Rumen Health: The Key To High-yielding Cows
Since high-yielding cows rely heavily on rumen efficiency, every challenge, such as heat stress, must be compensated for by (nutrition) management. One of the nutrient solutions can be found in an effective rumen buffer supplement.
Different factors can put a healthy rumen into a state of stress. However, too low a rumen pH results in the greatest impact of ruminal acidosis. Rumen acidosis is a metabolic disease characterized by acute rumen acidosis, but more commonly the subacute form (SARA). Some studies suggest that 19-26% of cows are treated with SARA. Ruminal efficiency is greatly reduced during SARA. Less digestion, lower absorption of volatile fatty acids (VFA), more endotoxin production, and even damage to the rumen wall. But heat stress can also have a huge impact on rumen health. Here, we explain in more detail what it contains and what other factors can damage the rumen, thereby destroying the milk production.
The effects of heat stress in dairy cows may include a range of factors, such as reduced dry matter intake. Photo: Shutterstock
Heat stress is a very broad term, but what does it mean? Usually the temperature should be the first indicator, but to estimate the actual impact on the cow, humidity must also be considered. Of course, cows lose heat by non-evaporative cooling (radiation, conduction, convection). When the temperature rises, the cows begin to use an evaporative cooling mechanism (sweating, gasping). These evaporation strategies are effective, but when the humidity rises, the cow cannot lose enough body heat to prevent the body temperature from rising. In order to better estimate the thermal stress risk, the temperature and humidity index (THI) gives a good indication (Figure 1).
Figure 1 – The Temperature Humidity Index.
Above the THI index of 72, cows begin to suffer from heat stress. The effects of heat stress can include a range of things. Lower dry matter intake is one of the first reactions in dairy cows that directly affect energy balance in a negative way during heat stress. Another important risk is the change in the ratio of concentrate to roughage, especially when the cow is able to choose a concentrate. Along with a smaller number of meals, resulting in a larger meal size during heat stress, the risk of ruminal acidosis will be greatly increased. Feed digestion will be strongly affected during periods of low rumen pH. In addition, endotoxin levels will increase by as much as 10-20 times the healthy rumen (Li et al, 2012).
More factors to reduce milk productio
If we observe a lower DMI during heat stress, this only accounts for 35-50% of the milk production reduction. What are the other reasons for producing a small amount of milk? Like cows affected by heat stress, early lactating cows also experience a negative energy balance. However, early lactating cows have a compensation mechanism. Because of the low insulin levels and insulin resistance in the early stages of lactation, they can make up a large part of the “missing” energy by using body fat. Cows with heat stress have very normal insulin concentrations in the blood, which prevents the use of body fat as an alternative energy. In this case, the cow becomes very dependent on glucose as a source of energy. The more glucose required for energy, the lower the glucose that can be used to produce lactose, which is directly related to low milk production. A large increase in endotoxin production has led to a further decline in milk production. Oxidative stress causes damage to the natural barrier function of GIT. Similarly, hypoxia is a lower oxygen content in epithelial cells due to heat stress, impairing the natural barrier function of GIT. Higher permeability of the gastrointestinal wall results in higher absorption of endotoxin. Moreover, these endotoxins are present at increased levels in the case of heat stress. Once inside the body, they use a lot of energy in the form of glucose to activate the immune system. This higher glucose usage again results in less available glucose for milk production
Figure 2 – Consequences of heat stress in cattle.
To protect cows from the negative effects of heat stress, rumen buffer can be used. In practice, sodium monocarbonate is often used, which has a large buffering capacity but is only a short time after consumption. In order to obtain good cushioning characteristics throughout the rumen area, it is necessary to have a good combination of fast, medium and slow buffering components. In this way, the rumen will be buffered as needed and the rumen needs adjusted in time. Some products do more, such as new supplements*, which also guide the bacterial population in a good direction. Supporting cellulolytic bacteria will result in lower lactic acid production. In addition, stimulation of lactic acid-consuming bacteria will minimize the reduction in rumen pH. Finally, the use of natural antioxidants in this buffer reduces the stress in the body. Different natural ingredients effectively reduce the negative effects of stress by protecting the barrier function of the intestinal wall. This minimizes the amount of endotoxin absorbed in the body, thereby reducing the waste of glucose and healthier, more effective animals.