Objective 1. To determine if warm-season grasses will increase forage availability during summer months when compared to a traditional cool-season system.
Objective 2. To determine the most productive and economically advantageous method of establishment (monoculture or interseeded) for the two warm-season test forages in horse pastures.
Objective 3. To determine if sequential grazing in integrated cool- and warm-season pastures provides adequate nutrition to maintain optimal horse body condition.
Objective 4. To determine if any advantage in production cost exists when integrating either a warm-season annual or perennial into a traditional cool-season horse grazing system.
The purpose of this project is to investigate the potential for increasing pasture productivity, thereby extending the number of grazing days and decreasing producer feed costs through implementation of an integrated cool- and warm-season grass grazing system in horse pastures. Traditional pasture forages in temperate regions of the United States are mainly cool-season perennial grasses. Cool-season grasses are well adapted for survival of cold winters and growth in periods of cooler temperatures in spring, early summer and fall. However, these species are less tolerant of heat and drought, which leads to a period of low forage productivity often called the “summer slump”. Conversely, warm-season grasses produce their greatest yields during the hot summer months while cool-season grasses are semi-dormant. Warm-season grasses, therefore, present an intriguing option for bridging the “summer slump” forage gap.
The “summer slump” presents management challenges to horse producers, with both economic and environmental implications. Supplemental feed is often needed to meet the nutritional needs of horses during the “summer slump,” which increases feed costs during this period. Often, producers will provide supplemental feed to horses in existing pastures. Leaving horses on low productivity pastures can result in overgrazing, leading to negative consequences for the environment. If forage is overgrazed, over time vegetative cover will be reduced. Decreases in vegetative cover increase the potential for soil erosion and nutrient runoff. Furthermore, overgrazing may result in decreased forage stand persistence and weed invasion. This may necessitate more frequent pasture renovation, conferring additional cost to producers. Alternatively, producers may choose to confine horses to dry lots, allowing the pasture forage time to rest and regrow. However, dry lots often have a high stocking density and lack vegetative filtration, increasing the risk for nutrient runoff and erosion. Thus, the “summer slump” negatively impacts economic and environmental sustainability in horse operations.
Developing a grazing system comprised of complementary cool- and warm-season forage varieties would potentially provide more uniform productivity over the grazing season, increasing overall yield and reducing costs associated with supplemental feeding during periods of summer drought. This management strategy is recommended to producers in various industry and extension programs and publications, but little research has been conducted to support the utility of integrated grazing systems for horse producers. Most recommendations are based upon cattle grazing studies. Extrapolating data from studies in other livestock species is often of limited value in management decisions for horse operations. Forage preference, grazing behaviors, nutritional requirements, digestive physiology, animal management goals, and drivers of enterprise profitability are vastly different. While studies in cattle have not shown an economic benefit associated with implementation of integrated cool- and warm- season rotational grazing systems, integrating warm-season grasses into a cool-season pasture system may be better suited to feeding and nutritional goals of horse producers as horses are fed to maintain weight and sustain athletic performance rather than for maximal growth. In fact, over-consumption of cool-season grasses high in non-structural carbohydrates has been linked to many negative health outcomes in horses related to equine metabolic syndrome including obesity, insulin resistance and pasture-associated laminitis.
The goal of this project is to determine if two warm-season forage grasses, “Red River” crabgrass and “Wrangler” bermudagrass, possess utility and economic advantage as alternative summer forages in temperate equine grazing systems. The results of this project will provide much-needed data on forage yield, persistence (vegetative cover), nutritional value, and production costs associated with integration of warm-season grasses into cool-season temperate pastures in the upper transition zone. Discoveries in this area could have real-world impact on horse producers, informing management decisions and shaping best management practices in equine grazing designed to improve economic and environmental sustainability of equine operations. In addition, these results will provide key information for other livestock producers interested in alternative forages.
