Type of Document Master's Thesis Author McFadden, Michael Patrick URN etd-06102012-040239 Title Effects of prenatal androgen exposure on postnatal growth, estrous cyclicity and behavior in female beef cattle Degree Master of Science Department Animal Science Advisory Committee
Advisor Name Title Beal, W. E. Committee Chair Akers, Robert Michael Committee Member Knight, James W. Committee Member Keywords
- Beef cattle
Date of Defense 1988-03-15 Availability restricted AbstractThis study assessed the effects of prenatal androgen exposure
during three periods, of gestation on the external genitalia,
estrous cyclicity, postnatal growth, social dominance and
sexual behavior of female beef cattle. Pregnant cows
recieved 17a methyl-testosterone (250 mg/d, sq) on d 40 to
100 (group 1), 70 to 130 (group 2) or 100 to 160 (group 3)
of gestation. Control cows (group 0) received no treatment.
Group 1 females exhibited completely masculinized external.
genitalia. No vulval opening was present and the
ano-genital distance (A-g) was similar to that of control
male calves. Group 2 females exhibited small vulval openings
and enlarged clitoral structures while group 3 females exhibited
normally appearing female external genitalia. Anogenital
distances for the heifers in groups 2 and 3 were
similar to those of the control heifers. Androgen exposure
during the three periods of gestation did not affect age at puberty (P<.80), estrous cycle length (P<.63) or postnatal
growth (P<.60) of the heifers.
At 9, 16 and 21 mo of age, social dominance values (SDV)
were determined for each heifer by 3 min random pair contests
for a restricted feed source. The animal with the greatest
feed source control time was awarded a win. Social dominance
value was calculated as 10 times the number of wins divided
by the number of competitions for each animal. Group 3
heifers had significantly greater SDV values than group 1 and
2 females (P<.03). SDV did not differ among groups at 16 mo
of age (P<.59). Group 1 females had greater SDV than group
2 females at 21 mo of age (P<:.04).
At 9, 16 and 21, mo of age, sexual behavior of the heifers
was characterized by exposure of the heifers to a teaser female in estrus. Sexual behavior, as indicated by the number
of mounts, head placements and interest time, was lower for
group 3 females compared to females in groups 1 and 2 at 9
mo of age (P<.04). There were no treatment differences for
any sexual behavior variable at 16 or 21 mo of age.
These results indicate that there is little potential
for increasing postnatal growth or altering the estrous
cyclicity of female cattle by exposure of the fetus to
testosterone during the periods of gestation selected in this
study. External genitalia of females were masculinized by
androgen exposure during d-40 to 100 of gestation. Social
dominance values were increased and sexual behavior was reduced in females by exposure to androgen during d 100 to 160 of gestation. Social dominance values were increased and sexual behavior was reduced
in females by exposure to androgen during d 100 to 160
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