[Jacob-list] birthing

[Jacobflock at aol.com]

In a message dated 11/14/2003 10:23:29 AM Central Standard Time, 
shepherdofspots at yahoo.com writes:

> One thing I've learned about lambing.......
> 
> When the lambs are ready (and not before) they will
> come.
> 
> Doesn't seem to make a difference when you feed.
> 
> Most times, you look out in the pasture and say, "Oh
> look! A lamb!"
> 
> Joy
> 
> --- ACAMDA at aol.com wrote:
> >Good morning, everyone!
> >
> >My husband has several friends in the cattlemen's
> >association, and they were 
> >discussing when calves were born.  It seems an
> >informal study showed that if 
> >you fed your cows at night, the calves would be born
> >during the day.  If you 
> >fed your cows in the morning, the calves would be
> >born during the night.  Has 
> >anyone seen a similar correlation for our lovely
> >sheep?
> >
> >Just curious.  Lambing makes me nervous, as we're
> >new shepherds.  (I have 
> >three children and still haven't recovered from
> >labor pains!)
> >
> >Kathey
> >Sweet Georgia Valley
> 

Each year there seems to be a discussion of controlling birthing time; many 
trying feeding "tactics".  The feeding theory is based on the assumption thaat 
the ewe controls the delivery process.  However, the actual time of delivery 
is controlled by the lamb.  Gestation varies by breed, sex of the lamb, number 
of lambs, age of the ewe and diet.

The cattlemen feeding time theory is called the Konefal method named after 
Gus Konafel who bred Herefords and Dr. Bellows who tried to replicate the study. 
 About 85% of calvings occured between 6AM and 6PM for cows fed between 5PM 
and 10PM and the association was a two degree rise in cow temperature 16 hours 
before calving.  The speculation was that the temperature rise after eating 
was antagonistic to the temperature drop that occurs before calving and delays 
the calf birth time.

In sheep, the FETAL LAMB DETERIMINES THE BIRTH TIME.  In simple terms, the 
time of birth is based on signals from the lamb fetal brain (human fetus 
operates on the mother's placental signals).  About halfway thru gestation, the 
lamb's fetal brain brain begins to produce a hormone called CRH which excites the 
pituitary gland to produce ACTH.  ACTH (adrenocorticotropin, a hormone) in the 
lamb fetus' adrenal gland then produces Cortisol. The cortisol converts the 
ewe's progesterone to estrogen.  The lamb's ACTH builds up, the cortisol 
prepares the lungs for air (gets rid of the "water in the lungs")  As the ewe's 
estrogen rises, cells of the uterine muscle synthesize connexin which sets up the 
uterine contractions..  Ocytocin produces the electrical muscle stimulator that 
starts contractions.  The estrogen also produces prostaglandins that turn the 
cervix soft.

There have been a number of studies to control gestation time (a separate 
issue from actual lambing hour).  The most interesting are those that limit diet; 
i.e., underfeed the ewe.  This actually promotes the production of ACTH and 
the lamb's signals come on earlier in the gestation process.

To "control the lamb's birth time", one must control the fetal production of 
cortisol, ACTH and the hormone CRH (corticotrophin) which controls the 
production of ACTH; all major hormones that control the lambs "readiness".  

It happens when the lamb says "I'm ready" but the "birth process" so 
beautiful in design is rather well understood.  In a way it's the reverse of human 
birthing signals.

Perhaps more than you wanted to know.    Fred Horak
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