The best strategy under your condition is the
1. Selection of divesified charactered male from the herd (phenotypically). Then group male A, B C, D, and E (five best males) for breeding. In case of pan mating, similar diversified group of 5 different females should be made and crossing among them should be performed.
2. As and when chances of male introduction from other place comes, that should be introduce and replace the A to E group from them.
3. In case no option is available, selection will be the only tool availabile for you to fetch benefit of heterosis.
4. If cryopreserved semen, you can bring from other region, that will also bring heterogenicity in your flock.
Best wishes
Dr. Prabhat Pankaj,
Thank you for your contribution, I intend to follow the strategy proposed in the future. the result requires a longer time.
Sincerely yours.
Please give detail of your flock with respect of male and female composition....
Tadmit the Algerian race, a cross between the Australian Merino and Algerian Ouled Djellal. Our herd consists of over 80 female and 20 male. and we must follow the genealogy of the herd.
1. simply you can go for random mating if you do not want to apply any specific strategy.
2. Method 1. suggested by Dr. Pankaj sir will be quite handy
3. You can go either for positive assortative mating or NAM but certainly not the both.
4. After applying any of the above, second or third generation onward selection will be the best way to avoid inbreeding...rest all depends on the local condition and resources available....
Dear Jay Prakash Gupta,
Thank you again for your suggestions, I will apply one of the last two methods.
cordially yours
Yo can avoid inbreeding with a good record system and creating a several mating groups (minimun 4) as reported by Nomura and Yonezawa, 1996.
http://www.biomedcentral.com/content/pdf/1297-9686-28-2-141.pdf
Dear Axel Villalobos Iván Cortés,
thank you very much for your contribution, I see more clearly the issue.
Best regards
We have had a closed flock(n=100) since 1985. No problem with Inbreeding. But to be save try to use an Unrelated ram each year.
You have to increase your ram to ewe ratio to increase the effective population size of your closed flock and to purge out the artificially induced inbreeding gradually. And/or if you are happy introduce a ram from elsewhere and it can loose to a considerable extent the genetic bottleneck you flock has experienced.
each ram and ewe should have a replacement, use rams for limited time, have rams even number of offsprings, mate unrelated animals, 1:1 ram:ewe ratio would be the best, but try to increase the number of rams used.
Its better to replace the rams after 2 to 3 years. Moreover, not be selected the lamb sires of your herd for breeding. not to be grazed the ewes with growing lamb sires presented in the herd.
It is better to use an unrelated male to avoid inbreeding. Look around you for farmers with good flock of sheep and proper management records, then, you can purchase a younger male from good ancestors with excellent performance record. This male can be introduced to your flock for mating. On the other hand, if you can purchase semen from rams with proven record, then, inseminate your animals. As a matter of fact, insemination appears to be your best bet. Thereafter, you need to properly tag your animals for proper identification and management procedures. Proper identification is necessary for better management and meaningful genetic improvement.
You should not use the same ram for breeding in a population of sheep for a long time. Try to introduce another superior ram in your population of sheep from other population of sheep.
After reading some of the comments - what if the flock 120 animals is a special flock that would be harmed by outside genetics?
Split your flock in at least 3 groups, say, A, B and C, and assign 3 good unrelated rams respectively to separate mating groups. In the next mating season, you select the best ram lamb from group A and assign it to sire ewes from group B. A selected ram from group B goes to mate females in group C, and so on. It is not advisable to select a ram from a ewe that has produced a selected ram lamb before. in this way, you can retard inbreeding for several years. If you could split into more groups, all the better. The catch is that you need to identify all your dams and organize mating groups during tupping. Once ewes are pregnant you can manage the flock in one group. Hope this makes sense...
you must control the mating procedure by use pedigree record and avoid mating between fullsibs and halfsibs .
Good Luck
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