Effect of milk somatic cell level on lifetime milk related performances in Italian water buffaloes

Dairy buffalo industry plays an important role in the Italian agricultural sector, especially for the high quality and market value of mozzarella cheese. Long living cows are supposed to provide more profit to the farmer, however, lactating animals keep memory of early productive life events and stressors, such as mastitis. The present study aimed to estimate the effect of somatic cell score (SCS) in first lactation on the lifetime cow performances. Data on 270-d milk, fat and protein yields, and on test-day somatic cell count were available for four lactations (first to fourth) of 5757 cows, for a total of 23.028 lactations. At least five test day records within each lactation were ensured to compute lactation mean SCS. Three classes of milk SCS infirst lactation were defined using mean (2.67) and standard deviation (1.21): high (SCS > mean + SD), medium (SCS within mean ± SD) and low (SCS < mean – SD). Statistical analyses were performed separately by parity. Milk yield traits were analysed using a mixed linear model that included herd as random effect (minimum three cows/herd), and classes of SCS in first lactation, year of calving, season of calving and age at calving as fixed effects. Pearson correlations between lactation mean SCS treated as different trait in different par- ities ranged from 0.26 (first and fourth lactation) to 0.60 (sec- ond and third lactation). Approximately 47% of cows with high mean SCS in first lactation had high mean SCS also in second lactation. Cows that were in the high SCS class in first lactation produced significantly less milk in second lactation compared with cows that were in low or medium SCS class in first lacta- tion. In subsequent lactations, milk yield did not differ signifi- cantly among SCS classes, even if a lower milk production was found in the high SCS class, compared to medium and low SCS classes. Overall, the lifetime milk yield loss was greater than 100 kg. The fat yield of cows that were in the high SCS class in first lactation was similar in the four lactations. Protein yield of second lactation cows was greater for medium SCS class, compared with high and low SCS classes. In conclusion, cows with high SCS in first lactation tended to produce less milk with high SCS for the entire life. Therefore, cow udder health has to be monitored starting from early career in order to reduce health-related costs and improve the farm profit.