The high temperature in summer results in the decrease of appetite, depression and milk production of dairy cows. Strengthening feeding and management can reduce the degree of heat stress and maintain stable and high yield of dairy cows in summer. So, what should we pay attention to the breeding of dairy cows in summer?
1. Temperature, Humidity and Temperature-Humidity Index
Dairy cows are cold-resistant and not heat-resistant animals. The optimum temperature for dairy cows is 10 - 20 ℃, under which the heat exchange of dairy cows is in equilibrium. In summer, high temperature and humidity lead to an imbalance of the body and systemic reaction, which is called heat stress. When the average temperature is above 25 ℃, cow's feed intake, milk production, and daily gain are significantly reduced; when the temperature is 40 ℃, cow's feed intake is 60% lower than that at 10-20 ℃; 50-60% relative humidity is suitable for cow's production performance, and high humidity is not conducive to heat regulation. Temperature- humidity index in meteorological elements is used to synthetically characterize the degree of comfort of animals in the meteorological environment. Mild heat stress was observed when the temperature-humidity index was 22-26 ℃, moderate heat stress was observed in 27-31℃ and severe heat stress was observed in 32-37℃. Dairy cows with a temperature-humidity index greater than 38 ℃were exposed to death threats.
2. Use cooling facilities to increase air circulation
For semi-enclosed cowshed, doors and windows should be opened, and a windproof curtain should be opened to increase ventilation. For open cowshed, if conditions permit, ventilation facilities or electric fans can be installed, which can reduce the temperature of the shed by 2 ~3 ℃ and accelerate the heat dissipation of the cow body. Installation of water mist spray or water curtain facilities and spray the head and chest of cows with cold water mist to reduce the temperature of the cow's body. But should pay attention to spraying water generally in hot noon, time should not be too long and the number of times should not be too frequent, otherwise, it will lead to excessive humidity in the shed, resulting in difficulties in heat dissipation of cows. Usually, the cowshed should be kept dry, without water accumulation, and the relative humidity should be kept below 80%.
3. Improving feeding methods
Adjust the feeding time and feed early and cool in the evening (before 7 am or after 9 pm). Increase feeding times and night feeding appropriately. It is suggested that more than 60% of the diet should be fed at night in summer, which can make up for the inadequate intake of dairy cows due to high-temperature anorexia.
4. Increase the nutrient concentration of the diet and adjust the composition of feed materials.
When the dry matter intake of dairy cows is reduced, the nutrient intake should not be reduced too much as possible. Improving the nutrient concentration of diet is an important measure. This includes two aspects. One is to adjust the ratio of concentrate to roughage in the diet, that is, to increase the proportion of concentrate and reduce the amount of roughage. This is not only because of the poor palatability and low nutrient concentrations of roughage relative to concentrates but also because of the more heat consumption and heat dissipation of roughage in the process of digestion and metabolism. However, it should be noted that the maximum proportion of concentrate should not exceed 60%. The second is to adjust the feed material of the diet, reduce the amount of general feed and increase high-quality feed such as whole cottonseed, soybean, high-quality forage, whole plant silage, etc. In the pre-lactation and high-yield dairy cow diets, fatty acid calcium, amino acid, and other rumen feed varieties should be added.
Rumen buffer was used. Due to the increase of concentrate ratio in summer diet, 0.750%~1.50% baking soda or 0.350%~0.40% magnesium oxide should be added to the diet to facilitate the digestion and absorption of nutrients in the rumen.
Addition of heat stress-relieving substances. Although the content of potassium, sodium, and magnesium in the general feed is relatively rich, due to the increase of sweating in hot weather, the general diet can not meet the needs of electrolytes in cows at this time, and the supplement of potassium, sodium, and magnesium in the diet is needed. To balance cation and anion in the diet of dairy cows, 30 to 50 grams of potassium carbonate, 60 to 100 grams of magnesium sulfate and 120 to 160 grams of salt can be added to the diet of each cow. As heat stress increases the consumption of vitamin A in dairy cows, the amount of vitamin A in summer diets should be doubled.
5. Ensure clean drinking water
Milk contains more than 87% water and it takes about 4 kilograms of drinking water per kilogram of milk production. So water is very important for dairy cows. The amount of drinking water of dairy cows is related to the amount of lactation and temperature. The lack of drinking water will directly affect the milk yield. In summer, the water consumption of lactating cows can be 3 to 5 times as much as that of lactating yield. Wash the sink and disinfect it regularly, replace drinking water to keep fresh and cool, and let the cows drink freely. This not only ensures milk production, but also increases cow excretion, takes away excess heat in the body, and maintains normal body temperature.
6. Strengthen hygiene management and disinfection
There are many mosquitoes and flies in summer, which not only disturb the rest of the dairy cows and affect milk production but also easily transmit the disease. Aerosol insecticides can be used to spray the body of cows and the surrounding environment regularly to eliminate mosquitoes and flies. It is necessary to clear the feces in time and keep the cowshed and livestock farm clean and dry. Sterilize cowshed with 5% Lysol or 2% caustic sodium solution once a week, or use quicklime powder to sterilize cowshed, deodorize and dehumidify, to reduce the occurrence of diseases in summer.