Forage Quality and Nitrate Testing
This year’s drought has caused severe hardships not only for grain producers, but also those that require forages for their animal operations. Not only has increased forage costs put financial pressures on producers, it has also caused herd liquidations that may have implications for years to come. Drought can also affect different forages in different manners.
Alfalfa is relatively drought resistant because its deeper root systems allow alfalfa fields to recover from drought conditions. However, drought conditions can severely limit production. In these conditions, producers should allow alfalfa to reach 10% bloom in order to help support the plant. Drought conditions may allow for slightly greater protein content at similar stages of maturity but stage of maturity still has the greatest influence on quality. Drought conditions can reduce the NDF content and improve digestibility because the reduction in stem growth may be greater than the reduction in leaf growth.
Alfalfa grown on fields fertilized with potassium may result in greater potassium content of the resulting forage, primarily due to the lower total dry matter produced. This can have a negative effect causing increased potential for milk fever, hypocalcaemia.
Drought conditions may also allow for increased weed content of alfalfa stands. Hoary Alyssum is a toxic weed that grows well in drought conditions and is particularly toxic to horses. It is also commonly found in pastures and most animals will avoid eating it if other forages are available, but this potential is greater in severe droughts. Its consumption can cause joint issues in many species and even founder in horses.
Producers using alfalfa should also be on the lookout for Blister Beetles (genus Epicauta) which may be greater in drought affected alfalfa fields in conjunction with later plant maturity, harvesting and lowered yields. Blister beetles can cause severe irritation and blistering that can prevent animal from eating.
Similar to Alfalfa, drought conditions will reduce dry matter production in grasses. Grass nutrient content can be affected to a greater level than alfalfa. Crude protein (Nitrogen) content can be elevated in grasses during drought conditions. However, significant amounts of this increased nitrogen content may be in the form of nitrates and other non-protein compounds. Horse owners in particular should have drought affected forages tested, as the true protein can often be limiting in these forages. When tested, total nitrogen, nitrate and non-protein nitrogen can be determined.
Sorghum and Sudan grass – and to a lesser extent Johnson grass and Indiangrass – can have higher prussic acid contents. Prussic acid poisoning results in reduced oxygen transport and may affect ruminants to a greater degree than non-ruminants.
With reduced grain yield, many producers are looking at harvesting the plant rather than just the grain. Drought conditions tend to increase nitrate content, particularly in lower parts of the plant.
Several days of severe heat (above 95°F) prior to pollination may reduce ear length and the number of kernels. Drought stress is most severe when it occurs within two weeks prior to and following silking. Leaf rolling in corn is a way for the corn plant to respond when it is stressed. The rolling of the leaves causes a reduction of photosynthesis within the plant.
Nitrate poisoning is the primary concern when feeding drought stressed corn plants to livestock. If the decision to harvest the crop for silage is made, farmers should consider the following strategies to minimize nitrate levels in stressed corn.
- Drought stressed corn may be salvageable as usable feed if the concentration of nitrate nitrogen level is lower than 1100 parts per million (ppm).
- Properly sample and test green silage for nitrate nitrogen and feed value before animal consumption. Sample at least 10 whole plants to get a representative sample.
- Leave at least 6 to 12 inch stubble at harvest in the field. Nitrate concentration is highest in the lower part of the stalk and may decrease as you move up toward the ear. Leaves and tassels are usually within acceptable levels for feeding.
- Ensiling drought stressed corn is preferred to baling because it may reduce nitrate levels by about 1/5 to 2/3. Fermentation takes 14 to 21 days for completion and drought stressed corn should not be feed for at least three weeks after the silo has been filled. The moisture in the plant influences the length of fermentation. The optimum range in 60%-65% moisture and the minimum for ensiling corn with nitrate nitrogen is 55% moisture. Moisture above 75% will result in seepage losses and production.
- Adjust the ratio to keep nitrate nitrogen below the toxicity level (1100 ppm) by blending high nitrate corn with low nitrate feed.
This year’s drought conditions have not only reduced forage yields, but also affected forage quality. Testing forages for fiber, protein, and nitrates can give producers a better understanding of the true value of the forages in the diet and suggest changes to the concentrate portion of the diet to help compensate for deficiencies. For more information on our feed, forage, and silage testing services, please contact:
1511 E Main St
Belleville, IL 62221
SGS Analytical Services
241 34th Avenue
Brookings, SD 57006
t: (605) 692-7611, ext. 5
f: (605) 692-5908
SGS is the world’s leading inspection, verification, testing and certification company. SGS is recognized as the global benchmark for quality and integrity. With more than 70,000 employees, SGS operates a network of over 1,350 offices and laboratories around the world.