested starting about 50% NDF and legumes by 40% NDF, with mixed stands between 40 and 50 based on the legume content. Neutral Detergent Fiber Digestibility (NDFD), a measure of how quickly and completely forage can be digested in a cow’s rumen, higher NDFD is better. Undigestible Fiber (uNDF 240hr), this is a new measure of the fiber that will never be digested, and is correlated with how much of a forage a cow can eat, determining dry matter intake potential. Lower uNDF 240hr is better.