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If you have any questions, ideas or additions for the Scrapie program up to now or for the coming future please contact the Scrapie program co—ordinator. The Scrapie committee meets annually or upon any specific requests.

August 2005 Scrapie Canada Update:

Tips for using genotype information to breed for scrapie resistance in sheep

Hossain Farid–Department of Plant and Animal Sciences, Nova Scotia Agricultural College

Breeders who participated in the genotyping project in Nova Scotia and British Columbia now know the genotype of their ewes and rams at codons 136, 154 and 171 of the prion protein gene. The question is how should the breeder interpret and apply the genotype information to increase the natural resistance of their sheep to scrapie?

One important question is if there is any relationship between scrapie resistant genotypes and sheep productivity? There is limited information on this topic, and published reports are often contradictory. Some Nova Scotia sheep breeders who took a serious look at their genotype results last year noticed that some of their best rams had the susceptible genotype (QQ171). The same observation was made by at least one breeder in British Columbia. Is it a bad luck or is there a negative genetic relationship between the resistant genotype and performance and/or conformation?

Analysis of the genotype results of the Nova Scotia purebred sheep indicated that, in a few breeds, a higher than expected proportion of breeder rams carried the scrapie susceptible allele (Q171). This observation suggests that rams that carried Q171 had some characteristics that appealed to breeders, i.e. there may in fact be a negative relationship between resistance to scrapie and conformation or performance in some breeds. We currently have a project to look into this issue.

Breeding strategies for your flock should be based on the fact that, at present, it is unclear whether scrapie resistance is related to production performance. Keeping this in mind, below are a few suggestions on how to use genotype information in your breeding and selection scheme.

  1. Do not sacrifice high production for genetic resistance to scrapie. A low-performing resistant sheep has little market value.
  2. Rams do not transmit the scrapie agent to your flock, but they have a marked effect on the genetic status of your flock. Where possible, use very resistant (AA136RR154RR171) rams.
  3. When you are purchasing a ram, try to obtain a high-performing resistant (RR171) animal.
  4. Cull your low-performing susceptible QQ171 ewes, particularly those with VV136 or VA136 genotypes that are very susceptible, or use such ewes only for market lamb production.
  5. Information on the genotype of both ewes and rams in your flock provide you with the opportunity to arrange breeding strategies that will produce genetically resistant lambs in the next lambing season, thereby accelerating the rate of progress toward establishing your scrapie resistant flock. If you have no RR171 rams, breed high performance QR171 and QQ171 ewes with high performance QR171 rams, and vice versa, to produce RR171 or QR171 lambs. With this strategy, it will take longer to establish a resistant flock, but it will allow you to maintain a high performance flock.

I greatly appreciate constructive comments from Judith Glibbery from BC and Marg Zillig from NS.

Two Sheep

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