Here is a detailed overview of its application:

1. Pharmacological Action: Toltrazuril is a broad-spectrum anticoccidial drug belonging to the triazinetrione class. Its mechanism of action involves interfering with the division of the coccidian cell nucleus and the respiratory and metabolic functions of the mitochondria, as well as causing the endoplasmic reticulum to swell and form vacuoles, leading to the death of the coccidia. It is effective against various Eimeria species in chickens, including Eimeria acervulina, Eimeria brunetti, Eimeria maxima, Eimeria mitis, Eimeria necatrix, and Eimeria tenella, and is also effective against strains resistant to other anticoccidial drugs.
2. Indications: Toltrazuril is used for the prevention and treatment of coccidiosis in poultry, and it does not affect the chickens' ability to develop immunity to coccidia. It is used for both treatment and prevention of avian coccidiosis.
3. Dosage and Administration: Administered orally at a rate of 25 mg per liter of water for chickens, once a day for two consecutive days.
4. Safety: Toltrazuril has a wide safety margin, and poultry can tolerate more than 10 times the recommended dose.
5. Absorption and Metabolism: After oral administration in poultry, more than 50% is absorbed. The drug is primarily distributed in the liver and kidneys and is rapidly metabolized into sulfone compounds. The half-life in chicks is approximately two days.
6. Withdrawal Period: The withdrawal period for chickens is 16 days.
7. Resistance: Frequent and repeated use of the same class of anticoccidial drugs or underestimating the weight of live poultry, leading to insufficient drug administration, can lead to the development of drug resistance.
8. Precautions: The diluted solution should not be used for poultry consumption after 48 hours, and it should not be used in animals known to be allergic to the product.

Through the above information, we can see that Toltrazuril's main application in chickens is as an anticoccidial drug for the prevention and treatment of coccidiosis, with broad-spectrum activity and high safety. At the same time, rational use and attention to resistance management are key to ensuring its effectiveness.