Rumen
The rumen develops from a very small organ in the new-born calf (1-2 ltrs) to the most important part of the gut (25-30 ltrs) by three months. Given the right feeding strategy, it can enlarge quickly in the first few weeks of life.
When born, the calf’s rumen is sterile and most of the milk bypasses the rumen into the abomasum. A fully functioning rumen is like a giant fermentation vat where digestion of feeds takes place by microbes in an anaerobic environment.
The microbes come from the environment the calf is living in – the pasture, contact with the dam and other calves, the housing and so on. Once the calf begins consuming dry feed the microbes have a food source to grow on and hence rapidly multiply.
The products of fermentation, volatile fatty acids (VFA’s) also impact on rumen development. Of note, propionic acid is produced from the fermentation of starch. Propionic acid is significant because it has a positive effect on the growth of the rumen papillae (leaf like structures on the internal surface) which increase the surface area of the rumen and hence its ability to absorb feed. Starches from grains and concentrates are the best source of propionic acid.
Rumination can begin at about 2 weeks and is a good indication that rumen development is occurring. Dry feeds stimulate saliva production, which is a good source of sodium bicarbonate. This acts as a buffer in the rumen to maintain the correct pH for an optimal growing environment for the rumen microbes.
Successful calf rearers should aim for early rumen development. Early rumen development allows the rearer to wean calves off expensive milk quickly, with minimal growth checks and prepares the calf for high feed intake and growth rates.
Early rumen development is achieved through early dry feed intake. While a calf may not eat much dry feed in the first weeks of life, the amount it does consume is important because it triggers the start of rumen development. Early dry feed intake is improved by high palatability and the addition of Bovatec.