DNA. periodically during the 28 days study from each calf and tested for the presence of spp. using microscopic and molecular methods. Generalized estimating equations models were used to determine if the effects of the various treatments and/or rearing systems on the presence of diarrhoea and illness were statistically significant. Further analysis (classification trees models) was carried out to explore possible risk factors for cryptosporidiosis and relationships between treatments and rearing systems. Halofuginone lactate was shown to be effective in reducing medical indications of cryptosporidiosis and environmental contamination. However, the treatment did not delay the onset of diarrhoea and did not reduce the risk of illness amongst calves reared (+)-MK 801 Maleate collectively in a highly contaminated environment. The use of halofuginone lactate in combination with good hygienic actions, such as rearing animals in clean individual pens, was the most effective method to reduce the risk of cryptosporidiosis amongst 7C13 days old calves. It was concluded that the control of the parasite could be achieved by the combination of using effective preventive drugs, such as halofuginone lactate and good animal husbandry methods. is considered the most common enteropathogen of neonatal calves (de la Fuente et al., 1998, Santin et al., 2008). Infected calves can show medical indications ranging from asymptomatic illness to profuse diarrhoea and dehydration (Fayer et al., 1998, Thompson et al., 2007). These animals readily contaminate their immediate environment as total oocysts output per infected calf can be up to 1010 over a week (Fayer et al., 2004). A major problem concerning is the lack of an effective means for controlling illness and reducing environmental contamination with oocysts. Because oocysts are highly resistant to environmental tensions and to many disinfectants, hygienic measures on their own are not adequate to avoid illness and long term contamination of calf rearing facilities (ODonoghue, 1995). In addition, many medicines and vaccines have been evaluated as potential restorative or prophylactic providers for cryptosporidiosis but with little success (Santin and Trout, 2008). Halofuginone lactate is definitely a synthetic quinazolinone with cryptosporidiostatic activity within the sporozoite and merozoite phases of (Jarvie et al., 2005). It has been recommended for both restorative and prophylactic use as it delays the onset of illness, reduces dropping of oocysts, and decreases the severity of cryptosporidiosis in calves (Joachim et al., 2003, Jarvie et al., 2005). Its performance like a prophylactic treatment has not been evaluated for the various calf rearing systems used in Ireland. The primary objective of this study was to evaluate the effect of halofuginone lactate in reducing the number of diarrhoeic calves kept in two rearing systems on a dairy farm with a high prevalence of cryptosporidiosis amongst neonatal calves. The secondary objective was to test the effect treatment and (+)-MK 801 Maleate rearing systems may have within the onset of diarrhoeic indications and oocysts dropping, as well as on the number of calves excreting oocysts and the level of this excretion. 2.?Materials and methods 2.1. Study design A randomized double-blind trial was carried out during the period March to May 2005 inside a dairy herd of 400 cows situated in Co. Westmeath, Ireland. The herd was selected on the basis of a previous study in which the prevalence of was estimated by Bayesian analysis to be 98% (trustworthiness interval: 92C100) in 2-week-old calves (unpublished data). With this herd, calving occurred throughout the year. Cows were relocated to a calving pen approximately 1 week before calving and Hdac11 re-introduced to the milking herd 24?h after calving. The straw bed linens of the maternity pen was changed every 6 weeks. Calves were fed 2?l of their dam’s colostrum and separated using their mother within 12?h of birth. Commercial vaccines were not given to cows or calves. All Holstein Friesian calves created during the 3-week period, March 29thCApril 19th, 2005, were included in the experiment, with the exception of one calf that died a few hours after birth. Newborn calves (having a ration comprising soya, wheat and citrus pulp which was combined within the (+)-MK 801 Maleate farm. 2.2. Guidelines recorded Serum was collected on (+)-MK 801 Maleate one occasion from each 1-week-old calf. This was analyzed for the transfer of maternally-derived immunoglobulins using the zinc sulfate test (ZST) (McEwan et al., 1970). A (+)-MK 801 Maleate total of ten faecal samples (2?g) were taken from each calf. The calves were sampled on days 1 and 2, and thereafter every second day time on days 4, 6, 8, 10, 12 and 14. A further two samples were.