Quality grasses and legumes are fairly self-sustaining and provide necessary nutrients to the herd, and because pasture is the primary feedstuff for your herd, any decrease in pasture performance can cause a drop in herd performance.
To avoid seasonal pasture slumps, create a long-term grazing management plan for herd and pasture productivity.
A successful pasture growing season typically results from actions taken in the spring. Cool-season grasses growing during this period provide nutrients to the cow herd, but stocking the pasture too early or overgrazing during the summer can stunt plant growth and reduce pasture productivity.
For optimum grazing, pastures should maintain 1,000 to 1,500 pounds of dry matter per acre. On average, a 3-inch to 4-inch bluegrass-white clover sward has about 1,000 pounds of dry matter per acre; in tall grasses and legumes, 6 to 8 inches of growth will contain this amount.
To promote these levels, grasses should reach 8 to 10 inches in height before cows are placed on pasture in spring.
Once forage height drops to 4 inches, cows should be moved to another paddock to allow the pasture to recover, regrow and build nutrients for the next rotation.
The amount of time required between paddock rotations varies based on pasture fertility and stocking density – or the number of cows a pasture can carry sustainably.
Stocking densities should be customized per pasture and per operation. The number that’s right for your herd is based on region, forage and soil quality, and grass growth potential.
A nutritionist or area expert can help determine the stocking density of each particular pasture.
Regardless of the stocking density, adequate soil quality is required to support the pasture through all seasons. To measure soil quality, producers can test soil pH, potassium and phosphorus levels.
Results of the soil test will determine the amount of fertilizer required by the pasture and the application time that is best for the type of grasses and legumes that grow in the paddock.
Once a stocking density and management strategy is established for the specific pasture, producers and nutritionists can work together to evaluate trends for that piece of land.
By combining lessons from past performance with results of forage and soil quality tests, a nutrient management plan can be formulated.
Supplying nutrients to the pasture a season in advance promotes soil fertility when it is most needed.
Trends in the Midwest show that pastures are often able to supply the necessary nutrients to the cow herd in the beginning of the season but generally taper off as the growing season continues.
Late spring and early summer are a time of rapid growth in cool-season grasses which provide high-quality forage to the herd.
This surge in quality forage helps the pasture meet the added requirements of the spring-calving cow. These added nutrients are needed as the nutrient requirement of a cow nursing a calf is almost two times higher than after the calves have been weaned.
Planning your calving season as part of your grazing management plan can help ensure cows are getting maximum benefit from pastures.
In the Midwest, the growth of cool-season grasses is followed by warm-season grasses and legumes in late June and July.
Adequate nutrients are also provided by most pastures at this time, but as the warm-season grasses mature, forage quality can begin to fall in terms of protein content in late summer and early autumn.
In any of these seasons, it is the quality of the forage available in the correct quantity that supplies necessary nutrients to the herd.
If the pasture is unable to provide the adequate nutrients the herd requires, decreases in performance may result.
For instance, a lack of protein in the ration can result in inadequate feed digestion. Without quality protein in the cow’s diet, feed intake can decline rapidly and consumption levels can drop.
Decreased feed intake caused by protein deficiencies can then lead to weight loss, poor cow and calf growth, depressed reproductive performance and reduced milk production – often leading to slower calf growth.
Mineral levels should also be examined based on season. For example, magnesium levels in spring-calving herds grazing fertilized cool-season grasses should be monitored to prevent grass tetany while calcium and phosphorous levels should be observed for optimal milk production and return to estrus, respectively.
To avoid deficiencies, a balanced mineral product in loose or tub form should always be available to the herd.
Newer, weather-resistant mineral technologies provide more consistent cow intake by reducing damage and other losses to the mineral due to rain and clumping. This technology helps reduce the mineral cost per cow.
Additional fluctuations in pasture performance can be stabilized through pasture supplementation or forage substitution.
Choose to supplement the pasture or substitute with added forages based on available stored forages and the amount of quality grass in the pasture.
Supplementing protein and minerals or substituting pasture forage with stored forage should be planned in advance to prevent production problems before they occur.
Substitution, or providing additional forage to the herd, may need to be done during times of slow pasture growth in late summer and autumn or periods of low rainfall.
Added forage may also be required during winter periods in colder climates or through drought conditions. In either instance, make the switch before the pasture is below 4 inches of growth. After grass levels decrease to that extent, regrowth is difficult.
When pasture height is above 4 inches, supplementation may be a more economic option. Protein and mineral supplementation using free-choice sources allows us to provide necessary nutrients to the herd without tapping into stored forages by filling a portion of the void left by the pasture.
Intake-modifying technology found in protein and energy supplements can complement pastures and allow for ad libitum supplementation rather than changing supplementation based on season.
Ad libitum feeding of these supplements is possible because the technology results in cows consuming smaller portions multiple times per day, enabling them to use the forage they consume more effectively.
The amount of supplement consumed by the cow will vary with the available forage quality and quantity.
This sustained nutrition program approach (allowing cows access to ad libitum protein and mineral supplements at all times) has been shown to be more cost-effective than seasonal supplementation.
Through this type of program, cows have access to the nutrients they need to maintain a more consistent body condition – helping the pasture to not be overexerted and herd performance potential to remain steady through all seasons. 
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