Estimated reading time: 4 minutes

Don’t feel like reading? Then simply listen to this article.

The largest immune system

The largest immune system in mammals is the gut. More precisely, its microbiome, meaning the community of microorganisms living in it. We also know the microbiome as intestinal flora. It consists of a wide variety of bacteria and fungi and develops individually in each animal. These microorganisms ensure good digestion and can even intercept harmful pathogens to a certain extent and render them harmless. However, if this community is disturbed, it can lead to severe digestive problems that may even become life-threatening.

A world of its own

The word “microbiome” comes from Greek and means “small life” – and the name is quite fitting. The bacteria and fungi form their own community that changes depending on the situation. It is influenced by various factors. In addition to genetics, feed and environment play an important role. For example, if the ration is changed, the microbiome also changes and adapts. In stressful situations, the digestive tract is affected first – in addition to the stomach, the intestinal microbiome also suffers. The result: weak points develop and harmful germs gain the upper hand. This can, for example, trigger diarrhea. It is a natural reaction to quickly eliminate harmful organisms. However, this costs the body a lot of water, which can become life-threatening, especially for young calves.

Special features in calves

Since the young calf has a different digestive tract than a fully grown cow and goes through several developmental stages and feed changes in the first weeks, the microbiome also faces several challenges. Not only must the gut be colonized by these small helpers, but also the developing rumen. Right after birth, there is practically no microbiome yet. It develops over time in three stages:

1. 1. Initial colonization (day 0–2)
      The microbiome develops due to various environmental microbes, including from colostrum, the mother cow, and the barn environment – a young calf really comes into contact with everything.
   2. Transition phase (day 3–15)
      Here, mainly the milk feeding plays a role.
   3. Maturation phase
      In this phase, solid feed intake increases and the microbiome must reorganize and stabilize accordingly.

The rumen microbiome

The rumen only develops over time, and so does its microbiome. Once fully developed, it is the only organ capable of utilizing plant fiber – a unique feature of ruminants. How we can influence its development is now no longer a secret: processed starch supports the growth of rumen papillae, increasing surface area. Roughage, on the other hand, promotes rumen volume. What is still not fully understood are the effects of different management practices – such as early or late weaning – on the rumen microbiome.

The mother cow

One thing, however, has already been scientifically proven: the difference in microbiome development depending on rearing methods. If the calf stays with the mother, it has a constant source of microbes. The bacterial diversity of the microbiome is then higher than in calves raised in individual hutches. Diversity is also higher in group housing. One indicator is protozoa, which are almost completely absent in individually housed calves. However, protozoa are particularly important for cellulose digestion in the rumen.

And now?

Research is still far from complete. For now, it remains to be seen, because even a calf that spends some time in an individual hutch can still become a high-performing cow. However, there is increasing evidence of the advantages of housing at least two calves together. Agriculture has changed significantly over the past 20 years alone. The more we understand, the better we can act accordingly and achieve progress.