August 2017 Articles

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Quality Hay Production Source: Pasture to Market, July—August 2017

Quality Hay Production Source: Pasture to Market, July—August 2017 Forage quality is a measure of the physical/chemical characteristics of the forage crop. Quality is related as the energy, crude protein and/or digestibility of the forage. Energy is typically reported as total digestible nutrients (TDN), which is an estimate of the nutrients digested from the forage. The term crude protein (CP) is used in reporting forage protein for ruminants since it is calculated from the measured nitrogen (N) content of the forage and not an actual measurement of protein. Although the actual protein is not determined, microorganisms in the rumen can utilize the N to synthesize amino acids and thus protein so the N measurement gives a good estimate of the potential protein for the ruminant. The fiber component is referred to as neutral detergent fiber (NDF) and acid detergent fiber (ADF). Neutral detergent fiber is a measure of the structural fiber of the plant. Percentage of highly digestible soluble compounds in the forage can be determined by subtracting the NDF from 100. Some components of NDF are digestible but ADF is a measure of mostly indigestible or very slowly digestible components. Nutritional need of the livestock is another factor, along with the forage quality analysis, that should be considered when determining the quality of hay on hand. The forage quality needs of the hay can vary depending on stage of production of the animals. If feeding to maintain a dry mature cow, then adequate quality hay could contain about 8% CP and 50-55% TDN. If the livestock being fed are in lactation or are young, growing animals, then the previous hay would be considered low quality since it would not nearly meet the nutritional needs of the animal. Good quality hay for these animals would need to be about 12-14% CP and close to or greater than 60% TDN. So basically, the quality of hay should be determined by how it meets the nutritional needs of the animal and be considered high quality only if it requires minimum or no additional supplementation. There are many factors that affect forage quality, and understanding these is an important part of producing quality hay. The single most important determinant of forage quality that a manager has control over is plant stage of growth. The more mature the plant the lower the forage quality. The highest quality component of the plant is the leaves and leaves are at their best quality soon after emergence and the quality of each leaf declines as it ages. This decline in quality is primarily a result of an increase in cell wall thickness which reduces the concentration of highly digestible soluble compounds. Another factor of maturity is the development of the stem which tends to be relatively more lignified than leaves, and as the stem grows, the ratio of leaves to stems declines, causing forage quality to decrease. Fertilization with N will not overcome the impact of plant maturity but does promote more rapid growth so will accumulate enough quantity to facilitate more frequent harvest which does enhance quality. Plant species can also have some influence on forage quality, and one of the more feasible options is to include legumes in the hay mix. Forage quality tends to decline as temperature rises, so focusing on producing higher quality hay early in the season may be an option to consider. The goal of hay harvest should be to maintain the highest nutritive quality possible during harvest. Hay should be cut during a period when rapid dry down will occur to reduce respiration losses during curing. This can be aided by cutting when the ground is dry and leaving enough stubble to keep the hay off the ground for better air movement. If a tedder is needed, it should be used before the leaves are too dry to avoid leaf shatter and raking should be accomplished before complete dry down to again avoid leaf shatter as much as possible. Hay should be less than 20% moisture before baling to reduce the likelihood of excessive heat buildup and molding. Close attention to all aspects of hay production (growing and harvesting) are required to produce high quality and quantity of livestock feed. — M. W. Alison, LSU AgCenter