Florida pasture grasses contain lower sugar content than in other parts of the country. Even so, pasture access might need to be limited to help control calorie intake. Limiting grazing time may cause some horses to overeat when they are turned out, so consider using a grazing muzzle or feeding horses some hay before turnout to slow intake. Photo Credit: Amy Parker
Marcelo Wallau, Lori Warren, Carissa Wickens, Jose Dubeux and Doug Mayo, UF/IFAS Extension
As extension specialists, we are often asked about nonstructural carbohydrates (NSC) in forages and the potential risks grazing poses to insulin-resistant horses. Numerous blog posts and reports have been written on the topic, alarming horse owners everywhere. However, for horses managed on pastures in Florida, is over-consumption of NSC actually a problem?
Nonstructural carbohydrates are a form of energy reserve in plants, and include simple sugars, fructan and starch. The major source of NSC in a horse’s diet is usually from grains, which range from 60 to 85% starch, and commercial concentrate feeds, frequently containing molasses and other ingredients to increase palatability. In forages, the concentration of NSC depends on plant type, management, and season of the year, typically highest in the spring and fall when growth is slow and seedheads are present. Temperate climate forages (e.g. orchard, timothy, or our cool-season species here in Florida, such as oats, ryegrass and clovers) tend to have more NSC (around 16%) than our warm summer grasses (around 8%), such as bahiagrass and bermudagrass.
Several factors are known to contribute to the development of metabolic disorders in horses, including genetics (Morgans, Arabians, ponies, and Spanish breeds are most affected), overfeeding (of anything, not just grain), overweight/obese animals (those prone to being “easy keepers”), and lack of exercise. The most common metabolic disorders are Cushing’s Disease (pituitary pars intermedia dysfunction) usually associated with aging, and equine metabolic syndrome (resulting from the genetic and management factors described above). What they share in common is insulin resistance (similar to, but not exactly like Type 2 diabetes in humans), making them susceptible to secondary diseases such as laminitis or founder. These horses tend to be more sensitive to sugar, starch, and fructan in the diet. Not all horses have these problems. In fact, the frequency of laminitis in horses is low, ranging from 2 to 5% (Kane et al., 2000) and normally is related to horses which have a predisposition, either genetic or acquired from sub-optimal management practices.
For horses with metabolic disease or a history of laminitis, feeding diets with less than 10% NSC is recommended. Reducing NSC in the diet can be accomplished by cutting back on grain consumption and any other sort of treat containing high sugar levels. For lush pastures containing cool-season forages, there may be a need for limiting pasture access and timing turnout to occur in the period from late night to early morning when sugar and fructan levels in the grass will be at their lowest. For pastures containing Florida’s warm-season forages, NSC is less of a problem, but pasture access might need to be limited to help control calorie intake. Note that limiting grazing time may cause some horses to overeat when they are turned out, so consider using a grazing muzzle or feeding horses some hay before turnout to slow intake. These approaches combined with monitoring horses’ body condition and weight will allow owners and farm managers to safely utilize forages in feeding horses diagnosed with metabolic disorders.
Although the incidence of insulin-resistance is relatively low, many people worry about the health of their horses housed on pasture. What is important, however, is to provide a balanced diet which is in accordance with the category and use of the animal: growing, lactating and active horses (working or athlete) need a more nutrient dense diet to meet their requirements, while most leisure horses’ nutrient requirements can be met primarily by forages and a vitamin-mineral supplement. Nevertheless, the low NSC content of most forages in Florida represent a low risk, even for horses with pre-disposition for metabolic disorders
The following are some additional references and suggestions for further reading on this topic:
- Kronfeld DS, Harris PA. 2003. Equine grain-associated disorders (EGAD). Compendium on continuing education for the practising veterinarian. 25:974–83.
- Lameness and laminitis in U.S. horses. 2000. USDA: APHIS: VA, CEAH, National Animal Health Monitoring System. Fort Collins,CO. Contract No.:N318.0400.
- Kane AJ, Traub-Dargatz J, Losinger WC, Garber LP. 2000. The occurrence and causes of lameness and laminitis in the U.S. horse population. San Antonio TX: Proceedings of the 46th AAEP; Nov 26–29; p.277–280.
