Explorative study of blood urea nitrogen (BUN), serum estrogen, and conception rate (CR) in small-scale dairy farms based on quantity of feed concentrate consumed by the cattle

   The purpose of this study was to measure the level of BUN in dairy cows and its influence on services per conception (S/C) rate, milk output, and the forage to concentrate (F/C) ratio.

   Oestrogen concentrations were also assessed based on BUN level and pregnancy rate. Three blood samples were taken for the measurement of estrogen on the day of AI (D0), seven days later (D + 7), and twenty-two days later (D + 22). From the entire herd, a batch of eighteen dairy cows in total were chosen at random and split to the groups based on S/C, milk output, F/C ratio, BUN, and pregnancy rate. The means of BUN based on F/C ratio showed significant difference (p < 0.05) of the results. Each group’s estrogen concentration on D0 and D + 7 did not significantly differ (p>0.05) in regards to BUN and pregnancy rate, while the group of non-pregnant cows with high BUN featured lower value. However, in D + 22, the group of non-pregnant cows with high BUN showed a lower estrogen concentration than the group of pregnant cows with low BUN (p < 0.05), while the group of pregnant cows with low BUN had a higher BUN concentration than the group of non-pregnant cows with low BUN (p > 0.05). These results indicated that while feed could alter BUN concentrations, non-feeding factors should also be taken into account. S/C and milk yield were found to provide no effect on BUN concentrations. According to these findings, a higher BUN concentration decreased the CR value, and concentrations of BUN ≥ 18 mg/dL led to lower levels of estrogen.

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