Re:  Effects of PGF on CL

A few years ago we published this paper:

Morbeck, D. E., H. D. Tyler and J. H. Britt.  1991.  Duration of estrous
cycles subsequent to two injections of prostaglandin F2a given at a 14-day
interval in non-lactating Holstein cows.  J. Dairy Sci. 74: 2342-2346.

In it we noted:

"If the first prostaglandin F2a was given when progesterone was greater than
1 ng/ml, the estrous cycle following treatment was longer than if the first
prostaglandin F2a was given when progesterone was less than 1 ng/ml (26.0 vs
22.6 d).  This experiment demonstrates that two injections of prostaglandin
F2a increases the incidence of estrous cycles greater than 25 d. Stage of
the estrous cycle at time of the first injection of prostaglandin F2a may
contribute to this effect."

We suspect the effect that we reported is due to a change in pattern of
follicle waves and this could lead  to longer cycles.  However, the effect
could also be related to function of the CL after the 2nd PGF2a injection.

If you read this paper in the Journal, please note that there is a error in
Figure 2 for Cow 748.  The lengths of tje two cycles should be 27 and 23
day, respectively, rather than 23 and 27 days (the values are switched in
the figure).

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==============================
Jack H. Britt, Associate Dean
Research & Graduate Programs
NCSU College of Veterinary Med.
4700 Hillsborough Street
Raleigh, NC 27606  USA
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