[Jacob-list] Lambing question

[Jacobflock at aol.com]

In a message dated 2/11/2005 2:09:05 PM Central Standard Time, 
shepherdofspots at yahoo.com writes:

> Does where you live determine the time of day for
> lambing? Is it random?
> 
> Read once that it depending upon what time of day you
> fed -- I feed usually at night.
> 
> Eager to hear what others think about this.
> 
> Joy
> 

The birth of a lamb is determined by the lamb.  The time from conception to 
birth varies by breed, sex of the lamb, number of lambs, age of the ewe, health 
of the ewe and of course, diet.  

The actual onset of parturition is controlled by a hormone called ACTH which 
signals the lamb to produce cortisol which develops the lambs lungs (expels 
liquid) and starts the ewe's contractions by producing estrogen and 
prostoglandins that soften the cervix and there it is.

Where you live does not determine lambing time nor is it a random event.  The 
time the lamb is ready to leave the ewe follows some pretty rigorous 
chemistry and is extremely complex.  

A cattle breeder Gus Konafel said in the early 1970s that he controlled 
calving to the hours of 6AM to 6PM by feeding between 5PM and 10PM; successful 
about 85% of the time.  In this case, the temperature rise following eating was 
antagonistic to the temperature drop that usually occurs before calving. Thus 
about a 12 hour delay between eating and calving.

There are numersous studies that one can shorten gestation by several days by 
"underfeeding" the ewe; reducing placental nutrition and stressing the fetus 
so that the fetal lamb produces the ACTH to start the "I want to get out of 
here" hormone rush to the ewe.

Fred Horak

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