grazing management – Livestock and Poultry Environmental Learning Community

March 5, 2019March 20, 2019

How Farmers and Ranchers Are Adapting to Local Weather Extremes

Most farmers and ranchers are acutely aware of weather and how it factors into their risk management planing. Climatologists have indicated that the trend toward more extreme events and greater extremes is going to continue. This has many implications for animal agriculture producers. The farmers featured in this Waste to Worth panel all provided their perspectives on adapting to extreme events through diversity, building resilience, and keeping an eye toward long-term profitability.

Diversity, Resilience and Manure Management with Cover Crops

A former ag teacher, Keith Berns understands that you need to be open to multiple ways of achieving a goal. His desire to build resilience into his farm system led to a business selling cover crop seeds that emphasize diversity. He outlines several scenarios where he uses cover crops on his farm and also several ways his seed customers utilize diverse cover crop and annual forage mixes. High stocking densities naturally incorporate manure, and residue helps conserve and hold valuable moisture during/after extreme rainfall events. [Nebraska/Kansas]

Perspectives On a Changing Climate

Dr. Sandra Matheson, DVM (retired) raises grass-fed beef cattle on her northwestern ranch. Weather extremes have created more dust, mud, and she has seen an increase in disease and health issues with cattle. She utilizes the decision-making process, holistic management, and planned grazing to create a system with the greatest amount of adaptability and resilience for her environment and its potential extremes. Her goals converge around building the soil. [Washington]

Grazing Dairy Finds Plants that Work in Low Water Environments

Michael DeSmet watched his cows when they entered a new paddock and noticed something surprising – they liked weeds. Upon further investigation, he found out that the weeds they were selecting were high-protein, palatable, and could survive on very small amounts of precipitation. Michael was no stranger to making changes; he had already converted the family dairy operation into a grazing-based system selling milk into niche markets. He continues to examine forage options for his pastures that allow the farm to utilize limited water, extend the grazing season, and improve soil quality. [New Mexico]

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2015. Title of presentation. Waste to Worth: Spreading Science and Solutions. Seattle, WA. March 31-April 3, 2015. URL of this page. Accessed on: today’s date.

March 5, 2019March 6, 2019

Measuring Pasture Dry Matter Intake of Horses

Why Is It Important to Accurately Measure Horse Dry Matter Intake?*

The ability to predict a horse’s rate of pasture dry matter intake (DMI) assists horse owners/managers in accounting for pasture’s contribution toward a horse’s daily nutrient requirements. Accounting for nutrients obtained from pasture improves the ability to accurately balance rations thereby preventing inefficiencies associated with over- or under- feeding nutrients. This presentation will review pasture DMI estimates for horses reported in scientific literature, sources of variation associated with the measurements, and methods used to measure pasture DMI.

Pasture dry matter intake varies considerably. Estimates for continuously grazing horses range from 1.5 to 2.5% of body weight in dry matter (DM). Factors contributing to variability in pasture DMI include herbage mass available for grazing, sward height, plant maturity, plant chemical composition, plant palatability, horse physiological status and time allowed for grazing. Dry matter intake tends to increase as pasture herbage mass increases, provided forage does not become over-mature. Sward height may also play a role in dry matter intake as it can influence harvest efficiency (e.g., bit size and rate of chewing necessary to swallow ingested forage). Level of plant maturity and sward height are also related to plant chemical composition. As plants reach maturity acid detergent fiber (ADF) and neutral detergent fiber (NDF) increase. Both ADF and NDF concentration are negatively correlated to a horse’s preference for forage. Plant nonstructural carbohydrate (NSC) has been reported to be positively correlated with horse pasture plant preference. Therefore plant chemical composition (ADF, NDF, NSC) influences horse preference and likely influences pasture DM intake. Dry matter intake is also influenced by horse physiological status. Horses having physiological states with nutrient requirements above maintenance may also have greater pasture dry matter intakes (e.g., lactating mares). Dry matter intake is also influenced by the amount of time a horse is allowed to graze. As the amount of time allowed for grazing is restricted a horse’s rate of dry matter intake increases. Therefore it is possible in some cases for horses to have restricted pasture access yet still consume a significant amount of forage DM due to an increased rate of DMI.

