Variation of somatic cell count-derived phenotypes for udder health monitoring in Italian buffalo

Mastitis data are usually not available on a large scale for all species intended for dairy, thus somatic cell count (SCC) is often used as indicator of udder health. In Italian buffalo, scarce attention has been given to SCC so far and there is need to improve udder health and mastitis resistance in the population to limit direct economic loss due to decrease in milk production and veterinary treatments. Moreover, elevated SCC in buffalo bulk milk is not currently penalise by payment systems. In cattle, high milk SCC is generally associated with a decrease of milk production and poor milk quality, as protein composition, pH and technological properties. Conventionally, the logarithmic transformation of SCC (SCS) is used for statistical analysis as it is normally distributed. Data consisted of 45,312 lactations of 35,623 animals occurred in Southern Italy between 2013 and 2017. Based on recent approach used in cattle, mean (SCS_M) and standard deviation (SCS_SD) of SCS in the first 150 DIM were calculated and severity was defined as the ratio of the n. of test-day SCC above 200,000 cells/ml (‘high’) to the total n. of test-day SCC (minimum set to 5) in the first 150 DIM. The first test-day SCC was recorded within 35 DIM and the interval between 2 consecutive test-day was lower than 60 days. Fixed effects included in the analysis of variance were parity, season of calving, year of calving and their interactions; cow, herd and residual were the random factors. Both SCS_M and severity increased with parity, whereas SCS_SD decreased. Buffaloes that calved in winter and autumn had significantly greater SCS_M and lower SCS_SD in milk compared to buffaloes that calved in spring and summer. Severity was the greatest (0.23) in lactations that started in autumn. Results indicated that the variation for these traits exists in buffaloes and multiparous animals might be monitored for udder health through SCC trend. Further studies should validate such potential indicators of udder health with clinical mastitis data and future efforts may focus on improving farmers’ sensitivity on SCC data interpretation and exploitation.