Effect of cationic source and anion-cation difference of dairy cow ration in early lactation on ruminal digestibility, methane gas production and ruminal microbial population by competitive polymerase chain reaction method

The aim of this study was to evaluate the effect of source and balance of dietary anion-cation (DCAD) of dairy cows on protozoa and methanogens populations, ammonia nitrogen concentration, methane gas and digestibility of dry matter in vitro. Competitive polymerase chain reaction (cPCR) techniques were used to count the protozoan and methanogens population. This design for dairy cow in early lactation with an average body weight of 580 kg, age 25 months and daily production of 35 kg was carried out in the form of a 2 × 2 × 3 factorial experiment. Effective factors included DCAD (+150 meq / kgDM, +250 and +350 meq / kgDM), potassium sources (potassium carbonate (KC) and Potassium carbonate sesquihydrate (KCS)) and magnesium sources (magnesium oxide (MO) and magnesium carbonate (MC)). The effect of experimental treatments on ammonia nitrogen concentration was not significant. In all treatments, DCAD increased cause reduced ammonia nitrogen concentration in the rumen. The effect of experimental treatments on gas production, dry matter digestibility, protozoan and methanogens population was significant. The results of this study showed that the treatment containing DCAD +250 meq / kgDM provided by Potassium carbonate sesquihydrate and magnesium carbonate is reduced the protozoa and methanogens population, production of methane and increasing the digestibility of dry matter. Considering that there was no significant difference between DCAD +250 and +350, it seems that the sources of Potassium carbonate sesquihydrate and magnesium carbonate plus the anion-cation balance level of +250 meq / kgDM through the rumen buffering conditions improve, improves the parameters of rumen fermentation. Therefore, these two sources are probably appropriate supplements in the dietary of dairy cows.