estrus

also n.
The periodic state of sexual excitement in the female of most mammals, excluding humans, that immediately precedes ovulation and during which the female is most receptive to mating; heat.

[New Latin, from Latin oestrus, frenzy, gadfly, from Greek oistros.]

For more information on estrus, visit Britannica.com.

The period in mammals during which the female ovulates and is receptive to mating. It is commonly referred to as rut or heat. From one estrus period to the next there occurs a series of changes, particularly in the ovary, uterus, and vagina, termed the estrous cycle. With reference to the ovary, the cycle can be divided into a follicular phase, during which the Graafian follicles are ripening, and a luteal phase, during which the corpora lutea develop in the ovulated follicles. During these two phases, mainly estrogen and progesterone, respectively, are secreted, and these hormones control the uterine and vaginal changes. The beginning of the follicular phase is termed proestrus, and the luteal phase metestrus. Following the latter, there is a period of relatively little change, termed diestrus. In species in which the latter is prolonged, it is termed anestrus. See also Estrogen; Ovum; Reproduction (animal).

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also oestrus

noun

A regular period of sexual excitement in female mammals: heat, rut², season. See sex/asexual.

The time during the reproductive cycle in animals when the female displays interest in mating and in most species will stand to be mounted by both sexes and mated by males. In most cases the animal is about to or has just ovulated, and is therefore pregnable, but some, including pregnant ones, may not be in true estrus.
At the time of estrus there are behavioral signs and changes in the external genitalia. In cows these include the passage of very clear mucus, swelling of the lips of the vulva and hoof brush marks on the side of the rump. Mares show frequent urination with squatting, elevation of the tail, swelling and winking of the vulva and rhythmic extrusion of the clitoris. Ewes are not demonstrative other than positioning themselves close to the rams or teasers. Goat does bleat a lot, rub themselves against fixed objects and hold their tail high, urinate frequently and evert the clitoris. Bitches wander away, stand with their tails held to one side and are attractive and receptive to males. Queens may be very demonstrative, especially Siamese. They rub against anything, crawl with their belly close to the floor, roll and vocalize with a deep, throaty growl.

• e. detection — in natural mating the male is, in most situations, the best possible detector. In artificial breeding or in hand mating the need to pick cows which are on heat is of paramount importance. Techniques available include the use of infertile teasers combined with heat mount detectors, tail paint, chin ball or siresine harnesses. In dairy herds it is usual to dispense with the teasers and depend on other cows to pick out and mount the cows that are in heat.
— In sheep crayon or paint marking harnesses are used. In mares individual teasing with a pony or similar manageable male is used. In the other species detection is by simple visualization.
• e. expectancy chart — a wall chart for use at the dairy which points out those cows which are due to come into estrus during the next day or two and need to be observed closely.
• false e. — behavioral and external genital signs of estrus without ovulation occurring.
• e. induction — see estrus synchronization (below).
• no visible e. — abbreviated NVO (to accommodate the British spelling of oestrus) or NVE. Diagnosis indicating reproductive inefficiency; applied to cows which are not observed as being in estrus for a variable period, usually 50 days, after calving. Includes cows with anestrus due to various causes and failure of staff to observe or record estrus. A percentage of more than 10% of cows in a herd which have no visible estrus is an indication of a herd problem.
• silent e. — ovulation occurs, as detected by palpation or estrogen levels in the blood in the absence of behavioral signs.
• e. suppression — prevention of estral activity in companion animals without spaying them is practiced frequently. A variety of progestins are available and, at times, intravaginal and intrauterine devices have been used for this purpose. See also contraception.
• e. synchronization — aimed at having all of the animals in estrus, and later calving or lambing, at the same time. Prostaglandin injection is a common technique used to induce estrus in cows.
• unexpressed e. — see silent estrus (above).

Dansk (Danish)
n. - brunst, løbetid

Nederlands (Dutch)
oestrus (bronst)

Français (French)
n. - ¯strus

Deutsch (German)
n. - Östrus (Periode sexueller Erregung bei männlichen Säugetieren)

Ελληνική (Greek)
n. - (βιολ.) οίστρος, (σεξουαλικός) οργασμός

Italiano (Italian)
estro

Português (Portuguese)
n. - cio (m), libido (f)

Русский (Russian)
течка

Español (Spanish)
n. - estro, estímulo, inspiración

Svenska (Swedish)
n. - inspiration

中文（简体）(Chinese (Simplified))
动情期, 动情周期

中文（繁體）(Chinese (Traditional))
n. - 動情期, 動情周期

한국어 (Korean)
n. - 격렬한 자극

日本語 (Japanese)
n. - 発情, 発情期

العربيه (Arabic)
‏(الاسم) الدورة النزويه عند الحيوان‏

עברית (Hebrew)
n. - ‮תקופת הייחום, ייחום‬

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