Non-traditional Forages in a Managed Grazing System for Control of Gastrointestinal Parasites in Sheep

Non-traditional Forages in a Managed Grazing System for Control of Gastrointestinal Parasites in Sheep

Summary

The second grazing season of this two-year project to investigate the potential of forage chicory in the control of internal parasites of sheep was conducted in 2010. Farm data collection began in the spring and concluded in late September. Chicory (cultivar: Forage Feast) planted in May of 2009 was growing in May of 2010 on all three farms although on one farm (Cline) significant winter frost/heaving occurred, leaving taproots exposed and dying. At one farm (Rickard) the stand had improved greatly over 2009 with respect to annual weed pressure and number of actively growing chicory plants. Stand quality at the third farm (Anderson) remained very good. Brown mid-rib sorghum sudangrass (BMR) was planted in late May and early June and was ready to graze in early July. As a result of our experiences in 2009, the ewe flock on each farm was dewormed with a targeted approach: thin ewes and twin- and triplet-rearing ewes were dewormed leaving single-rearing ewes untreated. This was done to reduce pasture contamination at turnout to grass and to assist ewes rearing multiple lambs while still leaving a refugia of untreated worms to retard further selection for drug resistance. As reported last year, each farm has resistance to multiple classes of dewormers. In 2010 we showed with fecal egg counting techniques that the Rickard and Anderson farms have a low level of resistance to ivermectin not suggested by the 2009 DrenchRite Assay result. This drug is still useable on these farms, but it will be important to continue to use deworming strategies that minimize further selection for resistance.

On one farm (Cline) in both 2009 and 2010, alfalfa was grazed by ewes and lambs or lambs only for a short period prior to starting the project with chicory and BMR. This procedure will likely continue on that farm, and we made observations that may prove useful to other farmers with respect to including this forage in their parasite management strategies. In addition, two participating farms (Cline and Rickard) used ultra high density grazing techniques (“mob grazing”), and in 2010 we obtained pictures and relevant data that suggest that grazing lambs may acquire significant worm burdens in spite of forage sward height. Our observations indicate that sheep will selectively graze short tender plants in a tall sward and as the sward is reduced to a mat.

Extended snow cover for the winter of 2009/2010 and an early warming period in late April may have resulted in increased parasite challenge to lambs in May and June of 2010. On two farms (Cline and Anderson) the ewes and lambs were strip grazed across pastures not grazed since August and early September of 2009 until the chicory and BMR pastures were ready. A back fence was used to prevent animal access to the strips they had contaminated with parasites while grazing, and animals were moved every 3 days to prevent them from becoming infected by third stage, infective larvae developing from eggs deposited by ewes in the spring of 2010. In spite of these procedures, severe parasitism (Haemonchus contortus anemia) in the lambs was noted at both farms by early July when the BMR was ready to graze. We believe this level of parasitism could have resulted only from the ingestion of large numbers of Haemonchus contortus larvae surviving on pastures from the 2009 grazing season. This observation is contrary to the conventional opinion of many parasitologists that the larvae of this worm do not survive our cold winters well. Data collected as part of another project on one of the farms in the spring and summer of 2008 (Cline) as well as observations at the Anderson farm in 2009 support the idea that winter survival of larvae of this worm species may be a more important feature in the epidemiology of parasites in our region than previously recognized. This data has been informally presented to a few parasitologists, and we anticipate presenting this as novel findings in professional meetings.

The severe parasitism in the lambs described in the preceding paragraph required us to deworm all the lambs on these two farms just prior to our intended date for grazing BMR and chicory. Consequently, we had to allow the animals to recover and then acquire sufficient worm burdens before we could graze the chicory and BMR as planned. As a result, we were only able to graze the chicory and BMR plantings once on two of the three farms in 2010. We had considered a planned deworming of all lambs in May or June in anticipation of this type of problem, but opted not to do so because of the narrow window of grazing opportunity offered by BMR. The timing of deworming relative to planting, growth, and subsequent availability of high quality BMR forage could be complicated by weather, and our need for lambs with a small worm burden necessitated time for natural reinfection post deworming. Maturation of BMR during the reinfection period would have meant clipping unsuitable mature forage and a delay in grazing while plants regrew. In addition, on one farm (Cline) only moxidectin is effective as a dewormer. The persistent activity of this chemical (~35 days) would prevent new infections from becoming established and compound the problem of timing further.

