Presence of Selected Methanogens, Fibrolytic Bacteria, and Proteobacteria in the Gastrointestinal Tract of Neonatal Dairy Calves from Birth to 72 Hours

Abstract

The microbial communities in the gastrointestinal tract of a young calf are essential for the anatomical and physiological development that permits a transition from milk to solid feed. Selected methanogens, fibrolytic bacteria, and proteobacteria were quantified in the rumen fluid and tissue, abomasum fluid, cecum fluid and tissue, and feces of Holstein bull calves on day 0 (0-20 mins after birth), day 1 (24 ± 1 h after birth), day 2 (48 ± 1 h after birth), and day 3 (72 ± 1 h after birth). Methanogens, fibrolytic bacteria, and Geobacter spp. were found to be already present from birth, indicating that microbial colonization of the gastrointestinal tract occurred before or during delivery. The abundance of methanogens and Geobacter spp. differed between the days tested and between compartments of the digestive tract and feces, but such difference was not observed for fibrolytic bacteria. Our findings suggests that methanogens might have an alternative hydrogen provider such as Geobacter spp. during these early stages of postnatal development. In addition, fibrolytic bacteria were present in the rumen well before the availability of fibrous substrates, suggesting that they might use nutrients other than cellulose and hemicellose.

Fig 1. Relative abundance of different species of microorganisms in different parts of the digestive tract of calves during the first four days after birth.

The abundance of Methanomicrobiales mobile, Methanococcales votae, Methanobrevibacter spp. and Geobacter spp. was determined in (A) rumen fluid, (B) rumen tissue, (C) abomasum, (D) cecum fluid, (E) cecum tissue, and (F) feces of calves of 0 days old (blue bars), 1 day old (orange bars), 2 days old (grey bars), and 3 days old (yellow bars). Abundance, as Log₁₀ copy number per μl of 16S ribosomal DNA, is expressed relative to the lowest value among all species. Data are means ± SEM (n = 3). For each species, data without a common letter are significantly different (ANOVA, P < 0.05). Note the logarithmic scale of the y-axis.