We depend on grass as our primary source of forage, whether it be rangeland, pasture or hay. While we carefully select species to plant in our fields and utilize as cover crops or plan a total mixed ration (TMR), many ranchers do not know the primary grass species being consumed by their livestock.
Knowing the predominant grass species is important because not all grass is created equally. Different species have different growth patterns and nutritional content. Thus, the optimal time to graze these resources varies. To achieve optimal forage and livestock production, a grazing system should be planned around the type of grazing resources available.
Cool vs. warm-season grasses
Native grasslands consist of a mixture of cool- and warm-season grasses. Native cool-season grasses begin growing once the average temperature is 32ºF or greater for five consecutive days, whereas warm-season grasses start growing once the average temperature is 40ºF or greater for five consecutive days. This results in approximately a one-month difference in when these plants reach grazing readiness.
Pasture, on the other hand, typically consists of cool-season grasses in the northern regions of the country and warm-season grasses in the southern regions. Cool-season grasses exhibit rapid growth and need less growing degree days to reach grazing readiness in the spring. This extends the grazing season by enabling ranchers to turn out to pasture earlier in the spring.
Irrelevant of grass species, grazing before plants reach the appropriate stage of growth for grazing readiness causes a reduction in herbage production by as much as 60%, which can reduce carrying capacity (number of livestock or length of grazing season) and animal performance. Grazing readiness for most domesticated pasture is at the three-leaf stage, whereas grazing readiness for most native range grasses is the 3.5-leaf stage.
Grazing readiness of grasses can be further delayed, and subsequent forage production reduced, by drought and poor grazing management. This is especially true for cool-season grasses, which develop tillers in the fall. The development of these tillers has a direct impact on plant growth the next growing season. The North Dakota State University Extension (NDSU) has found that heavy grazing use (greater than 80% use) in the fall can reduce forage production of cool-season-dominated rangeland and pasture by over 50% the following grazing season.
If livestock graze tillers of cool-season grasses below the growing point in the fall (in between the bottom two leaves), the grasses usually will not survive the winter. If they do survive the winter, plant vigor (health) is low and forage production is reduced. Drought stress also affects the survival of fall tillers. Fall droughts either don’t allow buds to come out of dormancy, thus no new tiller growth, or cause death to those tillers that did grow. If tillers do not establish or survive the fall, a delay in growth and development will occur the following growing season as new tillers will need to be developed in the spring. This loss of fall tillers can create a delay in grazing readiness the following spring by 10 to 14 days. When drought and poor grazing management in the fall occur simultaneously, grazing readiness can be delayed even longer.
Drought strategies
Drought-stressed pastures will require special care this spring to help them recover. These pastures must be given adequate time to recover. Grazing too early will reduce plant vigor, thin existing stands, lower total forage production, and increase disease, insect and weed infestations. Pastures and range damaged by grazing too early may take several years of deferment or even rest before the stand regains productivity.
NDSU Extension specialists observed as much as a three-week delay in grazing readiness for introduced cool-season species and four weeks for native cool-season species following drought.
Consider these grazing management strategies to optimize forage production and livestock performance.
- Determine the predominant grass species in your pasture and rangeland.
- Monitor grazing readiness of predominant grass species and delay grazing start date until these species reach grazing readiness. For more information, refer to the NDSU Extension grazing readiness resources.
- Monitor grazing use throughout the grazing season.
Depending on your forage resources and growing season conditions, it can be difficult to delay grazing until grasses reach grazing readiness. We recommend the following strategies, depending on the resources available.
- Start grazing annual forages and/or domestic cool-season pastures, which will reach grazing readiness earlier in the spring.
- Provide supplemental forage to livestock on domesticated pasture or hay land. However, be careful not to graze your hay lands too early, too short or if muddy, as stands will be dramatically reduced in forage production due to reduced vigor and plant damage, leading to new infestations of weeds.
- Continue dry lot feeding in May.
- If grazing cannot be delayed, minimize the impact to a small area of your pastures or in one of your cells. Then rest that cell or area the remainder of the grazing season and defer from grazing (no spring grazing) the next year.
While it may be tempting to start grazing early due to a lack of forage resources, it can have long-term impacts on forage production and plant health. Remember, it takes grass leaves to replenish the root food reserves needed to grow grass. Early spring grazing, especially following a drought, can be costly in terms of total forage production during the entire grazing season.
As the grazing season progresses, monitor degree of use to prevent negative impacts to developing tillers, especially in the fall. The recommended utilization level for proper use of grasslands is 40% to 60%, with some native grass species only tolerating 40% to 50% use. At this level, rangeland utilization is fairly uniform, with 65% to 80% of the height of desirable forage species being grazed. Livestock should be removed when this level is exceeded.
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