High-yielding dairy animals need diets containing high concentrates to meet their nutritional needs, the consumption of these diets increases the risk of subacute ruminal acidosis (SARA) due to their high starch content. It is a common and costly metabolic disease in high-yielding dairy cows. Subacute acidosis occurs if the average rumen pH falls below 6.5 for more than 3 hours per day.
Etiology of SARA
Excessive amounts of fast-fermenting carbohydrates in the diet
High consumption of concentrate
Rapid changes in diet composition (increasing the amount of concentrate)
Deficiency of physically effective fiber in the diet (peNDF)
Mistake in ration distribution
Consequences of SARA
Reduction of dry matter consumption
Decreased fiber digestion (20-25%)
inflammation of the rumen
Decrease in production efficiency
Reduce milk fat
Decreased milk production
Reduction of milk protein
Reduce rumination time
The increase of elimination livestock and the reduction of the economic life of cows
The financial losses of acidosis are related to the reduction of milk production, reduction of milk production efficiency, premature elimination and increase of losses in lactating animals. They reported a decrease in milk production by 3 kg per day per cow, a decrease in milk fat production by 3 grams per kilogram of milk, and a decrease in milk protein production by 1.2 grams per kilogram of milk due to subacute acidosis.
Difficulties in diagnosing SARA are due to the lack of specific pathogenomic symptoms, diurnal fluctuations in rumen fermentation, and difficulties in collecting rumen fluid samples to measure rumen pH. However, in farm conditions some intuitive parameters seem to be a good guide.
Feeding pattern: changes in feeding behavior, refusal to eat due to a sharp drop in rumen pH and an increase in the osmolarity of rumen fluids are observed, and rumination time is also reduced (typically 40% of cows should be ruminating at any time).
Feces: When faced with subacute acidosis, the feces of cows is bright, yellowish with a sour smell, sometimes it is seen as diarrhea with foam (gas bubbles) and undigested fiber or grain can be seen in the feces more than normal.
Ruminal fluid parameters: In ruminal fluid collection by Romino-synthesizer method, if pH ≤ 5 is considered as positive SARA, pH ≥ 5.8 is considered as negative SARA.
Milk parameters: A study conducted in a large farm in New York State showed that SARA reduces milk production by 2.7 kg per day, milk fat by 3% and milk protein by 12%.
Blood parameters: A decrease in blood pH, bicarbonate, as well as an increase in base (metabolic acidosis) and an increase in (LPS lipopolysaccharide) in blood have been reported in Perurai calves.
Urinary parameters: Assessment of net renal acid-base excretion (NABE) determined by urine titration is more accurate than pH determination, because acidosis causes more inorganic phosphate to be excreted in the urine (phosphate acts as a buffer).
Nutritional guidelines to reduce SARA
The basic principles of SARA prevention in dairy herds include limiting the consumption of rapidly fermentable carbohydrates, providing adequate buffer in the rumen, and allowing the rumen to adapt to high-grain diets.
Limit the consumption of fast-fermenting carbohydrates:
Cows should not receive more than 3-5 kg of dry matter through grain in the first week after calving, grain feeding should be gradually increased by 110-220 grams per day per cow, until at 6-8 weeks after calving reach the maximum The net energy of the diet can be increased by using fat supplements to reduce grain consumption.
Use of fat supplements in the diet
Increasing dietary fat in dairy cows is a common method of increasing dietary energy concentration and energy intake, which ultimately helps meet the energy needs of newborn cows.
Fat feeding is a useful way to limit overfeeding of fermentable carbohydrates (high starch diets), thereby reducing the risk of subacute acidosis and reducing milk fat. Ranchers need to carefully consider the type, composition, and nutritional level of fat in order to benefit from the use of this energy source.
While cow diets typically contain 2 to 4 percent crude fat, high-energy diets for early calving cows may contain 4 to 7 percent crude fat. Fat supplement nutrition should focus on providing fatty acids. We now know that different fatty acids can regulate the cow’s metabolism, energy allocation towards growth or lactation, fertility, and health. In this context, the composition of fatty acids in the fat supplement and the total fat in the diet are important factors that should be considered for newborn cows.
Another important point for checking the fat supplement is the digestibility of fatty acids. Fatty acid digestibility is a measure of the amount of fatty acids available to the cow for absorption. To evaluate the quality of a fat supplement, three things should be considered: physical form, chemical composition, and fatty acid profile.
Omega-3 fatty acids such as C18:3 and C22:6 are anti-inflammatory compounds that may increase insulin sensitivity. These fatty acids (which escape rumen biohydrogenation) likely have great potential to minimize body fat loss, enhance liver health, prevent inflammation, and reduce the incidence of postpartum disease.
The physical form of grain is a useful aid in assessing the risk of SARA in dairy herds. Powdered, steam-flaked, and extruded grains are fermented more rapidly in the rumen than unprocessed or bulked grains. Wheat or barley starch ferments faster and more than corn starch and increases the possibility of subacute acidosis.
Provision of sufficient rumen buffer:
Coarse forages are more effective in stimulating saliva production than finely ground forages. The length of fiber particles with a size of 4 cm and above is considered to be at least 7% and at most 15%. The buffering capacity of the ration depends on the amount of DCAD of feed and fodder, which is +275 to +400 milliequivalents per kg of dry matter in early lactation and in mid-lactation cows, respectively. Ration with high DCAD increases the need to add buffer. Forage has a higher DCAD than corn silage, and concentrates usually have low or negative DCAD.
A period of 3 to 5 weeks is considered in order to adapt to rations with a lot of grains. It is important to consider the adaptation period for microbial adaptation (especially lactate-consuming bacteria, these bacteria grow more slowly than lactate-producing bacteria) and rumen papilla length (larger papilla absorb more volatile fatty acids and are effective in controlling pH).
Some nutritional measures without restricting grain feeding that are effective in preventing SARA are summarized below.
Increase of rumen lactate consumers: Adding specific yeast strains in diets can increase lactate consumption in the rumen.
Preparation of microbes to deal with lactate: adding lactate to the diet or using lactate-containing food ingredients can improve the ability of the rumen to adapt to a sudden increase in lactate production.
Adding ionophores: feeding ionophores reduces rumen lactate production and increases competition between lactate consumers due to the inhibition of lactate-producing bacteria. Monensin has been approved for use in dairy farms in the United States.
Subacute acidosis is one of the most important metabolic diseases in dairy farms, which causes disturbances in performance, cow health, and animal welfare. The lack of ration buffer capacity can be solved by adding a suitable buffer. Using buffer can increase dry matter consumption, milk production and milk fat percentage. Direct addition of bacteria such as Enterococcus faecium and Saccharomyces cerevisiae can improve digestion and reduce rumen acidity. By inhibiting lactate producing bacteria and increasing the competition between lactate users, the addition of ionophores reduces rumen lactate production, and also the use of fat supplements and energy supply for livestock and reducing the consumption of fermentable carbohydrates reduces subacute acidosis.
Dinalac and Omega 3 fat supplement, product of UFAC, England, and fat powder, product of DUA CUDA, Indonesia, with careful design and consideration of fatty acids needed for newborn cows, providing energy and improving immune system function, prevent subacute metabolic acidosis and damage are caused by it.