Cattle drenching

Pour-on (Back-spraying) Pour-on drench is applied to the back of cattle and is the most common method used. The process involves a water-based chemical solution applied to the back of an animal through a squirting pump attached to a pack worn on the back of the operator. The operator must put the cows head in a head bail or crush and use one hand to pry open its mouth and the other to slowly release the drench into the throat. Depending on the type of chemical used it can either be injected into the skin or muscle of the neck. The amount of drench used depends on the weight of the cows, but is usually between 2-5 mL. No more than one dose should be administered, as two doses could lead to death or serious sickness. Injecting cattle needs to be done carefully as irritation can cause large lumps on the side of the beast and be rendered ineffective. == Cattle Parasites ==

Buffalo fly The buffalo fly (Haematobia exigua) is a very common pest among cattle producers. Buffalo flies cause sores and ulcers causing large hide impairments on cattle as they rub themselves causing disturbances in feeding and hide quality reduction. Cattle ticks also cause tick fever triggering anaemia, high temperatures, and weakness which can potentially lead to death. The disease initially causes anaemia, licking and rubbing at bite sites (tick worry), tick sores, ulceration and lack of energy. Liver fluke cause a variety of diseases and health issues due to their migration from the liver causing blood loss and liver failure. Lice cause cattle to rub, bite and scratch, causing disturbances in feeding and loss of hide quality. Small brown worms do not feed on blood but damage the lining of the stomach as they reach adulthood. In more severe cases they cause death, collapses, weight loss, damage and inflammation of the gut resulting in diarrhoea and scours. Macrocyclic lactones are the most common form of drenches used in the pour on form; however oral benzimidazole (BZ) drenches provide similar control. == Categories of drenches ==

Anthelmintic is any drug that acts to expel parasites mainly helminths from the host's body through either stunning or killing the parasite. They aim is to expel the parasite without causing harm to the host. Macrocyclic lactones (avermectins and milbemycins) Macrocyclic lactones (avermectins and milbemycins) are chemical products of soil microorganisms developed in the 1970s/1980s for cattle use. Macrocyclic lactones also exhibit relatively long periods of persistent activity within cattle this is good for a long feeding season but leads to increased resistance. The original benzimidazole was thiabendazole; however, other, newer chemicals have been introduced with a range of commercial names. == Biological impact ==

The main biological impact of drenches is the expelling of any parasites, flies, worms and other insects which come in contact with the cattle drenched. Some chemicals used infiltrate the meat and can stay in the system of the animal for a period of time. The chemicals which are applied to cattle may potentially thus need a period of time where the owners cannot sell, butcher or transport the cattle. These withholding periods are needed due to this infiltration of chemicals into the meat of cattle which need time to break down the chemical residues. Cattle may also be under an export slaughter interval which means they can not be transported or slaughtered overseas for a period of time. The potential impacts of an early kill or even a natural death followed by wildlife eating the animal would see the meat sold permeated with the chemicals causing sickness or death. == Resistance to drenching ==

Resistance to drenches occurs through a genetic feature of the parasite, fly or worm that results in minimal or zero impact by the drench. Resistance to drenches first became known in the mid-1960s, however, widespread education was only used in the 1980s when farmers were educated on the unnecessary use of drenches in controlling parasites and to the need to create a wider range of drenches to stop resistance. Resistance to drenches has been controlled since however concerns about the build-up of these parasites with resistance in a colony is an issue. This occurs when the parasite survives and passes on their genes to the next generation. If the genetic selection becomes a major part of the gene makeup of the colony, then issues arise in controlling and new drenches must be manufactured. Resistance to drenching chemicals occurs due to over-drenching, under-dosing, long-acting treatments, low worm population treatment and consistent use of the same drench. Causing drench resistance is a common occurrence on smaller isolated communities and is an issue for agricultural industries that relies on clean cattle to trade. There are different management strategies to manage resistance to drenches including avoiding unnecessary drenching to older cattle, using shorter-acting drenches when possible and using the correct dose while varying the drench used year to year. == See also ==