Adaptation Period during Changing Diet of Dairy Cows Changes Rumen Fermentation Characteristics, Microbial Qualities and Communities

Adaptation period is important during evaluation of in vivo nutritional studies. Populational and metabolic changes occur in the rumen microbiota during this period. Thus, we determined the changes in the rumen fermentation characteristics, microbial quantities and communities. Three Holstein-Friesian cows were used in this study and assigned as replicates. They were initially fed with Italian ryegrass ad libitum and 2 kg concentrate diet per day and for 30 days. Then, the concentrate diet was increased to 8 kg/day for 14 days and decreased to 2 kg/day for another 14 days. Rumen fluids were collected 2 h after morning feeding through stomach tubing at the start of the experiment, at day 7 and 14 of the diets. pH, VFA, microbial quantities, and communities were determined using pH meter, HPLC, qPCR, and Illumina MiSeq, respectively. All analyses were carried out using SAS. The highest pH (7.02) was observed at the start of the experiment. Concentrations of acetate, propionate, and butyrate also peaked at day 14 day of consuming 8 kg concentrate at 56.76 mM (P<0.001), 13.28 mM (P<0.008), and 6.60 mM (P<0.011), respectively. The total bacteria quantity was comparable throughout the feeding trials. Ruminococcus flavefaciens (4.64 and 5.08) and protozoa (1.94 and 2.00) log copies were highest at day 7 of feeding 8 kg and 2 kg concentrate diets while the lowest methanogen quantity was observed at the start of the experiment (2.96 log copies) with increasing copies until the end of the feeding trial. Bacteroidetes predominates the bacterial communities in this study and found the highest with lower feed concentrate (2 kg/day) while the opposite was observed with higher feed concentrate (8 kg/day) given to the animals. Relative abundances of Spirochaetes and Chloroflexi increased with increased feed concentrate (8 kg/day) given to animals. Prevotella ruminicola had the predominates the species level which was found highest at the start of the experiment. Notably, Olsenella profusa and Syntrophococcus sucromutans increased its relative abundances with increased concentrate (8 kg/day) given to the animals. The rumen fermentation characteristics, microbial quantities, and bacterial communities changed with changing diet during adaptation period.