Table 1.

Factors influencing pre-weaned calf rumen/gut microbiota.

Factor	Study
Age	(17, 26–28, 30, 46, 47, 49)
Diet (colostrum, calf starter)	(28, 29, 32, 33, 46, 51, 52)
Feeding method (suckling, bottle feeding)	(53)
Probiotic, prebiotics	(39, 41)
Exposure to dam	(19, 53)
Sample site	(21, 43, 48, 49)
Sample type (fluid, content, mucosa)	(20, 21, 49)
Host (individuality)	(27)
Infections	(47)