Study of the estrous and ovarian activities of damascus goats under different weaning systems .
Abstract: The effect of lactation and suckling manipulation on the reproductive
performance was studied in 37 Damascus does raised in Egypt during the
period from March/ April till estrus occurrence and mating. Following
parturition, does were divided into lactating and non- lactating groups.
Lactating does were grouped according to their weaning systems: group A
(suckled for 60 days) and group B (suckled for 120 days). Group C included does which did not kid (non- lactating does).
The time of the resumption of sexual activity was not significantly
different between lactating and non- lactating does or between does groups of the different suckling length.
Plasma progesterone levels were low in all does during the first 14- 15
weeks from the start of the experiment (March/ April), which indicate the
absence of ovarian activity during this period. An increase in progesterone
concentrations was detected at the end of June till the onset of the 1st estrus in all doe groups, indicating the occurrence of one or more ovulatory anestrous (silent ovulation).
Prolactin concentrations in the three groups showed that lactating does
had significantly higher levels than non- lactating does. In addition, prolactin levels were significantly higher in lactating does during suckling than when machine milked. During postpartum progesterone levels were significantly negatively correlated with prolactin levels, but progesterone levels were found to be unaffected directly by prolactin concentration.
Average progesterone levels in all does before the onset of the 1st
estrus were lower than those detected during the luteal phase. A decline in
plasma progesterone concentrations between 60- 24 hours before the second estrus, indicating corpus luteum regression, was observed. Progesterone
concentrations in pregnant does averaged 4.57±2.83 and 24.46±3.05 ng/ml at 2 and 12 weeks of gestation respectively; sudden decrease then followed just before kidding.
Estradiol levels during the luteal phase in all groups were lower than the pre-ovulatory peak. During the 2nd heat does of group A showed successive elevation in estradiol to reach the highest level at the end of the estrus, while does of groups Band C manifested estradiol peak at the onset of estrus followed by successive decline reaching the lowest level at the end of estrus.
No distinct trend for LH was detected during the estrous cycle. LH
levels at the onset of the 1st estrus in the three groups were higher than
average levels before estrus. LH levels were significantly correlated with
estradiol levels (P<0.03, r = 0.2).
Plasma FSH levels in all doe groups were found to be negatively significantly correlated with estradiol levels (P<0.01, r = -0.2), as well as, with progesterone levels (P<0.001, r = -0.3) before the 1st heat and during the luteal phase, suggesting that FSH level is controlled by the negative effect of the high progesterone or estradiol concentrations. In all groups, high FSH levels were observed at the time when progesterone or estradiol levels were low.
During the 2nd heat FSH levels were negatively, however, non- significantly, correlated with progesterone levels. Prolactin levels were negatively significantly correlated with progesterone levels. Prolactin levels showed an increase at the onset of estrus in all does of the different groups. The pre-ovulatory prolactin may be involved in the establishment and function of corpora lutea.
The relation between sex hormones before and during the 1st estrous
cycle and the 2nd heat was discussed. In addition, the effects of lactation and suckling regimes on the resumption of the estrous activity and the changes of hormonal profiles were disputed.
Key words: Goat, Damascus, ewes, postpartum, estrous, heat, ovarian
activity, suckling, lactation, progesterone, estradiol, LH, FSH, prolactin,
Publication year 2002
Availability location مكتبة معهد بحوث الانتاج الحيوانى - شارع نادى االصيد - الدقى - الجيزة
Availability number 756
Organization Name
Department Sheep and Goat Research Department
Author(s) from ARC
Agris Categories Animal physiology - Reproduction
AGROVOC
TERMS		 Ewes. Fsh. Goats. Lactation. LH. Ovarian cysts. Progesterone. Prolactin. Suckling.
Proposed Agrovoc ovarian activity, suckling ;
Publication Type PhD Thesis
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