Does intestinal bacteria diversity drive multi-dimensional sheep (Ovis aries) health?

Although previous research has shown that several health disorders affect gastrointestinal microbiome flora, there is no consensus on the relationship between gastrointestinal microorganism diversity and ruminant health. Therefore, we revealed how intestinal bacterial flora diversity affects the overall health of sheep (Ovis aries) from multiple perspectives. We gathered total 17 data on behaviour (time allocation and action intensity on a 3-dimensional axis), nutrition (blood parameters, body condition), physical attributes, and resistance to parasitic infection (blood parameters, blood cell components, and eggs per gram [EPG] counts) from 20 sheep—both housed and grazing—at a Japanese farm. We defined an abnormal individual as one out of the normal range for blood parameters and the confidence interval among the 20 sheep in each behaviour. The species composition and diversity of intestinal bacteria in each sheep were determined by 1) extracting DNA from collected faeces, 2) identifying the species based on genetic approaches, and 3) calculating the diversity index using species composition at the phylum and genus levels. The calculated diversity indices were compared with those of the sheep group classified by the sum of abnormal measurements. The Shannon and Simpson diversity indices at the phylum and genus levels were 1.69 and 4.47 and 0.55 and 0.93, respectively. The sum of abnormal health measurements in each sheep ranged from 4 to 7, including mainly blood biological properties. Healthy sheep with lower total numbers of abnormal measurements tended to have higher Simpson lambda (p = 0.095) and Shannon–Weiner H′ indices (p = 0.085) of intestinal microbiota at the genus level. Therefore, it can be considered that the higher the diversity of intestinal microbiota at the genus level, the more functional species (working in the intestine in absorption, ingestion, immunity, and physiologically) would coexist, playing a role in overall ruminant health.