002 Effects of cold temperature and fat supplementation on rumen microbial populations in Korean cattle

Abstract

In lower critical temperature, cattle increase their metabolic rate to supply more body heat. This increases nutrient requirements, particularly energy, and may affect rumen fermentation characteristics and thus the 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 mo 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 in metabolic cages in a temperature-controlled room with 2 different temperature conditions. Animals were grown in natural cold condition for 12 d with 2 different diets, and they were then grown in neutral normal temperature for 12 d. There was a 10-d resting period between the 2 temperature conditions in a feedlot with the control diet. The minimum ambient temperature (−6.24°C) of the cold environment was lower (P < 0.01) than that (15.8°C) of the normal temperature condition. Rumen fluid samples were obtained via stomach tube on the last day of each of 2 experimental periods 3 h after the morning feeding. Rumen fluids were frozen in liquid nitrogen and stored at −70°C. Genomic DNA was extracted and used for 16S rRNA metagenomics sequencing by an Illumina HiSeq 2000 system. Raw sequencing data was processed by QIIME. Statistical analysis was conducted by 2-way (diet and temperature) ANOVA. Bacteroidetes was the most abundant phylum followed by Firmicutes in all rumen fluid samples. Relative abundances of the genera 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 the 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 the fat diet group than in the 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.