Farm Ireland

Saturday 17 March 2018

Learning how animals react to feed will help improve finishing


Gerry Giggins

The winter feeding season is in full swing throughout the country. Many farms are now looking at finishing animals as quickly as possible so as to reduce overall costs.

The market requirements for cattle to be slaughtered at younger ages and at lower carcase weights, and the switch from steer beef to bull beef, is seeing greater levels of concentrates being fed to finishing animals.

Farmers are, therefore, looking for higher daily liveweight gains in their cattle. The single biggest factor influencing daily liveweight gain of an individual animal is energy intake.

As the beef animal can physically only take in a defined quantity of feed on a daily basis (ie, around 2pc of its body weight on a dry matter basis), the only way to improve energy intake is to increase the energy density of the diet.

This means using a higher proportion of high energy products. However, the practical consequences of using high levels of high-energy raw materials on some farms can be catastrophic in terms of the animal's health and ultimate performance. Imagine driving a racing car; the faster we drive it the more likely we are to crash. The same is true when looking for high levels of performance in fattening cattle; the harder we push them, the more likely they are to crash.

As a beef nutritionist who visits cattle fattening farms and feedlots, the most common problems I come across are acidosis, laminitis, and lameness caused by pathogens.


All the above can be related to poor ration design or poor ration management. In order to get a better understanding of how we can prevent these problems, we need to get a grip on what happens when we feed animals.

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The feed ingested by a ruminant is first of all masticated and chewed around in the mouth before being passed down to the rumen. The rumen is a massive muscular sack containing gasses, liquids and solids. It is populated by different types of living organisms, whose role is to break down the food ingested by the animal into simpler, more digestible nutrients, which can be used by the animal more slowly.

The control of acid levels in the rumen is commonly known as buffering. The pH (acidity level) is controlled by a number of different mechanisms. We know that cud chewing is stimulated by the presence of long fibre in the diet, and straw at the correct length is most effective. A mature animal chews for up to a maximum of 14 hours a day.

The main source of this buffer is saliva, which is produced while chewing. We can see that when they are not chewing, the pH of the rumen starts to drop. The ideal pH range for the rumen in beef animals is 5.5-6. When pH drops below 5.5, we are entering the acidosis zone.


As the pH drops below 5.5, we also see an increasing amount of lactic acid being produced.

We have now entered the area of sub-acute acidosis. It is not desirable for the animal to be in this pH range for too long during any given day. If they are in this phase for a long period, the rumen starts to shut down. This stage is recognised as acute acidosis.

Prolonged low rumen pH (ie, below 5.5) leads to a build-up of lactic acid in the blood stream. This leads to a deterioration of the small blood capillaries in the extremities, leading to reduced blood flow to the hooves.

There is a build-up of toxins resulting in poor keratin growth in the hooves and the onset of laminitis, and eventually hoof breakdown, which facilitates the entry of pathogenic organisms, leading to infectious diseases such as mortellaro, etc.

It's at this stage that I generally get the phone call about a shed of lame animals gone off their feet and off their feed.

Adding buffers to the diet of finishing cattle is a huge aid in the management and control of acidosis. Buffers basically act by controlling excess acid in the rumen and, thus, help to control pH levels. They can act in two ways:

•Direct control of rumen pH: Addition of various neutralising agents such as sodium bicarbonate or calcium carbonate. Calcium carbonate (limestone) is, in theory, a good buffer. Unfortunately, its solubility in the rumen is very limited, therefore it can be regarded as an ineffective buffer.

•Indirect control of rumen pH: By eliminating or promoting proliferation of certain microbes in the overall rumen microbe population.

Mineral should contain proper levels of antioxidants, copper, zinc, calcium, sodium, phosphorus, buffers and yeast.

Gerry Giggins is a livestock nutritionist and can be contacted on

Indo Farming