BACKGROUND: Heat treatment of colostrum has been suggested as a control measure to eliminate or reduce the transfer of colostrum-borne pathogens to dairy calves.Objectives: The aims of this study were to determine the effects of on-farm heat treatment of bovine colostrum on colostral bacterial counts and IgG concentration and evaluation of passive transfer of immunity in neonatal dairy calves. Methods: Ninety-six L of first milking colostrum was collected from Holstein cows and pooled to create a uniform batch. Twenty-four calves were enrolled in 4 treatment groups before suckling occurred and fed raw colostrum (n=6), heat-treated colostrum at 60 ºC for 30 min (n=6), heat-treated colostrum at 60 ºC for 60 min (n=6) and heat-treated colostrum at 60 ºC for 90 min (n=6). Colostrum samples were collected before and after heat treatment and cultured for total bacterial count and analyzed for total IgG concentration. For the first and second feeding 2 L of colostrum was bottle fed by 2 and 12 h of age respectively. Serum samples were collected from calves at 0 h (precolostrum) and 6, 24, 48, 72 h (postcolostrum) and analyzed for serum total protein and IgG concentrations. Results: Heat treatment of colostrum at 60 ºC for 30 and 60 min reduced total bacterial count, yet maintained colostrul IgG concentration compared to the control. There was no difference between treatment groups when examining serum total protein and IgG concentrations, but apparent efficiency of IgG absorption was significantly greater at 6 h in calves that were fed heat-treated colostrum compared to calves fed raw colostrum. ConclusionS: There was no effect of on-farm batch heat treatment of colostrum at 60 ºC till 90 min on serum concentration of IgG.

BACKGROUND: The immunity and health of newborn calf are related to immunoglobulins uptake from colostrum where treatment of colostrum may improve the uptake. Objectives: The purpose of this study was to investigate the effect of controlled heat-treating of colostrum and antibiotic addition on immunoglobulins absorption, performance and health parameters of calf. Methods: The colostrum pool was prepared from multiparous dams and was frozen after the treatments. Colostrum was fed immediately after the birth three times a day for 2 days. Twelve newborn Holstein calves were divided into three treatment groups including 1) raw colostrum (control), 2) heat-treated colostrum, and 3) colostrum with oxytetracyclin in a completely randomized design. Blood samples were obtained in days 0, 7, 14, 21 and 28 via jugular vein. Health score and fecal point were determined daily. Results: Results showed that heat-treating of colostrum increased immunoglobulins uptake and their apparent efficiency of absorption (p<0.01), where a 24% increase in blood immunoglobulins concentrations and a 15% in their apparent efficiency of absorption were observed by heating the colostrum compared with control group and a lower increase was observed compared with antibiotic group. No significant differences were observed in weight gain, weaning time and weight as well as the amount and time of beginning starter intake among groups. Feed conversion ratio did not affected by the treatments. There were no significant differences in blood cells counts among groups. Calves fecal point was not affected by the treatments but health score was increased by using heat-treated colostrum where scour incidence was reduced (p<0.05). Conclusions: Results of the study showed that controlled heat-treating of colostrum is an effective and practical method to improve immunoglobulins absorption and reduce scour incidence in calf.