Sustainable Internal Parasite Control for Sheep in a Forage Based System

PROJECT BACKGROUND

Misty Oaks Farm is a 100-acre farm in southwestern Holmes County. Our flock consists of registered Katahdin Hair Sheep, with 4 rams and 18 ewes lambing in 2005. Katahdin Hair Sheep are known for their high parasite tolerance and are a hardy, medium-sized, efficient, low maintenance breed.

The primary source of income generated by the sheep is from breeding stock; lambs that are not breeding quality are direct marketed as grass-fed lamb. We are slowly growing our flock, while developing existing pastures. Approximately six acres of orchard grass/clover pastures are available for the ewes and lambs. An additional four acres of rough pasture are fenced and being improved.

We started our flock with eight unrelated lines of ewes and still have four distinct groups, so although our flock is small, we have good genetic diversity. This has allowed us to keep replacement rams from within our own flock in the short term and has proven very useful in trying to identify resistant lines.

Before receiving this grant we managed our farm with little or no chemical use, except for the anthelmintics used on the sheep. Becoming certified organic is not cost effective for our farm with the small number of meat lambs we sell each year, but we try to follow the organic standards. For this reason and because we were concerned about the growing problem of drug resistant parasites, we wanted to eliminate our reliance on chemical dewormers. Yet, because of our concern for the animals’ welfare, we were reluctant to simply stop using chemical anthelmintics. We learned of a new system, called FAMACHA, developed to estimate the level of parasite-induced anemia in sheep at the 2003 Katahdin Hair Sheep International Gathering hosted by the Katahdin Hair Sheep Upgrade Project (LNE 03-178).

In 2004 we received a grant from the Ohio State University’s Paul C. and Edna H Warner Endowment Fund for Sustainable Agriculture Interdisciplinary Grant Program for On-farm Research to start monitoring the parasite levels in our flock. We used several biologically based parasite control methods, including the use of pasture rotation, nutritional supplementation and selective deworming strategies. We carefully monitored the flock using fecal egg counts (FEC), FAMACHA and body condition scoring. As opposed to conventional systems, we avoided scheduled prophylactic dewormings of the whole flock and used only selective deworming approaches. The award of this SARE grant allowed us to continue this important project for a second year.

Our ultimate goal is to develop a flock of genetically parasite resistant sheep while maintaining excellent production. We plan to continue selecting replacement ewe and ram lambs based on an index of low fecal egg counts and production traits. This will allow us to eventually eliminate the use of chemicals, and also possibly increase our stocking density, since pasture contamination will be greatly reduced. The progress we have made towards this goal in just two years is exciting and encouraging.

PROJECT DESCRIPTION AND RESULTS

Project Goals
The specific objectives of this project were:
1. Develop a sustainable parasite management plan for our sheep flock that can be applied to other farm flocks typical of Ohio and surrounding states.
2. Provide preliminary data for integrating sheep into organic research at Ohio State University’s Organic Food and Farming Research and Education Program (OFFER) at the Ohio Agricultural Research and Development Center.
3. Provide preliminary data to be used in applying for a SARE Research and Education grant for sustainable parasite control in sheep.

PROCESS

The goal of this project was to combine several biologically based parasite control methods to develop a sustainable sheep production system based on an organic model where parasites may be present in small number but do not affect the health or performance of our flock. The parasite management plan included pasture management, rotational grazing, nutritional supplementation, adjustment of stocking rates, careful monitoring and selective deworming.

Monitoring Tools
Two monitoring tools were used in this project. Fecal eggs counts (FEC), expressed in eggs per gram (EPG) of feces, were used to estimate the number of parasite eggs being deposited on the pastures over the summer and to identify which individual sheep were shedding the most eggs. FEC is also useful in determining those individual sheep with consistently low egg counts. While fecal egg counts provide valuable information, they are very time consuming, especially in large numbers, and require a microscope and procedures not easily used by most sheep producers. If done by a veterinarian or laboratory they can be expensive in large numbers.

