Normal feline reproduction: The queen

Abstract

Practical relevance: Cats are seasonally polyestrous, meaning they exhibit multiple estrous cycles within a season, followed by a period of non-cyclicity. Cats cycle when the day length is long but can be induced to cycle year-round with 14 h of continuous artificial lighting. The feline estrous cycle includes the following stages: proestrus, estrus, interestrus and, if ovulation occurs, diestrus. Cats are induced ovulators and ovulate in response to multiple natural matings. Successful breeding in a cattery requires knowledge of the female's reproductive cycle, behavior and management, and often improper management can be the sole cause of infertility.

Aim: The aim of this review is to provide readers with an overview of normal anatomy, cyclicity, management and behavior of the queen. It includes a series of questions veterinarians can ask to obtain a baseline knowledge of the management of the specific breeding set-up.

Evidence base: The information in this article is based on the author's experience, as well as drawing on historical and current literature, and provides the most up-to-date review as possible.

Keywords: Female anatomy; breeding management; cattery management; estrous cycle; puberty.

Figure 1

Reproductive anatomy of the queen. Figure designed by Jamie M Douglas

Figure 2

(a) Ultrasound image of a normal postpubertal queen. The uterus (between the measuring calipers) is imaged longitudinally and measures 0.78 cm in diameter and is of normal echotexture. (b) Ultrasound image of a postpubertal aged queen with cystic endometrial hyperplasia. The uterus is imaged longitudinally. The uterine folds are prominent and can be observed as light and dark striping within the uterus. Although not shown, the uterus measured 1.4 cm in diameter in this queen, which had presented for subfertility

Figure 3:

Complete reproductive tract of a normal queen in diestrus, with the caudal tract opened to show the luminal anatomy. The red arrow indicates the urethral opening and the urinary bladder can be visualized just above the arrow. The vestibule has a larger diameter caudal to the urethral opening and the vagina narrows as it approaches the cervix (green arrow). The uterus is partially opened through the body and base of each horn to show the normal endometrium. The remainder of the uterine horn is toned and tortuous, indicating diestrus and the influence of progesterone. Several corpora lutea can be seen on the ovary on the right (white arrows)

Figure 4

Diagram showing the progression through the feline estrous cycle. Figure designed by Jamie M Douglas

Figure 5

Vaginal cytology of a queen in estrus. In this field, all cells are showing some degree of cornification based on the rough, irregular cell border and flattened appearance. Approximately half of the cells have retained nuclei (arrows), but these are small and dark, indicating pyknosis

Figure 6

Gross specimen from a queen in estrus at the time of ovariohysterectomy. Three follicles can be seen on the surface of the ovary (arrows) and measure 2–3 mm each

Figure 7

Vaginal cytology of a queen in the interestrus phase of the cycle. Some cells are cornified but make up <50% of all cells and the nuclei are not pyknotic. The remaining cells are smaller with less cytoplasm (intermediate and parabasal cells)

Figure 8

A queen in diestrus at the time of ovariohysterectomy. Three corpora lutea (CLs; arrows) are clearly visible within the ovary. Additional CLs were observed on the other ovary of this queen

Figure 9

Vaginal cytology of a queen in diestrus, showing predominantly parabasal cells

Figure 10

Vaginal cytology in a sedated queen. The moistened cotton swab is inserted into the vulva approximately 1 cm (just the cotton tip). The swab is rotated 1–2 times and then removed. The sample should be rolled evenly onto a clean slide and stained with Diff-Quik for evaluation. This procedure is tolerated well by most domestic cats that are in heat, and can usually be performed without sedation

Figure 11

This is the typical estrus posture, with crouched front legs and elevated hind end. The queen was displaying in front of the cage of an intact male and was also treading with her hind legs