Title page for ETD etd-06102012-040239


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
Abstract
This 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

of gestation.

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