High moisture influences the test weight of grain but test weight has no or limited relationship to grain performance says FAR CEO, Nick Pyke
What is the relationship between grain moisture and test weight?
Grain moisture and test weight are related from the standpoint that as moisture increases, test weight decreases. It doesn’t matter whether the drying is done naturally in the field or artificially in a bin. Nick Pyke, FAR CEO says there has recently been some suggestion that test weights are lower and therefore grain quality is reduced. He said “the fact that grain is being harvested at higher moisture contents than is normally the case may explain why some test weights are lower than expected. One reason why test weight increases as grain dries is that dry kernels pack together more easily than wet ones. As moisture decreases, the kernels shrink and this allows for more kernels to fill a volume.”
What factors influence test weight?
Test weight is most often influenced by stresses that occur during the grain-filling period of the plant. Factors that decrease the rate or duration of grain fill can result in lower test weights at harvest. These stresses can be subtle or fairly dramatic. Included among these factors are drought, excessive soil moisture, nutrient deficiencies, lack of sunlight, temperature extremes, insect damage to leaf and stem tissue, frost, and hail. There are also differences between varieties. This last season has generally seen a long grain fill period so as a rule test weights should generally be higher.
Example of test weight variation due to moisture content in a sample of wheat.
|
|
Moisture Content |
Test weight |
|
Grain |
% |
(Kg/hl) |
|
Wheat |
11.5 |
76.7 |
|
|
13.5 |
75 |
|
|
15.5 |
73.3 |
Test weight and quality
In general, correlations of flour yield with test weight are poor and cannot be used as a good predictor of flour yield. Test weight/flour yield relationships are influenced by year, growing site, variety and endosperm texture.
International literature indicates that, except at very low test weights (less than 62.5), animal performance is not affected by changes in test weight.
Sprouting on feed quality
Sprouting is the early stage of germination in wheat. Sprouting does not appear to reduce the nutritive value of grain and there are some reports of improved feed value of sprouted grain. Studies with wheat have shown no change in feed efficiency when up to 60% of sprouted grain is fed to yearling steers, feedlot cattle and pigs.