- Longland, A.C., and B.M. Byrd. 2006. Pasture Nonstructural Carbohydrates and Equine Laminitis. J. Nutr. 136(7): 2099S–2102S
- Wickens, C. 2016. Monitoring Body Condition in Horses: Helpful Smart Phone Apps for Horse Owners.
Stroma stage of Myriogenospora atramentosa on Argentine bahiagrass pasture in North Florida. Photo credit: Ko-Hsuan Chen, UF/IFAS
Ann Blount, Sunny Liao, Ko-Hsuan Chen, Marcello Wallau, Doug Mayo, Brittney Justesen and Clay Cooper
Stroma stage of Myriogenospora atramentosa on Pensacola bahiagrass leaf blade. Photo credit: Ko-Hsuan Chen, UF/IFAS
Endophytes are naturally occurring organisms that often live in symbiosis internally in many of our forage species. Basically, endophytes are good for plants to associate with. They are typically a bacteria or fungus that lives within a plant for all or part of its life-cycle. These organisms occur in most plant species and can boost the plant’s tolerance to abiotic stresses, such as drought, and assist the plant to acquire nutrients, enhance growth, and resist insects and diseases that might harm the plant. They can also aid the plant by reducing overgrazing by wildlife or livestock. In return for aiding the host plant with survival, the endophyte receives nutrients from the host plant, such as carbon or nitrogen.
Recently, these endophytes have been suspected as a possible cause of animal health issues on Florida cattle ranches. This, however, is not a new phenomenon. The most commonly known pasture endophyte relationship occurs in fescue. Cattlemen who rely on fescue-based pastures know what the mycotoxin (ergovaline) from the endophyte fungus Neotyphodium coenophialum in fescue does to cattle. There is a long history of studies to reduce the associated problems of fescue-related mycotoxin toxicity in livestock with better pasture management and fescue variety breeding.
Similar to this phenomena in fescue, endophytic fungi also infect sub-tropical grasses, and in some cases, these endophytes may also produce mycotoxins. Researchers have documented mycotoxin issues in southern grass pastures, but they have not typically been so apparent or serious as fescue toxicosis.
Stroma stage of Balansia epichloe on Smutgrass leaf blade. Photo credit: Ko-Hsuan Chen, UF/IFAS
Why the sudden interest in this topic now? Probably because producers have become better livestock stewards and have the annual performance records that document small changes in animal behavior and variation in performance from year to year.
If you research old publications, you will find a number of studies that document the occurrence of these endophytes in many sub-tropical grasses. Old published research articles, dating back to the 1950s and again in the early 1980s, implicate animal health concerns with livestock grazing bermudagrass, bahiagrass, smutgrass and broomsedge.
Over the past three years, several ranchers in Florida have reported livestock problems related to early abortion in cattle, poor bull performance, and heat stress, and have implicated the forages. These performance issues may have been due to a wide range of other factors. Isolating the forages as the cause is hard to confirm. Therefore, a research grant was secured from the Florida Cattlemen’s Association to allow UF/IFAS researchers to do a two-year, statewide study in 13 locations.
A team of 12 University of Florida state specialists and 12 county agents have teamed up with the 13 Florida cattle ranches to do on-farm sampling of Bermudagrass, bahiagrass, and limpograss to determine the level of endophyte toxicity in the state. Four of the 13 locations are in North Florida. Forage samples will be collected six times per year in 2018 and 2019. The goal of this statewide study is to identify the endophytes that are present at different points in the year, so that future studies can focus on how these specific endophytes affect animal performance.
So far, the research team has confirmed the identification of several fungal families living endophytically in pasture grasses, such as Fusarium spp., Balansia spp. and Myriogenospora spp. They have also found seasonal mycotoxin activity in these forages. From recently processed forage samples researchers have identified and quantified the presence of zearalenone, ZEAR-4-sulfate Q1, alternariol, ergine and 15-AcetylDON, as well as several other mycotoxins of potential concern to animal health.
It is still much too early to know if the mycotoxin concentrations from these initial forage plant samples are impacting cattle health or performance. Once this study is complete, future research will focus on the specific endophytes of concern to identify potential management options to recommend to cattle producers in the region.
