Monitoring feeding adequacy in dairy cows using milk urea and milk protein contents under farm condition

The experiment was conducted on 264 crossbred Karan-Fries (Holstein Friesian x Tharparkar) cows, over one year to explore the possibility of using milk urea (MU) concentration and milk protein content to monitor feeding adequacy under farm condition and to investigate the effects of different animal factors and season on MU concentration. Individual noon (1200 to 1300 h) milk samples were collected once in every month and analysed for urea and protein contents. Representative feed samples were also collected on the same day of milk collection and were analysed for CP content. A significant positive association (p < 0.01) between MU concentration and milk yield was observed. MU concentrations (mg/dl) were found to be significantly (p < 0.01) higher and lower in first lactation (44.8 +/- 0.7) and in early lactation stage (40.7 +/- 0.5), respectively. Average MU values were found to be significantly (p < 0.01) higher in winter (50.7 +/- 0.3) and lower in summer (32.9 +/- 0.6). During the investigation, of the total MU observations, 50.3% were within the range of 30 to 50 mg/dl, 21.4% were < 30 mg/dl and only 7.5% were > 60 mg/dl. MU concentration was found to be associated significantly (p < 0.05) with CP content of forages rather than concentrate. A close positive association (p < 0.01) between MU level and daily milk protein (DMP) yield was observed during the investigation. The regression equation, DMP yield (g) = -24.6+33.5 daily milk yield (kg) +0.9 MU (mg/dl) was developed to establish the reference level of DMP yield. The result indicates that the effect of parity and stage of lactation may be ignored while interpreting MU values. However, reference MU values may be standardised separately for high milk yielders as level of milk yield contributes significantly to the variation of MU. The study revealed that the MU values together with DMP yield and milk protein content could be used as a potential non-invasive pointer to monitor feeding adequacy in dairy cows under farm conditions.