Some of you may be wondering how weather conditions may have affected the feed value of grain if you are calculating rations for feeding or deciding on a purchase price for off-farm grain.
This is what you may expect with:
Drought = lower energy, higher protein. Moisture stress can cause premature death of leaves, reducing the ability to photosynthesise and consequently the amount of carbohydrate (starch energy) available for filling grain. The rate of carbohydrate storage also declines during moisture stress, resulting in a higher protein percentage. Â
Heat stress = lower energy, higher protein. Grain yield decreases by 5% for every degree increase in the average daily temperature above 14°C for wheat and 15°C for barley, during grain fill. The result is reduced starch synthesis, a reduction in grain weight and higher protein levels. Â
If the temperature rises above 30°C to 35°C, stress increases and the plant can experience heat shock. The maximum temperature determines the extent of the damage, not the length of time temperature is high, and unfortunately the effects are not reversible.
Flowering Frost = higher energy, higher protein. Frost during flowering results in complete sterility in some grains, but surviving grains will fill well.
Stem and Grain-Fill Frosts = lower energy, lower protein. Stem frost and frost during grain-fill blocks translocation of carbohydrates and protein. Grain does not fill and is often pinched.
Pre-harvest sprouting = lower energy, lower protein. Occurs when rainfall triggers the enzyme alpha amylase to begin breaking down starch and protein as part of germination.Â
All grain can be valuable feed, but it pays to measure the nutrient content so you can tailor your ration to meet the nutrient needs of your class of sheep properly. Reasons for specifications for feed barley grades can vary between seasons and delivery sites. A feedtest is the only way to know the real nutrient value of your grain.Â
As usual, gradually introduce stock to grain. Take particular care when using screenings which, anecdotally, in cases have caused grain poisoning (acidosis) – thought due to a smaller grain size having greater surface area for rumen microbes and enzymes to digest (similar to the effect of milling), and can give a greater flush of carbohydrate which the rumen might not yet be adapted to. To avoid any potential ill-effects, follow the recommended cereal grain introduction program outlined in table 10, page 24 in the Drought Feeding and Management of Sheep guide (click here).
Remember also to add 1% limestone to high cereal grain rations (greater than 50%) to provide calcium to balance the Ca:P ratio, and vaccinate against enterotoxaemia.
