Effect of subclinical mastitis and stage of lactation on somatic cell count, milk composition, and plasmin activity in goat milk
R. Shangguan, L. Spicer, C. DeWitt, J. Z. Wang, and S. S. ZengJournal of Animal Science 89(E-Supplement 2):397. 2011
A total of 91 goat milk samples from individual udders of Alpine does during early, middle, and late lactations were used to investigate the impact of subclinical mastitis induced SCC increase on changes in chemical composition and plasmin (PL) activity in milk. Samples were collected and analyzed for fat, protein, lactose, solids non-fat (SNF), total solids (TS), SCC, and PL activity. Within three stages of lactation, all milk samples were sorted into three groups based on levels of SCC (low < 2.5 × 106, middle = 2.5 - 5.0 × 106, high > 5.0 × 106) and statistically analyzed in a 3 × 3 factorial ANOVA. There were no interactions of level of SCC and stage of lactation on variables measured (P > 0.05). Log10 (SCC) and percentage lactose in milk were negatively correlated (r = -0.34, P = 0.001). Fat, protein, SNF, TS, and PL were altered by stage of lactation (P < 0.05). PL activity was greatest in early lactation. In conclusion, in high SCC milk, lactose content may be more indicative of SCC level than milk fat, protein, SNF, TS, and PL activity during lactation. Stage of lactation is an important factor affecting milk composition and PL activity in goats with infection, and thus a necessary parameter in optimizing goat milk quality in conditions of subclinical mastitis.
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