Of all the factors affecting hay quality, stage of maturity when harvested is the most important and the one in which greatest progress can be made. As legumes and grasses advance from the vegetative to reproductive (seed) stage, they become higher in fiber and lignin content and lower in protein content, digestibility, and acceptability to livestock.
The optimum stages of maturity to harvest for yield-quality persistence compromise is usually when plants are making a transition from vegetative (leafy) to reproductive (flower-seed) stage. Making the first hay cut early permits aftermath growth to begin at a time when temperature and soil moisture are usually more favorable for plant growth and generally increases total yield per acre.
After mowing, poor weather and handling conditions can lower hay quality. Rain can cause leaf loss and can leach nutrients from plants during curing. Sunlight can lower hay quality through bleaching and lowering Vitamin A content. Raking and/or tedding dry, brittle hay can cause excessive leaf loss.
Hay plants with an 80 percent moisture content must lose approximately 6,000 pounds of water to produce a ton of hay at 20 percent moisture. Crushing stems (conditioning) at time of mowing will cause stems to dry at more nearly the same rate as leaves. Conditioning will usually decrease the drying time of large-stemmed plants by up to a day and can result in leaf and nutrient savings.
Raking and/or tedding while hay is moist (about 40 percent moisture) and baling before hay is too dry (below 15 percent moisture) will help reduce leaf losses. Store to minimize loss, preserve quality and feed for efficiency. For more information on forage quality see the publication "Understanding Forage Quality".
Source: Garry D. Lacefield, Kentucky Extension Forage Specialist