Rumen pH in ruminants is controlled by absorption of volatile fatty acids from the rumen wall and saliva secretion.
About 0.1% of saliva is sodium bicarbonate, which is known as the primary buffer. Saliva secretion depends on the amount of fiber in the diet, and with an increase in fiber in the diet, chewing activity is stimulated and more saliva is secreted. Therefore, cows can maintain a stable rumen pH by internal buffer production, microbial adaptation and absorption of volatile fatty acids.
However, due to the use of high amounts of non-structural carbohydrates in the diet of high-yielding cows, the need for additives with buffering properties in the feed of dairy cows is increasing.
When adding buffers, the following should be considered:
1-The chemical composition of the buffer
2-The ratio of fodder to grain, the fiber content of the total diet and the length of fodder particles
4-Feeding system (TMR, feeding frequency, price and supplement level)
Livestock buffer is a weak acid and its salt or a strong acid and its salt. So far, many chemicals have been tested as buffers in feeding ruminants. Adding some of these buffers, such as sodium bicarbonate, magnesium carbonate, and potassium bicarbonate, only neutralizes rumen acidity. While some buffers also increase rumen pH.
Buffers provide resistance to changes in acidity. True buffers prevent the increase in acidity (decrease in pH). But they do not raise the pH above a certain limit. Sodium bicarbonate (NaHCo3), sodium bentonite are real buffers. Bactericidal compounds reduce acidity, but can cause a large increase in pH.
Magnesium oxide (MgO) is an acting compound and not a true buffer. Different compounds known as buffers act differently in the digestive system. In general, there are two mechanisms for the action of buffers in the rumen, and the other is to increase the speed of liquid passing through the rumen. Among the reasons for increasing the speed of liquids passing through the rumen is the increase in the osmotic concentration of liquids and the release of water from the rumen wall. A positive correlation has been reported between the total volume of rumen fluids and the amount of minerals in the feed. The higher the amount of dissolved mineral elements in the feed, the osmotic pressure of the rumen fluid and the specific weight of the feed particles will increase, and as a result, their passage through the rumen will increase. Adding minerals to feed containing fodder or a mixture of fodder and dense materials leads to an increase in the speed of passage of suspended particles in the non-solid part of the rumen contents. These particles mainly include amino acids, soluble sugars, proteins and minerals.
However, apart from the addition of minerals and buffers, any action that increases the osmolarity of rumen liquid will prevent the adverse effect of increasing the level of feed on digestibility and ultimately improve feed efficiency. By increasing osmolarity, minerals stimulate receptors in the rumen, increase water consumption, and increase the speed of material passing through the rumen. It should be noted that changes in rumen osmolarity have been reported during consumption of most minerals. In addition to additives and minerals, factors such as temperature, physical activity, increasing the rate of wetting of feed particles through processing, are among the factors affecting the passage speed.
The diets used now have high amounts of soluble carbohydrates and are small in particle size. In addition, the consumption of fermented foods in diets has increased compared to previous years, which generally have low pH values and high water content, which is different from traditional foods. In addition, at the same time as these changes, due to the complexity of the management processes, the number of feeding times to livestock has decreased, which has increased the health problems of the herds, due to the challenges created in the acid-base balance towards creating a more acidic rumen environment.
Various researches have been conducted in relation to the identification of mineral buffers or alkalizing compounds and to determine the efficiency of these compounds in reducing acid stress caused by intensive feeding and management programs. However, any mineral supplement that is added to the feed causes costs to be imposed on the livestock farmers. Therefore, it is necessary to calculate the buffering capability of the foods themselves in the buffering content of the rations and formulate a ration that uses the buffering capability of the foods as much as possible.
The researchers determined the buffering ability of 35 substances in the laboratory using rumen fluid obtained from cows that received diets containing concentrate and forage or only diets containing concentrate.
The obtained results indicate that sodium and buffers containing sodium are the best types of buffers. Potassium is better than calcium and calcium is better than aluminum, magnesium, manganese and ammonium. Zinc salts show very little buffering ability. The best buffer anions include acetate, bicarbonate, carbonate and diphosphates.
Borate, citrate, lactate, and propionate are weak anions and microlites are moderate buffers, while bentonites are good buffers when allowed to dissolve in rumen fluid. Buffers are also used in meat production systems based on concentrate diets to increase or maintain A stable rumen pH is consumed.
Acid production in the rumen is always associated with swelling and inflammation of the rumen wall, lameness and purulent swellings of the liver and may be caused by rapid habituation to highly concentrated diets. In research, it has been found that the use of buffers during the habituation period has increased efficiency.
In animals adapted to fattening diets, the chronic or subclinical form of acidosis is usually observed with a decrease in rumen pH in the range of 5-5.5 due to an increase in the concentration of volatile fatty acids produced and not an increase in lactate production, which is often common. In general, it should be said that the benefits of supplementing rations throughout the feeding period of animals are not small, therefore, in order to maintain the stability of the rumen environment, better digestion, animal health and more production, care is always taken in formulating the rations and using appropriate additives and considering Getting enough habituation period to prevent the occurrence of metabolic abnormalities.
The need to use a buffer supplement in the ration of dairy cows:
Necessity of using buffer supplement in the ration of dairy cows: Today, nutritional and management programs are designed in such a way that it brings the highest efficiency and production in ruminants.
Diets containing low fiber and high levels of concentrate are used to provide the energy needed by dairy cows.
However, due to the decrease in saliva secretion, increase in the production of volatile fatty acids and the accumulation of lactic acid in the rumen, these diets decrease the pH of the rumen liquid and as a result decrease parameters such as dry matter consumption, fiber digestion, milk production, milk fat percentage, and as a result, the incidence of Diarrhea and lameness occur in lactating cows.
The different effects of adding a buffer to the diet strongly depend on the type of forage consumed in the diet:
Previous studies did not observe a response from adding buffers to forage-based diets other than corn silage (dried alfalfa or silage of other forages such as barley, wheat, sorghum, and triticale).
This could be related to the effectiveness of dry alfalfa in stimulating rumination, the high buffering capacity of alfalfa, or the higher initial pH of alfalfa silage compared to corn silage.
According to Hu et al.’s (2005) meta-analysis research, it is possible that adding a buffer to the high-concentrate diet of cows will reduce the production of C18:1 trans fatty acids in the rumen.
Therefore, an increase in rumen pH in cows fed with buffered diets can lead to a decrease in the flow of C18:1 trans fatty acids to the duodenum and reduce milk fat loss.