Blood Urea Nitrogen in Guernsey Cattle

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Abstract
The blood urea N (BUN) of 236 Guernsey cows was measured quarterly for 2 years to determine the normal variations in BUN of animals as related to age, inheritance, pregnancy and season. The mean was 11.83 mg/100 ml blood plasma (range-2.9-22.4). Seasonal changes showed a significant (P< .005) peak (15.49 mg%) in the spring corresponding to pasture; the lows (< 8.5 mg%) were observed in the winter months. Advancing age and pregnancy were associated with a decline in BUN. There was no significant (P<.05) difference in mean BUN among daughters of 7 sires.