الفهرس 
AbstractOnly 14 pages are availabe for public view
 |  | from | 102 |  |  |
| | | from | 102 | | |
Abstract
The present study was carried out on a total of 75 primiparous Holstein cows belonging to Al-Bostan dairy farm, National company of animal production, Armed Forces, Egypt during the period from January 2019 To October 2020. Cows were submitted to three experiments in order to fulfill the following objectives:
1. Study the effect of Propylene glycol drenching during the fresh period on pregnancy rate per timed AI following ovsynch protocol.
2. Study the influence of cow’s hormonal milieu and ultrasonographic features of ovarian structures during ovsynch on pregnancy rate per AI following ovsynch protocol.
3. Determine the impact of modification of the ordinary ovsynch protocol and AI strategy on PR/AI in primiparous Holstein cows.
In experiments one and two, 45 cows were used. 25 cows were drenched 250 ml propylene glycol once daily from calving to day 30 postpartum. The other 20 cows served as untreated controls. On day 55 postpartum, cows were enrolled into ovsynch protocol for synchronization of ovulation. Serum samples were obtained from cows on three occasions, at the first GnRH of ovsynch, on day of PGF injection and at TAI to measure progesterone. Concurrent with sampling, ultrasound examination was carried out to measure sizes of ovarian structures. On day 35 post-insemination, cows were checked for pregnancy using ultrasonography.
Results showed that drenching of propylene glycol did not affect PR/TAI significantly. Cows with subluteal progesterone concentrations at the start of ovsynch had numerically higher PR/TAI. In addition, greater progesterone at PGF and lower progesterone at TAI were associated with greater PR/TAI in synchronized cows, regardless of treatment. Further, milk production was greater in pregnant cows and was negatively correlated with circulating progesterone levels. Ultrasound exams revealed that drenching of propylene glycol did not affect size of CL at PGF or size of POF at TAI, meanwhile, size of POF was greater in pregnant cows.
In experiment three, 30 cows were submitted to ovsynch protocol, the first 10 cows served as control, the second ten cows received a second dose of PGF2 alpha 24 hours after the first one. The third group included 10 cows which received intrauterine AI. Serum was obtained at TAI and also measurements as ano-genital distance, heart girth and weathers length were recorded for each cow at TAI. Pregnancy was diagnosed using trans-rectal ultrasonography on day 35 post-insemination. Results of this experiment showed that a second dose of PGF2 alpha given 24 hours after the first PGF2 alpha of ovsynch gave higher PR/TAI, compared to intrauterine insemination and control cows, but the difference was not significant. Also, this double PGF dose was associated with numerically lower progesterone values at TAI. Correlation analysis showed a favorable correlation between AGD and PR/TAI regardless of treatment. Meanwhile, unfavorable correlations were observed between serum progesterone at TAI and PR/TAI and between heart girth and PR/TAI.