Recently, a new system called FAMACHA has been developed in South Africa that compares the color of mucus membranes of the eye to a color chart in order to estimate the level of parasite=induced anemia. Using the system, a score of 1 denoted a sheep with normal eye color and red blood cell levels, while a score of 5 denotes severe anemia. Research suggests that regular FAMACHA scoring and deworming of animals with levels of anemia that correspond to scores 3, 4, and 5 (lambs and lactating ewes) or 4 and 5 (dry ewes) can treat the animals that most need deworming while reducing the selection pressure for drug resistant worms. It is important to note that the FAMACHA system can only be used to identify levels of the blood-sucking parasite, Hemonchus contortus, or barber-pole worm. But, since this is one of the major parasites affecting Ohio and Midwest sheep flocks, it is felt to be an excellent tool for identifying those individual animals requiring deworming. This allows for selective rather than whole-flock deworming, controlling parasites caused by H. contortus while reducing selection for anthelmintic resistant parasites. Using both techniques both techniques in this project allowed us to establish criteria for selective deworming when necessary, and to both monitor the rate of pasture contamination and identify individuals with consistently high or low parasite burdens.

Selective Deworming Method

FEC, body condition scoring (BCS) and FAMACHA scoring were done weekly on each ewe beginning in late February, three weeks before the start of lambing. Since lactation is a tremendous stress on the ewes and severely reduces their ability to respond to parasite infections, weekly fecal egg counts were continues on the ewes until weaning on June 3. FECs were then done monthly for the rest of summer. FAMACHA scoring and body condition scoring were done weekly during lactation, then every two weeks for the rest of the summer.

Lambs typically begin nibbling grass, and therefore ingesting parasite larvae, by the age of one month. Therefore, weekly FAMACHA scoring was started at 30 days of age and continues through the end of August, the peak Hemonchus season , then reduced to every other week through October. FECs were done weekly on the lambs from the age of eight weeks through the end of August, then every other week through October. Weights and body condition scores were collected every two weeks to track rates of gain and condition.

Lactating ewes and lambs were dewormed only with a FAMACHA score of 3 or higher. We were prepared to deworm dry ewes with a FAMACHA score of 4 or higher, but none of the dry ewes ever had a score higher than 2. FECs were useful in estimating the level of pasture contamination and identifying individual lambs with consistently low or high FECs.

Pasture and Nutrition
We have chosen to lamb in late March so that we have the largest number of animals consuming forage in May and June when it is most abundant. We are then able to sell registered ewe lambs in July, when the grass growth slows down. This reduction in stocking rate is also effective at reducing the number of parasites being deposited on the pasture.

Another parasite control strategy we used was nutritional supplementation. Ewes were supplemented with up to one pound of corn each, beginning three weeks before and continuing until four weeks after lambing. One-quarter pound of soybean meal was added during the four weeks of lactation.

The summer of 2004 was a very wet and cook year, excellent for forage (and Parasites). By comparison, the summer of 2005 was hot and dry from mid May through June. Rains resumed in July with average moisture, but temperatures were very hot and humid for the remainder of the summer. Ewes and lambs rotationally grazed the existing six acres of orchard grass/clover pastures twice prior to weaning, moving approximately every 3 days and returning to same paddock approximately every 21-28 days. Since lactation is when the ewes are shedding the heaviest numbers of worm eggs, this resulted in fairly heavy pasture contamination. Although it would be preferable to move the lambs to a clean pasture after weaning, we don’t have the acreage to make this possible. After weaning, ewes followed lambs over the same pastures for the remainder of the summer. This allowed the lambs to graze the tops of the grass, while the dry ewes with more immunity to parasites grazed lower to the ground. While this helped the lambs and the pasture utilization, the dry ewes put on too much weight and should be moved to a lower quality pasture in the future.

Handling System
With support from this SARE grant we were able to purchase a simple sheep handling system, consisting of a catch pen, swing gate, chute, stop gates and sorting gates, and utilizing our existing livestock scale. We found that having this very handy equipment set up and ready to go made the weekly monitoring not only easier, but less likely to be put off. It also greatly reduced stress on the animals- and the shepherd.

PEOPLE
Liz Skolmutch, a local FFA student was hired to assist with the project and proved to be a tremendous help and an integral part of the project. She learned quickly and developed expertise in handling the ewes and lambs, performing fecal egg counts offered by Dr. Shulaw in Columbus in July, and gained experience in preparing the fecal samples and use of the microscope to read the slides.

William P Shulaw, DVM, MS, Extension Veterinarian, Beef/Sheep, the Ohio State University, helped develop the monitoring plan and provided oversight for the monitoring of fecal egg counts and FAMACHA scoring. He also provided assistance in analyzing the data.

