الفهرس 
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Abstract
The present study was carried out to evaluate the protective potentials of egg yolk antibodies against Rota virus diarrhea in newborn calves.
A total number of ten laying hens (Red Bovins-German) that proved to be free from Rota virus antibodies (ELISA titer < 1/50) were immunized with attenuated Rota virus vaccine in an incomplete freuond’s adjuvant. Each bird received 0.5 ml of the attenuated virus at different sites of the breast muscle; the injection was repeated four at weeks, eleven weeks and fourteen weeks after the first injection as boostering.
Blood samples (for serum separation) and eggs (for yolk preparation) were collected at different intervals of immunization.
Serum and yolk were used for estimation of total protein, total immunoglobulins (estimated by zinc sulphate turbidity test) and Rotavirus antibodies (estimated by ELISA). The obtained results were as follow:
1.The total protein increased in the serum and yolk after immunization and reached to its peak at 3 weeks after fourth dose of immunization. There was a correlation between serum and egg yolk proteins.
2.The result of zinc sulphate turbidity test indicated that the total immunoglobulins were progressively increased as a result of immunization in serum and yolk of hens and reached its maximum values at the 3rd week after the fourth immunization then mentained high till the end of this study (14t1’ week after the fourth immunization). There was a strong positive correlation between serum and yolk globulin.
3.The Rotavirus antibody titer was markedly elevated after the 1st dose immunization and continued to increase with boostering, reached its peak at the 3rd week after fourth immunization (mean titer of 13120, 12800 in serum and yolk respectively) and then mentained high till the end of this study. The correlation between serum and yolk antibodies was strong positive indicating that hyperimmunization of egg yolk can be monitored and assessed by serum antibody titration.
4.The hyperimmune yolk was pooled diluted as recommended and defatted then administrated to two groups; three calves for each.
5.Field evaluation of protecti’e effect of egg yolk :
i.Calves in the 1st group received yolk only in milk from birth up to 14th days of age; while calves in the 2nd group received egg yolk in combination with colosno for the first 3 days of life; then in milk of their dams up to the le day of age. The third group received colostrum only for the same period.
The total body weight gain was markedly improved in calves received yolk during the neonatal period of life more than those received colostrum only or combination of both. Diarrhea was detected only in one calf received a combination of yolk and colostnim during the rd week of age.
ii.Values of total protein in calves received yolk only were slightly elevated than those received colostrum or combination of both. Along
the period of study; the total immunoglobulins profile was running parallel to that of the total protein.
iii. The Rota antibody titers were markedly higher in calves received
colostrum than those received a combination of colostrum and yolk (mean titers were 1706, 4266, 3413 and 2133 in calves received colostnun compared to 1066, 3413, 2560 and 1706 in calves received a combination of colostrum and yolk during 24 hours, one week, 2 weeks, and 3 weeks of age respectively.
6.The passive mice protection test proved that 100% protection was obtained with serum of one week old calves who received colostrum or combination of colostnun and yolk and Variable percentages of protection were obtained by the serum of the other period of life while there was no protection (0.0%) with serum of calves group taken yolk alone.
7.from the obtained results it could be concluded that the egg yolk could be used in a large scale for protection against diarrhea of calves due to rotavirus infection during the neonatal period.