Sheep Industry News August 2022

GEMS PROJECT Continued from Page 25

suited to individual farms. For sheep living in warmer, more humid cli mates, tools include genetic resistance, good nutrition, optimum body condition – 3.5 out of 5 is best – rotational grazing and dewormers that work to selectively treat animals in need," Burke said. "Dewormer resistance by GIN can be catastrophic for those relying only on anthel mintics. Use of copper oxide wire particles alone or in combination with a dewormer can be e ff ective for acute barber pole or mixed worm infections.” In Sheep GEMS, fecal egg counts and FAMACHA scores are both being collected. How are those measurements best combined to im prove genetic control of GIN? “Fecal egg counts determined on a group of animals can indicate which animals are resistant to GIN infection and which ones are more susceptible that might be culled," Burke said. "Fecal egg count data are submitted to NSIP to give an EBV on parasite resistance. Th more negative the value, the more resistant the animal. "FAMACHA scores – on the other hand – are an indication of how resilient the animals are to infection. A high FAMACHA score – a score of 3 or greater – indicates that an animal is anemic and likely in need of deworming. Lower scores mean that the animal would not need to be dewormed, even if it had a high fecal egg count. Both indicator

receive back are genotypes for conditions such as Scrapie and Ovine Progressive Pneumonia susceptibility. Still, there is some uncertainty in the industry as to exactly what is meant by a genetic condition and how they are best used. “A genetic condition,” Freking explained, “can be described as varia tion that has a known genetic basis. An animal’s status for a known condition can be determined directly from a DNA sample. For each ge netic condition, prior knowledge of the specifi type of gene action and which alleles are either favorable or unfavorable is needed. For example, the favorable allele from the TMEM154 gene associated with suscep tibility to OPP is required to be present as two copies in an animal to confer the desired lower risk category.” As an important stipulation, he added, “each genetic condition requires understanding these associations and what your goals are for the animals tested. Selection to move a population toward the most favorable versions for these conditions is an accurate and e ff ective tool but requires long-term planning for the breeding objective.” Another novel trait being considered in Sheep GEMS is lamb surviv al. Is there work already underway to better understand lamb survival? If so, how does it dovetail with the aims of Sheep GEMS? “We have an experiment at USMARC that we hope has relevance to lamb survival and the overall aims of Sheep GEMS. It is being con ducted within a maternal composite breed we refer to as our Composite IV fl ock – which is half Romanov, one-quarter White Dorper and one quarter Katahdin. We are measuring several indicator traits of maternal fi ness under intensive conditions of barn lambing. Our objective, though, is predicting how well individuals will perform under more extensive pasture lambing conditions. "Genetically, matched halves of the fl ock will alternate annually between lambing in the barn and on pasture. When on pasture, we will only be able to measure lamb weaning survival on ewes. However, when in the barn, we will measure uniformity of lamb birth weight, ewe colostrum quality, transfer of immune function to the lambs, reproductive hormone status, udder morphology, subclinical mastitis status, and maternal behavior traits at parturition. Th se are all indica tor traits of weaning survival.” In circling back to Sheep GEMS, he continued, “By better under standing the genetic relationships between these more intensive mea sures and lamb survival in ewes at pasture, we can provide better advice on what to measure in producers’ fl cks to make gains.” Parasite resistance is another trait being considered in Sheep GEMS. Dr. Joan Burke is a research animal scientist at the USDA/ARS Dale Bumpers Small Farms Research Center in Arkansas. Among her contri butions to Sheep GEMS is her knowledge of genetic and management tools to control gastrointestinal parasites. Anthelmintic resistance is a growing concern in our sheep industry. How should the sheep industry best strategize to deal with GIN? “Th best strategy is a holistic approach that includes tools best

Sheep at the U.S. Sheep Experiment Station in Dubois, Idaho.

traits are heritable and can be used to improve genetic resistance and resilience to GIN infection.” FAMACHA is scored from 1 to 5 based on inspecting the inner membrane of the eye, with lower scores indicating less anemia. Is formal training needed to reliably collect FAMACHA scores? If so, how can someone receive such training? “Yes, formal training is necessary to use the FAMACHA system to understand the biology and dynamics of the worms and the animal. It involves watching a video or slides on integrated parasite management and proper FAMACHA technique. Training may be available through your extension agent or veterinarian, or through the University of Rhode Island or Virginia State University (Wormx.info/online-fama cha-certifi ation).” Dr. Bret Taylor is a research animal scientist and the research leader at the USDA/ARS U.S. Sheep Experiment Station. Th pioneering pro gram he oversees focuses on sheep managed under extensive Western grazing conditions. Ewe longevity is another of the traits being considered in Sheep

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