In the past two years, with the rapid increase in the yield of dairy cows, the problems of dairy cows in terms of health, longevity, and reproduction have become increasingly prominent. The proportion of cattle with reproductive disabilities such as post-partum complications and repeated infertility has increased year by year. In particular, post-partum irritability has become a widespread breeding problem in high-yielding dairy herds, directly affecting reproduction rates and the economic benefits of cattle farms. Domestic and foreign scholars have conducted extensive experimental research on the treatment of post-partum dairy cows, with different results. The author believes that the key to effectively solve the post-partum uneasiness problem is to "find the cause, symptomatic treatment."
First, the main factors causing dairy cows postpartum languor
1, nutrition
High or low nutritional levels or nutritional imbalances are the most important factors affecting post-partum dairy cows. Inadequate energy supply during the perinatal period can lead to the body condition not being able to recover in time, delayed uterine involution, ovarian dysfunction, and severe nutritional deficiency ketosis. Conversely, if the perinatal energy is excessive, leading to obese prenatal obesity, postpartum will use more body fat for milk production, and severe cases will cause consumption of ketosis, which will also lead to postpartum compulsions and low conception rates. Low or high dietary protein concentrations can also result in low fecundity of dairy cows. Bruckental (1989) has shown that crude protein in dietary dry matter exceeds 19%, increasing the number of empty days, delaying the first estrus after childbirth and reducing the conception rate. People often feed high-level protein diets in pursuit of milk production. On the one hand, cows consume more energy to metabolize excess nitrogen, which is more likely to cause negative energy balance. On the other hand, too much protein (whether rumen-degrading protein or ruminal protein) will eventually enter the blood as urea nitrogen, leading to increased blood and milk urea nitrogen levels, which will lower the intrauterine pH and change intrauterine The composition of the liquid produces toxic effects on sperm, eggs, and embryos. At the same time, it will reduce the synthesis of prostaglandins, reduce the concentration of progesterone, and reduce macrophage immune function, thereby delaying the first estrus time, reducing the conception rate, and postponing the self-purification of the uterus. In addition, the imbalance of calcium and phosphorus, vitamin A deficiency, and the lack of copper, iodine, manganese, cobalt and other trace elements can also lead to postpartum languor, irregular estrus cycle, low conception rate and so on.
2. Disease
Some of the diseases that occur during the perinatal period of cows can also lead to long periods of postpartum cramps. When cows suffer from metabolic diseases such as ketosis, acidosis, indigestion and true gastric transposition, they are prone to cause tediousness and low conception rates. These metabolic diseases are directly related to nutrition and feeding management and are the manifestations of nutritional abnormalities in dairy cows. Inflammation of the uterus can also cause cows to be irritated, and no placenta is the main cause of metritis. In addition, the timing of midwifery and midwifery may lead to injury of the birth canal. In this case, if the environment is unsanitary and the midwifery tools are unclean, it can cause uterine inflammation, and severe cases can cause systemic infection and develop sepsis. When cows suffer from metritis, the endometrium does not release PG, and the mechanism of dissolving the corpus luteum in the body is destroyed. Generally, the first post-partum estrus time is delayed and the estrus is irregular; others have regular estrus cycles, but are often infertile. Mastitis can also affect reproduction. The fever caused by mastitis has a negative effect on the developing follicles and embryos, and the fever also causes a decrease in feed intake, which indirectly aggravates the negative energy balance in early lactation. In addition, some compounds or hormones secreted by the body's immune response to mastitis are not good for maintaining pregnancy. Foot disease can also lead to lack of love. The pain and discomfort caused by hoof disease causes cows to limp. Cows with hoof disease are reluctant to move, lie for long periods of time, and have reduced contact with the same group of cows. As a result, the estrus symptoms are not obvious, or the estrus is not estrus. In addition, the disease caused by the decline in feed intake, which affects the milk production, resulting in weight loss and exacerbated the negative balance of energy.
