I was recently asked, if I could give one piece of advice regarding winter feeding and forages, what would it be? My response: sample your forages.
I have a lot of producers who contact me to ask what nutrient levels their forages might be at and how they should supplement their livestock. I can give them averages, but there is such a wide range of possibilities as well as so many factors that this is not always an ideal situation. I realize that you can tell a lot about the quality of your forage based on how your animal performs, but my question always is, are you okay with your cattle potentially losing weight and decreasing performance before you supplement?
We know that forages are going to be much lower in quality in the winter months compared to during the growing season, but the question remains — how much lower? Environment plays an important role, as well as species, maturity at the time of killing frost, management, etc. So I often dread that question, because I don't want to overestimate the quality and cause performance issues in their animals or underestimate the quality and increase the amount spent on supplements.
Testing your forages is simple, and relatively inexpensive to find out the basic information such as protein and energy. These are the two most commonly supplemented nutrients, as they are the most common to be deficient. Other micro and macronutrients can be an issue, but that is very dependent on location. For instance, selenium is often a deficiency in many forages in the western part of Montana but is usually adequate in eastern Montana into North Dakota and South Dakota.
When we compare forage quality of different species, we see a wide range in possibilities. For legumes such as alfalfa, we can still have protein levels in the mid-teens, around 12-14 percent. In this case, we often wouldn't need to supplement for protein. And even energy in legumes may still be at high enough levels to remain adequate for many animals. However, as the animal progresses in pregnancy, moving from first to third trimester, those needs increase, and supplementation becomes a more real possibility.
In the case of grasses, we can see protein levels decrease all the way to 3 percent. Species such as crested wheatgrass or Russian wildrye have pronounced quality decreases, and often will not meet animal needs without supplementation. In the case of other forages such as tall fescue, which are generally better suited for stockpiled winter grazing, protein levels may still remain around 7 percent, in which case we would require much less supplement. But energy may still be limiting, particularly if lignin levels are high.
While it may be at times a cumbersome chore, especially when temperatures drop to near zero and snow starts to fall, testing forages is something that we can really benefit from. Sample close to when you will be grazing that pasture or feeding hay to ensure that there will be no further extreme changes in quality between sampling and time of grazing.
From research, we know that once forages go dormant, protein levels usually don't change significantly. Fiber and energy values can change, mainly from decreases in water-soluble carbohydrates, which makes the timing especially important. How we are grazing can also influence how much those levels may change. Studies have found that in forage that was swathed and grazed later fiber and protein levels stayed much more constant compared to forage that was allowed to mature and go dormant at the first killing frost. The reason for this is due to our ability to time the maturity at harvest with swathing versus naturally allowing the plant to enter dormancy. As mentioned above, protein levels usually do not change significantly, provided a significant amount of leaf material was not lost during swathing.
One final item that should also be considered is the risk of any anti-quality factors. Particularly for annual forages, nitrate toxicity is a risk and should definitely be evaluated before allowing animals to consume any forage. In warm-season grasses such as sorghum, sorgo x sudan, and even millet and corn, prussic acid can be another concern on top of nitrates. Prussic acid is much more difficult to test for versus nitrates, as the cyanic acid (what causes the toxicity) volatilizes quickly. If your forage is less than 18 inches or has been severely stressed, I highly recommend you contact your Extension agent, Natural Resources Conservation Service consultant, certified crop advisor or myself to discuss what options are available.