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Cattle production: Manage the rumen for profit

Cattle are ruminants that can eat and digest inexpensive, high-fibre plant material, unavailable to non-ruminant animals, and turn it into protein and energy.

Inside the rumen, one of the earth’s most densely populated microbial habitats, billions of micro-organisms transform grass into nutrients for themselves and for the host cow. During periods of declining forage quality, livestock managers can enhance the microbial landscape of the cow and help their cattle maintain condition and gut health.

The ruminant gut is uniquely adapted to enable the cow to consume and digest large quantities of fibrous plant material. Once this material has been converted into energy for growth, reproduction and lactation, it is used to produce meat and milk.

This extraordinary achievement is made possible by abundant and diverse communities of bacteria, protozoa and fungi resident in the gastro-intestinal tract. Microbial communities ferment, degrade and convert plant material into digestible compounds, some for the cow, some of it for their own sustenance. Microbes are the cow’s power supply, and it is in the farmer’s greatest interests to keep them functioning optimally so that his cattle remain productive and profitable.


The largest of the cow’s 4 stomachs is the rumen, often called the fermentation vat of the bovine digestive system. The rumen can hold as much as 180 litres, which gives it considerable storage capacity.

A functional rumen moves rhythmically, contracting every 90 seconds to 3 minutes. The contractions can be felt by putting one’s fist into a hollow called the paralumbar fossa, which is behind the last rib and below the lumbar vertebrae of the spine.

Inside the rumen, complex, layered and diverse communities of microbes colonise bits of ingested fibre of various sizes, and break them down through enzyme action. Some of the energy, protein, minerals and vitamins, released from the ingested roughage, are absorbed through the rumen wall into the bloodstream for the immediate energy needs of the cow.

The remainder is used to supply microbes with the necessary nutrients for growth and multiplication. Endless streams of these protein-rich micro-organisms, formed from expanding microbial communities, flow through the filters of the omasum into the abomasum, or true stomach, where they are digested by the animal’s own enzymes.


Although rumen microbes can utilise a variety of feed like pasture and veld grass, hay, root crops, the fermented waste of apple and citrus harvests, grain and oilseed crop residues, ensiled feed and urea, they are not adapted to mainly grain, or high fat diets, and they are intolerant of sudden dietary changes.

Sudden changes to the diet may cause the sensitive rumen microbes to die off. Declining microbe populations translate into reduced rumen activity with consequent, and serious, digestive health issues. An animal in this state will not survive without intervention which should be early, rather than late.

The practice of maintaining cow health, and assisting recovery from disease, by adding to, and enhancing, microbe populations in the rumen is not a new one. For decades, farmers have used healthy rumen fluid (usually from slaughter cows, sometimes from fistulated animals) to help cattle acclimatise to new feeding regimes, or to rebuild microbe populations that have died off because of illness and the accompanying reduced intake.

For microbes to remain viable the rumen fluid must get to the target animal within 2 hours of harvesting so the logistics of getting healthy rumen fluid from one animal to another may not be that simple. (veterinarian Dr. Faffa Malan says an oily film on top of the transported rumen fluid will extend the life of the anaerobic biota in the fluid.)


There is a growing range of rumen additives that have a greater convenience factor than rumen fluid. These products seek to increase “good” microbe numbers, inhibit the growth of pathogens, improve feed use and fibre digestibility, maintain a stable rumen pH (ideally between 6 and 7) to reduce acidosis risk, boost immunity, minimise the threat of bloat and reduce methane emissions.

Rumen additives act as a buffer against toxins, help combat the negative effects of transport stress and keep microbe populations stable during dietary transition. An example of this would be changing from a high-fibre, grass diet to a primarily grain-based diet of rapidly fermentable starches.

Using rumen additives to improve the digestibility of dry, fibrous, low-protein forage is particularly relevant to beef farmers who overwinter their cattle on sourveld, and other ranges, where veld grasses dry out and lignify during late autumn, winter and early spring.

The low protein content of lignified forage causes reduced feed intake, a drop in microbe numbers and a subsequent deficiency in protein and energy. Using additives can maintain microbiota and stop the decline of microbes in the rumen during the dry, cold period.


Probiotics or direct fed microbials (DFM) are live micro-organisms that benefit the host animal when fed in sufficiently large quantities.

Probiotics may be single- and multi-strain, bacterial, fungal, or a combination of both. They are dispensed in powders, pastes, capsules and boluses and use feed or water as carriers.

Probiotics increase beneficial microbes in the rumen, improve fibre digestion, reduce pathogen populations, increase digestive capacity, keep the pH stable (ideally between 6 and 7), limit acidosis, improve immunity in the gut and remove toxic molecules.

Some farmers use probiotics to boost the rumen when animals have suffered a bout of redwater, heartwater or gall sickness.

Rumenpro, a Green Bio product, is a probiotic blend of various Bacillus species and yeasts. It is popular among cattle ranchers who practice high density grazing. Rumenpro is applied at 1 g/day/animal in extensive beef systems.

Levabon Rumen E, a Biomin product, is a microbe-rich, yeast derived probiotic with amino acids and B vitamins. It promotes the growth of fibre-digesting bacteria, supplies nutrients for beneficial rumen microbes and for components that stick to pathogens. It improves feed efficiency and organic matter digestibility and supports the rumen environment.

Non-microbial additives

McCosker’s Brew is a strategic supplement for dry season feeding formulated by Australian range and cattle expert Terry McCosker. The supplement optimises rumen activity on low protein, unpalatable lignified sourveld. McCosker has incorporated feed-grade urea and crude protein in a formula that supplies rumen-digestible Nitrogen (in the urea) to stimulate microbe growth and generate protein.

The urea stimulates microbial growth in a way that mimics plant protein stimulation. Urea should be gradually introduced, starting at a time prior to the dry season when there is still some green plant material on the veld. The percentage of urea in the supplement can also be gradually increased. Generous quantities of standing or baled hay and water must be available.

Browse Plus, a Virbac product, is a polyethylene glycol (PEG) formulation. This rumen supplement allows increased use of woody species with high tannins. PEG stops tannins from binding proteins and from forming indigestible compounds in the rumen.

Farmers in the group Profitable Ranching report that they get good results using Rumenpro and PEG in combination with standard winter (protein) licks. Browse Plus may be added to drinking water, feed or lick and is applied at 1 g to 4 g per animal per day depending on quality of the vegetation.

Product resources:
For more information on Rumenpro go to
For more information on Levabon Rumen E contact
For more information on McCosker’s Brew go to
For more information on Browse Plus go to

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