Rodenticides come in many different bait formulations, including paraffin wax blocks, extruded blocks, pelleted bait, grain bait, liquid bait, tracking powders and bait concentrates. For rodenticides to be effective, target rodents must voluntarily eat enough bait. Therefore, successful control requires the type of bait used to be palatable and enticing to rodents. The features, application and suitability (for use in poultry operations) of the different bait formulation types are described below.
Grain and pelleted baits
Grain and pelleted baits are the most palatable and widely accepted formulation for rodents because they are similar to preferred natural food sources (grains, nuts, vegetables). However, these bait types are difficult to house securely. Because rodents tend to hoard food, they will often try to remove bait from bait stations to take it to their burrows or nests to eat later. This can potentially cause bait to be scattered in areas where it may become hazardous to non-target animals, including birds. Consequently, because of the higher secondary poisoning risks associated with grain and pelleted baits, they are unsuitable for use in poultry operations.
Block rodenticides
The most commonly used bait types are paraffin wax and extruded blocks. They are useful in areas with a high level of moisture, which may cause other bait types to clump or spoil. Rats will accept blocks less readily than loose or pelleted grain baits, but their design enables them to be tied down in bait stations with skewers, wire or zip ties. This prevents rats from removing bait from secure bait stations and minimises the risk of secondary poisoning of non-target species. For this reason, extruded and wax blocks are the most favourable bait formulation in poultry operations, provided they are securely housed in enclosed bait stations in areas that birds or non-target animals cannot access.
Liquid rodenticides
Sodium salts of anticoagulants are available as concentrates that can be mixed with water to create liquid bait. Like most mammals, rats need fresh water to survive, so restricting access to natural sources of water can drive rodents to consume these liquid rodenticides. However, liquid bait may also be enticing to non-target animals, therefore this bait formulation must be used carefully to prevent non-target animals from accessing it. In poultry operations, the use of liquid bait is generally advised only for internal shed areas during cleanout when birds are absent.
Tracking powders
Tracking powders are powders or dusts containing active concentrations of a rodenticide placed on the ground where rodents are highly active. As rodents walk through the powder, it sticks to their fur and paws, and is inadvertently consumed during self-grooming. The amount of powder ingested during grooming is likely to be small, therefore the active concentration of tracking powders is much higher than in consumable bait formulations with the same active compound. Tracking powders can be advantageous in environments with an abundant food supply for rodents and, therefore, where rodents have difficulty accepting ingestible bait formulations, such as wax blocks or liquid concentrates. However, the high active concentration and generally unsecured nature of tracking powders means that using it carries a greater risk of secondary poisoning or contamination (Timm, 1994). Extreme care must be taken to ensure that tracking powders are not placed in areas where they may come into contact with animal feed, human food products or non-target animals. Therefore, there is limited potential for the safe use of tracking powders in poultry operations.