In 2009 we observed that some lambs with FAMACHA scores that would indicate mild anemia (score 3) did not have high worm egg counts. This suggested to us that perhaps we were scoring lambs too conservatively resulting in the unnecessary removal of a few lambs from the study. In 2010 we received IACUC clearance for a modification of our protocol to collect blood from lambs to determine packed cell volume (PCV), an objective measure of circulating red blood cells. The results of PCV determinations supported our FAMACHA scores in most cases, but we believe that young lambs (60-90 days) can be more difficult to score than adult animals. In the interest of animal welfare, a conservative scoring of lambs is warranted.

In 2010 we again observed that there were some places in the chicory fields on some farms where lambs did not like to eat the plant. This was observed and recorded on film on one farm (Cline) in 2010 and suspected on another (Anderson) based on very low weight gain on chicory and apparent compensatory gain after removal to grass. In 2010 we collected additional samples of plants and soils at the Cline farm where refusal was most obvious and the plants were subjected to additional biochemical analysis. A scientific manuscript is being prepared to describe our observations and findings.

Statistical analysis of the data began in late 2010 and continues in 2011. Preliminary analysis suggests that weight gains, when adjusted for farm effect, year, and other factors, were somewhat less for chicory lambs than BMR lambs. However, there was indication that worm egg counts may have been somewhat depressed in the chicory group over that of the BMR group. Additional analysis is being done to attempt to quantify and characterize these observations further.

On January 27, 2011, all the participants in the project met at The Ohio State University to review the data collected in the project and the initial findings of statistical analysis and to plan educational activities. In addition we prepared a summary of things we believe we have learned in the past two grazing seasons relative to the plants we grazed and our specific objectives in the project as well as about parasite control in sheep in general. These include:

Overall
• FAMACHA use must be correlated with record keeping and analysis; farmers must take time to look at trends in the animals that are being FAMACHA scored; FAMACHA can be an early warning system of approaching trouble with Haemonchus.
• FAMACHA is a great tool but probably cannot be used as the only selective deworming strategy in large flocks.
• Lambs can be difficult to FAMACHA score correctly; our impression is that they may be somewhat paler than the PCV indicates in the middle range scores (2 and 3).
• We have learned some strategies to minimize the use of chemical de-wormer and to minimize infection levels but THERE ARE NO EASY ANSWERS.
• The message of parasite biology and lifecycle needs to be repeated and heard numerous times before it is understood well enough for farmers to make independent management decisions.
• Overall, the use of annual forages as a necessary component of parasite management is going to be difficult to implement. Stand establishment and timing is very weather dependent; topography and soil type will limit the acreage that can be used for annuals.
• It is critical to know what your farm profile is on parasite drug resistance because designing a forage-based management system that does not require the selective use of dewormers will be very difficult for most farmers.
• On-farm research can positively affect the practices of the farmer and the experience base of all of the persons associated with the research.
• The use of management practices and forages with various benefits for parasite control can help extend the effective life of dewormers.

Management
• Along with selective deworming practices one must think about the parasite life cycle when making management decisions such as pasture rotations.
• Overwintered Haemonchus contortus larvae (L3s) on pastures must be a management consideration through the month of June.
• Lambs grazed during lactation can be weaned at 60 days and be expected to have normal grazing behavior. They will subsequently need high quality nutrition to maintain acceptable performance and maintain reasonable resilience to parasite challenge.
• Egg shedding by ewes drops off rapidly at weaning; earlier weaning and separating ewes from lambs can reduce overall pasture contamination and allow more grazing strategies tailored to the needs of lambs. Shortening up the time the ewes are lactating can lower the farm pasture contamination.
• Making hay from grazed forages, followed by a rest during regrowth, does not necessarily reduce the level of pasture larval contamination to very low levels. Subsequent grazing by susceptible lambs can still result in significant worm acquisition.
• “Never underestimate the ability of Haemonchus contortus to mess up your plans.”

