Study of milk coagulation properties in multibreed Italian dairy herds

The Italian dairy industry is making notable efforts to improve milk coagulation properties (MCP), as they affect the efficiency of cheese-making process. Individual milk samples (n = 8,525) of 3,057 Holstein-Friesian (HF), Brown Swiss (BS), and Simmental (SI) cows from 39 multibreed herds of Veneto region (northeast Italy) were collected from September 2011 to February 2012, and evaluated for quality traits and MCP predicted by mid-infrared spectroscopy (MIRS). Daily milk yield for each cow was also available. Milk coagulation properties were rennet coagulation time (RCT, min) and curd firmness (a30, mm). Data were analyzed through a generalized linear mixed model including the fixed effects of month of sampling, parity, days in milk (DIM), herd, breed, and interactions between parity and breed, and DIM and breed. The random effects were cow nested within breed and residual. Breed and DIM were the most important sources of variation for MCP (P < 0.001). Milk from BS cows showed the shortest RCT (19.1 min) and the highest a30 (26.8 mm), whereas milk from HF cows had the worst MCP, with values of 21.0 min for RCT and 20.8 mm for a30. Days in milk, breed, month of sampling, and herd effects were highly significant (P < 0.001) for all studied traits. Results from this study indicate that, under similar environmental and management conditions, the HF exhibits less favourable technological properties of milk than BS and SI breeds.