3, hormone secretion disorder
High-yielding dairy cows are more vulnerable than low-yielding dairy cows. This is because high-producing dairy cows have high prolactin levels in the peripheral blood during lactation. Negative feedback suppresses the secretion of hypothalamic gonadotropin-releasing hormone and reduces the secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in the anterior pituitary. At the same time, the normal response of the ovary to LH is reduced, resulting in tediousness. In addition, if the cow's ovaries develop persistent luteum, corpus luteum cysts, follicular cysts, and ovarian quiescence, they can cause hormone disruption, the feedback regulation of the hypothalamus-pituitary-ovarian axis can not be restored, and the cow's normal estrus cycle is disturbed. Cause cows postpartum languor. In recent years, some newly discovered hormones such as Leptin and Ghrelin have also been closely linked to the estrus of dairy cows and deserve attention.
4, environmental stress
High-yielding dairy cows are subject to various stresses during the perinatal period, including environmental changes, dietary changes, sudden changes in physiological function before and after delivery, and so on. The more adverse stress a cow receives, the greater the negative impact it will have, and this will trigger a series of chain reactions that ultimately result in decreased milk production and decreased reproductive performance. Therefore, a good management plan should be able to minimize various adverse effects of dairy cows during the perinatal period.
5. Reserve cattle breeding
The cultivation of reserve cattle will indirectly cause breeding problems such as lack of post-partum dairy cows. The first-in fetal cow has higher lactating persistence than the calf, while the first-born fetus is still in the process of continuous development. Therefore, the demand for nutrients from the first fetal cow is higher than that of the mature cow. If the young cows have low birth weights, it will directly lead to insufficient dry matter intake, which will restrict the growth and development of the first-born cattle, which will exacerbate the negative balance of nutrition and lead to prolonged post-partum weight loss and long-term estrus. At the same time, ignoring the breeding of reserve cattle can easily lead to delayed development of reproductive organs of the reserve cows, which is characterized by small ovarian volume, hard texture, inactivity, and infantile development of the uterus, which delays the age of the mating month. Therefore, we must pay attention to the cultivation of reserve cows, and control the daily weight gain from 0.7 to 0.8 kg, so that the body condition score at the time of breeding reaches 3.0. If the daily increase is greater than 0.9 kg, it will cause obesity, causing difficulties in mating, dystocia and metabolic disorders. At the same time to do timely breeding, physical (body height and body condition) is the factor that determines whether the reserve cow participates in breeding, not age. You can participate in breeding when the initial cow body height reaches 127-130 cm and the body weight is 375 kg.
6, reproductive management
Inadequate reproductive management will directly induce a series of reproductive diseases, such as post-partum dairy cows, especially the timing of cow midwifery, midwifery hygiene, and postnatal monitoring. In general, cows will naturally give birth, but sometimes because the fetus is too large or the calf's body size is small, it often requires human intervention to deliver and implement different degrees of midwifery. If the midwifery is too early, it is easy to cause damage to the birth canal, which may cause hidden troubles in the uterus infection; and if the midwifery is too late, it can easily cause the fetus to suffocate and die. In addition, rough handling, excessive strength, and weak sterility consciousness during the midwifery process can also lead to unnecessary injuries and uterine inflammation. In the early postpartum period, the cow's birth canal has varying degrees of damage, the cervix is ​​not completely closed, the endometrium has not yet formed an effective white cell barrier, and a large amount of pus, lochia, or effusion accumulates in the uterus, all of which contribute to the invasion of pathogenic microorganisms. The favorable conditions. At this time, if postpartum monitoring is not in place, some placenta won't be discharged, lochia will not be drained for a long period of time, and endometritis cows will not receive timely follow-up treatment, which will cause uterine involution to be postponed and miss the best timing of treatment, leading to postpartum longevity. The lack of time, repeated infertility and a series of reproductive problems.
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