Two and three wave estrous cycles
Key words: bovine, estrous, estrus, cycle, follicle, wave, Ovsynch,
prostaglandin
A diagram modified from several sources of two and three
wave estrous cycles. One cow has two waves of follicle growth with the follicle
in the second wave eventually ovulating. The other has three waves, with the
last wave providing the follicle that ovulates. The length of the estrous cycle
is one or two days longer in cows that have three follicle waves instead of two.
A minority of cows have four follicle-wave estrous cycles.
This physiology is important in everyday dairy practice when
prostaglandins are used to shorten the inter-estrous period because follicles
are more likely to large and ready to ovulate if cows have more follicle waves
during the estrous cycle. There is usually only one follicle per wave but once
a follicle has grown to its maximum size it begins to regress, it cannot be
utilized. Therefore, many follicles and their oocytes are wasted. The physiology
of two or three follicle waves is also important during “Ov-sych” treatment to
synchronize ovulation in cattle.
