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= Cattle Drenching = Cattle Drenching is the process of administrating chemicals solutions (anthelmintics) to Cattle or Bos Taurus with the purpose of protecting livestock from parasites, worms, fluke, cattle ticks, lice and flies. Cattle can contract diseases from parasites whom carry diseases or be negatively impacted by co-dependent parasites. Cattle drenches can be applied through a solution poured on the back, down the throat or injection. Cattle drenches are predominately necessary for young cattle with weaker immune systems that are susceptible to parasite

infestation. Drenching is a common method for controlling parasites in the meat and dairy industries. Drenching cattle improves the health, condition and fertility of cattle leading to increased calving rates, weight gain, and milk production.

Pour-on (Back-spraying)
Drench applied to the back of cattle is the most common drench 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 chemical then seeps into the skin on the back of the animal and into the blood stream of the animal ridding the cattle of the parasites the drench targets.

Oral
Using an oral drench gun attached to the back of the operator. The anthelmintic chemicals are shot down the throat of cattle attached to a pack worn on the back. Oral drenching can cause problems if the drench is administered to the wrong part of the throat causing the drench to go into the lungs. This could potentially kill or make a cow seriously sick. The trachea leading to the lungs is located at the middle back of the throat. The oesophagus is in the back left and this is where the drench is aimed. The operator must put the cows head in a head bail or crush and us one hand to pry open its mouth and the other to slowly release the drench into the throat. Care must be taken not to damage the tongue, gums or throat.

Injection
Injection through a syringe is applied to the neck of the cow. 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, normally the Drench is 1 or 2 mls per 10-20kgs. Or 2-5 mls when using the injection method. Administer the amount that the drench has specified and no more. The logic “One dose is good. Two doses is better” is not true and could lead to death or serious sickness.

Categories of Drenches
Anthelmintic is any drug that acts to expel parasites mainly Helminths from the hosts body through either stunning or killing the parasite. They aim is to expel the parasite without causing harm to the host. There are a wide range of Anthelmintic drugs that can be used however three classes are available for sale on the livestock market including Macrocyclic Lactones, Benzimidazoles and Levamisole.

Macrocyclic Lactones (avermectins and milbemycins)
Macrocyclic Lactones (avermectins and milbemycins) are chemical products of soil microorganisms developed in the 1970/80’s for cattle use. Macrocyclic lactones offer a wide range of internal and external parasite protection. They are a commonly used drench and this is due to their low impact on cattle production and ability to expel adult parasites through to immature parasites (Lavae). 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. They have been open to for producers for over 40 years in the commercial form and continue to be effective in expelling parasites even with the increasing resistance issues. There are five types of macrocyclic lactones active ingredients that are used Eprinomectin, Moxidectin, Ivermectin, Doramectin and Abamectin. All five ingredients can be administrated through easy to use pour-on solutions (Back Spraying) and some oral drenches.

Benzimidazoles
Benzimidazoles are another chemical family which is effective in the eradication of some parasite infections with particular focus on nematodes and trematodes. The original Benzimidazole was thiabendazole however other newer chemicals have been introduced with a range of commercial names. All but one Benzimidazoles products must be administered orally which has led to their reduction in use as pour-on drenches are more popular due to there easy administration. There are three different type of active ingredients that are used Albendazole, Oxfendazole and Fenbendazole.

Levamisole
Levamisole is another chemical that has more impact in expelling the adult parasites in livestock however exhibits less effective rates in reducing larvae. Levamisole is available for administration by injection, pour-on and oral routes which offers a variety of choice which is found in the commercial chemicals. Some products use Levamisole in conjunction with other chemicals.

Biological Impact
The main biological impact of drenches is to expel any parasites, flies, worms and other insects whom comes in contact with the cattle drenched. This in turn impacts the number of parasites, flies, worms and other insects ability to reproduce and impacts the role that they play in the ecosystem. Parasites are vital in protecting some animals from diseases and bacteria.

In addition the chemicals used to expel parasites are often still present in faeces that is excreted by cattle the impact of this on the environment comes in a few forms. Many dung dwelling insects are adversely effected by the process as dung is a habitat and full of minerals needed by animals. Firstly dung beetles play a large role in fertilising the land and spreading cow dung. However some chemicals once excreted from cattle are poisonous to dung beetles resulting in reduced habitat, less feeding and mating grounds and even mortality of some dung beetles.

The chemicals which are applied to cattle may potentially have a period of time where the owners cannot sell, butcher or transport the cattle. These withholding periods (WHP) are needed due to the infiltration of these chemicals into the meat of cattle as cattle take time to break down chemical residues. Cattle may also be under a export slaughter interval (ESI) which means they can't be transported or slaughtered overseas for a period of time. The potential impacts of a early kill would see the meat sold permeated with the chemicals and have impacts of eating the meat.

Resistance to Drenching
Resistance to drenches occurs through a genetic feature of the parasite, fly or worm that results in minimal or zero impacted by the drench. Resistance to drenches first became known in the mid 1960’s however only in the 1980's was it seen to educate farmers on the unnecessary use of drenches in controlling parasites and to create wider range of drenches.

Resistance to drenches has been controlled 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 occur 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 and is an issue for agricultural industries that relies on clean cattle to trade.

There are different management styles to manage resistance to drenches including avoiding unnecessary drenching to older cattle, using shorter acting drenches when you can and using the correct dose while varying the drench you use each year.