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- To understand how dry gallsickness develops, one must first understand how grass is digested in the rumen of a ruminant
- Grazing cattle ingest grass until their rumens are at capacity.
- If no protein supplement is given in winter, the number of organisms in the rumen will decrease and they will die.
- Animals will no longer be able to digest the grass, leading to them developing dry gallsickness.
- The microbes must be replaced by dosing the cow with rumen fluid from a healthy cow.
To understand how dry gallsickness develops, one must first understand how grass is digested in the rumen of a ruminant (in this case, cattle).
Grazing cattle ingest grass until their rumens are at capacity. Hence, the amount of grass the animal can ingest every day depends on the amount that can be consumed at a time, and the rate at which the grass is digested in the rumen to make room for more.
When the rumen is full, the animal will rest (lie down or stand), regurgitate a bolus, and ruminate the partially digested grass. The rumination action continues until all the grass from the rumen is finely ground by the animal’s molars. This broken-down grass fibres are now accessible for digestion by the microbes (single-celled organisms) in the rumen. These microbes secrete enzymes that digest the finely chewed cud.
Microbial action
The animal itself does not secrete any enzymes in the rumen. The digestion process is entirely dependent on microbial action. The nutrients released during the digestion of grass serve as a source of nutrition for these organisms. The availability of enough protein, the main limiting factor, allows these microbes to divide and multiply quickly. The millions of organisms formed can be compared to minced meat (microbial protein).
The digested grass is now fine enough to move to the reticulum and from there to the omasum and then to the abomasum. Here the microbes are killed and digested by the animal’s own digestive enzymes secreted by the wall of the abomasum. Digested nutrients are absorbed into the blood through the wall of the small intestine.
Figure 1: The development of dry gallsickness.
Protein supplementation in winter
Supplements are meant to supply enough protein to the rumen microbes so that they don’t die and their numbers decrease. The digestion of the grass is fully dependent on these microbes.
Supplementing cattle’s diet with approximately 350g of protein lick (40 to 50% protein value) has only one purpose, namely supplying these microbes with enough protein, a little extra energy, and vitamins and minerals so they can actively divide and multiply.
If no protein supplement is given in winter, especially in regions with sourveld grazing where the crude protein percentage in the grass can drop below 4%, the number of organisms in the rumen will decrease and they will die. Animals will no longer be able to digest the grass, leading to them developing dry gallsickness (the rumen basically stops functioning). The animal will lie down and die within a few days.
Treatment and prevention
Dry gallsickness is difficult to treat. The microbes must be replaced by dosing the cow with rumen fluid from a healthy cow. Rumen stimulants and high-quality roughage such as lucerne hay must be given to restart the digestive process. Consult a veterinarian in this regard. In most cases, treatment is unsuccessful if the condition is too advanced and the cow has been down for one or more days.
The only course of action is to supply protein supplements in autumn and winter to prevent dry gallsickness. Enlist the help of a nutritionist or veterinarian for a complete supplementary feeding programme for the year. Implement the plan monthly in accordance with the season and the cattle’s production stage. – Dr Danie Odendaal, Veterinarian Network
For more information, contact Dr Danie Odendaal at 082 454 0532.
