Use of acid-consuming bacteria and various buffers to improve digestion and fermentation of highly concentrated diets

The use of highly concentrated rations in the fattening of ruminant animals is done to improve the performance per unit of feed consumption. Increasing the amount of concentrate in the ration improves the food conversion ratio and the weight gain of fattening lambs, and the production of volatile fatty acids. However, some in vivo experiments have reported that long-term use of highly concentrated diets is not always associated with increased performance. Therefore, feeding diets containing high amounts of concentrate (with a limited amount of effective fiber) often leads to metabolic disorders, the most important of which is subacute ruminal acidosis which causes a decrease in dry matter consumption and reduces the fiber digestibility, milk fat, lameness, and liver abscess, and even leads to the death of the animal. Moreover, sub-acute acidosis leads to significant economic losses. Therefore, preventive measures to prevent acidosis and improve starch digestion, such as the use of antibiotics, probiotics, and buffers, have been taken into consideration. Lactate-consuming bacteria metabolize lactic acid and control its accumulation in the rumen. This process is important when the animal diet contains a large amount of grain. Megasphaera elsdenii and Selenomonas ruminantium are the dominant strains that consume lactic acid in the rumen, and among these two strains, Megasphaer alsdeni consumes 65 to 95% of the lactate in the rumen. The use of biological methods in controlling pH changes can also reduce the dependence of livestock on chemical additives to some extent. Therefore, the present experiment was conducted to compare the effect of different chemical and biological buffers (acid-consuming bacteria) on the digestion and fermentation of highly concentrated diets.
The experimental treatments included: 1. The control diet (without additives and containing 70% concentrate + 30% fodder or basal diet), 2. Basal diet + 3 mL of bacteria Megasphaera elsdenii (bacteria- 4.5 × 108 cfu/3mL), 3. Basal diet + 1% sodium bentonite, 4. Basal diet + 1% sodium bentonite + 3 mL of bacteria, 5. Basal diet + 1% sodium bicarbonate, 6. Basal diet + 1% sodium bicarbonate + 3 mL bacteria, 7. Basal diet + 1% magnesium oxide, 8. Basal diet + 1% magnesium oxide + 3 mL bacteria, 9. Basal diet + 1% zeolite, 10. Basal diet + 1% zeolite + 3 mL bacteria, 11. Basal diet + 1% sodium sesquicarbonate, and 12. Basal diet + 1% sodium-sesquicarbonate + 3 mL bacteria. Megasphaera elsdenii bacteria were isolated and prepared from Najdi goats at the Agricultural Sciences and Natural Resources University of Khuzestan (Ahvaz, Iran) and their activity was investigated in experiments. In gas production experiments, the experimental samples were ground with a mill containing a 1 mL sieve. About 200 mg of the dry matter of the desired sample was weighed and poured into 100 mL vials, and eight replicates were considered for each treatment. The produced gas of the samples was recorded at 0, 2, 4, 6, 8, 12, 24, 48, 72, and 96 hours of incubation using a digital barometer.
The effect of experimental treatments on potential and rate of gas production, partitioning factor, microbial biomass production, microbial biomass production efficiency, pH, ammonia nitrogen concentration, apparent dry matter digestibility, and protozoa population was significant (P<0.05), and except for ammonia nitrogen, all parameters in buffer treatments were higher than the control. The highest gas production potential (68.26 mg), microbial biomass production (1212.31 mg), and microbial biomass production efficiency (79%) were observed in the treatment containing sodium bicarbonate + bacteria (P<0.05). The highest pH and ammonia nitrogen were for the treatment containing bacteria (6.60) and control (27.30 mg/100 mL). The total protozoa population was the highest in the treatment of sodium bentonite + bacteria.
In general, the results of the present experiment showed that the use of buffers improved digestion and fermentation conditions, and each of the buffers had a greater effect on one or more parameters than the others. In addition, acid-consuming bacteria as a pH regulator had competitive effects with chemical buffers, especially bicarbonate buffer, and even better in some cases. The effect of some chemical buffers used in the present experiment, such as bicarbonate, has been further investigated, but the effect of other chemical and biological buffers mentioned in the present experiment on the digestive and fermentation properties of ruminant animals has been investigated less. Therefore, it is recommended to investigate the effect of chemical buffers used in the present experiment alone or together with acid-consuming bacteria in feeding ruminant animals.