Deborah Stinner, Research Scientist, Administrative Coordinator, IFFER Program, Ohio State University/Ohio Agricultural Research and Development Center, provided advice on organic and sustainable practices.

RESULTS
Objective 1: Develop a sustainable parasite management plan for our sheep flock that can be applied to other farm flocks typical of Ohio and surrounding states.
Summary of Results:
• Rutine use of FECs was effective at identifying lambs with consistently low or high worm burdens, but was extremely time consuming and expensive.
• Selective deworming was practical and effective using the FAMACHA system. FECs in ewes started to rise earlier in 2005 than in 2004 and were higher through the first half of lactation, possibly because ewes had been routinely dewormed in the fall of 2003, but not all in the fall of 2004.
• Ewes lambing as yearlings in 2005 that were selected for low FEC as lambs had a significantly lower average FEC than the flock average during lactation even with a lambing rate of 166%.
• Significantly fewer lambs required deworming in 2005 than in 2004 (based on FAMACHA score of 3 or higher).
• Lambs appeared to be most vulnerable to parasites between the ages of 12 to 16 weeks and never required deworming after 20 weeks.
• Differences were observed between lambs with different sires. One ram had offspring with consistently higher FECs than the flock average; his offspring were the only ones requiring deworming in 2005.
• Two rams had offspring with consistently lower average FECs than the flock average; their offspring requires no deworming.

Research has suggested that selective deworming can significantly reduce the need for drug use in sheep, including lambs and lactating ewes, and still provide excellent protection from clinical parasitism. Our experiences in out flock this summer support this. The FAMACHA system has proven to be a practical and effective indicator for the need to deworm individual lambs and ewes, while FEC had helped to identify those animals shedding the most worm eggs and thus the heaviest contaminators of the pastures. FEC was also very effective in identifying lambs and ewes with consistently low worm burdens.

We found that egg counts in the ewes started to rise two to three weeks earlier in 2005 than we observed in 2004 and remained higher through the first half of lactation. This is most likely because the ewes had been routinely dewormed in the fall of 2003, but not at all in 2004, so carried a higher number of dormant (hypobiotic) larvae through the winter. In 2005 we had 34 lambs (33 live births) born to 17 ewes (194% lambing rate for live births). We only had to deworm one ewe in 2005: a two-year-old ewe with twins, at about four weeks after lambing.

Ewes lambing as yearlings are typically under more stress and tend to have a more pronounced periparturient rise (higher egg counts during lacation) than older ewes. However, the average FEC of the yearling ewes in our flock in 2005 (selected as replacements based on their low FECs as lambs) was significantly lower than the flock average, even with a lambing rate of 166%. This was much lower than the average FEC of yearlings in 2004, which had been selected based only on production traits. (Figure 1) Four of these six yearling ewes in 2005 have never required deworming, while two were dewormed only once each as lambs. This supports research done in Australia that resistant ewes produce fewer eggs before lambing and during lactation. Thus, breeding for parasite resistance has the potential to reduce the periparturient rise, resulting in less pasture contamination.

Egg counts in the lambs were already higher when we did our first FEC at about eight weeks of age this year, than they were at the same age in 2004. Weaning was done at approximately 10 weeks of age in both years. The flock average FEC for the lambs at weaning was higher this year than in 2004, and more of the lambs had higher egg counts at weaning than in the previous year. In both years, a FAMACHA score of 1 was observed in all lambs at weaning, so even those lambs with higher FECs had not developed anemia.

In spite of having higher counts at weaning, all but one of the lambs in 2005 had FECs in the low to moderate range until early July, four weeks after weaning. This was unlike the sudden spike in FECs seen within the first two weeks after weaning the previous year, and was probably due to the very dry conditions in June. Within two weeks of the first significant rainfall, FECs rose on most of the lambs.

Two lambs required deworming suing Levamisole (Prohibit) on July 8, based on a FAMACHA scare of 3. One additional lamb was dewormed on August 12. This total of only three out of 32 lambs (9%) that requires deworming compares very favorably with 2004 when 8 of 21 lambs (38%) were dewormed. No treatments have been administered to lambs since the single lamb was treated on August 12. All the lambs requiring deworming were treated before the age of 16 weeks, with the exception of one lamb each year. Rarely did a lamb have a FAMACHA score over 1 after the age of 20 weeks, and none required deworming (FAMACHA score 3 or higher) after that age, in spite of a flock average of 700-1200 EPG from late August through September both years. By the end of October in both years the flock average had fallen naturally to about 300 EPR.