Doug Mayo, Jackson County Extension sampling Tifton 85 Bermudagrass in July 2018 in Jackson County. Photo credit: Ann Blount, UF/IFAS
The UF/IFAS Forage Endophyte team will provide updates as they identify specific endophytes and mycotoxins in Florida forages. They will also be studying their seasonal occurrence and what environmental conditions are favorable for production of mycotoxins.
Stroma stage of Myriogenospora atramentosa on Argentine bahiagrass pasture in Jackson County. Photo credit: Doug Mayo
Limpograss shows real potential as an alternative forage grass for North Florida, providing significant summer growth, and can be stockpiled for grazing through December. Photo credit: Yoana Newman
Jose Dubeux, Erick Santos, David Jaramillo, Liza Garcia, UF-IFAS NFREC
Limpograss (Hemarthria altissima) has been successfully adopted in South Florida by livestock producers. This unique grass grows well in flatwood soils, and maintains its digestibility for longer periods than other warm-season grasses (e.g. bahiagrass and bermudagrass), making it a good candidate for stockpiling. Limpograss is also less sensitive to day-length than other grasses, growing during the cool-season, especially in mild-winters in South Florida. After a frost, limpograss will be one of the first warm-season grasses to initiate regrowth. The first cultivars were released in Florida during the 1970s and 80s, and include the diploids “Redalta” and “Greenalta” and the tetraploids “Bigalta” and “Floralta” (Newman et al., 2014). Recently, two new cultivars were released, “Kenhy” and “Gibtuck.” These cultivars provide increased grazing tolerance, greater productivity, and nutritive value compared to previously released cultivars (Wallau et al., 2015). Limpograss is often used for stockpiling, considering its slower loss of digestibility compared to other warm-season grasses.
The potential of limpograss in North Florida, however, has not fully been assessed. Although limpograss collections have been established in North Florida since 2005, a comprehensive evaluation including biomass productivity and nutritive value of the new cultivars has not been evaluated. The persistence of limpograss throughout these years, however, shows the possibility to grow this species in North Florida, despite the cooler temperatures compared to South Florida.
Along the Florida Panhandle there are vast areas that can potentially be used with limpograss, especially along the Gulf coast. One of the concerns of growing limpograss in North Florida is the shorter growing season, as compared to South Florida, because of the earlier frost. Comprehensive evaluations are necessary in order to assess these potential differences of limpograss performance in contrasting Florida environments.
Researchers established a limpograss trial at the UF-IFAS North Florida Research and Education Center (NFREC) in Marianna, Florida. Plots were established in July 2014 and included four limpograss cultivars (breeding line 1 and the cultivars Kenhy, Floralta, and Gibtuck). For comparison, the trial also included Tifton-85 bermudagrass as a control. From May 2015 to Feb 2017, researchers evaluated biomass productivity and digestibility (IVOMD) of these different grasses. Harvesting started in May of each year, with 5-week intervals between harvests and 7 inches cutting height. From May to August, after each harvest, plots received 60 lb. N/acre, 15 lb. P2O5/acre, and 60 lb. K2O/acre. Starting in September, a stockpiling scenario was simulated by letting the plants grow and harvesting only a portion of each plot every 5 weeks. Forage harvest measurements were taken to evaluate the cumulative growth since August.
During the summer growth of 2016, forage growth peaked in July. Gibtuck was one of the most productive among the limpograss cultivars with comparable growth to Tifton-85 Bermudagrass, which is considered one of the most productive Bermudagrass cultivars available (Figure 1). Starting in September, plants accumulated biomass until December, showing their potential for use for stockpiling in North Florida. During the primary stockpiling period, Kenhy showed the greatest potential. After December, there was limited gain in biomass accumulation for most of the cultivars (Figure 1).
Figure 1. Herbage accumulation of limpograss germplasm and Tifton-85 bermudagrass from May 2015 to Jan 2016. UF-IFAS NFREC, Marianna, FL.
In the second year (May 2016 to Jan 2017), forages peaked earlier in the growing season and declined during the summer. This likely reflects the reduced rainfall combined with the frequent harvesting (5 weeks) compromising the productivity not only of the limpograss, but also of the Tifton-85 bermudagrass. During the stockpiling period, the grasses demonstrated a similar trend of biomass accumulation until December (Figure 2).
