Managing forage quality and forage production are critical for most cow-calf and stocker operations. This article will focus on the factors that affect forage quality to help producers improve animal performance and produce better-quality hay, which can reduce or eliminate winter supplementation needs.
When evaluating forage quality, two of the most important components are energy and crude protein (CP). The higher the digestibility of the forage, the higher the energy content will be. Energy is commonly estimated as total digestible nutrients (TDN); the higher the TDN value, the better. The primary factors that affect forage energy and protein include forage species, plant maturity, temperature and nitrogen fertilizer. In most forage situations, getting desirable TDN levels is more challenging than getting adequate protein levels.
In general, TDN levels will be higher in cool-season forages than warm-season forages. Additionally, when grown under similar conditions, TDN is typically higher in annual forages than perennial forages.
Bermudagrass has a lot of desirable attributes from a hay-making standpoint. However, from a TDN standpoint, when grown under similar conditions, it is lower than other forages like sorghum-sudangrass, sudangrass, johnsongrass, pearl millet, Tifton 85, little bluestem and others. That doesn’t mean that good TDN levels can’t be obtained with bermudagrass; it just means it is even more critical to manage bermudagrass to try to improve hay quality.
As plants grow and mature, digestibility and quality decreases. From a hay standpoint, one of the easiest ways to improve quality is to cut hay sooner so that the overall maturity of the forage in the field is less.
In grazing situations, the approach to managing maturity is slightly different. In a stand of forage that is 18 inches tall, the top 6 inches will be the least mature and have the highest digestibility, and the bottom 6 inches will have the lowest digestibility. Allowing animals to only graze the top third or half of the stand will result in improved animal performance.
As temperatures increase, forage digestibility decreases. This effect is independent of rainfall or irrigation, so hay that is cut in the spring or fall is generally higher quality than hay that is cut during the summer.
The crude protein content of hay is primarily influenced by maturity and nitrogen fertilizer. Protein levels decrease as hay matures. Additionally, increasing nitrogen fertilizer generally results in both increased protein levels and increased forage production.