What Did We Do?

Several methods exist to measure pasture intake among grazing horses, yet none are perfect and all face challenges in their application. The primary methods are herbage mass difference, difference in BW pre- versus post-grazing, and marker techniques (e.g., alkanes, acid-insoluble ash etc…). Herbage mass difference measures the herbage mass prior to grazing and again following grazing. This is accomplished by harvesting multiple small forage sub-samples each having the same area (e.g., a sub-sample is harvested within a .25 m x .25 m frame at a height of 2.5 cm above the ground). The difference between pre- and post-grazing herbage mass reflects the amount of forage consumed by the horse. However, as the time between pre- and post-grazing increases, pasture re-growth contributes to error in this measurement. An additional source of error in this measurement results from variability in sub-samples used to predict pre- and post-grazing herbage mass. Therefore this met hod tends to work best in small areas where grazing takes place less than 12 h. Change in body weight during a grazing bout, corrected for fecal, urine and other water loss, is another method used to predict dry matter intake. However, this method requires an efficient means of collecting feces and urine (e.g., collection harness apparatus) and requires a livestock scale having a relatively high sensitivity. The sensitivity of many livestock scales is ± 1 kg, which can represent considerable variation for smaller intakes. Chemical markers, either inherent to the plant or provided externally, provide a means of measuring DMI in a natural grazing setting. Markers rely on the following principle: Intake = fecal output/indigestibility. Fecal output is determined by feeding a known amount of an external marker, not present in pasture plants (e.g., even-chained alkanes) and then measuring its dilution in the feces. Indigestibility is calculated as 1 – digestibility. Digestibility is determined by the ratio of a marker concentration within the plant to that in the feces. Internal markers used for estimating digestibility in horses include odd-chained alkanes and acid-insoluble ash. Marker methods provide accurate measures but are relatively expensive and require considerable care when sampling forage (e.g., the composition of forage sampled must reflect the composition of the forage consumed).

What Did We Learn?

Although each of these methods has their short comings they can provide a starting point to estimate dry matter intake. Coupling these estimates with horse performance measures (change in BW or body condition, average daily gain for growing horses) should be used in conjunction with these estimates in order to validate them and correct for their sources of error. Ultimately, these methods can be used to develop models that incorporate factors responsible for variation in DMI among horses to more accurately predict pasture intake thereby facilitating efficient use of pasture derived nutrients in feeding horses.

Author

Paul D. Siciliano is a Professor of Equine Management and Nutrition in the Department of Animal Science, North Carolina State University. He teaches classes in equine management and conducts research in the area of equine grazing management. Paul_Siciliano@ncsu.edu

Additional Information

Chavez, S.J., P.D. Siciliano and G.B. Huntington. 2014. Intake estimation of horses grazing tall fescue (Lolium arundinaceum) or fed tall fescue hay. Journal of Animal Science. 92:p.2304–2308.

Siciliano, P.D. 2012. Estimation of pasture dry matter intake and its practical application in grazing management for horses. Page 9-12 in Proc. 10th Mid-Atlantic Nutrition Conference. N.G. Zimmermann ed., Timonium, MA, March 2012.

March 5, 2019March 20, 2019

Livestock grazing in a changing climate: Implications for adaptive management

How Could Climate Change Impact Grazing Livestock?

