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 Keywords
Date of Defense 1987-04-25 Availability restricted AbstractThe 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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