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Variation in Milk Yield, Contents and Incomes According to Somatic Cell Count in a Large Dairy Goat Population

Francisco Javier Pleguezuelos, Luis Fernando De La Fuente and Carlos Gonzalo

Between 2009 and 2014, 758,382 monthly test-day records were obtained from 65,056 Murciano-Granadina goats in 132 Spanish dairy flocks. Variables measured were somatic cell count (SCC), milk yield and fat and protein percentages; means were 5.78log10 cells/ml, 2.04 L/day, 5.37% and 3.67%, respectively. Significant effects of year, herd test date, season, parity, month of lactation, litter size and covariables milk yield, fat and protein contents were evidenced on SCC. The regression slopes were negative for milk yield an d positive for fat and protein content, thus pointing out that high SCC in milk were associated with low milk yield and high contents. A second ANOVA was built to evaluate the evolution of test-day variables as SCC level increased within lactation. The percentages estimated in losses of milk yield for SCC levels 1 million cells/ml, 2 million cells/ml, 3 million cells/ml and >7 million cells/ml were 11.4%, 19.5%, 24.2% and 35.7%, respectively. Milk contents gains were also quantified. Milk incomes per goat and day (according to current payment system) revealed important economic losses (from 9.5% to 31.6%) for abovementioned SCC levels. Results emphasize the importance of SCC as a limiting factor for milk incomes in dairy goats.