Grasses have carbohydrates, proteins, minerals and other nutrients that make them desirable to grazing animals. But it is the proportion of sugars (energy) to protein that affects nutrient uptake the most.
We can smell the grass and describe the smell as sweet, not sweet, sour, putrid or many other descriptions. Cattle choose their grazing based on smell, flavor and how the plant makes them feel afterwards.
When we allow cattle selection in their grazing (growing plants) we know they usually select the highest energy part or species first because they are sweet and good-tasting to them.
Nitrates are very bitter and usually are in higher concentrations in the lower portion of the plant; energy or sugars are lower in the bottom part of the plant. That is why when we force cattle to graze down a green growing sward to where the yellow part of the grass plant is exposed they don’t like eating it because it tastes bitter.
When there are nitrates and not enough sugars to convert them to true protein it leads to an imbalance in the rumen with ammonia being liberated. In turn, this creates an alkaline pH problem where nutrients are not efficiently digested (ammonia is very alkaline). The same happens when there is a protein excess in relation to available energy.
A pH of 8 is considered alkaline. When pH is 8 and higher your cattle will have nutrient absorption problems. A pH of 7 is considered neutral, and is the desired number for better absorption of nutrients.
When the grass plant matures, the energy and protein percentages go down and the nitrate levels diminish even further. A mature grass plant normally produces no nitrate problems.
Conversely, one of the worst times for high nitrogen-to-energy ratios in the plant is early in the spring.
When we are confronted with a high pH (as measured with pH paper in the urine) we can improve the nutrition by managing grazing so we have enough some older, stockpiled forage going into the growing season. The new, green grass grows through this stockpiled forage and our cattle can graze both.
This will allow them to balance their diet much better and avoid the scours which normally hinders good gains the first few weeks of green up.
The rumen is a fermentation vat and it is inside the rumen where it’s decided how much of any nutrient is going to be digested for further breakdown in the next compartments. If we manage our grazing correctly it we can create more efficient digestion, making for better health of our cattle and our wallets.
For example, it makes no sense to offer the best mineral program if we do not manage our cattle grazing correctly and we will have in effect a mineral that is not absorbed by the animal.
This will vary with environment with a higher-fiber, sub-tropical environment requiring a different grass management than a more temperate or dry one. That is why we need to differentiate our conversations and our grazing plans and practices between high-and low-octane environments.