1. Biological characteristics of chicken: Chicken is avian in zoology and has the biological characteristics of birds. In the past 100 years, due to people's continuous cultivation and improvement of their environmental conditions, especially in recent decades, with the development of modern genetic breeding, nutritional chemistry, electronic physics and other scientific technologies, the production capacity has been greatly improved. The biological characteristics of the chicken after transformation are the economic and biological characteristics of the chicken.
(1) The metabolism is strong: the body temperature of adult chicken is 41.5 ° C, and the pulse per minute can reach 200-350 times. Therefore, the basal metabolism of chicken is higher than other animals, with rapid growth, early maturity and short production cycle.
(2) Strong fertility: Chickens are oviparous animals, and the offspring must be subjected to sperm hatching. The hen's ovaries showed 12,000 follicles under the microscope. The high-yielding laying hens have more than 300 eggs per year, and a large group of 280 eggs have been produced. The cock's reproductive capacity is also quite strong. Although the cock's semen volume is small, the concentration is large, the number of sperm is large and the survival period is long. Only the cock with 10-15 hens can obtain a higher fertilization rate. The sperm of the chicken can survive in the hen's fallopian tube for 5-10 days, and the individual can survive for more than 30 days.
(3) High nutritional requirements for feed: A high-yield hen produces an egg weight of 15-17 kg a year, which is 10 times its body weight. Because the chicken mouth has no chewing action and the large intestine is short, a small amount can be digested except the cecum. In addition to cellulose, other parts of the digestive tract cannot digest cellulose, so chickens must feed on nutrients rich in nutrients.
(4) Sensitive to environmental changes: Chicken's vision is very sensitive, and all abnormal factors such as light and abnormal color can cause “shocking”; chickens are not as good as mammals, but sudden noise can cause chickens. The group is panic-stricken; in addition, the evaporation of the body water and the regulation of heat energy are mainly achieved by the respiration, so it is sensitive to environmental changes, so the chicken industry should pay attention to controlling environmental changes and reducing the stress of the flock.
(5) Poor disease resistance: Due to the anatomical characteristics of chickens, the disease resistance of chickens is determined to be poor. In particular, the lungs of chickens are connected to many chest and abdomen airbags. These airbags are filled in various parts of the chicken body and even enter the bone cavity. Therefore, the infectious diseases of chickens are transmitted by the respiratory tract, and the speed of transmission is fast, the incidence is serious, and the mortality rate is high. . Undead also seriously affects laying.
(6) Suitable for large-scale breeding: Due to the strong colonization of chickens, it can still exhibit high production performance under high-density cage conditions. In addition, the chicken's feces and urine are thicker, and the drinking water is less and not chaotic, which creates favorable conditions for mechanized feeding management. In particular, chickens are small in size, and each chicken occupies only 400 square centimeters of the bottom of the cage, that is, 25 chickens per square meter of cage bottom area. Therefore, in the livestock and poultry breeding industry, the highest level of factory feeding is the breeding of chickens.
2. Classification of chickens of different varieties: At present, there are more than 2,000 varieties of chickens known in the world, and there are several varieties of each variety. Different varieties reflect different body types, external forms, internal structures, production performance and economic uses. In order to facilitate research and practicality, chicken breeds are often divided. The usual classification methods are:
Standard taxonomy: Before the 1950s, chickens were classified into classes (by region of origin), type (according to use), varieties (based on breeding characteristics), and varieties according to internationally recognized standard classifications.
Modern classification: In order to adapt to the production and exhibition of modern poultry industry, it can be divided into egg-based and meat-based (ie, laying hen and broiler) according to economic performance.
(1) Laying hens: The production should be used to produce commercial eggs. According to the color of the eggshell, it is divided into white shell chicken and brown shell chicken. Its characteristics are: the general body is smaller, the body is longer, the hindquarters are developed, the skin is thin and thin, the muscles are firm, the feathers are tight, and the temperament is lively and active. Generally, the annual output of eggs can reach 270-300 pieces.
(2) Broiler chicken: It is mainly selected into broiler chickens through the hybridization of meat-type chickens. It is characterized by large body size, wide body and deep and short, muscular chest, and a square tube shape; small crown, short and thick neck, thick short bone; muscular, gentle temperament, slow movement, rapid growth and easy fattening Generally, the weight of 6-7 weeks old can reach 2 kg or more.
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