INFLUENCE OF DIETARY-PROTEIN ON UREA LEVELS IN BLOOD AND MILK OF BUFFALO COWS

The aim of the study described herein, was to verify the influence of changing protein levels in buffalo cow diets on quantity-quality of mi lk yield, blood (BU) and milk (MU) urea, metabolic profile and milk fr eezing point (MFP). The experiment was carried out on eight buffaloes divided into two trials (trial 1 and trial 2), each trial divided into tree periods (P1, P2 and P3). The levels of CP/DM in the three period s were 9%, 12% and 9%, respectively. Buffaloes of trials 1 and 2 were different for days in milk (DIM = 164 vs. 132, respectively) and for m ilk yield (7 kg vs. 10 kg, respectively). Protein requirements were co nsistently met in trial 1 buffaloes, while the subjects of trial 2 wer e protein deficient in periods P1 and P3. The increase of CP/DM (P2) i ncreased milk protein level and quantity, and MU in trial 2. The CP/DM increase caused, moreover, a decrease, and therefore an improvement i n the MFP, and an increase in BU values in both trials. Multiple regre ssion analyses showed a strong link between MU and BU (R-2 = 0.769; P < 0.01) and between MU and BU as regards protein/energy ratio. The MFP , moreover, varied according to MU values (R-2 = 0.685; P < 0.01). The increase in protein concentration in subjects whose protein requireme nts had already been met, (trial 1) brought about an excess of protein which probably triggered a more intense gluconeogenesis confirmed by the higher glycemia levels (P < 0.01) in P2. In trial 2, on the other hand, the protein requirements met in P2 resulted in greater milk yiel d, which, not being backed up by the energy levels in the diet, caused a relative energy deficiency in the animals. This hypothesis is confi rmed by the increase in beta-hydroxybutyrate and lipoproteins as well as the lower body condition score levels in P2 vs. P1 and P3. The exis ting connection between protein/energy ratio and MU could indicate tha t in buffalo, as in cattle, MU can be used as a valid parameter in ord er to highlight the existence of an alteration in the protein/energy r atio of the diet. The normalization of the MFP upon the increase of th e CP/DM ratio confirms that in a diet rich in fermentable energy, it i s necessary to increase the dietary protein concentration and meet req uirements, in order to avoid abnormalities of the physical characteris tics of the milk. (C) 1998 Elsevier Science B.V.