Genome-Wide Associations for Coagulation Traits, Individual Cheese Yield and Curd Nutrient Recoveries in Bovine Milk

The cow’s ability to produce cheese was decomposed into eleven milk coagulation curd-firming and syneresis properties (MCP), three cheese yield (CY) and 4 milk component recoveries into the curd (REC) traits, and genome-wide association analyses were conducted. The MCP traits were: 3 traditional single point lacto-dynamographic properties (RCT: rennet coagulation time, min; k : time to a curd firmness (CF) of 20 mm, min; a : CF 30 min after rennet addition), 6 parameters modeling 360 CF data for each milk sample (CF : potential asymptotic CF at infinite time, mm; k : curd firming instant rate constant, %×min ; k : syneresis instant rate constant, %×min ; RCT : RCT from modeling; CFMAX : maximum CF, mm; tMAX : time at CFMAX, min), milk- protein (%) and pH. The 3 CY traits were the weight (wt) of fresh curd (%CYCURD), curd solids (%CYSOLIDS), and curd moisture (%CYWATER) as % of wt of milk processed. The 4 REC (RECFAT, RECPROTEIN, RECSOLIDS, and RECENERGY) were calculated as the % ratio between the nutrient in curd and the corresponding nutrient in processed milk. Animals (n=1,043) from 85 herds were genotyped with the Illumina SNP50 Beadchip v.2. A single marker regression was fitted using the GenABEL R package (GRAMMAR-GC). The %CYCURD was linked to chromosome 6 (P<5x10 ). However, SNP located in 16 more chromosomes (1, 2, 9, 11, 12, 13, 14, 15, 16, 18, 19, 20, 23, 26, 27 and 28) were significantly associated to other traits, displaying the importance of decomposing a complex phenotype into different parts, to unravel its genomic background. Acknowledgements: Trento Province (Italy), Italian Brown Swiss Cattle Breeders Association (ANARB, Verona, Italy) and Superbrown Consortium of Bolzano and Trento.