Table 1.

Factors that influence the development of gut microbiota of ruminants

Factor	Ruminant	Treatment	Result	Reference
Probiotics	Preweaning calves	Calves were inoculated through a rumen cannula with 250 mL of skim milk that contained potential probiotics isolated from the cow intestine (1010 CFU)	Probiotics reduced the level of carriage of E. coli O157:H7	[105]
	Calves at 7–56 d	Lactobacillus acidophilus or Bifidobacterium pseudolongum were administered every morning with milk replacer (3 × 109 CFU)	Body weight was increased, and feed conversion and fecal score were improved	[106]
	Newborn Holstein calves	Compound probiotics that contained Bifidobacterium thermophilum (1010 CFU), Enterococcus faecium (1010 CFU), and Lactobacillus acidophilu (109 CFU) were administered every morning with milk replacer	Increased body weight and reduced diarrhea incidence	[106]
	Newborn Holstein calves	Calves were fed milk daily with compound probiotics that contained Lactococcus lactis, Pediococcus pentosaceus, Lactobacillus plantarum, Saccharomyces cerevisiae, and Kluyveromyces marxianus (at the total dose of 2 × 1010 CFU)	Calves in the compound probiotic group had closer intestinal microbiota and lower rates of diarrhea than those in the control group	[65]
	Weaned calves at 78.3 ± 7.2 d	Calves were fed Lactobacillus plantarum and Bacillus subtilis (0.2 kg/ton feed)	Diarrhea was inhibited	[107]
	Newborn Holstein calves	Saccharomyces cerevisiae (2 × 108 CFU), Lactobacillus acidophilus (2 × 108 CFU), Lactobacillus plantarum (2 × 108 CFU), Lactobacillus rhamnosus (2 × 108 CFU), Lactobacillus casei (2 × 108 CFU), Bifidobacterium bifidium (2 × 108 CFU), Pediococcus acidilactici (2 × 108 CFU), Bacillus subtilis (2 × 109 CFU), and Enterococcus faecium (2 × 108 CFU)	Digestion of NDF, growth preference, and rumen fermentation improved	[108]
Diet	Beef steers	Beef steers were fed with the step-up diets that contained grain and hay at ratios of 20:80, 40:60, 60:40, and 80:20	Megasphaera elsdenii, Streptococcus bovis, Selenomonas ruminantium, and Prevotella bryantii increased, while Butyrivibrio fibrisolvens and Fibrobacter succinogenes decreased in the rumen by high-concentrate diet	[109]
	Dairy cows	Cows were fed different ratios of fiber (88%, 76%, and 57.5%)	Fiber increased the population of Firmicutes (e.g., Ruminococcus, Butyvibrio, Pseudobutyrivibrio, Oscillibacter, and Eubacterium) and Fibrobacter	[110]
	Dairy cows	Cows were fed a low-fiber, high-PUFA (polyunsaturated fatty acid) diet or a high-fiber, low-PUFA diet for 21 d	Prococcus and Filamentous bacilli and increased Rumenomonas, and Megafococcus ellieri decreased by a high-fiber, low-PUFA diet	[111]
	Beefs	Beefs were fed different ratios of forage and concentrate (500:500 and 80:920) diets	High forage avoided dysbiosis associated with pathogenic species among Proteobacteria, and high forage increased drug-resistant bacteria and diseased related bacteria in the rumen	[112]
Age	Newborn calves	Newborn calves were fed for 14 or 42 d	Gut microbiome structure was different between the two age groups (14 and 42 d). Oscillibacter and Paraprevotella had a high richness at only 14 d, whereas Porphyromonas had higher richness at 42 d	[113]
	Newborn calves	From birth to 7-week-old	Chao1 index of the gut microbiome of calves increased from 0 to 7 weeks. Fusobacteria decreased gradually. Lactobacillus spp. and Bifidobacterium spp. reached a maximum of 15% at 4-week-old, and then decreased to 2%	[114]
	Newborn calves	From birth to adulthood	The rumen microbiota had significant age-related changes. Age decreased the diversity of bacteria and increased anaerobic bacteria and aerobic bacteria	[8]
Genotype	Twin and singleton calves		The twin calves had the same microbial community structure	[115]
	Herbivorous ruminants and non-ruminants		The community structure of different genotypes was different	[116]
	India cattle and buffalo		Indian cattle had a higher abundance of total anaerobic fungi and Ruminococcus flavefaciens. Buffalo had a higher abundance of cellulolytic bacteria Fibrobacter succinogenes and Ruminococcus albus	[117]
	Holstein and Jersey cows		Rumen microbiota was influenced by host species	[118]