New Zealand Journal of Agricultural Research abstracts
Hormonal treatments and the ram effect on synchronised oestrus in
Awassi ewes at the beginning of the breeding season
Mufeed Alnimer
Mohammad J. Tabbaa
Department of Animal Production
University of Jordan
Amman 11942, Jordan
amufeed@ju.edu.jo
Mohammad Amasheh
Husein Alzyoud
Livestock Department
National Centre for Agriculture Research and Technology Transfer
(NCARTT)
Al-Baqa’a, Jordan
Abstract Eighty-four Awassi ewes in five groups
were used to study the effect of using different hormonal treatments or
ram effect on oestrus synchronisation and fertility at the beginning of
the breeding season. At the onset of the treatments, gonadotropin
releasing hormone-prostaglandin F2α (Gn-PG, n
= 17) ewes received gonadotropin releasing hormone (GnRH) i.m. followed
with prostaglandin F2α (PGF2α)
5 days later. Ewes in the prostaglandin F2α-prostaglandin
F2α (PG-PG, n = 20)
group received two i.m. injections of PGF2α 10
days apart. Ewes in the fluorogestone acetate (FGA, n = 15)
group were fitted with FGA intravaginal pessaries, left for 14 days and
given an i.m. injection of pregnant mare serum gonadotropin (PMSG).
Ewes in hormonal treatments (Gn-PG, PG-PG, FGA) and the Close (n
= 17) group, were housed in a barn close to the rams’ barn for the last
15 days, while those in the Far (n = 15) group were left in a
barn completely separated from rams until the day of mating. Ten
fertile rams were introduced 48 h after the last treatments.
Plasma progesterone (P4) concentrations were similar at the onset and
at the last day of treatments for ewes in the five groups. On Days 8
and 11 (Day 0 = day of last treatment) a significant increase (P
< 0.05) in P4 level was observed in the Gn-PG and PG-PG
compared with the Close and Far groups. Plasma P4 remained higher in
the Gn-PG and PG-PG, compared to the other groups through Days 17–20
post-treatment. The average oestrus response was 80% and similar in all
groups. Pregnancy rate based on plasma P4 concentrations on Days 17 and
20 post-treatment were lower in the Close than other groups. The
proportion of ewes observed in oestrus in the hormone treated groups
tended to be greater (P < 0.1) than that in the
non-hormone treated (Close, Far) groups. Pregnancy rate, based on P4
concentrations and lambing rate, were significantly greater (P < 0.05)
in the treated groups than that in the non-treated groups, while
lambing rate from ewes rebreeding was similar. Results indicate that
Awassi sheep may be synchronised using either GnRH-PGF2α
program or two injections of PGF2α 10 days apart
as well as progestagen treatment, but with lower number of days
required for synchronisation. Similar pregnancy and first lambing rates
were observed in the treated groups and Far group, which may be due to
the sudden introduction of rams to the last group, but the Close group
was still low.
Keywords Awassi ewes; oestrus synchronisation;
hormonal treatment; ram effect; progesterone
A05026; Received 21 January 2005; accepted 21 June 2005; Online
publication date 11 October 2005
New Zealand Journal of Agricultural Research, 2005, Vol. 48:
473–480
0028–8233/05/4804–0473 © The Royal Society of New Zealand 2005
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