There were definite differenced observed between lambs with different sires. While this was more obvious in 2004, with no prior selection, it was still evident in 2005. These differences are discussed in detail below.

Objective 2: Provide Preliminary data for integrating sheep into organic research at Ohio State University’s Organic Food and Farming Research and Education Program (PFFER) at the Ohio Agricultural Research and Development Center.

An organic sheep planning team has been created through the OFFER program. This team includes OSU sheep researchers, an OSU Extension county agent, am NRCS sheep grazing expert, a retired OSU animal scientist who now advises the Katahdin Hair Sheep International organization, an OSU Extension veterinarian and several producers. A plan is being developed, with the first step being to establish a small flock of Katahdins at West Badger Farm. A proposal was recently submitted to the National Sheep Industry Improvement Center seeking funding for this important step. Results from this SARE project have been used to develop the plan and the proposal was recently submitted to the National Sheep Industry Improvement Center seeking funding for this important first step. Results from this SARE project have been used to develop the plan and the proposal. Other means of funding are also being pursued.

Objective 3: Provide preliminary data to be used in applying for a SARE Research and Education grant for sustainable parasite control in sheep.

It was felt that more data was needed before applying for a research and education grant. In order to gather additional data, a group of nine other Katahdin producers has chosen to work together with us to submit a proposal for a NCR SARE group farmer/rancher grant to identify a more “farmer friendly” method to collect data, and to see if results similar to ours can be obtained in different management systems. The results from this project provided the incentive and model for the new proposal.

DISCUSSION
Sheep that are considered resistant to parasites have the ability to suppress or resist the establishment of parasites, while resilient sheep have the ability to withstand the effects of a moderate parasite burden without developing anemia. Resistant animals have FECs well below the flock average when exposed to a parasite challenge, even during the periparturient rise and as lambs. Resilient animals will not develop anemia with a moderate parasite burden, but may or may not have low FEC, and some may actually be shedding more eggs than average. Both traits are heritable. Although resistance occurs more in the range from .2 to .4, it is similar to other production traits in sheep.

Hair sheep, including the Katahdin, have shown greater parasite resistance and resilience than wool sheep. While the rate of variability among individual animals of all breeds if high, the Katahdin breed, since it is a relatively new, composite breed, has considerable genetic variation for all traits, including parasite resistance. This could allow for rapid genetic improvement in a breed already known for increased resistance in a relatively short time.

Our work supports these findings. We observed definite differences in parasite resistance and resilience in the lambs from different sire groups. Four rams representing four different lines were used for breeding in the fall of 2004. Two of these (Rams A! and D!) were ram lambs selected for their consistently low FECs over the summer of 2004. A third ram lamb (Ram C1) was from a sire with suspected poor resistance, but with excellent growth and productivity. This ram lamb required deworming once as a lamb and once as a yearling. The fourth ram used was an adult ram (Ram B) that had produced lambs with consistently low FECs in 2004. Definite patterns were observed between sire groups. (Figures 2 and 3)

Ram A1 – During the summer of 2005, the offspring of Ram A1 had consistently lower FECs than the flock average and never had a FAMACHA score higher than 1. These lambs seem to show excellent resistance and resilience.

Ram B – Most of the offspring from Ram B initially had higher FECs than the lambs of Ram A1 or D1, but were able to self-cure, or return to lower counts without treatment by the end of August. Only one lamb developed a FAMACHA score of 2 with a fairly high FEC at about 16 weeks of age in late July, but returned to a score of 1 after only one week. Her FEC showed a self-cure by the end of August. The lambs of Ram B seemed to show excellent resilience and good resistance.

Ram C1- All of the lambs that required deworming in 2005 were the offspring og Ram C1, the ram that had been dewormed as a lamb. Half of his lambs developed a FAMACHA score of 2 or above over the summer. This group seems to have the least resistance and resiliency.

Ram D1 – The offspring of ram D1 had the lowest FECs in the flock through mid August, and then rose to become the highest group in late August and September. Although none required deworming, 60% developed a FAMACHA score of 2 for at least one week during the summer that was not usually associated with a high FEC. This group seems to have limited resilience but very good resistance.

Unfortunately, since we have such a small flock and have now been selecting for resistance for two years, it is getting difficult to follow this further in our flock alone. We are hoping to work with the producer who now owns the two rams identified with the best resistance, rams A2 and B, as well as other producers who own sons or brothers of these rams to see if these patterns are repeated in different management systems.

