Jorge Reyna from Sydney University has been researching embryo transfer and artificial insemination in alpacas. This is a glossary of terms used in reproductive medicine that we hope you will find useful.
BSc (Hons), MScVetSc (Sydney Univ.)
Alpaca Reproductive Technologies – ART
7/520 New Canterbury Rd, Dulwich Hill, NSW 2203 Australia
Phone: +61 2 9568 1370, Mobile +61 428 ALPACA
Embryo: Early stage of development of future offspring after fertilization of the oocyte (egg) by the sperm.
ET: Embryo transfer is one step in the process of removing one or more embryos from the reproductive tract of donor females and transferring them to one or more recipient females.
Donor: A female with superior genetic merits that are to be disseminated into the herd using superovulatory treatments to obtain multiple embryos to be transferred into recipients, thereby obtaining several valuable offspring per year.
Recipient: An inferior female that will carry a high quality embryo removed from the donor. Recipients need to be animals of proven fertility, good size and with a normal reproductive tract.
Hormone: A substance synthesized and secreted by a ductless endocrine gland that passes into the circulatory system for transport and inhibits, stimulates or regulates the functional activity of the target organ or tissue.
FSH: Follicle Stimulating Hormone is classified in the group of gonadotrophins that promote growth of the ovarian follicles, also called Graafian follicles. FSH is used in superovulatory treatments in donors to induce growth of several follicles at a time to obtain embryos.
LH: Luteinising Hormone secreted by the pituitary gland that is responsible for the rupture of the follicular wall and ovulation in the female.
GnRH: Gonadotrophin Release Hormone secreted by the anterior hypothalamic area, responsible for the release of FSH and also LH. GnRH is commonly used to induce ovulation in donors after the application of FSH, and also in recipients to synchronise reproductive status and to ensure that the recovered embryos will find the same conditions in the recipient’s uterus.
Oestrogens: Hormones produced by ovarian follicles that regulate the secretion of FSH and LH. Other functions are to promote sexual behavior, stimulate development of secondary sexual characteristics and also have an anabolic effect.
Progesterone: Hormone secreted by the luteal cells from the corpus luteum, the placenta and adrenal gland. When an alpaca is receptive to the male, it means that high levels of oestrogens are present in the blood. This animal will ovulate 24-30 hrs after mating and the ruptured follicle will form the corpus luteum. If fertilisation and implantation of the embryo occurs, the corpus luteum will secrete progesterone during the whole pregnancy period. If fertilisation does not occur, the corpus luteum will secrete progesterone until day 10-12 and then regress through the action of prostaglandin F2α. Progesterone is the hormone that makes the female unreceptive to the male.
Prostaglandin F2α: Hormone secreted by the uterus that induces luteolysis or destruction of the corpus luteum. When a female become pregnant, the developing embryo sends a signal to the uterus (maternal recognition of pregnancy), preventing the release of prostaglandin F2α.
Follicles: Rounded structures at the ovarian surface that looks dark when observed by transrectal ultrasound because of their liquid content. The follicle contains the egg or oocyte that will be released upon ovulation.
Follicular waves: A term proposed by Rajakoski in 1960 in cattle which refers to the growth and regression of ovarian follicles. Ovarian follicular dynamics in alpacas occur in waves as well. What this means is that when a new group of follicles start to grow at the ovary, there will be one which will grow faster and become dominant and will inhibit the growth of the rest. This dominant follicle will be present for a few days (10-12) and then regress. Then, a new group of follicles will start to grow again (new follicular wave) and a new dominant follicle will appear.
Corpus luteum: Solid structure present at the ovary after ovulation takes place. The CL is responsible for the production of progesterone, which maintains pregnancy in alpacas during the whole gestation period.
Induced ovulators: Those animals that need the copula stimuli to release LH and to ovulate. In these animals there is no oestrous cycle and the female present long periods of receptivity (>30 days) to the male, with short periods of non-receptivity (2-3 days). Camelidae are induced ovulators, as are cats. In the case of alpacas an induced ovulatory factor in the seminal plasma in males has been identified, which also produces the release of LH to ensure ovulation will take place after mating.
Superovulatory treatment in alpacas: A protocol to induce growth, maturation and ovulation of several follicles at the same time in order to obtain embryos from quality donors after natural mating. In general terms, a protocol to superovulate alpacas uses FSH in decreasing doses injected 12 hrs apart for 3 to 5 days. Twenty-four hours after the last FSH injection, a hormone to induce ovulation is applied, either LH or GnRH. At the end of the hormonal treatment, animals will be mated to fertilise those oocytes and will then be flushed 7 days later to recover the embryos.
Synchronisation of recipients: Preparing the recipient animals to accept the embryo harvested from the donor. It is necessary to have a synchrony between donor and recipients, so that the embryo removed from the donor will find exactly the same environment in the uterus of the recipient.
Cervix: Lower part of the uterus that connects with the vagina. In the case of alpacas, the cervix presents 2-3 regular or irregular rings.
Flushing: Procedure of collecting of embryos from the uterus of a donor female, using a Foley catheter that is introduced into the vagina, passing the cervix and reaching the uterine horns. It consists in repeated uterine injection of flushing media to remove the embryos and then collecting them to be assessed and transferred into the recipients. Flushing needs to be performed very carefully as the embryos can be damaged and will not then survive upon transfer to the recipients. In the case of alpacas, flushing is performed 7 days after mating.
Embryo assessments: Morphological evaluation of embryos in order to determine it they are transferable. For this purpose a stereomicroscope is used to determine which embryos are of sufficient quality to be transferred into a recipient.
Transferable embryo: Embryo that has passed the morphological assessment of quality and will be put into a recipient to complete pregnancy. A good embryo is evenly granulated and symmetrical.
Transfer to receptors: Procedure that consists in placing the embryo deep into the uterine horn using an insemination gun.
Transrectal ultrasound: A technique which uses the interaction of sound waves with a living tissue/organ to produce an image. Transrectal ultrasound uses a probe or transducer that is inserted into the rectum of the female and is led on to the ovarian surface, making possible a clear visualisation in real time, without direct manipulation, of the ovarian structure. It makes it possible to measure ovarian diameter, number and size of follicles, corpora lutea and to detect pathologies such as cystic ovarian disease.