Predictions that global population will reach nine billion persons by the mid-21^st century, combined with the rising middle class in Asia, increases the demand for animal protein production. Concurrent with the increasing human population is the continued directional rise in atmospheric carbon dioxide (CO₂) which just passed the 400 parts per million volume level. Projections are that this concentration will increase to 550 parts per million volume by the end of the 21^st century. Increases in greenhouse gases (like CO₂) can lead to 1) increasing temperatures, 2) influencing patterns and amounts of precipitation, 3) raising the sea level and 4) increasing the acidity of oceans. For vegetation, increases in CO₂ atmospheric concentrations result in greater water use efficiency, changes in species composition with “weedy” and “invasive” plants benefiting at the expense of native species, enhanced aboveground primary production, and lower forage quality. The predicted warmer air temperatures and associated longer growing seasons (i.e., earlier start of spring and later falls) should lead to an increased frequency and intensity of wildfires, as well as greater pest abundance and spread of disease. As the frequency and intensity/severity of extreme events (e.g., droughts) increases, animal heat stress is expected to become more problematic leading to reduced animal performance and as a result less livestock production.

Related: See the other presentations in this Western Region symposium (cattle selection, policy, climate hubs, ag outlook)

What Is Adaptive Management?

Although livestock managers have historically dealt with drought conditions (e.g., Dust Bowl year of the 1930s, the mid 1950s drought, and the 1988 drought), current efforts associated with the dry years of the early 21^st century demonstrate that there is a need for adaptive management to increase resiliency of the rangeland vegetation and sustainability of rural communities and economies. Adaptive management necessitates that 1) adjustments are made when temporally appropriate (both within and across years), 2) experiential and experimental knowledge is blended to provide sufficient capacity for flexibility with predicted long-term droughts that are more intense/severe, as well as “flash” droughts like the one experienced across a wide swath of the US in 2012, and 3) spatial and temporal variability are embraced rather than looked at as negatives. Key for livestock managers is how to increase flexibility in management to adapt to increasing weather variability associated with a changing climate. For many managers, matching animal management with intrinsically high inter- and intra-annual variability in forage production is difficult due to inherent maintenance of herd genetics and the lack of a proactive national drought policy. For example, although a majority (60%) of ranchers in Wyoming have a drought management plan, that still leaves 4 in ten ranchers without a pre-plan to shape management decisions when drought occurs (Kachergis et al. 2014).

Proactive (i.e., preparation) and reactive (i.e., response) drought management strategies are showcased in Figure 1 (per Kachergis et al. 2014).

Figure 1. Proactive and reactive drought management strategies employed by Wyoming ranchers (from Kachergis et al. 2014).

Figure 1. Proactive and reactive drought management strategies employed by Wyoming ranchers (from Kachergis et al. 2014).

Proactive strategies embrace 1) reserve forage supply and/or 2) varying stocking rate with forage supply, whereas reactive strategies address 1) reducing forage demand, 2) increasing forage supply and/or 3) increasing income, often from off-ranch sources or governmental drought declaration financial assistance. For proactive strategies, grassbanking, incorporating yearling livestock into the enterprise, and using seasonal weather predictions to adjust stocking rate are all practices that are currently limited in use (< 30% of the managers), but have high potential to increase drought management flexibility. This is important to managers as 40% of the ranchers surveyed in Wyoming thought that drought would be more influential in their management plans in the future compared to the past (Kachergis et al. 2014). For dealing with the temporal variability of forage production for livestock grazing, managers can implement adaptive management to 1) manage for reserve forage through conservative stocking rates and grassbanking, 2) match cattle numbers to forage availability by proactively developing enterprise capacity to quickly remove/add grazing animals, or add forage quickly through leasing land, purchasing feed or implementing regional risk reduction strategies such as cooperative arrangements with managers in other regions of the US to move cattle, and 3) understand sources and scales of variability at the ranch/landscape/regional levels due to soils, topography and rainfall.

Author

Justin D. Derner

USDA-Agricultural Research Service, Rangeland Resources Research Unit, Cheyenne, WY USA 82009

Literature Cited

Kachergis, E., J. D. Derner, B. B. Cutts, L. M. Roche, V. T. Eviner, M. N. Lubell, and K. W. Tate. 2014. Increasing flexibility in rangeland management during drought. Ecosphere 5:1-14.