Ultrasonographic assessment of superovulatory response in crossbred malabari goats
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Date
2007
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Department of Reproduction Gynaecology and Obstertrics, College Veterinary and Animal Science, Mannuthy
Abstract
A study was conducted to monitor the ovarian changes ultrasonographically in response to the superovulatory treatment in the crossbred Malabari goats and to compare the sonological findings with the direct visual appraisal of the ovaries.
Six does were superovulated with 133mg pFSH after the induction of oestrum using 1.5 mg norgestomet and 10 mg prostaglandin. Transrectal ultrasonography was performed during the various stages of the superovulatory treatment to ascertain the follicular development and dynamics in the responding does. Scanning done on the day of first dose of FSH treatment revealed the dominance of small follicles (10.83 + 1.70). By the day of AI small follicles reduced significantly and the number of medium as well as large follicles reached maximum (8.17 + 0.60 and 6.83 + 0.83 respectively). Ovary appeared distinctly enlarged due to the predominance of medium and large follicles. Ultrasonography was also performed on the previous day of embryo flushing to detect the ovulation rate which gave an indication regarding the probable embryo yield.
On day eighth after the onset of oestrus the does were subjected to surgical embryo collection and during this procedure, the superovulatory responses on both the ovaries were noted. Ovulation rate detected by ovarian ultrasonography was significantly lower than that observed on direct visual examination of the ovaries.
Out of the six animals selected for this study, three of them showed extensive adhesions in their reproductive tract and they failed to yield any embryo despite the presence of multiple ovulation sites on their ovaries. From the remaining three animals, a total of 22 embryo/ova could be recovered. The percentage of embryo recovery was found to be 50.1 and 82.18 of the recovered embryos were fertilized. The quality of the recovered embryos were assessed based on their morphology and developmental stage.
The present study indicated that ovarian ultrasonography helped to detect the follicle numbers as well as dynamics in the superovulated does. However, due to the underestimation of the closely lying CL, the inability to differentiate the prematurely regressing CL from the healthy ones and the presence of reproductive tract adhesions in the animals subjected to repeated embryo collection, the ovulation rate assessed by ultrasonography and that determined by direct visual examination of ovaries differed significantly.
The accuracy of this technique can be improved by eliminating animals subjected to repeated embryo collection and by minimizing the stressful situations due to the high frequency of manipulations and ultrasound scanning. The advancements in the ultrasonographic techniques and instruments in addition to the expertise of the technician will contribute for identifying follicular development in both normal cycling and superovulated does, thereby making it an integral part in the routine embryo collection and transfer in goats.
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