Identification of QTLs for low somatic cell count in Murrah buffaloes

Abstract

Mastitis, the most frequent and costly disease in buffalo, is the major cause of morbidity. The somatic cell count, an indirect indicator of susceptibility/resistance to mastitis, is a low heritable trait and thus a perfect candidate for marker assisted selection. Half sib families (12) were created and the somatic cell count was recorded at 3 stages of lactation during the first lactation of the 2,422 daughters belonging to 12 sires. Partial genome scan was carried out using interval mapping with different algorithms. The QTLs obtained for each half sib family were further subjected to meta analysis to identify chromosomal regions associated with somatic cell count on 8 chromosomes of buffalo. Four metaQTL regions were identified on chromosomes BBU1q, BBU8, and BBU10; 3 metaQTL regions on BBU2q, BBU9 and BBU15; 2 metaQTL regions on BBU6 and 1 on BBU7 of buffalo. Comparative genomics was used for finding out genes underlying the metaQTL regions; 1,065 genes were underlying the metaQTL regions in buffaloes assuming buffalo–cattle–human synteny. Genes (78) mapped to immune response. These genes are supposedly important candidate genes for further analysis. Gene ontology and network analysis was carried out on these genes. The genes identified belonged to immune response and defense mechanism. The QTL markers identified in the present analysis can be used in the breeding programs of buffalo to select the bulls, which are less susceptible to mastitis.