Usefulness of Milk Urea Concentration to Monitor the Herd Reproductive Performances in Crossbred Karan-fries Cows

The study was undertaken to investigate the validity of milk urea concentration as an index of the reproductive performances in crossbred Karan-Fries (Holstein Friesian${\times}$Tharparkar) cows under farm condition. Milk urea was analysed in noon milk samples (1200 to 1300 h) to interrelate with the interval from parturition to first service, number of insemination per conception, first service conception rate and service period. Milk progesterone (P4) was analysed in noon milk samples on the day 1, 10, 20 and 30 post insemination to study the effect of milk urea concentration on early embryonic mortality. The interval from parturition to first service was found significantly (p<0.01) higher ($77.2{\pm}5.5$ days) when milk urea concentration was ${\geq}63.4mg/dl$. The average milk urea concentrations (mg/dl) were found $42.1{\pm}2.5$, $47.9{\pm}1.5$ and $50.3{\pm}3.1$, respectively in cows that conceived at $1^{st}$, $2^{nd}$ and $3^{rd}$ insemination. However, the variation was not statistically significant. The first insemination conception rate was found significantly (p<0.05) higher (68.8%) when milk urea level was ${\leq}32.4mg/dl$. The service period was found significantly (p<0.05) higher ($125.4{\pm}8.8$ days) when milk urea concentration was ${\geq}45.1mg/dl$. The milk P4 level indicated that the cows, those were detected as non-pregnant on day 60 post insemination were initially pregnant but the pregnancy was terminated sometime during the day 30 to 60 post insemination. The study indicates that the milk urea values may be used as an index of reproductive performances in dairy herd when individual animals are not being monitored for nutritional status. The altered milk urea values may be utilised by the farmers as ready reference to rectify the protein and energy nutrition in cows to achieve the better reproductive performances in herd.