General Grazing System Methods (All Objectives): This project is being conducted at the Rutgers’ Ryders Lane Best Management Practices Demonstration Horse Farm. Three separate rotational grazing systems, each consisting of 6 sections, will be established. System 1 will serve as a control, and all sections will be planted with a cool-season grass mix. Kentucky bluegrass, orchardgrass and tall fescue will be planted in a 24-16-16 mix for a total seeding rate of 56 kg/ha. System 2 and System 3 will be integrated systems utilizing “Wrangler” bermudagrass or “Red River” crabgrass as test forages. Sections in each integrated system will be planted as follows: two as a cool-season grass mix, two in a test forage monoculture section, and two in which the test forage is interseeded with the cool-season grasses. “Wrangler” bermudagrass will be planted at a seeding rate of 34 kg/ha as a monoculture and 24 kg/ha interseeded. A seeding rate of 13 kg/ha will be used for the monoculture and 7 kg/ha will be used for interseeding “Red River” crabgrass. In the fall 2017, vegetation in all sections of each system will be killed with glyphosate (Roundup®) and all sections will be re-planted with the cool-season mix. After close grazing of two sections in the spring, the warm-season test forages will be planted in Systems 2 and 3. In the monoculture sections, glyphosate will be applied after close grazing to eliminate existing forage and the test forage will be no-till planted into the existing sod. In the interseeded section, test forages will be sown into the existing cool-season forage after close grazing, but no glyphosate will be used. Planting of the warm-season forage will occur in May after soil temperatures have reached 18°C.
Horses will begin spring grazing when the forage in cool-season sections has reached a height of approximately 15.2 cm. Horses will be allowed to graze a given section until forage has been reduced to approximately 7.6 cm sward height, at which time horses will be moved to a new section to begin grazing. Previously grazed sections will be allowed to regrow to a 15.2 cm sward height. Sequential grazing of warm-season sections will begin once the planted forage has reached at least 15.2 cm. All sections will then be managed with the take-half, leave-half rule as described above (Crider 1955). After horses have been removed from a grazed section, any remaining tall weeds will be mowed to a height of 7.6 cm and the pasture will be dragged to evenly spread out manure from defecation areas. Horses will be allowed 24-hour ad libitum access to pasture forage. If adequate pasture forage is not available (no sections at 15.2 cm) when horses are to be rotated, horses will be confined to a sacrifice lot and supplemental grass hay will be provided at 2% of body weight.
Horses (All Objectives): Nine adult Standardbred mares with a body condition score (BCS) of 5-7 out of 9 will be used for the study. Prior to grazing horses will be weighed and assigned a BCS. Horses will be grouped by body weight so that each group represents a similar carrying capacity on a per-kilogram basis. Groups of three horses will be randomly assigned to each of the three grazing systems.
Weather: Weather data will be tracked using the Rutgers Office of the State Climatologist for the New Brunswick station and will include daily temperature, daily precipitation, and relative humidity for each of the sampling days and monthly averages.
Methods (Objective 1): To determine if warm-season grasses will increase forage availability during summer months, grazing days, yield and persistence will be compared between traditional and integrated systems. The number of grazing days in each section of each system will be tracked and recorded. Prior to grazing of each section, herbage mass and sward height will be determined as measures of yield. Vegetative cover and species composition will be assessed as measures of forage species persistence. Herbage mass will be determined by hand-clipping random sub-quandrants of pasture forage to estimate yield. A 0.5 m wooden square will be placed randomly at 4 sites in each 0.4 ha section of pasture, and forage in each square will be clipped to 7.6 cm to represent minimum allowed grazing height. Forage clipped will be placed in a paper bag and dried at 60°C in a Thermocare oven to remove moisture content and obtain a dry matter weight. Herbage mass will then be estimated using the following equation: kg/ac = ¼ ([g/m2 [collected sample] x [4,047/1,000] x 2.47) (Kenny 2016). Sward height will be determined by dropping a styrofoam plate down a meter stick and recording the height where the plate rests on the forage (Burk et al., 2011). Twenty-five measurements will be taken per section of pasture. Species composition and vegetative cover will be evaluated using the Step Point method, performed by transecting each pasture approximately 8 times, stopping every 20 steps to pass a pin over the toe of the observer’s boot at a 30-40° angle into the forage canopy (Evans and Love, 1956). The first species touched by the pin (or potentially bare ground) will be identified. A total of 25 observations per section will be recorded. Results will be compared between the integrated-sequentially grazed systems and the traditional, cool-season system.
Methods (Objective 2): Differences between monoculture and interseeded sections will be evaluated both within and between test-forage treatments. The number of grazing days in each section will be recorded. Herbage mass will be determined using the hand-clipping method and equation described for Objective 1. Sward height will also be measured. The Step-Point method will be used for assessing species composition and vegetative cover. Costs for establishment of interseeded and monoculture sections for the test forages will be compared with days grazed and yield in each section.
