Twenty four (12 buffalo and 12 Friesian) weanling male and female calves aged 4 months were used in this study.  Average body weights of  buffalo and Friesian calves were 113.83 ± 2.30 and 122.83 ± 1.10 kg of males and were 100.0 ± 2.30 and 102.0 ± 1.10 and  kg of females, respectively.  They were randomly allocated within sex into two equal groups three of each  in each breed. The first group in each sex within each breed was injected weekly intramuscularly with 5 ml/head of viteselen (each one ml contains vitamin E 150 mg and sodium selenite 1.67 mg) and the other group served as control. The injection protocol continued for 90 days. Animals were housed outdoor during cold winter conditions (Dec-Feb, 1998). Body weights, daily gain and feed conversion were recorded. Rectal temperature (RT, °C) and respiration rate (RR, r.p.m) were recorded out at 6 a.m and 3 p.m. Blood samples were taken and plasma glucose, total lipids, total protein, triiodothyronine (T3) and thyroxin (T4) hormones, selenium and vitamin E were assayed. T4/T3 ratio was calculated.      Injected buffalo calves recorded better (P<0.05) growth rate and feed conversion than control. However, Injected Friesian calves showed insignificant response. Males in both buffalo and Friesian calves recorded better (P<0.05) growth rate and feed conversion than females. Injected buffalo calves had higher (P<0.05, P<0.01) plasma total lipids, total protein, T3, selenium, vitamin E and T4/T3 ratio than control. However, injected Friesian calves did not significantly differ in the same blood parameters than control.  Male buffalo calves had  higher (P<0.05) in plasma total lipids, selenium, and vitamin E than female ones. Injected buffalo calves had higher (P<0.05) RT and RR at 6 a.m and 3 p.m. than control. While, injected Friesian calves showed insignificant response. Male calves recorded higher (P<0.05, P<0.01) RT and RR in buffalo and in Friesian  than female ones.       In conclusion, viteselen injection in weanling cold stressed calves could improve growth rate, feed conversion and led to efficient metabolic activities that were accompanied by high thyroid activity. These improvement in buffalo calves were exhibited especially in males than females.