Association between milk β-casein protein polymorphism and reproductive indices in Holstein dairy cows

Document Type : Research Paper


1 DVM Graduated, Faculty of Veterinary Medicine, Shiraz University, Shiraz, Iran

2 Associate Professor, Department of Clinical Sciences, Faculty of Veterinary Medicine, Shiraz University, Shiraz, Iran

3 Professor, Department of Clinical Sciences, Faculty of Veterinary Medicine, Shiraz University, Shiraz, Iran

4 Assistant Professor, Department of Clinical Sciences, Faculty of Veterinary Medicine, University of Tabriz, Tabriz, Iran


    The aim of the present study was to detect Holstein dairy cows with two allelic forms of A1 and A2 of milk β-casein gene and compare their reproductive indices. The blood samples were collected from 41 multiparous (without pre and postpartum clinical diseases) Holstein cows in a modern dairy herd. DNA was extracted from whole blood and the β-casein genotype was detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis using BstDE I (Dde I) enzyme based on the replacement of the proline by histidine at position 67 β-casein protein in A1 milk. The PCR products sequenced for each genotype which used as control samples to validate the RFLP findings. The reproductive indices between cows with different genotypes were compared by Kruskal–Wallis test. The results of the present study indicated that A1A1, A1A2 and A2A2 genotype had a frequency of 13 (31.7%), 21 (51.2%) and 7 (17.1%). No significant difference was found in calving to first service interval, days open and service per conception indices between studied cows with different β-casein genotypes (P > 0.05). As results, it seems that the identification and proliferation of cows with the allelic form of A2 of β-casein gene can be considered without adverse effects on the fertility of dairy cows. However, further studies are needed to investigate the relationship between this genotype and milk yield of cows in the dairy herds.


Main Subjects

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