Building on Parasite Resistance Selection in Sheep

Building on Parasite Resistance Selection in Sheep

Summary

WORK ACTIVITIES
Producers participating in this project include:
• Jeff & Kathy Bielek - Misty Oaks Farm - Ohio
• Sue & Dave Ingram - DSI Katahdins - Missouri
• Donna & Doug Stoneback - Wade Jean Farm - Pennsylvania

For this project, three producers from three states (Ohio, Missouri, and Pennsylvania) continue work that was started through NCR SARE grants #FNC 04-523 and #FNC05-583. All three producers raise registered Katahdin Hair Sheep, are forage based, and use rotational grazing and selective deworming strategies. Flock sizes ranged from 25 to 32 ewes. Each farm used at least two rams, some closely related to rams used on other farms.

Our focus in this proposal is to investigate methods of identifying ewes with a reduced periparturient rise (PPR), the major source of pasture contamination in spring. We will also compare the fecal egg counts (FEC) of rams and ewes selected for their low fecal egg counts as lambs to determine how it relates to their adult parasite resistance and that of their offspring.

Ewes typically undergo a temporary weakening in their immunity to parasites during lactation. The subsequent increase in eggs being shed on the pasture in manure, measured by fecal egg counts, is called the periparturient rise (PPR). This increase is often dramatic and is the major source of the new generation of worm larvae on pasture at the beginning of each grazing season. These large numbers of parasite eggs contaminate the pasture at exactly the time when lambs are most susceptible. In addition, high parasite counts during PPR may adversely affect the ewe through loss of body condition and reduced milk production, forcing lambs to graze at a younger age. Thus, selection for ewes with lower fecal egg counts during lactation could lower the contamination of pasture and the exposure of young lambs to parasite larvae, while improving growth and leading to greater productivity.

Building on data from our NCR SARE grant # FNC05-583, we monitored the ewes that we identified and selected as replacement stock based in part on their low FECs, to see how they respond to the PPR as one and two year old ewes. We have decided to continue the project for another year to collect additional data. We will then analyze and compare the FECs of these ewes during lactation to both their own FECs as lambs, and the FECs of their offspring. In the fall 2007 and 2008, some of these low FEC ewes were mated with low FEC rams. We will compare the offspring of these matings to the offspring of other pairings of animals with known higher FECs to learn more about the accuracy of predicting parasite resistance.

Fecal samples were collected on all ewes 2-4 weeks before lambing to establish a base line. Then, FECs were done up to three additional times on the ewes: at lambing, at 4-5 weeks post lambing (the anticipated time of peak PPR); and at 8-9 weeks post lambing to determine if FECs have dropped. To ensure consistency, all FECs were performed by Virginia Tech’s veterinary parasitology laboratory. Body condition scoring and FAMACHA scoring were done and recorded on each ewe at regular intervals through lactation. Ewes were selectively dewormed as needed, and the information recorded. To monitor ewe productivity, weights of as many lambs as possible were collected at birth, 30, 60, 90 and 120 days.

All lambs were monitored every one to two weeks with FAMACHA, body condition and vigor scoring starting at 6-8 weeks of age. A group average FEC of at least 500 epg (eggs per gram) is necessary to ensure a sufficient parasite challenge to identify animals above or below the group average FEC. A parasite challenge was determined to exist when either 10% of the lambs had a FAMACHA score of 3 or higher, or a composite FEC consisting of fecal samples from 12-15 lambs reached at least 500 epg, Once a parasite challenge was confirmed, a FEC was collected on all lambs at that time and again at 21-28 day intervals for an additional one to two collections. FAMACHA scores were also recorded at each collection date. Sire ID, age of dam, sex, type of birth and rearing were collected on each lamb and maintained in a database.

The data was sent to the Bieleks after each collection date, where it was recorded and maintained in an electronic database. Periodic reports were provided to the collaborators, Dr. William Shulaw and Dr. Charles Parker.

All fecal egg counts were performed by the Parasitology Department of the Virginia-Maryland Regional College of Veterinary Medicine (Virginia Tech). Funds from this grant were used to pay for the fecal egg counts, including supplies for collecting the samples, postage and laboratory costs. In addition, each farm was given a stipend to fund a local FFA, 4-H or other interested student to assist with handling the sheep, FAMACHA scoring, weighing, fecal collections and record keeping. This was done to help stimulate an interest in sustainable agriculture and the sheep industry among young people in our local communities.

RESULTS
An analysis of the raw data from the last several years on one of the farms was done by the producers. Data were available for 149 lambs. Some observations include:
1) A ram's FEC as a lamb was the same as the average FEC of his offspring as lambs 76% of the time.
2) If only the sire had a low FEC as a lamb, 69% of his individual offspring had low FEC’s as lambs (dam was either unknown or had moderate or high FECs as a lamb). But, if both sire and dam had low FECs as lambs, 86% of the offspring had low FECs.
3) The dam's average FEC during PPR was the same as her daughters' average FEC during PPR 61% of the time (whether both were low, both were high, etc.).

Although a statistical analysis has not been performed, these preliminary results are very exciting and encouraging.

WORK PLAN FOR 2009
We plan to collect and perform FECs on ewes and lambs using the same protocol as in 2008. Samples will again be sent to an outside laboratory for analysis. In addition, each farm will submit composite fecal samples two-three times over the spring and summer for larval assays to determine if there is any significant change in the species of parasites during the grazing season.

As producers, we plan to continue analyzing the raw data from the other two farms. In addition, a statistical analysis of the combined data will be done by an honors student in the Ohio State University’s Animal Science Dept.

Data will again be sent to Dr. Notter for inclusion in his National Sheep Improvement Association (NSIP) fecal egg count EPD (expected progeny difference) project. We will work with Dr. Notter to correlate our on-farm observations with his NSIP FEC EPDs.

OUTREACH
Data and experiences from our previous NCR SARE grant (FNC05-583) and preliminary data from this project were presented at the annual Katahdin Hair Sheep Expo held in Hagerstown, MD on September 26, 2008.

Data collected during the first year of the project have been shared with our cooperators: Dr. David Notter for use in his work with the NSIP, and Dr. William Shulaw for use in his extension work and FAMACHA training.
Three students on two farms have assisted with handling the sheep, FAMACHA scoring, weighing and fecal collections. Two of the students assisted with data entry and recordkeeping. One of the students had no prior experience with sheep. All became very interested in the project and learned a new aspect of sustainable agriculture and sheep management.
Preliminary results will be shared with the Ohio State University Agricultural Technical Institute’s sheep class on February 19, 2009. Preliminary results will also be included as part of a presentation at the Ohio Ecological Food and Farming Association (OEFFA) annual conference on February 22, 2009.
The final report will be shared with the Katahdin Hair Sheep International (KHSI), the Ohio Sate University Sheep Team and Ohio Ecological Food and Farming Association (OEFFA) for inclusion in their newsletters, and an article submitted to the Shepherd magazine. The information may also be shared through presentations at the KHSI and OEFFA annual meetings and through a field day on at least one of the farms to share results and practical experience with other farmers.