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- Respiratory diseases are undoubtedly the number one cause of disease and death in feedlots.
- Cattle are especially susceptible to pneumonia.
- Administering antibiotics to treat especially pneumonia is a constant source of concern.
- Preventing respiratory diseases from taking hold mainly depends on the quality of the animals purchased for the feedlot.
- At the age of three months, calves destined for the feedlot should receive a respiratory and clostridial vaccine.
Respiratory diseases are undoubtedly the number one cause of disease (morbidity) and death (mortality) in feedlots due to the large number of animals grouped together. Newly weaned calves destined to be marketed as A-grades are exposed to a series of consecutive, highly stressful events – from weaning to being transported to the feedlot, processing, and then being penned together with a large group of unknown animals. These young animals are therefore highly susceptible to all kinds of viral and bacterial infections.
Dr Jarred Morris, feedlot specialist at S&E Feedlot Consulting, says that, in terms of respiratory diseases in cattle, primary virus transmission typically occurs during this initial mixing of animals from different sources in one pen. “Some of these primary viruses damage the animal’s upper respiratory tract, providing a foothold for bacteria. This leads to secondary bacterial pneumonia, which has a major impact on that animal’s performance in the feedlot.”
Cattle are especially susceptible to pneumonia because, of all the large domestic mammals, their lungs have the smallest surface area. Furthermore, they have a special opening, the tracheal bronchus, to one lobe of the lung which branches off to the lung lobe before the major bronchial branch. The lobe is easily accessible through the tracheal bronchus.
Antibiotic resistance
Administering antibiotics to treat especially pneumonia, he says, is a constant source of concern. “The growing resistance of bacteria to antibiotics is a serious problem. Producers also view the preventive use of antibiotics in food-producing animals with growing trepidation. The routine use of antibiotics to prevent pneumonia is always in the spotlight due to fears that drug residues can potentially contaminate the meat.”
Dr Morris warns against the misuse of especially the macrolide group of antibiotics. This group of antibiotics is commonly used in feedlots in winter; however, under no circumstances must it be used outside the feedlot as the possibility of resistance is simply too great. Therefore, it may only be used for feedlot animals destined for the abattoir.
Quality of animals
Preventing respiratory diseases from taking hold mainly depends on the quality of the animals purchased for the feedlot. This quality is influenced by the farm’s production practices.
“Production practices entail the correct and timely vaccination of in-calf cows and the nutritional status of cows before calving. This has a direct impact on the quality and quantity of the colostrum that newborn calves receive which, in turn, influences the development of the calf’s immune system.”
According to the guideline, the calf should ingest at least 10% of its bodyweight in colostrum within the first four hours after birth. However, ensuring that this guideline is met is difficult to monitor in an extensive cow-calf production system. That is why preparing the cow for calving is so important. In this regard, the cow must be vaccinated against respiratory and clostridial diseases a month before calving using inactivated vaccines. Her nutritional status must also be monitored.
“Vaccinating a month before calving means antibodies will have time to concentrate in the udder so the calf can ingest them with the colostrum when it suckles. Of course, cows conceive over a period of three months and therefore not all animals can be vaccinated a month before calving. Working according to an average based on pregnancy tests conducted after the mating season will suffice.”
Because the handling of heavily pregnant cows should be kept to a minimum, Dr Morris recommends that an Escherichia coli (E. coli), Salmonella and rotavirus vaccine be administered at this time. However, this is only necessary if a farm experiences issues with neonatal diarrhoea.
“To summarise: The essential vaccines to administer a month before calving are respiratory and clostridial vaccines. If calf diarrhoea is a problem, anti-diarrheal vaccines should be administered at the same time. The only condition is that all vaccines must be inactivated. Attenuated vaccines at that stage of pregnancy can lead to abortions.”
Care for the calf
If your cows were prepared correctly, your calves received sufficient colostrum, and your cows are given enough feed to support milk production, then the calf needs nothing more until it is three months old. “The only exception is if you know that the colostrum intake was not sufficient. Then you can administer an intranasal vaccine that targets mucosal immunity in young calves.”
At the age of three months, calves destined for the feedlot should receive a respiratory and clostridial vaccine. By employing this dam-calf management approach, the calves entering the feedlot will be in good health, which will drastically reduce respiratory diseases in the feedlot. – Izak Hofmeyr, Stockfarm
For more information, contact Dr Jarred Morris on 082 559 1941.
