Title page for ETD etd-08012012-040159

Type of Document Master's Thesis
Author Nugent, Russell A.
URN etd-08012012-040159
Title Effects of breed and ram exposure on Spring estrous behavior and Summer fertility in domestic ewes
Degree Master of Science
Department Animal Science
Advisory Committee
Advisor Name Title
Notter, David R. Committee Chair
Beal, W. E. Committee Member
Siegel, Paul B. Committee Member
Umberger, Steven H. Committee Member
  • Sheep
Date of Defense 1987-04-25
Availability restricted
The present studies were conducted to check the effects

of acute ram introduction into a flock of anestrus ewes in

Virginia. Ewes were bled via jugular venipuncture twice

weekly and serum samples were radioimmunoassayed for

progesterone (P4) content as an indicator of estrous activity.

All rams were fitted with crayon equipped marking harnesses

for use as an indicator of mating behavior in ewes.

The first study tested the effects of introduction of

vasectomized rams into a flock: of' 50 Dorset (D) and 50

Hampshire (H) purebred ewes in either May or June. More D

ewes ovulated (96% vs 72% for H ewes) and mated (80% vs 20%

for H ewes) in May. Of ewes which mated in May 65% D but no

H ewes continued to cycle in June after removal of rams. Of

ewes exposed to rams in June no difference among breeds was

observed in percentage of ewes ovulating but more D ewes

(72%) mated than H ewes (44%). Twenty-four percent of D but

no H ewes cycled continuously throughout the 68 d or the

study. Lambing date significantly affected mating behavior

in H but not D ewes.

The second study tested the effects of ram breed on incidence

of mating and subsequent lambing in Rambouillet x

Q Suffollk ewes In June and July of 1984 and 1985. Ewes were

Q pre-exposed to either confined Suffolk (S) or Dorset (D)

Q yearling rams or no (N) ram for 2 wk prior to breeding by

Q either S or D rams. Lambing date was significantly affected

by breeding treatment in 1984 and by pre-exposure treatment

in 1985. Sixty-three percent of the ewes lambed in 1984

while 65% lambed in 1985.

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