Figure 2. Herbage accumulation of limpograss germplasm and Tifton-85 bermudagrass from May 2016 to Jan 2017. UF-IFAS NFREC, Marianna, FL.
Digestibility (IVOMD) of limpograss was often greater than Tifton-85 bermudagrass, especially during the stockpiling period (Figure 3). Limpograss digestibility (IVOMD = 55-60%) was maintained through December 2016, when it was significantly reduced, due to colder temperatures and frosts. The growth and digestibility data indicate that limpograss can be used during the summer, and for stockpiling at least through December without significant loss in digestibility. This would be sufficient to fill the November-December forage gap that often occurs in the Panhandle, allowing time for the cool-season forage production to ramp up. As a result, stockpiled limpograss could be utilized to reduce hay requirements, and ultimately reduce winter feeding expenses.
Figure 3. In vitro organic matter digestibility (IVOMD) of limpograss germplasm and Tifton-85 bermudagrass from May 2015 to Feb 2016. UF-IFAS NFREC, Marianna, FL.
Take Home Message
The results of this two-year trial in Marianna are encouraging. Limpograss shows real potential as an alternative forage grass for North Florida. Limpograss provided significant summer growth, but adds the potential use for stockpiled grazing through December. In general, limpograss was more digestible than Tifton-85 bermudagrass, especially during the stockpiling period. Variations among limpograss cultivars occurred, but those differences were not consistent over the two years. Therefore, all the cultivars tested have potential for use in North Florida. Longer-term evaluation with animal performance is still needed to fully asses the potential of limpograss in North Florida, but the results from this trial show that further evaluation is warranted.
- Newman, Y.C., J. Vendramini, L.E. Sollenberger, and K. Quesenberry. 2014. Limpograss (Hemarthria altissima): overview and management. EDIS SS-AGR-320.
- Wallau, M.O., L.E. Sollenberger, J.M.B. Vendramini, M.K. Mullenix, K.H. Quesenberry, C.A.M. Gomide, V. Costa e Silva, and N. DiLorenzo. Herbage accumulation and nutritive value of limpograss breeding lines under stockpiling management. Crop Science 55:2377-2383.
Figure 1. Pawpaws are typically small shrubs that range from 2 to 4 feet tall in pastures. Photograph by B. Sellers.
Pawpaws (Asimina spp.) are members of the custard family, and 10 species are known to occur in the state. Of these 10, fourpetal pawpaw (Asimina tetramera) is on the endangered species list, but this species is found primarily in coastal pine scrub habitats in Martin and Palm Beach counties. Most pawpaw species in Florida are considered to be small shrubs and are 2-4 feet tall (Figure 1).
While pawpaw species are native, serve as a host for the zebra swallowtail butterfly, and the fruit are edible, they can become problematic in grazing areas (Figure 2). In fact, the problem seems to be increasing, based on calls coming into to County Extension Offices.
Figure 2. Illustration of pawpaw plants invading a pasture. Photograph by B. Sellers.
These woody species are usually multi-stemmed and stems arise from a very deep taproot that can be as big as 3 inches in diameter (Figure 3).
Figure 3. Pawpaw roots have a very large taproot, and once established are extremely difficult to control.
Leaves are present from early April through October, but may exist through December in some areas of the state. Flowering occurs in April to May, and seed production is reportedly low. Flowering often occurs before leaves begin to grow in the spring (Figure 4).
Figure 4. Flower formation in pawpaw typically occurs before leaves begin to grow in the spring. Photograph by B. Sellers.
As with lantana, pawpaw control appears to be somewhat difficult. Mowing typically results in an increase in the number of stems, and hand digging is likely the only “mechanical” method of removing pawpaw plants from improved pastures, as they do not tolerate root cutting. Considering the long and deep taproot of pawpaw, control with a single herbicide application should not be expected.
