Aufklärung aktueller tierzüchterischer und verbraucherrelevanter Fragestellungen durch molekulargenetische Strategien

Abstract

Claw diseases and disorders are the third leading reason for dairy cows leaving the herds and 90% of lameness cases are due to various claw diseases. As part of the FUGATO-plus GENE-FL project, the genetic causes of a pre-disposition for ailments of the feet and leg system in cattle, pigs, horses, and sheep were examined. For the investigations in cattle, samples from a total of 1.962 first-lactation Holstein Friesian cows were collected from seven high-producing commercial dairy herds from Mecklenburg-Western Pomerania with similar loose-housing systems and TMR feeding. The disorder status of the claws was recorded at time of trimming. As the basis of molecular biological investigations, positional and functional candidate genes with their asso-ciated biochemical pathways were determined by in silico analyses for conformation traits in cattle and other livestock species. A custom-made SNP-chip was developed from more than 1.000 ascertained candidate genes (384 SNP; 1 SNP/Gen). In total 1.183 cows were analyzed with this SNP-chip. A mixed threshold model analysis revealed a significant association between an intronic SNP (rs29017173, A/G) in IQGAP1 (BTA21) and sole hemorrhage status. This SNP also showed a significant association with breeding values for feet and leg conformation traits in a cohort of 2.394 A.I. bulls (Holstein Friesian). The beef cattle breed White Galloway exhibits four different coat colour phenotypes, well-marked (wsg), strongly marked (wsü), mismarked (wss), and fully black (wsch). The preferred phenotypes are well-marked and strongly marked. Mating of well-marked or strongly marked animals resulted in a certain percentage of mismarked or fully black animals. To elucidate the genetic background of the coat colour variations in White Galloway cattle, the four coat colour relevant genes mast/stem cell growth factor receptor (KIT), KIT ligand (KITLG), melanocortin 1 receptor (MC1R) and tyrosinase (TYR) were sequenced and analysed for causal coding sequence variants. No polymorphisms were detected in the potentially candidate genes, which explain the different coat colour variations. Due to these results, the genes were excluded as candidate genes. A recently described KIT gene duplication and aberrant insertion on BTA29 and/or re-insertion on BTA6 were analysed by Fluorescence in situ hybridisation (FISH), whole-genome sequencing, and PCR-based genotyping of the insertion break points in 178 White Galloway and 64 White Park cattle. In all cases, the coat colour variations of the two breeds can be explained by the recently described duplication and aberrant insertion of the KIT gene on chromosome 29. Food scandals have been reported from several countries repeatedly. In 2013, undeclared horsemeat was detected in convenience products. A precise quantification of the added undeclared species could not be determined reliably until now. As part of this study a method based on droplet digital PCR (ddPCR) was developed. The mito-chondrial CYTB gene and the nuclear F2 gene were used as targets. For the initial establishment of the method muscle, fat, tendon, and liver samples were used. While the number of mtDNA copies per cell differed up to 5 fold in these tissues, the nuclear DNA content was almost constant. Using various DNA- and meat mixtures of cattle, pig, and horse (50 % to 0.001 %) specificity and sensitivity of the method was analysed. A reliable quantification (LOQ) and detection (LOD) of admixtures of 0.01 % and 0.001 % was achieved using F2 as target, respectively.