When identifying the age of sheep in production practice, we should first make a rough judgment according to the body shape, appearance and behavior of sheep. For example, sheep with loose body structure, dull fur, dark and smooth horns, sunken eye sockets and low spirits, loose mouth, slow rumination, difficulty in getting up and down, poor movement and slow walking are generally older. On the contrary, you should be younger. But in order to identify the age of sheep more accurately, it is necessary to observe the mouth and teeth carefully.
Looking at the mouth (teeth) is a reliable way to identify the age of sheep. Mainly according to the growth, replacement, wear and tear of sheep's front teeth, and the shedding situation to judge the age of sheep.
Sheep's teeth are divided into incisors and molars, of which there are only four pairs of incisors in the lower jaw. The growth, replacement and wear of sheep change with the age of sheep. According to this changing law, the life of sheep can be divided into three age stages.
(1) deciduous tooth stage
Sheep's deciduous teeth are narrow and white.
From birth to 2 weeks old, from the first pair of exposed gums to the second pair of exposed gums;
The third pair grows, 2 ~ 3 weeks old;
The fourth pair grows, 3 ~ 4 weeks old;
All grow to the first pair, ranging from 4 weeks to 1 year.
(2) anterior teeth replacement stage
Sheep's permanent teeth are wide and yellowish.
The first pair of deciduous teeth fell off and the first pair of permanent teeth grew up, aged 1 ~ 1.5 years old;
The second pair of deciduous teeth fell off until the second pair of permanent teeth became 1.5 ~ 2 years old;
The third pair of deciduous teeth fell off until the third pair of permanent teeth grew to 2 ~ 3 years old;
When all the deciduous teeth (4 pairs) are replaced and the fourth pair of permanent teeth is flush, it is generally called "flush mouth", "new mouth" or "new lateral teeth", and the age is 3.5 ~ 4 years old.
(3) The tooth surface of permanent teeth appears obvious wear and fall-off stage.
The tooth surfaces of permanent teeth are all worn for 5 years, also known as "old mouth";
The tooth surfaces of permanent teeth are all ground into smaller squares, and the tooth gap becomes larger. At the age of 6, it is also called "water leakage";
Teeth loose or falling off, 7 years old, also known as "break";
The gums (gums) only have point roots or "point teeth", 8 years old, also known as old mouth;
All teeth are smooth or fall off, ranging from 9 years old to 10 years old, also known as mouth slip.
In view of the fact that it is difficult to judge the age of a sheep only by looking at its mouth when it is 6 years old, it is often judged whether it is useful by observing the wear of molars in production practice. Generally speaking, the molars of any useful old sheep should be intact. When the upper and lower jaws of sheep are closed, those whose jaws are not easy to move left and right still have the value of utilization or feeding.
Sheep are also born with four teeth (two pairs), and the replacement time and wear degree will also be related to the individual, the physical form of feed, the water quality, and even the age and nutritional status of ewes when they are pregnant. Generally speaking, the teeth of individuals born to strong, healthy ewes who are in prime of life are more wear-resistant and fall off later, and it is easier to judge the age by mouth than the actual age. Under the condition of house feeding, especially the sheep incisors fed with fine soft forage, it is easy to wear and fall off after harvesting or fine crushing, and it is often difficult to identify their age mainly based on tooth wear and fall off after 4 years old. Poor physical fitness and health, mainly grazing on the grassland with poor grass, drinking water with excessive fluorine all the year round, the front teeth of sheep born to the old, weak and sick ewes generally wear faster and lose their teeth earlier, and the age judged mainly by the change of mouth teeth is also easy to be older than the actual age. Because it is not very reliable to identify the age by mouth, in order to determine the age of sheep more accurately, in the case of group breeding, especially large-scale sheep breeding, it is best to wear ear tags marked with the year of birth.