To obtain the best results the subjects should have attained their maximum yield of milk and be from five to seven years old. The best period is six weeks to two and a half months after calving. Neglect of these considerations is liable to be followed by inappreciable, doubtful, or bad results.
The influence of castration on fattening is explained by the suppression of œstrum.
Manual Technique.—An ovariotome with a hidden blade and an écraseur with an extra long stem are the only instruments required. The animals should be prepared for some days by diminishing their food supply and administering gentle laxatives.
Acute or chronic lesions of the genital tract should be held to contra-indicate operation, and it should be noted that tuberculous animals are particularly liable to awkward complications.
On the day of operation an abundant enema is given, to empty the rectum, after which the vagina is washed out freely with a lukewarm solution of some non-irritant antiseptic. The hind quarters, and particularly the neighbourhood of the anus, vulva, base of the tail, etc., should be carefully washed and disinfected with a solution of lysol, cresyl or carbolic acid.
Fig. 319.—Ovariotome.
The patients are secured in a standing position, a rope being passed in the form of the figure 8 around the hind limbs above the hocks, and the animal is then firmly thrust against a wall by several strong assistants.
The operator’s hands and instruments must be rigorously disinfected.
The operation comprises three stages: