Ultrasonic Evaluation of Superovulation in Cattle

Cattoni, Javier (1991) Ultrasonic Evaluation of Superovulation in Cattle. MVM(R) thesis, University of Glasgow.

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Abstract

Embryo transfer is now a standard management technique. Effective embryo transfer is dependent upon the success of superovulation used to increase the yield of viable, transferable embryos. Numerous studies have identified problems with repeatability and predictability of response to superovulation. Given these problems, an effective method of monitoring follicular growth, ovulation and formation of corpora lutea would be a useful adjunct to the embryo transfer procedure. This study evaluated ultrasound for monitoring follicular growth, ovulation and formation of the corpora lutea in superovulated cows and correlated findings with embryo recovery and post mortem examination of the ovaries. Eleven cows were studied through a control and superovulated cycle; superovulation was achieved using pregnant mare serum gonadotrophin (PMSG, 3000 or 1500 i.u.). Ovarian response was monitored using a real time B-mode scanner equipped with a linear 7.5 Mhz rectal transducer. In the control cycle, which was similar in all cows, luteolysis was followed by growth of a single follicle to 1.4+/-0.2 cm. Ovulation was identified by collapse of the follicle and appearance of a corpus haemorrhagicum and was confirmed by measuring plasma LH and progesterone concentration. By day 5 the mature corpus luteum was visible. At the time of PMSG injection the majority of follicles were 6 mm. Two days later, 6-10 follicles > 8 mm were identified on most ovaries. Ovulation, in the superovulated cycle was identified as either disappearance of large follicles or obvious reduction in the size of the ovary. It was possible to identify but not to quantify corpora haemorrhagica. It was considered possible to quantitate corpora lutea on day 6 after oestrus. However, this estimate of corpora lutea number correlated poorly with the number counted at post mortem. Plasma progesterone concentration was monitored throughout the cycles, until embryo flushing. Very high progesterone concentrations were measured at embryo flushing; these levels correlated poorly with either the number of corpora lutea on the ovaries post mortem, or the number of embryos recovered. Histological study of the superovulated ovaries revealed many follicles showing differing degrees of lutcinisation. It was suspected that these luteinised follicles contributed to the high progesterone levels. It was impossible to categorise some fully luteinised structures as either corpora lutea or anovulatory follicles at post mortem. However, ovulation failure would have explained the poor embryo yield. In conclusion, ultrasound examination was useful for monitoring follicular growth in response to superovulation. It proved difficult to accurately quantify ovulation or numbers of corpora lutea. As an aid to predicting embryo recovery ultrasound monitoring was inadequate for the same reasons that rectal palpation, laparoscopy, laparotomy or progesterone concentrations have proven inaccurate, namely, abnormal luteinised structures on the ovary and aberrant progesterone production. This problem is inherant to the superovulatory treatment.

Item Type: Thesis (MVM(R))
Qualification Level: Masters
Keywords: Veterinary science, Animal sciences
Date of Award: 1991
Depositing User: Enlighten Team
Unique ID: glathesis:1991-78316
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 30 Jan 2020 15:33
Last Modified: 30 Jan 2020 15:33
URI: http://theses.gla.ac.uk/id/eprint/78316

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