MVSc

A study was conducted in Vechur cattle of Kerala to study the association of microsatellite marker alleles with the milk production and composition traits and to evaluate seven ancestors using microsatellite markers. Blood and semen was used as the source of DNA in this study. DNA samples were extracted from fifty unrelated animals and thirty three ancestors and progenies. Five microsatellite markers with established linkage to QTL controlling milk production traits like milk yield, fat percentage and protein percentage were used. The DNA samples obtained from the fifty unrelated Vechur cattle were typed using these five microsatellite markers. The five markers were found to be highly polymorphic with the PIC value ranging from 0.82 at the BM1508 locus to 0.89 at the HUJII77 locus. Data regarding the peak yield, days to attain peak yield, AFC and intercalving period were collected from the Vechur Conservation Centre, Mannuthy. Milk samples collected from the Vechur Conservation Centre were used to determine the milk fat percentage, protein percentage, SNF and total solids.

The mean fat percentage and AFC were found to differ significantly in different families. Statistical analysis revealed that the V43 and V88 families had a mean fat percentage significantly greater than the population mean. The mean AFC of V43 family was also found to be significantly greater than the population mean. The V44, V88 and V117 families had a mean AFC significantly lower than that of population mean. The V44 family had the lowest mean AFC and was also significantly different from the V88 and V117 families.

Microsatellite analysis was carried out for the thirty three combinations of ancestors and progeny using the same five markers. The allelic effect of microsatellite markers in the families was studied for fat percentage and AFC. The allelic mean for fat percentage of 223 bp size allele at the HUJII77 locus was found to be significantly higher when compared to those animals without this allele even though there were no earlier reports indicating linkage between this marker and QTL affecting fat percentage. The allelic mean of fat percentage for 205, 209 and 221 bp at the HUJII77 locus was significantly lower when compared to those of animals without this allele.

The mean of the animals with 208 bp allele at the ILSTS096 locus was found to be significantly greater for fat percentage when compared to the mean of those without this allele. There are earlier published reports indicating linkage between this marker and QTL affecting fat percentage. Selection for this allele will not be effective as it is already present in high frequency in the population.

The 252 bp allele at the BL41 locus had an allelic mean for fat percentage significantly lower than that for animals without this allele. The 238 bp size allele of this locus had an allelic mean for AFC significantly greater than that for animals without this allele. Earlier reports establish linkage between this marker and QTL affecting fat percentage but not AFC. Selection can be applied against this allele to prevent its frequency from increasing in the population.

The allelic mean of 158 bp allele at the BM1508 locus had a mean fat percentage significantly lower than that for the animals without this allele. There are earlier reports of linkage of this marker with QTL affecting protein percentage but not fat percentage. Selection against this allele is necessary as this allele is present in high frequency in the population.

Animals with 113 bp allele had an allelic mean of fat percentage significantly lower than that for the animals without this allele. This marker has linkage with QTL affecting milk fat percentage. It is advisable to select against this allele to increase the milk fat percentage in the population.

Even though the V44 sire can be selected for improving the fat percentage, the mean AFC of this sire was found to significantly greater than that of the population mean hence it is not preferred.

The sire V88 can be selected for improving the fat percentage as well as reducing the AFC. There is a possibility to improve the Vechur cattle maintained at the Vechur Conservation Centre, Mannuthy for fat percentage and AFC by adopting line breeding for V88 sire.