الفهرس 
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Abstract
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5-SUMMARY
Physiological Pa rt :
The present study was carried out during a period that lasted from
March, 1989 to December, 1989, at the cow’s experimental farm
belonging to Animal Production Department, Faculty or Agriculture, ;11
Moshtohor, Zagazig University.
It was aimed to detect the hormonal pattern of pituitary gland
(Prolactin) as well as ovary hormone (Oestradiol-I 713 ) during different
reporducrive periods (nonpregnancy period, pregnancy period (mel/ or
postpartum period).
Hormonal assays were carried out at the different interval times in
nonpregnant cows. Assays were carried also at three stages of pregnancy
namely early, mid and late pregnancy, however, at three interval times
postpartum period.
Besides, the relationship between both of the oestradiol, prolactin
hormones and milk yield during the three interval times of postpartum
period were also, investigated. Blood was were collected every week for
hormonal assays.
Hormonal assays were performed 111 the laboratories of
Endocrinology Research Unit, Radiobiology Department, Nuclear
Research Center, Atomic Energy Establishment, Enshas, Eb’YPt.
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Results obtained could be summcrized as follows:
Oestradiol (E2) level in nonpregnant cows:
1- Non of the factors studied (parity. cow within parity. stages of
reproductive periods, parity and stages of reproductive periods) had
significant effect on E2 level during the different intervals of times.
2- Serum E2 level showed insignificant variation among the various
intervals of nonpregnant cows. Its mean for the different intervals
amounted to 7.56 ± 2.24 pg/ml.
Oestradiol level in pregnant cows:
1- Variation due to either stages or cow within parity in serum E2 level
during pregnancy period was found to be significant.
2- Cow’s parity or interaction between parity and stage of pregnansy show
non-significant effect on serum E?
3- Serum E2 level increased as stage of pregnancy stage atvanced reaching
the wide individual variation particularly in the late stage where the
values varied from 12.8 - 72.0 pg/ml.
Oestradiol level in postpal”tum cows:
1- Variation due to either intervals, cow within parity or interaction
between parity and postpartum interval in serum E2 level during
postpartum intervals was found to be significant.
2- Different trend was found in serum E2 level due to cow’s parity.
3- The mean of serum E2 level of the different intervals was 8. I4±2 .31
pg/ml.
Prolactin (PRL) level in pregnant cows:
I
1- Variation due to stages in serum PRL level during pregnancy period
was found to be highly significant .
2- NOll of the factors studied had significant effect on serum PRL level.
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3- The mean values of the different stages amounted to 19.12 ± 3.18 ng/mJ.
Prolactin level in postpartum cows:
l-Serum PRL level effect on postpartum intervals exerted highly
si gni ficant.
2- Non of the factors studied had significant effect on serum PRL level.
3-The mean values of the different intervals amounted to 12.00±O.SR
ng/m1.
Oestradiol hormone and mill\. yield in postpartum cows:
I. Variation due to either postpartum intervals or cow within parity in milk
yield of postpartum intervals was found to be significant.
2- Parity and the interaction between parity and postpartum interval
showed non-significant effects on milk yield.
3- Parital linear and quadratic regressions of milk yield on oestradiol
hormone level were negative and nonsignificant.
Prolactin hOI”mone and milk yield in postpartum cows:
1- Variation due to postpartum stages or cow within parity in milk yield
during postpartum stages was significant.
2- Parity or the interaction between parity and Postpatum stages showed
nonsignificant effect on milk yield.
3- The parital linear and quadradic regression coefficients of milk yield on
PRL hormone were negative and nonsignificant.
Productive Part:
A total number of 2674 lactation records of local Egyptian cows
were used. Data covered the period from 1986 to 1991. These records
were used to investigate the non-genetic factors influencing 305-day milk
yre ld (305 MY), total milk yield (TMY), bi-weekly milk yield (BMY)
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lactation period eLP), number of services per conception (NSC), days
open (DO) gestation length (GL) and calving interval (Cl).
Results obtained can be summarized as follows:
1- Overall means of TMY~ 305MY~ BMY and LP were 2196.9Kg,
2189.0Kg, 100.5 Kg and 287.6 days, respectively. However, the
averages for NSC DO, GL and CI were 1.78, 139.3 days, 280.9 days
and 415.7 days, respectively.
2- Year of calving affected significantly (P<O.OOI) TMY, 305MY and
BMY and constituted a significant (P<0.05) source of variance in LP
and NSC. The contribution of year of calving in the variance of either
GL, DO or CI was insignificant.
3- Season-of-calving effects contributed significantly (P<O.OO1) to the
total variance ofTMY, 305 MY and BMY and nonsignificantly to the
variance of LP, NSC, DO, GL and Cl .
4- Parity affected significantly (P<O.O 1 or P< 0.001) BMY, NSC and GL.
However, no significant effects for parity on 305 MY, TMY, DO and
CI were detected.
5- Most estimates of partial linear and quadratic regressions of BMY on
age at calving were highly significant (P<O.OOI) while those of
305MY, TMY, NSC, DO, GL and CI were nonsignificant.
6- Most estimates of paritial linear and quadratic regressions of TMY,
305MY, BMY and LP on DO were not significant.
7- Cow effects were found to be mostly highly significant (P<O.OO1) on all
milk production traits as well as NSC, DO, and CI.