1. Harm
If the feedstuff provided by cattle farmers does not have a reasonable proportion of all kinds of nutritional facts, some nutrients will be insufficient or excessive, or the metabolic process of nutrients in the body of the dairy cow may be imbalanced, which may lead to the metabolic disease of the cow. If dairy cows eat diets containing too much high protein, but lack of carbohydrates and high-quality roughage, it will also lead to metabolic disease.
Feed purchased by dairy farms is of poor quality and contains low amounts of protein and fat. If dairy cows do not get enough protein and fat, metabolic diseases will also occur. Besides, if the proportion of calcium and phosphorus in the feed is not appropriate, or some trace elements are simply lacking, it will cause metabolic diseases. The nutrition needed daily for high yield, nutrition, delivery and lactation of cows can not be satisfying. The result is that the energy in the body is in a negative balance state.
Before and after delivery, the gastrointestinal tract of cows can only absorb a very low amount of calcium. After delivery, a large amount of blood calcium will be transferred to the colostrum. The ability of the cow to use bone calcium decreased after delivery because the decrease of blood magnesium content harmed the use of bone calcium. If the cows in dry milk supply too much energy, it will directly lead to overweight cows before delivery. Then the appetite of dairy cows will be correspondingly reduced after production, and the nutrient intake can not meet the needs of dairy cows, which eventually leads to metabolic diseases in dairy cows.
2. Pathogenic characteristics and manifestations
Ketosis - subclinical ketosis: In the actual clinical production, the incidence of clinical ketosis accounts for 2% and 20% of the lactating cows, which generally occurs in the first lactating month of dairy cows. But in production, the subclinical ketosis is more serious. The incidence is 1020 times of clinical ketosis. The milk production of infected cows is significantly reduced, resulting in a significant decline in their health level, but there is no obvious manifestation of the disease, so it is often neglected by the cattle breeders, resulting in serious economic losses.
In general, the highest incidence can be seen within 1030 days of postpartum dairy cows. Clinical symptoms can be divided into digestive and nervous types in actual production. The appetite of diseased dairy cows decreases, milk production decreases, obvious neurological symptoms can be seen, blood ketone content increases and blood sugar decreases. Specific ketone body odors can be detected in the exhaled gases, urine, and milk of diseased cows. Most of the subclinical dairy cows showed loss of appetite, decreased milk production and continued to lose weight. The incidence of postpartum mastitis and uteritis increased.
Postpartum paralysis, i.e. postpartum hypocalcemia, which is often referred to in clinical production, usually has a 1.2% 14.1% morbidity rate in dairy herds. Most of them will show symptoms of hypocalcemia within three days after dairy cow production, and even 75% of them will have clinical manifestations of hypocalcemia. But because the clinical manifestations are not very obvious, it is not allowed. It is easy to be found that if subclinical hypocalcemia occurs in dairy cows, it will cause more serious losses, and the milk yield and reproduction rate of diseased dairy cows will decrease significantly. The clinical type of cattle suffered from depression, general muscle weakness, coma, paralysis, lying on the ground and other symptoms. However, subclinical cows often suffer from decreased appetite, decreased milk production, postpartum diseases and so on.
Rumen acidosis and sporadic diseases are common in infected dairy cows. Infection can occur all year round, but especially in winter and spring. The incidence of 16 pregnant dairy female cows in the clinic is relatively large, which can generally account for 77% of the clinical incidence. The incidence of the disease is the highest among the dairy cows in labor and three days after delivery, and the incidence will exceed 70%. If the cow's milk production exceeds 6000 kg, the incidence is usually 65%. Dairy cows feed daily, if the supply of large amounts of concentrate, inadequate or lack of roughage, will lead to a relatively high incidence of dairy cows.
Endotoxin poisoning, if dairy cows eat a large amount of concentrate feed, the pathogenic substances in the rumen, such as histamine and bacterial endotoxin, will promote the process of disease. Because of the increase of histamine content in vivo, cows may suffer from hoof pain and hoof leaf inflammation in the clinic. After feeding concentrate, when the rumen pH value of cattle dropped to about 5.5, the activity and regeneration ability of ciliates disappeared, the microflora of rumen changed greatly, Gram-positive bacteria increased, Gram-negative bacteria died in large numbers and released bacterial endotoxins, endotoxin absorption, acting on tissues and organs, causing tissue damage, and increasing. It aggravates the pathological process of acidic dyspepsia syndrome.
Four stomach displacement, including left and right stomach displacement. The incidence of abomasum displacement is about 3%. Usually, the incidence of obese and High-yielding adult dairy cows aged 2-5 and 2-7 years is more frequent. The highest incidence period is 1-6 months after delivery, and the peak period is within 30 days after delivery. The prevalence of the disease is from November to May of the second year, and cattle have no previous medical history and have a high mortality rate.
Hypocalcemia is the direct cause of displacement in dairy cows during childbirth. Increased acidity of the abomasum and delayed abomasum caused by long-term feeding of excess concentrate are the main causes. Subclinical ketosis is a risk factor. Besides, some chronic consumptive and infectious diseases such as fetal placenta retention, lameness, abortion, endometritis, mastitis, fatty liver and delayed for gastric diseases lead to decreased immune system function, loss of appetite, stop of rumination and promote the occurrence of abdominal metastasis.
