The age of dairy cows has a certain relationship with production performance. Dairy cows generally have the highest milk production period between the ages of 3 and 8 years and then decrease with age. The ages of the cows were identified. There were three types of appearance identification, round-point identification, and tooth identification. According to the appearance of the identification of age, only the age of the cows can be identified, and the age of the cows cannot be known. When the age of the rounds is determined, the resulting errors are larger; the teeth identification is more reliable.
Milk cows have certain regularity in their growth. The number of pairs of teeth that can be exchanged before the cow's 5 years old is calculated by adding 1 to it, ie, 1 pair of teeth is 2 years old, 2 pairs of teeth are 3 years old, and 3 pairs of teeth are 4 years old. After age 5, it mainly depends on the tooth surface wear and the structure of the bovine tooth. At the beginning of the wear, the teeth are flattened first, and then the change of the tooth surface is observed, which is initially a square or a horizontal oval shape; it is later deepened with the degree of wear. For example, when the clamp teeth are 6 years old, they are square; when they are 7 years old, they are triangular; when they are 8 years old, they are quadrilateral; when they are 10 years old, they are round; when they are 12 years old, they become smaller; when they are 13 years old, they are vertically oval. The other incisors have the same regularity as the jaws. With age, all incisors begin to shorten.
According to the identification of the cow's teeth, its age is more reliable, but it is still an estimated result. Since the change of tooth dislocation, growth, and wear is influenced by many factors, the results of the identification sometimes differ from the actual age. Such as early maturing varieties and grazing cows, the normal change is about six months earlier than the above age; a few cows are not hard or deformed teeth, it is difficult to accurately identify their age. In addition, the quality of the forage also affects the identification results; cows fed all year round have a slow wear of teeth; cows grazing all year round have poor forage quality and fast teeth wear.
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