Effect of somatic cell count on lactation and soft cheese yield by dairy goats

Abstract

Somatic cell count (SCC), California mastitis test (CMT), milk acidity (pH and titratable acidity) and their relationship with artisan soft chevre-type goat cheese yield were studied, using individual samples taken from Alpine goats over a 7 month lactation period. Every animal ( n = 57) was sampled weekly for 2 months after parturition and every 15 days thereafter. Goats were hand-milked once a day in the morning and samples were collected accordingly. Titratable acidity Dornic (NaOH n 9 ) pH, CMT and SCC (Fossomatic 90) were measured and cheese yield determined. Samples from 1046 milk tests showed 44% with SCC lower than 250 × 10 3; 36% from 250 × 10 3 to 1000 × 10 3 cells per ml and 20% showed SCC above 1000 × 10 3. Results demonstrated interaction ( P < 0.001) between lactation stage CMT and SCC ( P < 0.05). Lactation stage affected cheese yield, CMT ( P < 0.001) and SCC ( P < 0.05), although it did not affect pH or Dornic acidity. Somatic cell count was high (50% above 500 × 10 3 and 35% above 1000 × 10 3) in the first 45 days of the lactation and again at the end of the milking period, from Days 170 to 210 (23% above 500 × 10 3 and 15% above 1000 × 10 3), but low (90% less than 500 × 10 3) during mid-lactation. High or low SCC did not have a significant correlation with clinical mastitis or udder infection. Cheese yield decreased from the second month of lactation, increased in the last 2 months of milking and had a significant negative correlation with CMT ( P < 0.001). Somatic cell count which was higher than 1000 × 10 3 and CMT = 2.5 or 3 showed a difference ( P < 0.001) in pH and Dornic values compared with the rest of the milk samples. Cheese yield did not have a significant correlation with SCC but did correlate negatively with CMT ( P < 0.001) and positively with Dornic acidity, pH and month of lactation in the early (first 45 days) and late (last months) milking period ( P < 0.001). CMT above 2.5 randomly tested bacteriologically show sub-clinical mastitis and increased amount of milk need to produce 1 kg of cheese (yield).