The appearance of the estrus cycle of dairy cows is the result of the periodic activity of the corpus luteum and follicles on the ovaries. The corpus luteum of the cow begins to shrink 5 days before the next estrus. The follicles begin to develop and gradually mature, which can be clearly distinguished on the cow B-ultrasound. The mature follicles secrete a large amount of estrogen, causing the cow to estrus. The cow ovulates 12-36 hours after the onset of estrus, with an average of about 27 hours. The corpus luteum begins to form 68 hours after ovulation, and the corpus luteum begins to secrete progesterone 4 days later. The corpus luteum is the largest 8 days after ovulation. This state is clearly known when the cow is observed with B-ultrasound. If the cow becomes pregnant after mating, the pregnant corpus luteum will shrink until 30 days after delivery, while the corpus luteum of the sexual cycle of the non-pregnant cow begins to shrink 14-15 days after ovulation or 5 days before the next estrus. The development of cow follicles can be divided into 4 periods, namely the emergence period, development period, maturity period and ovulation period. These four periods are very obvious when observed with B-ultrasound for cattle.

B-ultrasound training for cattle

During the follicle emergence period, the ovaries of cattle began to grow larger by B-ultrasound observation, and the follicles developed and protruded locally in the ovaries. The diameter was 0.5-0.75cm, and it was a hard bulge when palpated. At this time, the cow began to show estrus, but did not accept mounting. This stage generally lasts 6-12h.

Observed by B-ultrasound instrument for cattle, the follicles continued to grow to 1.0-1.5cm during the development period, and were round and obviously protruded from the surface of the ovaries. The follicle wall was tense and elastic, with a certain sense of fluctuation. At this time, the cow showed obvious estrus, accepted mounting, and could last for 10-12h.

Observed by B-ultrasound instrument for cattle, the follicles no longer grew larger during the follicle maturation period, and the follicle wall became thinner. The tension increased, and then softened, with a feeling of breaking at the touch. Uneven or excessive force when touching can easily cause the follicle to rupture. At this time, the cow's estrus performance weakened, refused to mount, and turned calm. Generally, it lasts for 6-12 hours, which is the best time for insemination and breeding. During the ovulation period, the follicle ruptures and ovulates, the follicular fluid is lost, the follicle wall becomes soft and concave, and it feels like two layers of skin when touched. It can also be observed by B-ultrasound in cattle. The corpus luteum begins to form 6-8 hours after ovulation. The diameter is about 0.6 cm and feels like meat.

link: https://www.bxlimage.com/nw/799.html