The relationship between milk urea and some blood metabolites with pregnancy of Holstein dairy cows

This study was conducted to investigate relationship between milk urea (MUN) and some of the blood metabolites with reproduction performance in Dasht Azarnegin dairy cattle farm. For conducting this research, the milk and blood samples from 90 lactating cows in five parities, two seasons (hot, cold) and at 2 reproduction stages (estrus time, 55 days after insemination) were used. The parameters such as MUN and blood urea nitrogen (BUN), glucose, BHBA and protein concentrations were measured by spectrophotometer. For analyzing the data two different statistical models were used. In first model, using analysis of variance procedure the effects of different independent variables such as season, time of sampling, parity and monthly milk production (MMP, as covariate) were considered on measured dependent variables. In the second model, using logistic regression procedure, the effects of all the variables were considered on reproduction performance of the cows. The results from the first analysis revealed that MMP and season had statistically significant (P<0.01) effect on MUN and BUN. Time of sampling, season and MMP was only significant (P<0.05) in cows 55 days after insemination, while in the cows at estrus the time of sampling was significant (P<0.01) only. The season, MPP and the time of sampling was significant (P<0.05) on glucose only. The time of sampling and MMP in cows 55 days after insemination was significant (P<0.01) on BHBA and blood protein concentration. Other variables were significant only in cows at estrus time. The parity had not any significant effect on measured metabolites. In the second model, the glucose, MMP (P<0.01) and MUN (P<0.05) was significant in cows at estrus time and BHBA (P<0.05) and MMP (P<0.01) in cows 55 days after insemination only. Pregnant cows compare to non-pregnant had more blood glucose and less MUN, BHBA and MMP. In conclusion, one of the reasons for repeated estrus in productive dairy cows can be attributed to unbalancing of high ration protein and with raw energy which causes increasing BUN and MUN and changing concentration of other metabolites.