Evaluating relationships among blood glucose, plasma urea nitrogen, performance, morbidity, and mortality in high-risk feedlot heifers
Keywords:bovine, glucose, plasma urea nitrogen, bovine respiratory disease, aetiology, animal health, beef cattle, blood chemistry, blood sugar, clinical aspects, feedlots, heifers, liveweight gain, morbidity, mortality, nitrogen, respiratory diseases, risk assessment, risk factors
Two experiments were conducted using crossbred beef heifers (Exp. 1: n=332, 403 lb [183 kg] BW; Exp. 2: n=334, 456 lb [207 kg] BW) to evaluate relationships between blood glucose, plasma urea nitrogen, average daily gain (ADG), and morbidity and mortality rates. Whole blood glucose (Glc) was measured 24 hours after arrival using a handheld Glc monitor. Plasma was obtained from 179 heifers in Exp. 1 and from 334 heifers in Exp. 2 to determine concentrations of plasma urea nitrogen (PUN) and plasma Glc measured using a spectrophotometer. Heifers were placed into blood Glc categories of high (HGlc) and low (LGlc) Glc and high (HPUN) and low (LPUN) plasma urea nitrogen categories based on whether they had higher or lower levels than the mean of the group with which they arrived. In Exp. 1 ADG was lower for heifers categorized as HGlc and HPUN (P<0.05), but in Exp. 2 ADG was lower (P<0.05) for LPUN than HPUN heifers. Clinical signs (CS), first treatment, and retreatment rates were not different among groups in Exp. 1, but mortality rate was highest for HGlc (10.3 vs 6.0%; P<0.03). In Exp. 2. CS. first treatment, and retreatment rates were lower for heifers categorized as LGlc vs HGlc heifers (P<0.03). Days to first treatment were greater (P<0.05) for heifers categorized as HPUN vs LPUN heifers in Exp. 1 and 2. Elevated PUN may be an indicator of existing catabolism and stress in feedlot calves.