Experiments were conducted in a pasture that was heavily infested with pawpaw in central Florida. Herbicide treatments included 1 qt/A triclopyr (Remedy Ultra), and triclopyr at 1 qt/A followed by triclopyr at 1 qt/A 6 months later, Pasturegard HL at 1 qt/A, and Pasturegard HL at 1 qt/A followed by an additional 1 qt/A 6 months later. Methylated seed oil (MSO) was added to each spray mixture at 1% v/v. The initial treatment was applied in May and the sequential treatments were applied in late November. To evaluate the level of pawpaw control, the number of pawpaw stems were counted in each plot on the day of application, 6 months after treatment (MAT), and 12 MAT.
Living stems in plots were very low at 6 MAT (at the time of the sequential application), with all treatments providing >90% reduction in stems, as compared to pre-treatment numbers. However, stems densities increased by 12 MAT (6 months after sequential treatment). A single application of Remedy or Pasturegard HL resulted in 49 and 40% less stems compared to pre-treatment stem counts, respectively. A sequential application of either herbicide resulted in >70% reduction in pawpaw stems counts compared to pre-treatment levels. Although stem densities did not differ significantly between Remedy and Pasturegard HL plots, pawpaw plants were typically shorter in plots treated with Pasturegard HL, indicating that regrowth of pawpaw plants was slower when treated with this herbicide as compared to Remedy.
In a separate study, these same treatments were applied in late November, but virtually no reduction in living stems was observed 6 MAT. This indicates that early Spring (April to May) application may be the best application timing for this species.
For more information on pasture weed control, and the herbicides registered for use in Florida pastures, use the following link:
Pasture fertilization is a significant expense. Photo Credit: Doug Mayo
One area of management that often comes up in discussions with producers managing smaller herds is pasture fertilization. There are several aspects that can be confusing. The first questions are, “Should I fertilize?” and, “Is it worth the money?” The next question is, “How much fertilizer do I need?” And generally, the final question, “What should I ask my supplier for?” When you ask these questions, however, be ready for the return question, “Have you taken a soil test?”
In declining cattle markets, the question of “Should I fertilize?” is a subject of much debate. You don’t have to fertilize bahiagrass pastures, but there are consequences if you don’t adjust your stocking rate. If you don’t fertilize or reduce your stocking rate, there may not be enough grass in the fall transition, and eventually there will be issues from thinning stands and weed encroachment.
Basic soil management for forages, or any crop, requires that the soil be maintained in the optimal pH range for the specific target crop to ensure productivity and persistence. For tropical forages, such as Bahiagrass, Bermudagrass, and Limpograss the optimal pH range is 5.0-5.5. Outside of the optimal pH range, soil nutrients are less available to the plant. This is one of the key reasons that periodic soil testing is recommended for pastures. Lime or dolomite are utilized interchangeably to raise the soil pH. Liming pastures is relatively inexpensive because it is generally only required every 2-4 years.
So, should you fertilize? If the soil pH falls below the optimal range, the answer is yes. For $40 per ton, the return on investment in lime or dolomite is high. If you do nothing else for your pastures this year, make sure to lime the Bahia and Bermuda fields that fall below 5.5, or limpograss fields below 5.0. If you can’t remember how long ago you had your soil tested, send in a soil sample, and and at least find out the pH status of your pastures.
Soil tests don’t provide the amount of nitrogen in the soil, because those amounts are constantly changing. Nitrogen (N), and to some degree potassium (K), move with water in the soil profile. With each heavy rain, some nitrogen is flushed down through the soil profile, away from the root zone of plants. There are 16 essential elements for plant growth and reproduction, but nitrogen is the key element that plants require for growth. In other words, “Nitrogen is the gas that makes grass grow!” The chart below is the summary of a classic six-year study conducted a the UF Beef Research Unit from 1966-71 by W.G. Blue, UF Soil Chemist: Role of Pensacola Bahiagrass Stolon-Root Systems in Leon Fine Sand.
What is interesting from this study is that the season-long forage yield more than doubled when 100 lbs.N/acre was applied as compared to no added N. However, with each increase beyond 100 lbs.N/acre, the return on investment diminished. It is important to note that all of the plots were fertilized equally with phosphorous and potassium, at a soil pH of 6.0, so the yield in the 0 N, or control plots, were only limited by the lack of nitrogen. These research plots received split applications of fertilizer, so none of these treatments were a single N application. This classic study shows what numerous others have shown since then, that nitrogen fertilization generates a significant boost to bahiagrass production.
