Genetic Approaches to Parasite Control

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Sheep GEMS News Brief 12 – March 2025 In the last Sheep GEMS news brief, we talked about the impact of parasites on production, and it was eluded that genetic selection can be a very promising means to manage worm parasites. Continuing with the Sheep GEMS theme of breeding for climatic resilience and robustness across environments, parasite resistant sheep express improved fitness. Determining fecal egg counts (FEC) at the time of weaning and post-weaning is a measure of parasite resistance already included in the National Sheep Improvement Program (NSIP). Collaboration with the GEMS innovation flocks and 3 USDA ARS facilities…

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How do Parasites Affect Production?

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Sheep GEMS News Brief 11 – Late February 2025 Gastrointestinal parasites are one of the main health concerns for grazing sheep because available dewormers are largely ineffective due to dewormer resistance. Parasitic worms are a year-round problem in tropical and sub-tropical environments affecting millions of small ruminants world-wide. However, resistance to multiple deworming drugs is common in small ruminants. Infection with gastrointestinal nematode parasites can cause reduced weight gains, fertility, fiber and milk production, as well as cause anemia, diarrhea, and death. The most pathogenic worm species is barber pole worm or Haemonchus contortus is a blood sucker and can…

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Genetic Aspects of Udder Health

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Sheep GEMS News Brief 10 – February 2025 In the last Sheep GEMS news brief, we presented the economics of subclinical mastitis in meat and wool ewes. Despite the major production impact that subclinical mastitis poses, the only way to diagnose it involves collecting and testing milk from every ewe. Take it from the guy who has milked the rankest Rambouillet and most cantankerous Katahdin ewes, you don’t want to go down that road! So, we’re at a bit of an impasse; we have a disease that costs us money, but we don’t know which ewes have it. How can…

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Economic Impacts of Udder Diseases

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Sheep GEMS News Brief 9 – January 2025 A nationwide survey conducted in 2011 by the USDA APHIS estimated that 14% of U.S. ewes (402,000 head) are culled each year. Of ewes culled, 56% are removed for old age. Culling for age is a good thing as these ewes have been productive for years, but we have limited resources and need to make room for younger, genetically superior females. The flip side is that 44% of cull ewes leave the flock early, which is not a good thing. The most common reasons for culling ewes prematurely are failure to lamb…

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Genetic Diversity within Breeds

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Sheep GEMS News Brief 8 – Early December 2024 The genetic diversity available within each sheep breed gives us tremendous opportunity to make genetic improvement. That snapshot of the genetic diversity currently available is extremely valuable since it provides a benchmark for comparing the consequences of selection over time in individual breeds. To establish that starting point, we used both pedigree- and molecular-based information to assess genetic diversity in the four breeds involved in Sheep GEMS. For each of the breeds we evaluated—Katahdin, Polypay, Rambouillet, and Suffolk—we found substantial genetic diversity. That coincides with low inbreeding levels. So, what do…

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Genetic Diversity

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Sheep GEMS News Brief 7 – October 2024 Genetic diversity is what allows for adaptation and evolution in response to change, whether that change is environmental or consumer driven. As we look across the array of domestic sheep breeds throughout the U.S., the genetic diversity is clear. From fine-wool to long-wool, hair to dairy, and all in-between, there is a wide variety of diversity that exists in sheep breeds. While the differences among breeds can be stark, shared characteristics among individuals are what define a breed. Yet within a breed, no two individuals are the same as considerable variation exists…

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Additional NSIP Genetic conditions from genotypes: PRNP, MSTN, FecB, CLPG

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Sheep GEMS Update – September 2024 The Sheep GEMS project has enabled producers to capture genetic information from their animals with the intent to simultaneously make genomic predictions of breeding values, verifying parentage, and identifying genetic condition status. Such multiple uses of a single genotyping platform will help avoid the extra costs of running DNA tests separately for these different purposes. Our objective was to develop and validate a process to accurately obtain genetic conditions as one outcome of genotyping with a common medium-density (50K markers) single nucleotide polymorphism (SNP) platform (assay), and to estimate frequencies of those genetic conditions…

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Using genotypes to reduce susceptibility to Ovine Progressive Pneumonia (OPP)

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Sheep GEMS News Brief 5 – late-August 2024 In the U.S., the disease Ovine Progressive Pneumonia (OPP) causes extensive welfare and financial losses due to decreased ewe productivity of about 20% and eventual culling or death of breeding stock. Surveys of U.S. sheep have shown that 36% of sheep operations have infected animals and 24% of all animals tested were seropositive. Once infected, sheep remain infected for life, and there is no effective treatment or vaccine. Sheep producers can eradicate OPP from a flock in two ways. First, is by serological testing and removing all infected sheep with the obvious…

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Building the foundations for genomic selection in U.S. sheep

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Sheep GEMS News Brief 4 – mid-August 2024 The Sheep GEMS project, together with NSIP members and other sheep industry organizations, have been working to create the building blocks for the implementation of genomic selection in the U.S. sheep industry. In this second article of the Sheep GEMS update related to genomic predictions, we describe the practical aspects for application of genomic selection in our industry. Genomic selection is the process by which genomically-enhanced estimated breeding values (GEBV) are used for selection of individuals to become the parents of the next generation. The first question one may ask is “How…

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Genomic selection: a new era in U.S. sheep breeding

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Sheep GEMS News Brief 3 – July 2024 Genomic information has been used in many livestock breeding programs for four primary applications: 1) parentage identification, 2) identification of carriers of genetic conditions, 3) evaluation of individual and populational genetic diversity, and 4) prediction of the genetic merit of selection candidates to be used for breeding. These applications show that genomic information has multiple uses key to implementing sustainable breeding programs. The U.S. sheep industry has recognized the added value of genomics and is moving to incorporate it into its genetic evaluations thought the National Sheep Improvement Program (NSIP). In this…

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