Cryptosporidiosis is a disease caused by a highly pathogenic protozoan parasite, belonging to the phylum Apicomplexa, which inhabits the intestinal tract of humans and animals causing outbreaks of diarrhoea worldwide. Cryptosporidiosis is regarded as a major concern for the dairy industry as it primarily affects neonatal calves, leading to increased morbidity and mortality rates. Calves younger than three weeks of age can have morbidity rates greater than 50% when infected with cryptosporidiosis. Diarrhoea alone accounts for roughly 75% of calf mortalities during the first three weeks of life due to mixed infections involving rotavirus, coronavirus, Escherichia (E.) coli, and Cryptosporidium spp. Given that Cryptosporidium spp. infections are a significant cause of diarrhoea and mortality in neonatal calves, it is important to implement effective management and prevention strategies on dairy farms. This will help to reduce the incidence and severity of infections, resulting in better calf health and welfare. In addition to the negative impact on the health and welfare of animals, it also leads to major economic losses for farmers, due to decreased milk production and increased veterinary expenses. The zoonotic potential and worldwide distribution of cryptosporidiosis raise public health concerns, especially in children and people with compromised immune systems. Although the Cryptosporidium parasite has been recognized for more than thirty years as the primary cause of diarrhoea, anti-parasitic therapy has been limited. There are currently no effective vaccinations or treatments for cryptosporidiosis based on the initial evaluation of available chemicals.

    The aim of the study is to compare the effectiveness of different inclusion levels of Allium sativum to potentially mitigate Cryptosporidium infection in naturally infected neonatal dairy heifer calves. The study objectives include:

• Determining the number of Cryptosporidium oocysts present in the faeces of dairy heifer calves after receiving different inclusion levels of Allium sativum.

• Evaluating the intake, growth, and performance of dairy heifer calves receiving different inclusion levels of the active component.

• Comparing the impact of no treatment and Allium sativum on the symptoms and immunity of dairy heifer calves.