Effects of GnRH on response to superovulation in cattle

THERIOGENOLOGY EFFECTS

OF GnRH ON RESPONSE

A. R. Prado

TO SUPEROVULATION

IN CATTLE

Delgado, R. P. Elsden, and G. E. Seidel, Animal Reproduction Laboratory Colorado State University Fort Collins, CO 80523 USA

Jr.

During 224 courses of superovulation, either 5 or 6 mg of FSH were injected twice daily for 3.5 to 4 days beginning on any one of days 9 to 14 post-estrus; prostaglandin (45 mg of PGF or 750 ug cloprostenol) was injected in a split dose on the fourth &y. Donors were divided into cows and heifers and subdivided according to previous superovulatior treatments; one to three treatments vs no treatment. Every other cow or heifer within each of the four subgroups was injected with 200 ug of GnRH (im) after being found in standing estrus. Only donors that showed estrus within 32 to 72 hours after the first prostaglandin injection were assigned to the project. Animals were inseminated artificially 12 and 24 hr after standing estrus was first observed. LEAST

SQUARES

MEANS

N

OF RESPONSES

TO SUPEROVULATION

Palpated

_._._______ Total

_ .LL__~_

__~_ Ova

__Transferable Embryos

GnRH Control

109 115

4.7 5.0

4.4 3.9

3.0 2.6

cows Heifers

86 138

5.1 4.7

5.1a 3.2a

3.2 2.4

a

_._._.__-~_ ._. Values

.~__~..____ .~..~_.__~~_.

are different

__~___.

(Pc.01)

No statistically significant differences were noted between the GnRH and control groups in the numbers of corpora lutea palpated, total ova, or transferable embryos recovered; however, two interactions were detected. Cows given GnRH had fewer palpable corpora lutea than control cows (P
254

JANUARY

1984 VOL. 21 NO. 1