How to choose black and white cows

Different uses of cattle have their own appearance, the body appearance of cattle to a certain extent can reflect its production performance, it can be said that the cow's body shape is a performance performance characterization, such as dairy cows have a well-developed breast organ - Breasts; Beef oxen has wide, deep and full-bodied body; oxen have strong bones and strong muscles and powerful limbs. Evaluation and selection of body shape of dairy cows is the first step in determining whether to stay with Amoy, followed by a comprehensive evaluation based on the genealogy and the production capacity to determine whether they are retained in the end. The methods for selecting these cows are described below. First, pedigree selection. Pedigree selection refers to the selection of the progeny and parental generation performance, and is actually the choice of genetic performance and heritability of dairy cows. The genetic properties and mutational properties of dairy cows are universal. Heritability is relative, and variability is absolute. According to calculations made by numerous experts at home and abroad, the heritability of milk production in dairy cows is 0.2-0.3, which means that only 20-30% of dairy cows' milk production is determined genetically by parents, while another 70-80% is bred Management, climate and other external environmental factors determine. According to this genetic rule, when selecting dairy cows, we must first look at its pedigrees, choose the progeny and parent generations (milk production rate, milk fat rate, lactation curve, etc.) to have good offspring, and then perform an appearance on the dairy cows. Select, affirm or negate on the basis of comprehensive assessment. Second, the choice of physical shape. The appearance of dairy cows is a characterization of the performance of dairy cows. The specific choice of dairy cows should focus on the selection of the entire body size. The ideal cow is delicate and graceful, with a wedge shape; the back is wide and straight, the buttocks are large and wide; the head and neck are delicate, and the two corners are short, thin, flat angles, with black angles bent forward and inward; limbs Smaller and clearer, tougher keys, strong hoof wall, small and compact hoof stitches, clear and flexible joints, hocks bending and moderate (to avoid joint bending too large or too small); body coat black and white (but not stressed black and white The proportion of hair is even less emphasized that the coat must be three large blocks of black). Cow's breast is an important identification rating site, the ideal shape of the breast is round and elastic; the length of the nipple is moderate, the nipple spacing is equal and moderate (bag and meaty breasts and breasts have sucking nipples and vice nipples Can not be left for species use); breast mirror should be flat and wide, close to the vulva and full of hind legs; milk veins should be thick and curved, milk wells should be large and round. Third, the choice of production performance. The choice of production performance mainly refers to the choice of milk production, milk fat rate (milk quality) and lactation performance. 1, milk production choices. Milk production refers to milk production in a lactation period (305 days), not measured on a certain day or at a certain stage. Dairy cows have different milk yields during lactation at different ages. Generally, milk production is measured from the second to the sixth birth. When the same cow measures the indicators of milk production, it is necessary to consider the times of birth, but also to consider the conditions of feeding and management. Blindly pursuing the milk production without considering these factors is a violation of the physiological laws of milk production of dairy cows, which will cause cows to age prematurely and lose their best. The time of milk production shortens the milk production life of dairy cows and reduces the milk production benefits of dairy cows throughout their lives. 2, milk quality choice. Milk quality refers to the level of milk fat content, milk fat rate and milk protein and non-fat solids ratio. At present, China mainly considers the level of milk fat, and the latter two items have less consideration. 3, milk speed selection. The speed of milk discharge refers to the average number of kilograms of milk extruded per minute during milking. The amount of milking is related to the frequency of milking and is also related to milking technology and proficiency. The standard milking frequency is 40-60 beats/minute, and the low frequency of milking will inevitably reduce the speed of milk discharge and reduce milk production. 4, pre-breast index selection. Pre-breast index = pre-breast milk production / total milk production 100%, the higher the index, the better the breast development, the higher the milk production. 5, the choice of lactation uniformity. Lactation uniformity refers to the stability of milk production during a lactation period, ie the normal distribution of the lactation curve. The milk production of high-yield dairy cows in the first three months of a lactation period is about 34% of the total milk production during the lactation period, and the milk production of the second three months (4-6 months after childbirth) is about 31.5%. Three months (7-9 months after childbirth) account for approximately 31.5% of milk production, and the final month's milk production accounts for approximately 3.0-3.5% of the total milk production during lactation. This is the characteristic of milk production of high-yielding dairy cows. . In addition, the choice of relationship between reproductive performance and longevity of dairy cows cannot be ignored.