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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 ?
The disparity in results between studies could be due to differences in animal genotypes, age of cow, sire, semen, methodology, estrus detection methods, timing of AI, treatment,lactation number, season of the year, and herd management.
Application of electronic estrus detection technologies to reproductive management of cattle.
evaluate the sensor's estrus detection ability compared to conventional methods.
Causes influencing AI including the number and motility of spermatozoa estrus detection and timing of AI as well as the animals' physical condition can serve to explain the difference.
AREAS TO ASSESS PROFICIENCY IN BREEDING AND GESTATION: * Weaning to estrus length, days * Estrus detection * Breeding * Pregnancy check * Return to estrus * Moving and handling * Farrowing rate * Total number of pigs born * Total number of pigs born alive * Stillbirth rate * Rate of mummies
A survey conducted on the rural small holder dairy farms of Punjab revealed the lack of farmer's awareness about accurate and efficient estrus detection procedures (Ghuman and Singh, 2009).
Based on the results of continuous observation, Figure 4 and 5 depict the findings to assess the precision of estrus detection, if the observation for estrus was to be carried out during the three periods established.
Comparison of estrus detection techniques in dairy heifers.
Reasons for repeat breeding are multi factorial and include estrus detection errors, inflammation or anatomical impediments in the female reproductive tract and embryonic mortality (Pursley et al.
2002), as well as estrus detection and reproductive management.