Cow age determination method
1, according to the teeth to determine the age of the cow's teeth can be divided into incisors, premolars, posterior molars, and the age of the cow is based on the occurrence of tooth cutting, removal and wear conditions to be determined. A total of 4 pairs of cutting teeth were symmetrically distributed, and the incisors, internal intermediate teeth, external intermediate teeth, and caries teeth were successively arranged from the middle to the two sides. According to the replacement of teeth, it is divided into milk teeth and permanent teeth. The correct distinction between milk teeth and permanent teeth is very important in age determination. The milk teeth are small and thin, and the teeth are whitish. The gap between the teeth is large and the teeth neck is obvious. The outer teeth are large in teeth, yellow or dark brown, the teeth and neck are not obvious, and the gap between the teeth is small. The relationship between tooth change and age in cattle is as follows: (1) Birth: There are 2 pairs of milk teeth (milk teeth and milk middle teeth) at the time of birth, and some of them also have milk middle teeth, and within one week, the milk teeth are also Grow out. (2) 3 to 4 months: Each milk tooth is fully developed, and the entire milk cutting tooth is arranged in an arc, and the leading edge of the tooth is arranged neatly. (3) 4 to 5 months: The teeth of the breast cup begin to wear, and the front edge of the incisor is linear. (4) 6 to 9 months: Each milk tooth wears in succession, the incisor and the inner and outer intermediate teeth have wear surfaces, the wear surface is in a horizontal oval shape, and the front edge of the molar teeth is in a strip shape. (5) 10 to 15 months: The crowns of the breast teeth and inner middle teeth have been worn. (6) 16 to 22 months: The tooth roots of the larvae become shorter and then fall off. At 18 months, 1 or 1 pair of permanent incisors appear. (7) 24 months: Permanent incisors are fully developed and reach the established height. (8) 2 years of age 1 to 6 months: Permanent incisors begin to wear, the roots of the intermediate teeth in the milk become shorter, and then fall off, giving birth to a permanent inner middle tooth at the age of 2 and a half years. (9) 3 years old: Permanent internal teeth are fully developed to reach the established height. Incisor wear, wear surface. (10) 3 years of age 1 to 6 months: Permanent inner teeth begin to wear out, the roots of the outer middle teeth become shorter and then fall off, and permanent outer middle teeth are produced at the age of 3 and a half years. (11) 4 years old: Permanent outer middle teeth are fully developed to reach the established height. The incisor and inner middle teeth continue to wear. (12) 4-year-old 1 to 6 months: The permanent outer middle tooth begins to wear, the root of the chylous tooth becomes shorter, and then falls off, giving birth to permanent caries at the age of 4 and a half years. (13) 5 years old: permanent dental caries fully developed to reach the established height. At this time, it is called "Qikou". (14) 5 to 7 months of age 5: The front of the molars is slightly worn and ribbon-like. The wear surfaces of other teeth become larger. (15) 6 years old and 2 months old: The wear surface of the caries occurs, and the wear surface from the cutting teeth, the inner and outer intermediate teeth to the caries teeth is in the form of a wide to narrow ellipse. (16) 6 years old 5 to 7 months: The tooth wear surface is square, and the wear surface of other teeth becomes larger. (17) 7-year-old soil 2 months: The tooth wear surface is nearly circular, and the inner and outer middle teeth wear a wide oval shape. (18) 7 years old 5 to 7 months: The tooth wear surface is round, the center tooth is square, and the wear surface of the tooth is widened. (19) 8-year-old soil for 2 months: The incisor wear surface shows a tooth star, and the inner middle tooth is nearly circular. For cows before Qikou, the age determination method is very accurate and is less than 3 months away from the actual age. As the age increases, the accuracy of the judgment decreases. 2, angle wheel judgment method This method is mainly suitable for cows. From the corner, one pit plus one adjacent bump is a corner wheel. Cows are prone to nutritional deficiencies during pregnancy and nucleation, and the development of horns is affected, forming a round of angles. In general, the first round of cows appears at the age of 2.5 to 3.0 for the first production floor of the cow. Calculating on an annual basis, the calving will increase one round at a time. This can add 1.5 to the total number of rounds. The ~2.0 year old is the estimated age of the cow. However, many factors have affected the accuracy of this method of judgment. Therefore, when using this method for age determination, it is better to combine the first method.