Methods (Objective 3): To determine if sequential grazing in integrated cool- and warm-season pastures provides adequate nutrition to maintain optimal horse body condition, the amount of forage consumed will be estimated, forage nutritive value will be analyzed, and horse body condition will be assessed. The amount of forage consumed will be determined by taking additional herbage mass measurements at the conclusion of grazing in each section using the method described for Objective 1 and subtracting those measurements from the measurements taken in Objective 1. Forage nutrient composition will be analyzed by collecting samples hand-clipped to a 7.6 cm height. Samples will be weighed before and after drying at 60º C for at least 36 hours in a Thermocore oven to calculate dry matter (DM). After drying, samples will be ground to 1 mm using a Wiley Mill and submitted to Equi-Analytical Laboratories (Ithaca, NY) for wet chemistry analysis. Digestible energy (DE), crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), water soluble carbohydrate (WSC), ethanol soluble carbohydrates (ESC), starch, calcium and phosphorus content will be determined. Horse body condition will be assessed by weight, percent body fat and body condition score (BSC). Weight will be measured by using an electronic scale. Percent body fat will be determined using the Westervelt method (1976), involving the use of a regression equation to convert ultrasonographic measurement of subcutaneous rump fat to an overall body fat percentage. BCS will be evaluated using the Henneke Body Condition Score scale (Henneke 1983). In this method, fat cover over 5 different areas of the body (crest of neck, topline, over the ribs, behind the shoulder, and over the tailhead) is assessed on a scale of 1-9, with 1 being emaciated and 9 morbidly obese.
Methods (Objective 4): To determine if any advantage in production cost exists in integrating either a warm-season annual or perennial into traditional cool-season grazing system, total production costs will be calculated and compared for each system. Relevant costs include cost of establishment (herbicide, fertilizer, seed, equipment and labor costs), pasture maintenance (mowing and dragging), and supplemental feeding (if any). As described above, in the event that pasture forage is inadequate for grazing, horses will be confined to a dry lot and fed supplemental hay at 2% of their body weight. Any hay provided will be weighed, and the cost of that feed will be calculated.
Research Results and Discussion:
Due to weather-related delays in establishment of pasture fields, full data collection for this project was postponed to the 2019 grazing season. Warm-season test forages planted in monoculture were utilized for collection of preliminary data and results are presented below.
Sample/data collection will not commence until the beginning of the 2018 grazing season (April-May 2018). Mean herbage mass prior to the first grazing rotation did not differ by forage type (CRAB 2,174.7 ± 189.4 kg/ha; BERM 2254.7 ± 268.3 kg/ha). Furthermore, yield recorded in CRAB and BERM was similar to herbage mass of cool-season pasture sections at their peak production prior to first grazing in late spring (2244 ± 140.6 kg/ha). However, due to late establishment, data was only collected on one rotation through all sections of each warm-season forage, and a full season of data collection will be necessary to fully evaluate pasture production in the integrated systems compared to the traditional cool-season control.
The mean nutrient content of pasture samples collected over 48-hr diurnal sampling periods is shown in Table 1. Both warm-season test forages were below the NSC risk threshold (10% NSC) for exacerbation of conditions associated with Equine Metabolic Syndrome such as pasture-associated laminitis (CRAB 8.15 ± 0.42%; BERM 4.89 ± 0.21%). Starch content was greater in CRAB (4.04 ± 0.42%) than BERM (0.86 ± 0.61%; p<0.0001). Crude protein was high in both test forages (CRAB 20.59 ± 0.33%; BERM 22.27 ± 0.43%). Digestible energy was also similar in CRAB (2.07 ± 0.02 Mcal/kg) and BERM (2.02 ± 0.02 Mcal/kg).
Diurnal variation in NSC was evident in both CRAB and BERM (Figure 1). Similar diurnal variation occurred in the water-soluble carbohydrate (WSC) fraction in BERM (Figure 1a). However, in CRAB, diurnal variation appeared to be driven by the starch fraction rather than WSC (Figure 1b).
Horses lost weight over the initial week of grazing BERM (-19.96 ± 3.12 %BW) while the horses on CRAB maintained BW (-0.79 ± 2.26 %BW). However, over a 2-3 weeks of adaptation to their respective warm-season test forage, horses on both forages exhibited little change in body weight. (BERM 2.68 ± 0.640 %BW; 0.47 ± 1.43 %BW). This indicates that nutrients supplied by the warm-season test varieties may be adequate to maintain body weight in the grazing horse while potentially limiting weight gain. More data is necessary to determine if results are similar in horses grazing in integrated systems over a full grazing season and weight and body condition differ from horses grazing traditional cool-season pasture.
In all, a full grazing season is necessary to evaluate the production benefits of integrated grazing seasons and the utility of the “Wrangler” bermudagrass and “Quick N Big” crabgrass varieties as potential alternative forage sources in equine grazing systems. However, preliminary results suggests that these test forages may offer adequate production and nutritional value to maintain horses on pasture over the “summer slump”.
