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(US), estrus, estrum
a regularly occurring period of sexual receptivity in most female mammals, except humans, during which ovulation occurs and copulation can take place; heat


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 Estrogen, Reproduction (animal)



(also heat or rut), a stage in the sex and reproductive cycle, or period of sexual activity, in female mammals. Estrus recurs regularly before coitus at intervals characteristic for each species of animal—several days, weeks, or months. During estrus the mating instinct is aroused, and in most mammals ovulation occurs at the end of estrus. In polyestrous animals, estrus recurs periodically throughout the year. In mice and rats, for example, it occurs every four to six days; in guinea pigs, every 18 days; and in cows, every 21 days. In monestrous animals, it occurs once or twice a year, as in dogs and foxes. During estrus, morphological changes occur in the vagina and uterus; they are especially marked in such rodents as mice, rats, and guinea pigs.


The period in female mammals during which ovulation occurs and the animal is receptive to mating.
References in periodicals archive ?
For conducting WST, 1 mL of estrual cervical mucus was heated with equal volume of 5-10% Sodium hydroxide upto boiling point and after cooling the intensity of color changes were studied and graded as normal (turbid or no color), mild infection (light yellow color), moderate infection (yellow color) and severe infection (dark yellow color).
In a herd setting, groups of estrual cows form sexually active groups and engage in mutual mounting.
Los hallazgos citologicos obtenidos en las cuatro fases del ciclo estrual se pueden observar en la Fig.
The pH of estrual cervico-vaginal mucus of all 4 groups was alkaline (above 8) prior to treatment.
The present finding with respect to the distribution pattern of micro-organisms isolated from estrual cervical mucus of repeat breeder cows was more or less in close conformity with the findings of several earlier workers (Das et al.
Sin embargo, algunos reportes en novillas y vacas adultas durante el periodo estrual, refieren una disminucion de magnesio sanguineo aun en animales suplementados [30].
In all the three animals, the estrual mucus was found at external os and developed typical fern pattern upon smearing.
El estres termico se ha reportado como determinante en la liberacion de altas concentraciones de Cortisol, que afectan a la hipofisis anterior en su liberacion de la hormona luteinizante (LH) originando bajas concentraciones que afectan el ciclo estrual [17].
0 ng/ml like maximum value in the luteal phase of the estrual cycle.
Estos resultados son aceptables, considerando que los cuerpos luteos son estructuras que per manecen por mas tiempo en el ovario normal durante el ciclo estrual (11-15 dias) en comparacion con las estructuras foliculares (1 a 5 dias).
7], quienes obtuvieron alta correlacion en los momentos en que la actividad del cuerpo luteo es variable como durante el ciclo estrual pero muy baja cuando la actividad del cuerpo luteo se mantiene estable como en el caso de la prenez.