Another interesting observation we made over the two years was what appear to be four distinct patterns in the lamb and yearling FECs and FAMACHA scores over the two summers. While similar to those described above, they are not always associated with the same sire group. All deworming was done with a FAMACHA score of 3 or higher.

• One group of lambs had consistently very low FECs throughout the summer. The lambs that were kept that had this pattern in 2004 showed inconsistent FECs in the spring of 2005 as yearlings. The ram lamb and one ewe lamb stayed very low as yearlings, while one the ewe lambs had very high FECs, although none required deworming as lambs or yearlings.
• A second group of lambs had high FECs when initially challenged, but all the lambs were able to self-cure within two to four weeks, and stayed low for the rest of the summer. As yearlings. This group stayed consistently low and never requires deworming as lambs or yearlings.
• A third group had high FECs when initially challenged and required deworming, usually at around 12-14 weeks of age, then gradually rose again through the summer, although none requires a second deworming as a lamb. Only one ram lamb was kept with this pattern and he required deworming again as a yearling. This was the only animal dewormed as a yearling in 2005.
• The fourth group of lambs showed a gradual increase in FEC over the summer and eventually requires a single deworming at approximately 16-18 weeks of age. Their FECs then stayed low the remainder of the summer. This group had consistently low FECs as yearlings and did not require further deworming.

The same general patterns were observed in the lambs in both years, but so far, only one year of yearling data is available. Until we have more data, we can only speculate about what this shows regarding lambs’ resistance and/or resiliencies. It will be interesting to see if the same results are seen when the 2005 lambs become yearlings, and ultimately, whether predictions can be made on future performance.

Detailed production records were kept on all the lambs, including 30, 60, 90 and 120 day weights, and were used to track rates of gain. Sixty day weights, adjusted for the age of ewe and the number of lambs born and raised, were used to calculate the total pounds of lamb weaned per ewe. We also calculated the average FEC on each ewe during lactation. This information was used to index and rank the ewes lambing in 2005. We selected 11 replacements ewe lambs from the ewe with the highest productivity and lowest FEC. (Figure 4)

This grant has been extremely helpful in several ways. It has allowed us to make tremendous progress towards our goal of eliminating dewormers in our flock. We were able to purchase a handling system that greatly increased handling ease while reducing stress. We had the opportunity to work with an outstanding student and she gained valuable agriculture experience. Finally, we have identified two lines that seem to have good parasite resistance and resilience. At the same time, this work has raised questions, including:
• Will the patterns we have identified, both in lamb FECs and heritability continue? Specifically, how will the replacements lambs, both rams and ewes, perform as yearlings, especially as regards the periparturient rise in the ewes?
• Can these patterns of heritability be seen under different management systems?
• Does using a production? FEC index provide an effective means of selecting replacement ewe lambs for resistance and production traits? Or is individual lamb FEC a better indicator?
• This level of data collection is not sustainable, so what method can be used to identify replacement animals from within our flock in the future?
• How can we identify and select new rams with parasite resistance from other flocks, since few or non have this information available?

OUTREACH
Two presentations on this project were given in lieu of a filed day. The first presentation was given at the Great Lakes Katahdin Hair Sheep Association’s meeting and sale in Van Wert, Ohio. On July 23, 2005, The second presentation was at the Ohio State University’s Farm Science Review in London, Ohio on September 20, 2005. Handouts were distributes at the Farm Science Review.

Project updates were published in the Great Lakes Katahdin Hair Sheep Association newsletter. In addition, an article was written by Kyle Sharp for Ohio’s Country Journal and published in the April 2005 issue about our flock and the SARE project.

Results have been shared routinely with Dr. William Shulaw. He has used this information in many of his extension presentations this summer, including the Ohio Sheep Day in July, and at eight FAMACHA training classes offered across the state over the summer and fall. He also offered a training class for producers to learn fecal egg counts in July and included information from this project in his presentation.

A final report of this project will be shared with Innovative Farmers of Ohio (IFO), and the Katahdin Hair Sheep International (KHSI) for inclusion in their newsletters, and with the OSUE Sheep Team. A poster will be created to display at the annual IFO and OFFER meetings.

PROGRAM EVALUATION

The ability to use graphs and charts in the final report would make reporting easier, more interesting and less wordy.