Forages
• Chicory is a high quality feed for lambs; however, chicory is difficult to establish and maintain in some soils. Chicory should be planted with other legumes, such as a non-competitive clover variety, to help with nitrogen supply to chicory and impede frost heaving of chicory plants and competition from weedy plant species.
• Chicory can be frost seeded as long as there is low competition from other plants in the spring. Bolted plants may produce enough seed to reseed to some extent , assuming there is not high sod competition. We need more observation on this. Reseeding must be addressed from the perspective of management recommendations to minimize the number of bolts.
• Making hay from chicory is not a viable option, and trampled herbage may provide a good environment to shelter parasite larvae.
• Chicory is good alternative forage, but some cultivars may be less palatable and more prone to frost heaving (such as Forage Feast). Palatability or preference may be animal species dependent. Soil environment may also affect palatability; this needs more study. Curt Cline observes that the Oasis cultivar (planted for another project in 2007) bolted more (number of stems/plant, number of bolted plants, onset and duration of bolting during the grazing season) than Forage Feast on his farm. This is not necessarily true at other locations.
• Brown mid-rib sorghum/sudan grass (BMR) produces a high quantity of forage in a short period of time following establishment.
• BMR is easier to establish than chicory.
• Although BMR can be a highly nutritious feed for lambs, the window of time it stays in the highly nutritious state is very short thus making it very difficult to manage correctly for lambs. It may be a more desirable forage for other classes of animals with less demanding nutritional requirements, such as mature ewes.
• Because BMR is seeded into a tilled soil (which helps with parasite control) and sheep will graze the leaves (high off the ground), the first grazing of a BMR seeding will provide parasite larvae-free forage. However, if annual grasses and broadleaf plants are present in the field, sheep may acquire larvae from these in subsequent re-grazing of the same area.

Objectives/Performance Targets

Objectives for 2010 were met with the limitations specified in the summary. In 2010 we completed the on-farm data collection and changes in parasite management strategies have been developed for 2011 for all three farms as a result of our observations over the past two grazing seasons.

We are now planning a series of educational events and written materials to describe what we have learned. On May 14, 2010, we have planned a field day at the Cline farm for veterinary students from the OSU Food Animal Club interested sheep and goats. We will visit the chicory fields and other fields to discuss the project and various grazing strategies for parasite control. We will demonstrate the FAMACHA system and describe how it can be used. We will also visit two other farms that day where we will have opportunities to discuss various aspects of parasite control including the use of genetically resistant sheep.

We have a series of evening meetings planned for August 4, 18, and 25 during which we will discuss this project, what we have learned, and basic parasite control strategies. These meetings will be held at one location (to be determined for each night) with a face-to-face audience, but they will be web cast using WebEx technology. This will allow multiple audience participation at other sites around the state as well as the region. We expect to announce these meetings in a variety of venues to increase participation and to include veterinarians. The meeting transcript will also be posted on our Extension website for viewing later.

Following the three meetings, we will hold a field day at the John Anderson farm on August 27, 2010, to present what we have learned in this project to farmers and others in attendance. We expect to visit the chicory field as well as other pastures and demonstrate various strip grazing techniques as well as present our observations about use of various forages in a parasite management program. We also plan to have a hands-on session to teach the FAMACHA scoring technique to interested farmers and others.

Approximately six fact sheets are being planned to describe what we have learned about chicory, BMR, and other plants and grazing techniques. These will be written by the project participants. In addition, we expect to submit two manuscripts for scientific publication emanating from this project.

Accomplishments/Milestones

Chicory and BMR stands were successfully established on the three farms and grazing by groups of lambs as planned was successfully carried out over a two-year period. Sample collections were conducted and animal measurements were obtained as planned.

In August of 2010, several project participants (Anderson, Cline, Lewandwoski, Shulaw) met with Joan Benjamin and Linda Kleinschmit of NC SARE during their site visit to Ohio. They described their participation in this project and their experiences. Ms. Benjamin and Ms. Kleinschmit visited the Cline farm on August 27. Statistical analysis of the two years worth of data is on-going.

