Sheep Industry News August 2022

Genetic Reference Flocks Established at ARS Stations

TOMMURPHY, PH.D., BRAD FREKING, PH.D., JOAN BURKE, PH.D. & J. BRET TAYLOR, PH.D. USDA Agricultural Research Service I n last August’s genetics issue, we presented the concept of setting up the U.S. Department of Agriculture's Agricultural Research Station locations as National Sheep Improvement Program Genetic Reference Flocks. We have established these GRF at the Dale Bumpers Small Farms Research Center in Booneville, Ark., the U.S. Sheep Experiment Station in Dubois, Idaho, and the U.S. Meat Animal Research Center in Clay Center, Neb. At it's core, the GRF scheme involves purchasing rams from industry NSIP fl cks and collecting standard and novel traits on their

the quantity and quality of milk they produce, among other negative eff ects. Accurately diagnosing subclinical mastitis requires milking ewes and testing milk samples for bacterial species or somatic cell concentration. Th California Mastitis Test is one method used to infer the latter. Th table below has data from CMT of Katahdin ewes at US MARC during the 2020 and 2021 lambing seasons. Milk was collected from 1- and 4-year-old ewes at approximately fi ve days aft er lambing and scored for CMT and related to their total weight of lamb weaned at 70 days. Very few fi rst lactation ewes had high CMT scores, whereas 20 percent of 4-year-old ewes had CMT values indicative of subclinical or undiagnosed clinical mastitis.

future progeny. Measuring these new traits on thousands of GRF animals while maintaining strong genetic connectedness with industry fl cks can make it possible for new genetic selection tools to become available for all users of NSIP breeding stock.

Data collected from these GRF is also instrumental in achieving the objectives of the Sheep GEMS project outlined by Dr. Ron Lewis, which initially focuses on Katahdin, Polypay, Rambouillet and Suf folk sheep. Katahdin sheep are reared at all three locations, Polypay and Su ff olk are reared at the USSES and USMARC, and Rambouillet are reared at the USSES. Th intent of this article is to provide some preliminary data and insights on traits collected within these GRF. UDDER CONFORMATION AND HEALTH According to USDA's Animal and Plant Health Inspection Service surveys, approximately half (56 percent) of United States ewes are culled each year because of age. Th erefore, half of these ewes are culled prematurely and for a variety of reasons such as failure to lamb (8 percent), teeth problems (8 percent), hard bag syndrome (7 percent), and mastitis (7 percent). However, we do not presently have ways of accurately selecting for enhanced ewe longevity in NSIP. Measuring variation in udder health and conformation to improve our understanding of the genetic and environmental factors that contribute to ewe longevity is a main objective of Sheep GEMS. Sheep producers usually encounter mastitis in the clinical state – swollen udder, abnormal milk, intramammary masses, etc. Fortu nately, the incidence of clinical mastitis is relatively low (i.e., less than 5 percent). In contrast, ewes that have subclinical mastitis do not display observable signs of disease despite harboring pathogens in their mammary tissue. Still, it’s likely that ewes with subclinical infec tion experience some degree of udder damage, which can reduce

Furthermore, total weight of lamb weaned decreased with increas ing CMT score. For example, ewes with a high CMT score weaned 22 percent less (12 pounds) lamb than ewes with a low CMT score. Past research by our group has found similar negative eff ects of subclini cal mastitis on range-type ewe productivity. Clearly, subclinical mastitis has major economic implications, but diagnosing it is labor intensive and expensive for industry fl cks. One of the objectives of Sheep GEMS is to identify more easily measured indicator traits which are related to ewe susceptibility to mastitis. We are concurrently evaluating udder and teat traits – ud der depth, teat placement, teat length, etc. – to determine optimal conformation associated with udder health, ewe longevity and lamb production. Milking ewes and collecting udder conformation traits does add to an already busy time of year for our ARS sheep crews. Th USMARC sheep crew has designed a chute with raised platform and head gate which enables researchers to rapidly milk ewes and collect approximately 10 udder and teat conformation traits in two minutes or less. KATAHDINS AT HOME ON THE RANGE Th Katahdin is the common breed reared at all three ARS loca tions and the latest addition to the USSES. Apart from general ad aptation to a new management system when bringing in ewes, some additional steps have been taken to ensure it is successful as a range sheep. We oft en stress the importance of improving reproductive ef

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