Cow embryonic development is abnormal. Heat stress, especially severe heat stress, damages the quality of eggs and embryonic development ability, and has an adverse effect on the embryonic development of dairy cows. Therefore, in hot weather, veterinary B-ultrasound is often used to detect the condition of the embryo. The effects of heat stress on the embryonic development of dairy cows can be summarized into the following four aspects: (1) The increase in temperature in the reproductive tract makes the uterine environment unfavorable for the development and implantation of fertilized eggs; (2) Oocyte aging, the quality and vitality of the embryo after fertilization are reduced; (3) Due to the need for heat dissipation on the body surface, the amount of blood flowing to the skin increases, which reduces the amount of blood flowing to the uterus, thereby reducing the nutritional supply for embryonic growth and development, causing embryonic development to be blocked; (4) For cattle that have been subjected to long-term heat stress, the progesterone level in their plasma decreases, and too low a progesterone concentration will produce a strong signal for dissolving the corpus luteum, causing the uterus to secrete prostaglandins, accelerating the dissolution of the corpus luteum, and causing early death of the embryo. It is very necessary to use veterinary B-ultrasound to detect the condition of the embryo in hot weather.

Measures to improve the reproductive efficiency of dairy cows in hot summer. Heat stress under high temperature and high humidity conditions is the direct cause of the low reproductive efficiency of dairy cows in hot summer. Therefore, physical methods such as ventilation and cooling, building sheds, and water mist spraying, chemical methods such as adding anti-heat stress additives, and changing feeding management methods such as increasing the concentration of feed nutrients, changing the work and rest time of dairy cows and the number of milking times, etc., can be adopted. All measures that can effectively weaken and reduce heat stress can reduce and slow down the heat stress reaction of dairy cows. This is the basis and premise for improving the reproductive efficiency of dairy cows under heat stress conditions, and veterinary B-ultrasound should be used frequently to observe the condition of cow embryos. Preventing the occurrence of reproductive diseases, strengthening estrus observation, improving the level of artificial insemination technology, and using veterinary B-ultrasound examinations are specific measures to improve the reproductive efficiency of dairy cows in hot summer.

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