Paromomycin improves clinical outcomes and growth performance compared with halofuginone in dairy calves naturally exposed to Cryptosporidium parvum.

Neonatal cryptosporidiosis is a major cause of diarrhea, impaired growth, and economic losses in dairy calves. This study compared the effects of halofuginone and paromomycin on diarrhea occurrence, oocyst shedding, and growth performance in preweaned Holstein calves naturally exposed to Cryptosporidium parvum. Seventy newborn calves were randomly allocated to receive halofuginone (n = 30; 100 µg/kg body weight) or paromomycin (n = 40; 50 mg/kg body weight) orally for seven consecutive days from 5 to 11 days of age. Diarrhea incidence, duration, hydration requirements, body weight development, and fecal oocyst excretion were monitored longitudinally. Calves treated with halofuginone had significantly higher odds of diarrhea compared with paromomycin-treated calves (OR = 4.93; 95% CI: 2.98-8.17; P < 0.0001). Halofuginone treatment was also associated with longer diarrhea duration (RR = 3.40; 95% CI: 2.20-5.24; P < 0.0001) and more days requiring hydration therapy (RR = 1.93; 95% CI: 1.48-2.50; P < 0.0001). From the second week of life onward, paromomycin-treated calves exhibited greater body weight, with significant differences observed during the preweaning period. Fecal oocyst shedding showed a pronounced peak in halofuginone-treated calves, whereas paromomycin-treated calves displayed a more stable and controlled excretion pattern. These findings indicate that paromomycin provides improved clinical control of neonatal diarrhea and supports better early-life growth compared with halofuginone in dairy calves naturally exposed to C. parvum.