MVSc

Immunogenetic studies were carried out in four hundred and eleven cross – bred cattle maintained at the University Livestock Farm, Mannuthy and Cattle Breeding Farm, Thumburmuzhi. The animals belonged to three genetic groups, viz. Jersey cross – breds, Brown – Swiss cross – breds and Holstein – Friesian cross – breds. The animals were typed for blood group factors and haemoglobin. Blood group reagents were produced from iso – immune sera, hetero – immune rabbit sera and colostrum of an immunised Cow. Eleven reagents were produced by the above cited methods and seven of them were comparable to international reagents. Serum from two animals (Animal Nos. 248 and 743) were used as sources of anti – J whose titres were being assessed periodically by haemolytic technique. The titre varied from 0 to 1:32, but no association with seasons of the year could be noticed.
Typing of cross – bred animals was done with 28 blood group reagents (14 internationally comparable and 14 new reagents). The internationally comparable reagents were B, Y2, E’3, C2, R, X1, F, V, J, L, S, H” and Z. Anti – J from two different sources (Animal Nos. 248 and 743) were used and one (Animal No. 743) seemed to be the sub type of other (Animal No. 248). Standard haemolytic test was carried out for typing animals for their blood group factors. The factors occurred in the three genetic groups with varying gene frequencies.
A good agreement was observed between the observed and expected numbers in each genotypes with respect to FV locus in all the population except in Holstein – Friesian crossbreds (P < 0.05)
The mode inheritance of blood group factors showed that the cattle red blood cell antigenic factors were inherited as dominant over their absence.
The cross – bred population was also typed for haemoglobin. Electrophoresis was carried out in polyacrylamide gel. Only two haemoglobin variants viz. HbA and HbB and three phenotypes viz. Hb AA, Hb AB and Hb BB were observed. The gene frequencies of HbA allele was 0.67, 0.66 and 0.83 in Jersey cross – breds, Brown – Swiss cross – breds and Holstein – Friesian cross – breds, respectively. The genotype frequencies at haemoglobin locus for the pooled cross – breds were 0.5031 (Hb AA), 0.4307 (Hb AB) and 0.0657 (Hb BB), respectively. Genetic variability of breeds was studied in terms of heterozygosity at Hb locus and Friesian cross – breds were found to have least heterozygosity, ie. 0.2822.
A good agreement was noticed between the observed and expected genotypes at haemoglobin locus and the populations were found to be in genetic equilibrium. The two alleles HbA and HbB showed co – dominance and equal penetrance when the inheritance pattern was studied.
An attempt was made to find out whether there existed any error in the recording. Exclusion of parentage was possible in 38 cases of recorded parentage and the error in breeding records was estimated to be 43.18 per cent.
The efficiency of each factors in solving the disputed cases was found to range from 0 to 26.3 per cent with higher efficiency being recorded for new blood group factors. Haemoglobin polymorphic system alone could detect three of the 38 disputed cases.
This showed that supplementing protein polymorphic loci with the blood group loci will increase the efficiency of parentage control.