Impacts and Contributions/Outcomes

All three farms have updated information about drug resistant parasites on their farms and have changed their parasite control strategies for 2011 based on observations made and new insights gained during these past two years. At one farm, the new strategy includes the acquisition of some Katahdin (greater resistance to parasites) rams in the fall of 2010 and implementation of a plan developed in December, 2010, to monitor the crossbred offspring in 2011 to determine if any genetic resistance to internal parasites can be measured. This is part of a long term strategy to maintain sustainability of the sheep enterprise at this farm.

Worm egg counting data, forage growth and quality information, selected grazing strategies, and images from 2009 and 2010 have been used in six presentations on control of parasites in sheep and goats to farmer audiences in 2010 and 2011. Two of these were conducted by Mr. Cline and Mr. Lewandowski. In addition, the following presentations and papers have been presented or prepared and describe data at least partially collected in this project:

• McCutcheon, J., Shulaw, W., Foster, J., Cooper, T., Rickard, B., and Wittum, T. 2010. Cultivar Preference of Lambs Grazing Forage Chicory in Ohio [Abstract]. 2010 American Forage & Grasslands Council, Proceedings & Abstracts. Springfield, MO. (June 21)
• Shulaw, W., Lewandowski, R., McCutcheon, J., Cline C., Foster, J., & Wittum, T. 2009. Non-traditional forages in a managed grazing system for control of gastrointestinal parasites in sheep: preliminary work. [Abstract]. 2009 Annual Meeting, American Forage & Grasslands Council on CD-ROM. Grand Rapids, MI.
• Foster, J., Cassida, K., Turner, K., Sanderson, M., Shulaw, W., McCutcheon, J., Cooper, T., Parish, J., & Rosskopf, E. 2009. Plant constituents: Opportunities to control Haemonchus contortus. In: Appalachian Workshop and Research Update
Improving Small Ruminant Grazing Practices Proceedings. Beaver, WV: 33-52.
http://www.mountainstate.edu/usda/PDF/Farm.pdf .
• Foster, J. G., Cassida, K. A., Turner, K. E., Sanderson, M. A., Shulaw, W. P., McCutcheon, J. S., Cooper, T. A., Parish, J. R. and Rosskopf, E. N. Plant constituents: Opportunities to control Haemonchus contortus, pp. 33-45. In Morales, M. R. (ed.) Improving Small Ruminant Grazing Practices, Proceedings of the Appalachian Small Ruminant Grazing Workshop, July 11, 2009, Beaver, WV. 2009. (Conference Proceedings)
• Foster, J. G., Cassida, K. A., Sanderson, M. A., Shulaw, W. P., McCutcheon, J., Cooper, T. and Parish, J. R.. Chicory cultivars differ in sesquiterpene lactone composition. In Proceedings of the American Forage and Grassland Council 2009 Annual Conference, June 21-23, 2009, Grand Rapids, MI. CDROM. 2009. (Conference Proceedings)
• Foster, J. G., Cassida, K. A. and Turner, K. E. Anthelmintic potential of chicory forage is influenced by sesquiterpene lactone composition. In Proceedings and Abstracts of the American Forage and Grassland Council, June 21-23, 2010, Springfield, MO. CDROM. 2010. (Conference Proceedings)
• Foster, J. G., Cassida, K. A. and Turner, K. E. 2011. In vitro analysis of the anthelmintic activity of forage chicory (Cichorium intybus L.) sesquiterpene lactones against a predominantly Haemonchus contortus egg population. Vet. Parasitol. in press.
• Foster, J. G., Cassida, K. A., Sanderson, M. A., Shulaw, W. P., McCutcheon, J. S., Cooper, T. A., and Parish, J. R. Sesquiterpene lactone composition varies among forage chicory cultivars. For Forage and Grazinglands (will be submitted April 2011)

• Chicory (Forage Feast cultivar) roots exposed by winter freeze thaw; spring 2011
• Chicory – (Forage Feast cultivar) pushed from the ground by frost heaving with damaged roots. Most of these plants died. July 7, 2010
• Curt Cline showing net electric fence and height of forage in ultra high density grazing used for ewes and lambs just prior to grazing chicory and BMR
• Sorting and paint branding project lambs at the Rickard farm June 28, 2010
• Ultra high density grazing May, 2010 – Lamb choosing forage near the ground which may have worm larvae.

Collaborators: