Effects of milk production level on milk quality in Italian Mediterranean buffaloes

The average milk yield of the Italian Mediterranean buffalo (8.34 kg/day/head) is the highest in the world with an average of 8.37% and 4.80% of fat and protein, respectively. Due to the increasing economic relevance of the dairy buffalo indus- try, interest is great in improving the production level of ani- mals maintaining at the same time good and stable values of milk quality parameters over the seasons. Aim of this study was to investigate the milk quality among buffalo cows with different production levels. From March to August 2016, 60 lactating buffaloes were monthly monitored for milk yield and composition. All buffaloes were kept in loose housing system and fed the same total mixed ration distributed once a day. The individual milk yield of the two-daily milking was recorded and milk samples were collected. Milk samples were analyzed to measure fat, protein, casein, lactose, urea, and cryoscopy index using Fourier Transform InfraRed (Milkoscan FTplus), calibrated with appropriate buffalo standards. Buffaloes were grouped in quartiles according to production level: Lower (LO): <7.6kg/d; Intermediate Lower (INLO): 7.6 to 10.2 kg/d; Intermediate Higher (INHI): 10.3 to 12.8 kg/d;Higher (HI): >12.8kg/d. Data were analyzed with PROC MIXED by SAS software including the parity (1, 2, and 3þ) and the classes of days in milking (11⁄40 - 30 d; 21⁄431 - 60 d;31⁄461-90d;41⁄491-120d;51⁄4121-150d;61⁄4>150d) of buffaloes as covariate. As expected, the average milk protein was significantly higher (p < .05) in LO group (4.95%) than INLO (4.76%), INHI (4.55%) and HI (4.48%) groups. The fat content showed a reverse trend over the production level, showing an average content significantly higher (p < .001) for the LO group (8.83%) and the lowest for the HI (7.82%) group. Lactose showed instead a reverse trend: the lowest average value for the LO (4.66%) and the highest for the HI (5.06%) group. Urea levels were not influenced by milk production level, although the urea milk content showed an increasing trend (p < .001) from March (35.86 mg/dL) to August (53.38 mg/dL). Results of this study point out that milk production level has a consistent effect on milk quality in mostly for protein and fat. Whereas, urea level was not affected by production level over the months. From these results, we also conclude that the buffalo cow diet should ensure a sufficient proteins per- centage, not only to meet requirements, but also taking into consideration the energy level.