[Jacob-list] Jacob Lamb Sex Ratios

[Jacobflock at aol.com]

Discouraged by the number of rams? The reporting of numbers of Jacob rams and 
ewes being born is interesting information but keep in mind the sex of a lamb 
is basically chance like a coin flip (say 50/50).  

Any variance of ram lambs and ewe lambs in the numbers of each sex being born 
are a result of the few selected rams and small ewe populations in each flock 
(the ram determines the sex of the lamb; the ewe the number of lambs).  Even 
the sum of all the ram lambs and ewe lambs born in all the flocks of all Jacob 
breeders may show some variance (registries are not sources for this data 
because registration is selective).  

But is any variance mere chance or is it significant?  A population of lambs, 
say 1,000, would be needed to identify a significant variance and even the 
definition of an includable lamb would have to be circumscribed (would aborted 
lambs be included, born and non-viable, viable until weaning, etc.).  To 
understand the variance, I suspect one would have to examine the population for 
equilibrium and random mating, identify the observed variance explainable by 
genotype (survival, adaptability, conformation, etc.) and environment (flock 
management, breeding systems and management, weather, etc.) seperately and then any 
variance derived from genetic/environmental interaction (ram/ewe disease and 
parasite resistance, and health and flock management issues related to these 
such as nutrition and pharmacological intervention).  In my opinion, this is not 
easy to accomplish but the only way one can explain whether "vinegar in the 
ewe's water" (or other significant intervention) actually determines the lamb's 
sex.

Too many rams?  Good news: In most populations the male is considered the 
more valued sex because of the heavy investment in a surviving, mature, 
successful breeding partner who has earned breeding status.  Bad news: Domestic animals 
are bred under our selection and control, more often than not, by a single 
ram based entirely on looks ... 

Rams are also food for thought.

Fred Horak



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