Could contract rearing be used to control Johnes disease?
A recent report from Animal Health Ireland (AHI) suggested that contract rearing could be an effective way of preventing the spread of Johnes disease from adult cattle to youngstock. Protecting youngstock from Mycobacterium avium subspecies paratuberculosis (MAP), spread from an infected animals dung, is critical to preventing the spread of Johnes disease. Although the primary objective of contract rearing will not be to protect youngstock from Johnes disease, it could be used an effective management practice to prevent the spread. This could be used in herds that are known to be infected with Johnes disease or for which the infection status is unknown. Contract rearing  Contract rearing is an agreement between a dairy farmer and another farmer (usually a dry stock farmer) to rear his replacements for a set period of time. This type of arrangement offers many benefits to both the farmer and rearer; these include:  Increased land area for milking cows;  Allows farmer to increase cow numbers;  Reduces the need for housing facilities;  Frees up time to complete other jobs;  Increase income for rearer;  Steady cashflow for rearer. Johnes disease spread  Protecting calves against exposure to MAP  the bacteria that causes Johnes disease  is an essential control measure, according to AHI. MAP is typically spread from contaminated dung. The spreading of Johnes disease from dairy cows typically occurs after the second calving or later, and very rarely before the first calving  but it can still happen. Preventing contact between young calves and other cattle is one of your best lines of defence. Advertisement  Calves will gradually acquire some age-related resistance against infection. So risk mitigation of young calves is more important during the first months, and becomes less critical as the animals age attains and exceeds 12 months. This is where AHI suggested that contract rearing could be a useful tool in preventing the spread of MAP. Risk of contract rearing  It is important to be aware of the risk of the potential exposure to Johnes disease on the contract rearing farm. If your herd has a known status of having Johnes infection, moving youngstock off the farm may help in preventing it spreading to them. But, if your herd does not have an issue with Johnes and the calves are moved off farm onto a farm that does or may have, this could lead to the calves becoming infected. Grazing your replacements should be arranged so that there is an interval between adult grazing or spreading slurry. Preferably, an interval of 12 months is advised, but if that is not attainable then the longer the better  before the calves graze the paddock. The sharing of pastures and sheds with heifers from other farms is not advised and should be avoided, as it carries risk in terms of biosecurity and Johnes disease.