Author:
Alnimer Mufeed A.,Abedal-Majed Mohamed A.,Shamoun Ahmad I.
Abstract
Abstract. The objective of this study was to test
whether prostaglandin (PG) injection on day 30 postpartum (pp) and detection of
estrus can affect the efficacy of injecting PG on days 5 and 6 in the timed
artificial insemination (TAI) protocol on pregnancy rate in a large dairy
herd in hot or cold seasons. Out of 2235 cows, 1998 received an injection
of PG at 30±3 d pp and estrus was observed. Cows that displayed
estrus during the estrous observation period after PG injection were
classified as estrus (E), while those that did not show estrus were
classified as nonestrus (NE). Cows in each group were assigned to two
treatments: CO-72 (control treatment) (ECO-72 and NECO-72) (day 44 GnRH, day 51
PGF2α, day 54 GnRH+TAI) or PG–PG (EPG–PG and NEPG–PG) (day 44
GnRH, day 49 PGF2α, day 50 PGF2α, day 52 GnRH+TAI).
Pregnancy was diagnosed on days 33 and 47 after artificial insemination (AI).
The proportion of cows in estrus on the day of TAI was higher (P≤0.05)
for cows that received two PG than for cows that received one PG.
Pregnancies per AI (P/AI) on days 33 and 47 for cows inseminated during and
after a voluntary waiting period in the NEPG–PG treatment had higher rates than
for cows in the EPG–PG, ECO-72 and NECO-72 treatments. Moreover, P/AI were
significantly (P≤0.05) affected by parity. Primiparous had higher P/AI
(37.0 %) than multiparous cows (31.6 %). Cows inseminated in cold
months had higher P/AI and reduced PL (35.6 % and 20.8 %) than cows
inseminated in hot months (29.1 % and 30.6 %, respectively). In
conclusion, treatments with PG on days 5 and 6 after the first GnRH injection
increased P/AI. Estrus detection before the beginning of TAI protocol did not
affect fertility. To maximize P/AI cows exhibiting heat at any time during
the synchronization protocol should be inseminated.
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