Effects of Cold Temperature and Fat Supplementation on Rumen Microbial Populations in Korean Cattle

In the lower critical temperature, cattle increase metabolic rate to supply more body heat. This increases nutrient requirements, particularly energy, and may affect rumen fermentation characteristics and thus rumen microbial ecosystem. This study was performed to examine whether cold temperature and fat supplementation affects rumen microbial populations in Korean cattle. Six Korean cattle steers (average 17 months of age and 375 kg of BW) were divided into a conventional control diet group (n=3) and a 1.75% fat supplementation group (n=3). Steers were allowed to receive daily a concentrate (1.5% of BW) and 3 kg of tall-fescue hay. Steers were raised on metabolic cages in a temperature-controlled room with two different temperature conditions. Animals were grown in natural cold condition for 12 days with two different diets, and they was then grown in neutral normal temperature for 12 days. There were 10 days of resting period between two temperature conditions in a feedlot with control diet. Minimum ambient temperature (-6.24℃) of cold environment were lower (p<0.01) than that (15.8℃) of normal temperature condition. Rumen fluid samples were obtained via stomach tube on the last day of each of two experimental periods 3 h after morning feeding. Rumen fluids were frozen in liquid nitrogen and stored at -70℃. Genomic DNA was extracted and used for 16S rRNA metagenomics sequencing by Illumina HiSeq 2000 system. Sequencing raw data was processed by QIIME. Statistical analysis was conducted by two-way (diet and temperature) ANOVA. Bacteroidetes were most abundant phylum followed by Firmicutes in all rumen fluid samples. Relative abundances of the genus Propionibacterium and Anaeroplasma were higher (p<0.05) in cold temperature than in normal temperature, whereas those of Desulfovibrio and Mogibacterium were lower (p<0.05) in cold temperature. Relative abundance of the family R4-45B was higher (p<0.05) in fat diet group than in control diet group, whereas that of Pyramidobacter was lower (p<0.05) in fat diet group. Real-time PCR was performed to validate the metagenomics data and to identify the changes of microbial population at species levels with 19 microbial primers. Succinimonas amylolytica was higher (p<0.05) in cold temperature than in normal temperature. Ruminococcus albus was higher (p<0.05) in fat diet group than in control diet group. In conclusion, metagenomics and real-time PCR results reveals that cold temperature and fat supplement affect microbial populations in the rumen of beef cattle.