Assessment of nutritional status of lactating crossbred cows

The study was taken up to assess the nutritional status of the lactating crossbred cows, on the basis of milk urea nitrogen (MUN). 72 lactating crossbred cows, of the university dairy herd were grouped according to parity (1^st- 5^th lactation). Within the parity, the animals were divided into high, medium and low yielders. Under each category, the animals were sub-divided, according to stage of lactation i.e. early, mid and late lactation. The data was analyzed by 5x3x3 factorial design. The secretion of MUN, purine derivatives (PD) and creatinine (CRT) in milk was not effected by lactation number, but total output of PD per day was observed to be lowest (P<0.05) in the 1^st lactation as compared to that in 5^th lactation. The milk yield per day increased with the advancement of parity. The parity of the animals however, showed no significant impact on the milk quality, except that milk protein and SNF was lower in the animals in 2^nd lactation. The MUN varied between 11.1 to 12.8 mg/dl. The production status, of the animals, did not influence the milk composition, except that total solids were highest (P<0.05) in high and medium yielders. The secretion of MUN in milk increased (P<0.05) with the increase in the production status of the animals. The secretion of PD and that of CRT in milk (on per unit basis) was not affected by the production status, though total output/d increased (P<0.05) with the increase in production status. All the constituents of milk increased with the advancement of stage of lactation, however milk yield and its’ density was depressed (P<0.05). The secretion of MUN, PD or CRT in milk was not affected by stage of lactation, though uric acid (UA) was low (P<0.05) in late lactation as compared to mid lactation. The total output of PD increased (P<0.05) up to mid lactation and declined thereafter. On the basis of MUN, it was observed that 55.6% of the animals were well fed, 41.7% of the animals were under fed, and only 2.8% of the animals were over fed. The study conclusively revealed that MUN could be used as an indicator for assessing the nutritional status (with respect to macro nutrients) of lactating animals, even under field conditions, so as to fine tune feeding management programme.