Study on associations between somatic cell count and some physicochemical characteristics of cow’s milk

Background: Milk quality is fundamentally linked to udder health, with Somatic Cell Count (SCC) being a key indicator. Elevations in SCC, often due to subclinical mastitis, can alter milk's properties. This study aimed to investigate the impact of elevated SCC on the physicochemical characteristics of raw cow's milk during summer. Methods: Following Iranian National Standard No. ۳۲۶, ۳۰ milk samples were collected from second-calving cows in their third month of lactation in a dairy herd in Alborz province. Samples were transported under sterile, cold conditions. Analyses included chemical parameters (fat, protein, moisture, dry matter, fat-free dry matter) and physical parameters (acidity, pH, density), alongside SCC, using established national standard methods. Results: The SCC distribution revealed a concerning udder health status: only ۱۹.۹۸% of samples had SCC <۱۰۰,۰۰۰ cells/mL (healthy), ۲۹.۳۹% were between ۱۰۰,۰۰۰-۲۰۰,۰۰۰, ۴۱.۱% were between ۲۰۰,۰۰۰-۳۰۰,۰۰۰, and ۱۰.۵۳% exceeded ۳۰۰,۰۰۰ cells/mL. Using a ۲۰۰,۰۰۰ cells/mL threshold, over half the herd was affected by subclinical mastitis, with a statistically significant mean log۱۰ SCC increase of ۰.۶ units in unhealthy milk. This elevated SCC significantly (p < ۰.۰۵) degraded milk quality: pH decreased from ۶.۶۹ to ۶.۶۰, acidity increased from ۱۴.۲۴ to ۱۵.۶۹ °D, and fat content decreased from ۳.۴۳% to ۳.۲۶%. Protein content decreased from ۳.۵۳% to ۳.۳۲%, but this was not statistically significant. Conclusion: Subclinical mastitis, indicated by high SCC, causes significant deterioration in the physicochemical quality of raw milk. The findings underscore that proactive herd management and regular SCC monitoring are essential economic and public health strategies to ensure milk quality, control infections, and benefit the entire production chain.

کلیدواژه ها:

raw cow's milk ، somatic cell count ، physicochemical characteristics