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Title: Use of FAMACHA system to evaluate gastrointestinal nematode resistance/resilience in offspring of stud rams

item Burke, Joan
item MILLER, J

Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/17/2008
Publication Date: 5/1/2008
Citation: Burke, J.M., Miller, J.E. 2008. Use of FAMACHA system to evaluate gastrointestinal nematode resistance/resilience in offspring of stud rams. Veterinary Parasitology. 153(1-2):85-92.

Interpretive Summary: Widespread resistance of gastrointestinal worms to chemical dewormers has led to the need for alternative parasite control. The FAMACHA© system, a tool to classify color of lower eye lid into stages of anemia which correlates with Haemonchus contortus infection, was recently validated in the U.S. by trained technicians, but its use for genetic selection has not been documented. Scientists at USDA, ARS in Booneville, AR and Louisiana State University determined that the FAMACHA© system can be used to identify superior sires with parasite resilience, thus, resilience within a flock can be increased. This information is important to producers, extension agents, and scientists.

Technical Abstract: High levels of anthelmintic resistance in gastrointestinal nematodes (GIN) of small ruminants have created the need for animals with greater resistance to these parasites. The objective of this experiment was to evaluate the effectiveness of the FAMACHA system in identification of parasite resilient/resistant offspring, thus identification of stud rams with greater resilience/resistance. Katahdin ewes bred in separate groups to two sires to lamb in spring (2004, 2005: #106 and #2178; 2006, 2007: #10 and #4067) at the USDA, Agricultural Research Station in Booneville, Arkansas produced 20 to 40 offspring/sire each year. Ewes and lambs grazed mixed grass (predominantly bermudagrass and ryegrass) pastures and were supplemented with corn/soybean meal between 30 days pre- and 60 days post-lambing (ewes) and starting 45 days of age until weaning (lambs; 95.0 ± 0.6 days of age). Blood samples and feces were collected to determine blood packed cell volume (PCV) and fecal egg counts (FEC) and FAMACHA scores were determined at 90, 120, and 150 days of age. Lambs were dewormed if anemic (PCV < 19% or FAMACHA score >2) and data removed within 30 days after deworming. Data were analyzed for the 2004/2005 and 2006/2007 groups using general linear models with year, sex of lamb, and sire nested within year as variables. There tended (P < 0.10) to be sire differences for FEC at 90 and 120 days of age, but not at 150 days of age. Sire differences were detected (P < 0.05 or less) for PCV and FAMACHA at all time points, but not FEC. Rams producing offspring that were less anemic were dewormed less by 150 days of age. The FAMACHA system can be used to identify superior sires for parasite resilience/resistance, thus increasing flock resilience, and perhaps resistance.