What are the harmful effects of heat stress in dairy cows?
In summer, when the weather is hot, even slightly improper management during dairy cattle farming can trigger heat stress in dairy cows. Heat stress is extremely harmful to dairy cows, and if it is not dealt with in time, it can cause huge losses for farmers. Many friends also do not understand what this heat stress is. Do not worry, let us take a look together with Qinnongwang.
What is heat stress in dairy cows
Heat stress refers to the sum of nonspecific responses produced by the dairy cow's body to a hot environment under high-temperature conditions. Its purpose is to mobilize the body's defense functions so that it can overcome the adverse effects of a high-temperature environment and maintain bodily stability. The normal body temperature of a dairy cow is around 38.5 degrees, and the suitable rearing temperature is between 10-20 degrees. In this temperature environment, it does not need to consume the body's energy to regulate body temperature, and at this time its milk yield is at its best. If the rearing environment exceeds 25 degrees, it must consume energy to regulate body temperature and develop a heat stress response. In a high-humidity environment, heat stress can occur at around 23 degrees.
The harmful effects of heat stress in dairy cows
1. Affects feed intake
The suitable growth temperature for dairy cows is 4-20 degrees. High temperatures cause them to develop a heat stress response, leading to faster body temperature, respiration, and heartbeat, increased metabolism, and frequent endocrine disorders, which can cause a severe drop in feed intake and thereby affect milk yield. When the suitable environmental temperature reaches 27 degrees, feed intake begins to decline; when the temperature is above 30 degrees, the feed intake of dairy cows drops severely; when the temperature reaches 40 degrees, the feed intake of dairy cows is 20% of normal or they do not eat.
2. Affects milk yield and milk composition
The heat stress response also leads to a decline in milk yield. As the temperature continues to rise, the milk protein content of dairy cows also continues to decline. For every 10-degree rise in temperature, protein synthesis decreases by 0.1 kg. When humidity is above 70%, for every 10-degree rise, the milk production of dairy cows decreases by 2 kg, and their milk protein content also drops substantially, affecting milk quality.
3. Affects reproductive ability
In the heat stress response caused by high temperatures, dairy cows mobilize everything in the body to regulate body temperature and dissipate heat. Their metabolism and peripheral blood circulation continuously increase, while blood circulation in the internal organs continuously weakens, causing their nutrition supply to become insufficient and affecting reproductive ability. According to data, the conception rate in summer is only 50%-60% of that in spring and autumn.
4. Affects resistance
The heat stress response affects the body resistance of dairy cows and makes them prone to disease. Summer is precisely the season when bacteria and microorganisms reproduce fastest. If the sanitation of the barn environment is poor, dairy cows are highly susceptible to infections such as mastitis and metritis. The incidence of retained placenta in dairy cows is also higher than in winter, and it can also easily cause miscarriage and stillbirth in dairy cows.
The above is the harm of heat stress in dairy cows brought to you by Qinnongwang. The introduction to the harm of heat stress response to dairy cows ends here. To learn more, please stay tuned to Qinnongwang.