Full Sample/data collection will not commence until the beginning of the 2019 grazing season (April-May 2019).
Education & Outreach Activities and Participation Summary
Several tours conducted at the Ryders Lane Best Management Practices Demonstration Horse Farm at Rutgers University in the fall of 2017 previewed the upcoming research funded through SARE. Tour groups included equine science students from Rowan College as well as international delegations from China. In addition, the research to be conducted over the 2018 grazing season was introduced during the NE-1441 Annual Meeting (webinar, 8-31-2017). The upcoming research was also highlighted in the Rutgers Equine Science Center Annual Report, which is available on the ESC website (http://esc.rutgers.edu/) and was distributed in print to stakeholders in the New Jersey equine industry.
This research project was previewed at the annual Rutgers Horse Management Seminar on February 11, 2018. Preliminary results were shared during the NE-1441 Annual Meeting on August 21, 2018, as well as at the Rutgers Equine Science Center Evening of Science and Celebration on November 9, 2018. Additional tours for university and public groups were also conducted at the Ryders Lane Farm throughout 2018.
The Rutgers Equine Science Center (ESC) provides an established vehicle for widespread dissemination of equine research conducted at Rutgers University. The ESC hosts several educational seminars each year and maintains a world-class website (http://esc.rutgers.edu/) and Facebook page with almost 2,000 followers (as of April 2017). As the project progresses, results will be presented and discussed at regular ESC-sponsored events including our annual Horse Management Seminar for horse and farm owners, which attracts over 100 participants each year; the Equine Science Update, which summarizes the Center’s recent research for the general public; Stakeholder Meetings, and monthly industry meetings. We will also schedule special “Pasture Walk” workshops at the Ryders Lane Best Management Practices Horse Farm to present the results of this project to horse owners and producers interested in implementing integrated grazing systems on their own farms. New Rutgers fact sheets will be published and posted on the NJAES publications page (http://njaes.rutgers.edu/pubs/) and the ESC website and Facebook page.
Scientific publications and presentations at scientific society meetings will also be planned. This material is appropriate for general academics in animal and plant science as well as veterinarians and would be appropriate in journals like The Journal of Animal Science, Journal of Equine Veterinary Science or The Veterinary Journal. The Equine Science Society Symposium, American Society of Animal Science, and Soil Health Conference are a few conferences where this material could be presented. There are also numerous university and regional student competitions including the Mid-Atlantic Nutrition Conference and the New Jersey Agriculture Experiment Station graduate student competition where this material will be presented.
The PI of this project is involved with a regional USDA project called NE-1441: Horses and the Environment. In its eighth year as a multi-state project, NE-1441 incorporates the best regionally available data about animal use, feed, manure storage and disposal, pasture/cropping management, soil and environmental quality, erosion control, and site characteristics to meet the goal of minimizing negative environmental impacts of equine operations on soil, water, and air quality. Participating states include NJ, VA, MA, SD, MD, MN, NC, FL and PA. NE-1441 provides a national format for disseminating the results of this study.
Primary data collection will occur April-November 2019.
However, we anticipate that the results of this project will provide much-needed data on forage yield, persistence (vegetative cover), nutritional value, and production costs associated with integration of warm-season grasses into cool-season temperate pastures in the upper transition zone. Discoveries in this area could have real-world impact on horse producers, informing management decisions and shaping best management practices in equine grazing designed to improve economic and environmental sustainability of equine operations. In addition, these results will provide key information for other livestock producers interested in alternative forages.
In New Jersey alone, there are 42,500 equine animals and 7,200 equine operations covering 176,000 acres of land (Rutgers Equine Science Center 2007). Results of this project have the potential to influence the pasture management decisions of many of these operators. From an environmental standpoint, continued development and promotion of best management practices in horse grazing serves to protect valuable resources, such as soil and water. From an economic perspective, teaching farm owners how to reduce costs through pasture best management practices can positively impact the financial sustainability of individual businesses, protecting the stability and viability of the entire industry.
Data collection for the full study will begin at the start of the 2019 grazing season (April-May 2019). As the research progresses, more details will be added to this section.
In addition to the production-centered research focused on in this project, additional grant funding has been secured to expand on the impact of integrating warm season grasses in to cool-season rotational grazing system on equine health. We are specifically interested in assessing if these alternative forages affect intake and if any alterations in intake are sufficient to elicit a physiological response in the horse in glucose/insulin dynamics. We will also evaluate the gut microbiome of grazing horses and determine if there are any differences in microbial community composition or diversity attributable to grazing warm season grasses.