Study on the relationship between milk urea nitrogen (MUN) and fertility in dairy cattle houses in Tabriz

The aim of this study was to assess the relationship between milk urea nitrogen (MUN) level and reproductive performance in high yielding dairy cattle houses in Tabriz, Iran. Among 213 selected dairy cattle, 76 heads (35.7%) have MUN < 16.00mg/dl (mean = 15.38 mg/dl) and 137 heads (64.3%) have MUN > 16 mg/dl (mean = 17.46 mg/dl). Our results indicated that MUN level in 81 heads of dairy cattle (total 124 heads) with mastitis, dystocia, laminitis, uterine infections or placenta replacement was higher than 16 mg/dl. We only observed a significantly positive association between MUN levels and dystocia (p= 0.032), while the association between MUN levels and incidence of other diseases was not statistically significant. The results of this study indicated that MUN level significantly influences the reproductive parameters including days open, calving to first service, first service conception risk, and number of services per conception (p<0.001). We concluded that measurement of MUN level in dairy cattle may be an effective approach to assess the outcome of the nitrogenous ingredients of ratios and prediction of reproductive status in post parturition stage.