Characterization of milk composition, coagulation properties, and cheese-making ability of goats reared in extensive farms

摘要

The aims of this study were to explore the variabilityof milk composition, coagulation properties, andcheese-making traits of the Sarda goat breed, and toinvestigate the effects of animal and farm factors, andthe geographic area (Central-East vs. South-West)of an insular region of Italy, Sardinia. A total of 570Sarda goats reared in 21 farms were milk-sampledduring morning milking. Individual milk samples wereanalyzed for composition, traditional milk coagulationproperties (MCP), modeled curd-firming over time parameters(CF_t), and cheese-making traits (cheese yield,%CY; recovery of nutrients, %REC; daily cheese yield,dCY). Farms were classified into 2 categories based onmilk energy level (MEL; high or low), defined accordingto the average net energy of milk daily produced by thelactating goats. Milk yield and composition were analyzedusing a mixed model including the fixed effectsof MEL, geographic area, days in milk, and parity, andthe random effect of farm within MEL and geographicarea. Data about MCP, CF_t, and the cheese-makingprocess were analyzed using the same model, with theinclusion of the effects of animal and pendulum of thelactodynamograph instrument, allowing the measure ofrepeatability of these traits. Results showed that animalhad greater influence on coagulation and cheesemakingtraits compared with farm effect. Days in milkinfluenced milk composition, whose changes partlyreflected the modifications of %CY traits. Moreover,large differences were observed between primiparousand multiparous goats: primiparous goats producedless milk of better quality (higher fat, lower somatic celland bacterial counts) and less cheese, but with higherrecovery of fat and protein in the curd, compared withmultiparous goats. The repeatability was very high, forboth coagulation (84.0 to 98.8%) and cheese-makingtraits (89.7 to 99.9%). The effect of MEL was significantfor daily productions of milk and cheese, coagulationtime, and recovery of protein in the curd, which werebetter in high-MEL farms. As regards geographic area,milk composition and percentage cheese yield were superiorin the Central-East area, whereas daily milk andcheese production and MCP were better in the South-West. This result was explainable by the phenomenonof crossbreeding Sarda goats with Maltese bucks, whichoccurred with greater intensity in the South-West thanin the Central-East area of the island. The resultsprovided by this study could be of great interest forthe goat dairy sector. Indeed, the methods described inthe present study could be applicable for other farmingmethods, goat breeds, and geographic areas. Thecollection of a wide range of phenotypes at individualanimal level is fundamental for the characterization oflocal populations and can be used to guarantee breedconservation and the persistence of traditional farmingsystems, and to increase farmers’ profit.