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Associations between the stearoyl-CoA desaturase 1 (SCD1) gene and the Diacylglycerol-O-acyltransferase 1 (DGAT1) polymorphisms with milk production traits were analyzed using data from 1061 Chinese Holstein cows located in the Delta Region of Yangtze River in China. Milk production traits included test day observations for milk yield (TDMY), fat content (FC), protein content (PC), lactose content (LC), total solid (TS), milk urea nitrogen (MUN), somatic cell score (SCS), as well as lactation records, i.e. 305-day FCM yield, 305-day fat yield and 305-day protein yield. A total of 8,162 test day records were analyzed using a linear mixed model including the fixed effects of sire, herd, test year, test season, parity, calving season, milking day, gene locus, and the random effect of the cow. The effects of the SCD1 genotype on TDMY, FCM (fat corrected milk yield), FC, PC, SCS and 305-day FCM yield were analyzed. Cows with genotype AA produced significantly higher TDMY and FCM compared to cows with genotype AV or VV, but had lower values for FC and PC. Furthermore, the effects of the DGAT1 genotype on TDMY, FCM, FC, PC, TS, 305-day FCM, 305-day fat yield and 305-day protein yield were analyzed. Association studies revealed significantly lower TDMY, FCM and 305-day FCM yield for cows with genotype KK compared to genotypes KA or AA. In contrast, the KK genotype was superior with regard to FC, PC and TS. Cows with genotype KA produced higher 305-day fat yield and 305-day protein yield compared to genotypes AA or KK. These findings suggest a possible use of SCD1 and DGAT1 loci in marker-assisted selection programs for the improvement of milk production traits in dairy cattle from the Delta Region of Yangtze River in China. |
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