Genetic variability of milk rheological parameters in Italian Friesian dairy cows

The aim of this study was to estimate the heritability of coagulation parameters (r, clotting time; k20, curd firming time; a30 and a45, curd firmness measured at 30 and 45 min after rennet addition, respectively), somatic cell count (SCC) and titratable acidity. Milk samples were taken from 238 Italian Friesian cows reared in a single herd located in the province of Pisa (northwestern Tuscany, Italy). All individual sample were taken from the morning milking. The heritability coefficient of the clotting time (r) was 0.26 (± 0.142), while for the other technological parameters the coefficient was rather low (0.08 ±0.162 for k 20, 0.09±0.195 for a30 and 0.12±0.204 for a45). Also the heritability coefficient of the SCC was low (h 2= 0.07±0.122) but not different from values reported elsewhere, as for titratable acidity (h2= 0.03±0.201) too.