Review/Oorsig Volume 23, Issue 02 - Page 18

Oorsig/Review percentages of in and around 434% in their total flock of around 500 ewes, and an adjusted lambing% of 535% after 3 lambings in a group of MATURE Finnsheep (1982/3), did the system not take off the way it should have? 3. The third aspect was their synchronisation program for natural mating - they synchronised using teaser rams only. In other words “no hormones” were used! We can only speculate on what would have happened had they used hormones, BUT, there was also a method in this "madness"... This is quite an important “nugget” – when selecting for multiples, “hormone produced” twins would in my mind not be a heritable trait, whereas using a more “natural stimulus” like this, might well be. They also only used natural mating i.e. no AI or laparoscopy! (I will discuss further at a later stage or in another article, when we look at the “principle of sperm competition” as described by Themonier et al., from Nouzilly, in France in the early 1970’s and its effect on fecundity or multiple births). Group mating increases both conception as well as fecundity, but is not a heritable trait! 4. The other important consideration is that they also selected strongly for “repeatability of fecundity” as opposed to the “traditional way of “us” (?) recommending using a ram that is one of a twin or multiple at birth. To become an ALL-STAR ewe and thereby a “ram mother”, Dorsets had to have twins in at least five successive STAR lambing oppotunities and FINNS had to have triplets at least at each given opportunity by 214 days post lambing What did Magee and Hogue do that is/was (in my opinion) far beyond the ordinary? • They worked out an excellent management system which: - - Produces lambs all year round based on the same principles we use on dairy farms to produce milk all year round. - - Has 73 day “cycles” which gives 5 “feedlot periods” in which lambs can be “rounded off” and kraals have enough “rest time” in between “lambing/feeding groups”. - - Gives enough time in which a ewe can raise her lambs herself and facilitate early weaning - - And gives enough recovery time for “complete involution” to take place before the next mating period. 18 • • • They selected ewes according to different reproductive measurements from those we use as “standard practice”: - - Repeatability of multiple births as opposed to fecundity alone - - Natural synchronisation with teasers, not using any “hormones” They identified “Ram Mothers” based on “fertility performance” first, and then used their sons and daughters to “multiply those genes” into the flock! After identifying the most “prolific ewes” and their offspring, they started investigating what made them “different”! In the rams they found that these had less variation in testicular circumference between spring and autumn! We know today that circumference alone is not the best measurement of testicular size and that testes volume is a much better indicator. We also know that there are other testicular measurements like testicular growth from days 90 to 180, with some adjustment for live weight, which have been proven to be effective. (Matos et al., 1992; Fossceco & Notter,1995; Al-Shorepy & Notter, 1996). I have started investigating variation in testicular size during the mating period and the recovery afterwards and I am excited about what I have found thus far with the “more fertile rams” seemingly having a bigger drop in “testicular volume” during the mating period as well as a quicker recovery back to their original size (and even bigger) thereafter. I believe that this definitely warrants further investigation. Our ultimate aim should be to find new ways of identifying the most fertile animals sooner, as well as to start applying methods that have been proven to make a difference! I believe that we have been missing this important concept of measuring testes size variation which Magee and Hogue applied many years ago but possibly “failed to convey across properly”! Instead of taking the “long route”, we can save a lot of time by doing this from the beginning and/or until we have enough data a few years down the line. The most important thing is that different ways of measuring and selecting for “fertility” were identified and applied by