Data were collected from 1552 reproductive records of 318 Friesian
crossbred cows and 230 Egyptian buffaloes belonging to Fa~ul!y of Awiculture.
University of Alexandria, Egypt over a period of 15 years started In 1970. The effects
of year of breeding, month and season of breeding, post partum first service, days
open, parity. age of parents and sire effect on the number of services required for
conception (NS/C) were studied. The results obtained could be summari ed in the
following:
t-Year of breeding had significant (P<0.01) effect on NS/C for cows and buffaloes and
it ranged from 1.0 to 3.2.
2· The lowest NS/C appeared In spring and autumn seasons of breedi g and the
highest values were in summer and winter. Both month and season of breeding had
significant effect in cows but non significant for buffaloes in this respect.
3-Buffalo and cow females having post partum period less than 3 months required
more NSIC and then it decreased for Ihose having a period (3-<6months). The effect
of post partum period on NSIC was significant (P significant In cows.
4- The average NS/C tended to increase significantly (P in both species.
5·Differences in breeding efficiency described by NS/C due to sire or bull effect were
significant (P<0.01) for bolh cows and buffaloes.
6· The average NS/C was high at t" parity and it decreased thereafter up 10 5th parity
and over. The differences due to parity In this respect were significant ( <0.05) for
buffaloes while non si9nificant for cows.
7·Buffalo heifers required more NS/C than buffalo cows and also those giVing birth to
males needed more NS/C than those giving birth to females whereas cows showed
a reverse trend.
s- The average NSJC showed an increase trend with the progress of sire's ge until <6
years old indicating that young bulls were more efficient than older ones and age of
sire hao significant (P<0.01) effect on NS/C for cows but non si nificant for
buffaloes.
9- The average NS/C decreased as age of dam increased in buffaloes a d it showed
contrary trend in cows. Age of dam significantly (P<0.01) affect NS C for both
species.
10- The highest conception percentages were obtained at the 2n~ service being 4S.9
and 41.7% for buffaloes and cows, respectively.