(a) Length of the estrus cycle The calculation method is: ? (adjacent) the number of days between two estrus (based on the date of occurrence); ? (adjacent) the number of days between two ovulation intervals. It is customary to count the occurrence of estrus as zero days, and zero days is the last day of the last estrus cycle. The cow's estrous cycle is 20-21 days, 18-24 days is a normal range. There are age differences in the length of the cycle, with young cows averaging 20 days and adult mothers having 21 days. (b) Length of estrus Metrics are based on the criterion of the length of estrus that is accepted for the duration of the climb. The range of estrus length varies greatly from 2 hours to 30 hours, usually 15-20 hours (c) Ovulation time 1 Measurement method Perform a rectal examination every interval (2 or 4 hours) until ovulation. 2 Calculation method Count the number of hours from the beginning of estrus to the time of ovulation. Or count the number of hours from the end of estrus to the interval of ovulation. In production practice, ovulation time and optimal insemination time should be estimated based on the time of occurrence of heat. The ovulation time of the cow is closely related to the nutritional status. About 75.3% of the cows with normal nutrition are concentrated within 21-35 hours after the start of estrus. Only 68.9% of the cows with low nutrition level are concentrated in the 21-35 hours. Inside. (D) Occurrence time of postpartum estrus The average estrus after delivery from beef calves was 63 (40-110) days after delivery, but most puerperal nursing cows did not have estrus during the year. Natural Field focus on produce Cosmetic Raw material, powder functions as an Antioxidant and whitening in cosmetic products. They can effectively treat freckles, old age spots, pigmentation, acne, delaying senescence and preventing ultraviolet radiation,absorbed by the skin through the cell membrane, and they are very effective as a cosmetic external applicatio. Skin-Whitening Cosmetic Ingredient,Skin-Whitening Powder,Skin-Whitening Extract,Skin Whitening Xi'an Natural Field Bio-Technique Co., Ltd. , http://www.nfingredients.com