OPPCONCERNED SHEEP BREEDERS SOCIETY
A TYPICAL OPP EWE
“Let’s suppose that I have a good ewe lamb that I breed to lamb at two years of age. She gives me a single, a lovely strong lamb. I forgive her for giving me a single since it is her first and she is a twin herself. Next year I get twins from her. Those are also nice but not quite as good as the previous one. That is assumed natural since they are twins. Mother is now three and since she raised twins she is not in as good a condition going into breeding as she was the previous year. In next lambing — she is now four — she twins again and this time the twins are born a good size but fail to thrive. And mother is positively thin after raising these two. At this time many would decide to sell the ewe, either (hopefully) to slaughter or to someone looking for cheap breeding stock. After all, the ewe is only 4-1/2 years old. If she has been sold for breeding, (good buy, she is a twinner and should have a few years left) she will probably be dead two years later. This would be a typical OPP ewe.”
STEFANIA DIGNUM (1945—2007)
RENOWNED ICELANDIC BREEDER
“THE SHEPHERD” MAGAZINE, 1989
Hello, and welcome to the OPP Society. We’re glad you found us!
OPP, or ovine progressive pneumonia, has been circulating in North America for more than 100 years. While first reported in the U.S. in 1914, it took decades before the impact was fully recognized. By 1942, a USDA senior veterinary pathologist declared that “Chronic progressive pneumonia is unquestionably of considerable economic importance.” And yet today, more than 75 years later, producers continue to wrangle over whether or not it matters if sheep have OPP.
So why the disconnect? It’s complicated and you’ve probably heard arguments both ways. While there are some areas worthy of debate, much of the discussion refers to a 40-year-old study that reported no difference in production between ewes harboring OPPv, the virus that causes OPP, and those free of infection. The problem, perhaps not understood at the time, was that about 600 ewes unable to feed even one lamb had been culled due to hard bag shortly before the study began.
Sometimes referred to as The Silent Thief, OPP is easy to miss. In a fairly young flock being heavily selected for genetic gain, it’s unlikely to see much difference in production between OPP test-negative and test-positive ewes since the negative effects don’t set in until years later. The net result is an industry which typically considers a ewe ready to cull by age 5 or 6, while if free of OPP she might easily produce to 8 or 9 leaving more ewe lambs to market or sell as replacements.
Former USDA research leader, Dr. Randall C. Cutlip, conducted the first experimental OPP eradication program in the ‘80s, providing an option beyond just “culling the lungers” for those willing to follow his protocol. Soon after, a small group led by Wisconsin producer Jim Schultz and his veterinarian, Dr. Bob Leder, established the OPP Concerned Sheep Breeders Society. Restocking from within after having culled heavily, Jim found it difficult to locate OPP-negative rams so an early priority of the Society was to establish a network of like-minded producers.
Word spread. (The Shepherd magazine assisted greatly, continuing their support today.) And before long OPP Society members from all over the U.S. and Canada were learning from each other and collaborating with researchers. Today, thanks to groundbreaking USDA investigation into modes of OPPv transmission, producers in Minnesota have demonstrated that the virus can be eradicated without costly orphan rearing of lambs or premature culling of test-positive ewes that remain productive. This new eradication strategy, which can be put into practice by anyone, is described in Minnesota’s Eradication Trial report (see ‘Library’ page).
Now well into our third decade, the OPP Society is an all-volunteer organization welcoming both purebred and commercial producers as well as veterinarians, researchers, educators, students and all others who share an interest in sheep health. Membership is not intended to indicate freedom from OPP, but rather an active concern about the effects of this disease within member flocks and within the North American sheep industry as a whole.
LARGE & SMALL FLOCKS WORKING TOGETHER
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