Bridging the ‘summer slump’ forage gap (Animal Science Update)
(Writer’s note: This article was guest written by my graduate student Jennifer Weinert. She is a Wisconsin native who grew up on a dairy farm, but gravitated more toward the horses than cows. She is a graduate of the University of Wisconsin-River Falls with an animal science degree, then went out to work for a reining trainer before going back to River Falls to manage its 70-plus-head herd of university teaching horses. She started her Ph.D. at Rutgers University in September 2016.)
As we pass the official start of the summer, grazing season is in full swing for equine producers managing their horses on pasture.
If a farm has followed best management practices (BMPs) for pasture and grazing management, ample pasture forage should still be available for grazing (for a great review on grazing BMPs, visit the following link to download the New Jersey Cooperative Extension Factsheet #368 on pasture management practices: https://njaes.rutgers.edu/pubs/publication.php?pid=FS368.).
This pasture forage can provide an economical means of meeting all or most of a horse’s daily nutrient requirements, particularly if that horse is considered to be at “maintenance” (i.e. not growing, lactating or in heavy work/exercise).
However, the with the return of hot, dry weather in mid- to late-summer, horse producers may face pasture management challenges, as these weather conditions often result in a period of low forage productivity commonly termed the “summer slump.”
Cool-season grasses, such as Kentucky Bluegrass or Tall Fescue, serve as the primary pasture forages utilized in northern and temperate regions of the United States.
These grass species are well adapted for survival of cold winters and growth in periods of cooler temperatures in spring, early summer and fall, but are less tolerant of heat and drought, resulting in this “summer slump” in forage production.
Management challenges presented by the “summer slump” can potentially have negative impacts on both the economic and environmental sustainability of equine operations. Supplemental feed is often needed to meet the nutritional needs of horses during the “summer slump,” which increases feed costs during this period.
Additionally, horses may overgraze low-yielding pastures, which can decrease vegetative cover in pastures over time, leading to increased risk of nutrient runoff and soil erosion.
Overgrazing may also decrease forage stand persistence and promote weed invasion, necessitating more frequent pasture renovation at significant financial expense.
An on-going research project at the Rutgers University Ryder’s Lane Best Management Practices Demonstration Horse Farm is aimed at developing pasture management strategies that address the challenges created by the “summer slump.”
In this study, researchers are investigating the potential for increasing pasture productivity, thereby extending the number of grazing days and decreasing producer feed costs, through implementation of an integrated rotational grazing system comprised of complementary cool- and warm-season forage varieties.
Unlike cool-season grasses, warm-season grasses produce their greatest yields during the hot summer months while cool-season grasses are semi-dormant.
Warm-season grasses, therefore, may present an option for bridging the “summer slump” forage gap.
This integrated cool- and warm-season grass rotational grazing approach has been previously explored for as a pasture management strategy for cattle, but there is little data on the use of this practice in equine operations.
Research in cattle has shown little economic benefit to adopting integrated rotational grazing systems, with any gains in pasture yield being offset by decreases in production (i.e. lower average daily gains).
However, this management strategy may be better-suited to feeding and nutritional goals of horse producers, which often focus on weight management rather than maximizing animal production.
Therefore, the goal of the current Rutgers study is to evaluate the production and economic impact of integrating of two warm-season grasses, “Quick N Big” crabgrass and “Wrangler” bermudagrass, into traditional equine rotational grazing systems.
Although crabgrass is typically thought of as a weed, “Quick N Big” is an improved variety developed for forage production.
Cold-tolerant bermudagrass varieties such as “Wrangler” are now commonly grown in the transition zone corresponding to USDA plant hardiness zones 5 through 7.
Preliminary results from the 2018 grazing season showed that estimated pre-grazing forage yields did not differ between cool-season grass rotational pasture sections and sections in which one of the warm-season varieties had been established as a monoculture.
These results are encouraging, as they suggest that these warm-season forages may indeed provide a high-yielding forage option to boost summer pasture production. In 2019, we have expanded the study to cover the full grazing season to gather data needed to determine if this practice can improve economic and environmental sustainability of equine operations.
Next month, we will shift gears to focus on the potential implications of managing horses within integrated grazing systems and maintaining horses on warm-season pasture grasses on equine nutrition and health.
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