Cattle production: Reducing risks to calves in feedlots


By Digital team | 11 May 2018
dehorn; calf; disease; calves
Photo: Louw Pretorius

It is important to minimise losses from disease and deaths – which should be lower than 1% – during feeding. This means that if you feed fewer than 100 calves, there should be no deaths, or you will not make a profit.

The decision to feed calves in a farm feedlot is based purely on economics. Profitability depends on 2 factors: the cost of the feed and the price at which you will sell the fattened calves.

Farmers who successfully feed weaner calves for the market usually have access to a cheap source of high-energy feed such as hominy chop, a by-product of maize milling, or have a direct undertaking with a butcher to slaughter and sell their calves at a good price.

The aim of feeding high-energy and protein feed to young cattle in a kraal is to cut down on how much energy the animal needs to walk and graze, and to maximise the digested nutrients available for growth and fattening.

When feeding calves, 2 major disease prevention factors change:

  • The calves are fed a high-energy feedlot ration to which their digestive systems have to adapt. This increases the risk of digestion-related problems which don’t normally occur when calves are simply grazing.
  • Contact between calves fed in a small kraal increases, and so does the chance of transmitting disease directly from a sick animal to healthy calves.

Extra disease prevention measures will have to be taken and these will depend on the level of extra risk incurred.

Also read: What is weaning shock?

LOWEST RISK FEEDING

Only calves produced on the farm are fed a feedlot ration that consists of less than 80% of a high-energy and protein ration. Calves should not be transported before feeding starts.

Also read: How to mix creep feed for calves

The most important risks to be managed under such circumstances are:

  • The adaptation of the calves’ rumen to the concentrated high energy and protein feedlot ration; and
  • The prevention of clostridial diseases that can damage the animals’ intestines, muscles or nervous system.

ADAPTING THE RUMEN TO A CONCENTRATED DIET

  • When cattle graze on grass only, they break down the grass fibres when they chew the cud (rumination).
  • Bacteria (germs) in the rumen (greater stomach) break the finely chewed fibres down further and slowly digest them.
  • This process produces low levels of acids which are absorbed through the stomach lining into the blood.
  • They form part of the nutrients cattle obtain from their food.
  • Slow production and fast absorption prevent the build-up of acid in the rumen.
  • When cattle are fed a milled high energy feedlot ration, a huge quantity of starch and sugars are directly available to the bacteria.
  • Digestion is very fast and the germs produce a huge amount of acid very fast.
  • If this cannot be used and removed fast enough, it will cause acidosis (build-up of acid), which burns the stomach.
  • In severe cases the animal will die.
  • In other cases, the acid creates sores in the stomach wall, or thickens it, which will decrease the effectiveness of digestion and uptake of digested nutrients for the entire feeding period.
  • Bacteria in the stomach can also get into the blood through these open wounds and then into the liver, where they cause liver abscesses.
  • Another complication from acidosis is laminitis, a disease in which all 4 hooves become inflamed and sore.
  • Such calves are lame and walk with great difficulty, which severely affects their growth.
  • Calves affected by acidosis need immediate treatment.
  • They have to be dosed, with a product such as magnesium oxide, to neutralise the acid.
  • Farmers should get this product, and guidelines for its use, from a veterinarian before they start fattening calves in a farm feedlot.
  • Cattle can adapt to high-energy rations, but it takes at least 3 weeks before the digestive system uses and removes the acid fast enough to prevent acidosis.

Cattle have to be adapted to a high-energy diet. The table below outlines the procedure for switching from a roughage only (grass) diet to feedlot rations.

A buffer, such as feed lime, may also be included, at 2% of the final ration, to help neutralise the lactic acid that forms when feeding high-energy rations.

PREVENTING CLOSTRIDIAL DISEASES IN THE FARM FEEDLOT

REDGUT

  • Bacteria such as clostridia occur naturally in the intestines, but their growth is limited because the cattle are only eating grass.
  • As soon as the nutrients are enhanced, such as when providing a high-energy supplement or feeding in a feedlot, the growth of these germs also increases because more nutrients are available to the germs.
  • When these specific germs grow very quickly, they produce a poison that can damage the intestines and, if absorbed into the blood, will kill the animals.
  • This is the same type of germ that causes Pulpy Kidney disease in sheep.

BLACK QUARTER

  • Other germs in the clostridial family occur in the environment, eg in the soil.
  • These germs, ingested when young calves start to graze, can get into the blood through small wounds, such as those that occur when calves get new teeth.
  • The circulating blood allows them to get to the muscles where they will stay.
  • They don’t cause immediate harm, but remain dormant (sleeping) in the big muscles.
  • Then, if calves are handled roughly through a crush or neck clamp, these big muscles are bruised and swelling and bleeding takes place inside the muscles.
  • This creates perfect conditions for the dormant germs to grow and produce a poison in the bruised muscles that will severely damage them and kill the animal.

BOTULISM

  • Another disease caused by clostridial bacteria is botulism which results in paralysis and death in cattle.
  • The germs grow in high-protein material such as animal carcases, and produce a potent poison as they do so.
  • The poison can get into feed – for example, when a dead rat is milled with it.
  • Animals can also be exposed to the poison in water – for example, when the carcases of birds or small animals rot in their water source – which will cause botulism and lead to death in most cattle.

PREVENTING CLOSTRIDIAL DISEASES

  • These three diseases can’t be managed by treatment.
  • They kill cattle so fast that there isn’t usually time for treatment.
  • And there is no cost-effective treatment available to fight botulism.
  • The only defence is to use a broad-spectrum clostridial vaccination at least 2 weeks before you start feeding calves in the farm feedlot and to repeat this vaccination at the start of feeding.
  • These vaccines provide specific protection, but most, such as Covexin, don’t include protection against botulism, so a botulism vaccination must be given separately.

HIGH-RISK FEEDING

  • Calves for feeding in the farm feedlot are bought in from a variety of owners and transported to the feedlot.
  • On arrival they’re stressed, partially dehydrated and some will show signs of respiratory disease.
  • After adaptation they will receive a very high energy and protein feedlot ration containing less than 10% roughage.
  • These conditions are typical of what is experienced at commercial feedlots, where more than 1 000 calves are fattened at a time.
  • Now respiratory diseases become the biggest problem.
  • The biggest difference here, is the mixing of calves from various farms, which carry germs that can cause damage to the airways (respiratory system) leading to complicated respiratory infections or pneumonia.
  • The germs causing the primary damage are the various respiratory viruses.
  • A very broad spectrum viral vaccination is needed to protect cattle against pneumonia, and also a vaccination to guard against pasteurella.
  • At this level of feeding, vaccination and disease prevention programmes can only be carried out effectively with the guidance of a veterinarian.

Also read: Play it safe – vaccinate your livestock

  • This article was written by dr. Danie Odendaal and first appeared in Farming SA.