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Animal feed or forage may be the source of a limited number of infections for farm animals that could lead to human illness. Likely organisms include Salmonella enterica, Toxoplasma gondii, Trichinella spiralis and possibly the agent of bovine spongiform encephalopathy. The risk to human health from other infectious agents which may contaminate either feed or forage appear to be either negligible, e.g. Bacillus anthracis and Mycobacterium bovis, or non-existent, e.g. Clostridium botulinum toxin and Listeria monocytogenes. Mycotoxins present in animal feed can result in foods of animal origin also containing them. This risk is well recognized but has yet to be quantified accurately and in some instances the risk may be of theoretical rather than practical importance. Pesticides, agricultural and industrial chemicals, heavy metals and radionuclides may pollute animal feed and forages. The methods available for controlling pollution from these sources are well understood from a technical point of view although the effective implementation of controls can be difficult.

At depopulation time, broilers have to be transferred from the grower's house to the transport and then conveyed to the processing plant. Traditionally birds are caught by hand and crated prior to transport. That task is labour intensive and is often carried out during unsocial hours (nighttime). Removal of 20 000 or more birds from a house could therefore take several hours. This is then followed by the transport phase and, upon arrival at the processing plant, there may be an additional delay before birds are removed from the transport and shackled prior to slaughter. Different catching (harvesting) systems have been introduced in recent years. In general, they are designed to minimise the amount of handling the birds receive. Catching teams only load live birds onto the transport yet processing plants routinely record an incidence of dead birds when the vehicle is unloaded at the factory. This paper reviews transport systems and describes a survey in which three systems were used. Data were analysed over a 24-month period and the results suggest areas where processing plants could direct their attention in order to reduce the incidence of dead-on-arrivals.