Ref Code: CAT37

Category

Teaching - 3 (Instructor : student ratio 1:3)

Research - 4

Objective

To visualise the structures of the reproductive tract and contents to describe the state of activity of the ovaries, the pregnancy status, number of foetuses, the stage of gestation (by embryo/foetal size), viability of the conceptus and any other significant features.

Alternatives to animal use for teaching

Students can be given preliminary instruction on abattoir material and demonstrations with visual aids but the technique must be applied to live animals.

Details of Procedure

Animals are examined while confined in a crush, with or without head bail restraint (depending on temperament). The contents of the rectum are carefully emptied using a gloved hand (with suitable lubrication) prior to insertion of the probe. The position of the tract may be determined during the preliminary operations. The ultrasound probe is then carefully inserted into the rectum. The operator needs to be aware of techniques to deal with straining and peristalsis of the rectum by the animal. Care must be taken to avoid perforation of the rectum by the hand or the probe.

The reproductive tract is located and the probe is moved over the extent of the uterine horns and body to determine pregnancy status, stage of gestation and number of foetuses present. The operator examines the uterine fluid, the embryo/foetus for viability and size and any other features of the tract or conceptus that may be relevant. The ovaries can be located and examined for presence and size of normal follicles, corpora lutea and significant structures such as cystic or luteinised follicles.

Suitability of animals for examination depends on their size and the size of the operator’s hands. In general, animals of 250-300kg liveweight or greater, pose no problems, but smaller animals may be examined with suitable precautions.

Drugs, chemicals, or biological agents

None are generally applicable. However, a spinal block anaesthetic (as used in non-surgical embryo collection) can be used if the procedure were to take more than about 10 minutes. This acts mainly to make the manipulation of the tract easier for the operator. Routine procedures usually take less than 5 minutes per cow with competent operators and therefore do not require any sedation or anaesthetic.

Impact of procedure on the wellbeing of animal(s)

Inexpert practice of the procedure may result in severe straining, ballooning and bleeding of the rectum. However, with competent operators, this procedure has minimal impact on the animals. No adverse effects on the cow or her conceptus particular to ultrasound examination have been found and the movement of the probe over the tract and ovaries is less of a disturbance than with palpation techniques. Examinations should not continue if severe discomfort is perceived.

Reuse and repeated use

Cows should not be used for more than two consecutive days if examined for more than a total of 2-4 hours in any one day. Daily examinations (or several times within a day) will cause no problems if examinations are of short duration (up to five minutes), provided other restrictions and cautions are observed.

As for manual pregnancy testing (SOP CAT36), there should be a maximum of five examinations per animal at the initial session, with a maximum of eight at subsequent sessions. Animals may be reused on a second day after an overnight rest.

Care of animal(s) during/after procedure

Generally, no special care is necessary, but awareness of the animal’s reactions to the procedure should be observed and undue stress prevented.

Pain relief measures

Examinations should be discontinued if undue stress or pain is apparent.

Qualifications, experience or training necessary to perform this procedure

Competence in handling cattle, followed by adequate demonstration and instruction. Users need to demonstrate proficiency by their accuracy of diagnoses and ability to conduct procedures within reasonable time constraints, while observing good animal handling techniques. Some procedures may be subject to restrictions by legislation.

Demonstrator: Experience with the procedure. Thorough knowledge of the physiology and anatomy involved. Demonstrators should have a sound knowledge of reproductive physiology, embryonic and foetal development, ovarian dynamics and the relevant endocrinology. Knowledge of the physics of ultrasound and associated equipment is also necessary.

Students: Students may be learning the techniques as part of certificate or degree courses, as technical assistants or may be livestock producers or service agents to the industry. Prior experience with handling livestock and a background knowledge in reproduction is desirable. The extent of knowledge of reproductive physiology required, will vary with the intended use of techniques by the student (eg research versus diagnoses for management decisions).

References

Pierson, R.A. and Ginther, O.J. (1988), Theriogenology. 29: 3-20

Pierson, R.A. et al., (1988), Theriogenology. 29: 21-37

Kastelic J.P. et al., (1988), Theriogenology. 29: 39-54.