Urea fertilizer (46% N) is currently priced at an average of $414/ton, which equates to 45¢/lb. of elemental N. The reported 119% season-long increase in forage production per acre would require a $45 investment in nitrogen fertilizer today. When you add the $7/acre cost to spread the fertilizer, and you have a stocking rate of 2 acres per cow-calf pair, the total cost is $104 per pair ($52/acre). So, based on the data from this classic study, a $104 investment provided 3.4 tons more feed per pair over the entire growing season for a unit cost of $31/ton. At the end of April, good quality Bermudagrass hay was selling for an average of $90/ton, and whole cottonseed $158/ton, so this is considerably cheaper than purchase feeds. This is also feed that requires limited labor to provide, with minimal waste, under typical weather conditions. In addition, fertilized grass provides more protein than unfertilized grass, so animal performance (gain/acre) would also be boosted, as compared to unfertilized pastures.
If you don’t have the funds to invest $52/acre for all of your pasture acreage, then consider applying only of 50 lbs.N/acre in the spring. You don’t have to fertilize every acre either. Invest in your most productive pastures first, and then rotate to other pastures in future years. Fertilizer is an expensive purchase, and when cattle prices are falling, every purchasing decision has to be scrutinized. The bottom line is that nitrogen fertilizer is really an investment in producing feed for your herd that they harvest for themselves. Conversely, if you make the decision to eliminate nitrogen fertilization, your pasture will produce less feed, so you also need to reduce the number of cattle your pastures are expected to feed.
P & K Fertilization
The next question is how much P & K fertilizer do you need for your bahiagrass pastures? In general, grasses need N-P-K fertilizer in a 4-1-2 ratio. So, you would not want to use 13-13-13 or 10-10-10 for grass pastures, but instead something like a mix of 16-4-8 or 20-5-10. The better option, however, is to send in a soil and tissue sample to get a lab test report that provides specific recommendations for the rate of lime, phosphorous (P) and potassium (K) fertilization on a per acre basis. The N fertilization level is a decision the manager has to make. The University of Florida’s soil test-based fertilizer recommendations provide options for three levels of nitrogen fertilization. The recommendations for P and K will be different based on the nitrogen fertilization level you select.
The final question I normally get is, “What should I order from my farm supply dealer?” This does sometimes get confusing, because recommendations are made in pounds of nutrients per acre, not the total pounds of fertilizer. Urea, for example, is only 46% elemental nitrogen, so it takes 109 pounds of urea to provide 50 lbs.N/acre. Ammonium nitrate is 34% N, so it takes 147 pounds to reach the 50 lbs.N/acre target. The same is true for the various sources used for P and K. Farm supply dealers handle a variety of products from different sources with varied mineral make up. There is no standard recipe. Take your soil test recommendations with you, so your dealer can help you do the calculations as to the total pounds of the blended fertilizer you want applied.
If you have questions about pasture fertilization, soil and tissue testing, or the soil test report recommendations, contact your local UF/IFAS County Extension Agent. Make sure you clearly understand the options, before making an investment of this magnitude.
On Thursday of this week, Sun South John Deere hosted a Hay Equipment Demo Day at the UF/IFAS Marianna Beef Research Unit. Participants at the event got to see a new product called B-Wrap demonstrated. This week’s featured video was produced by Tama Farm Grown Solutions to introduce their partnership with John Deere for this innovative product to protect round bale hay that is stored outside. B-Wrap was developed for use in John Deere round balers. B-Wrap is net wrap that includes a polymer plastic to protect hay from rain, sun, and ground moisture that degrade the outer surface of round bales, yet allows moisture from the bales to escape or “breath.” According to Tama, hay producers can produce “barn-quality hay without the barn.” If you store your hay outside, you should check out the video about this innovative product.
If you enjoyed this video, you might want to check out the featured videos from previous weeks: Friday Features
If you come across an interesting or humorous video, or a new product innovation related to agriculture, please send in a link, so we can share it with our readers. Send video links to: Doug Mayo