Effects of severity of dystocia on cold tolerance and serum concentrations of glucose and cortisol in neonatal beef calves.

Effects of dystocia on rectal temperature and serum cortisol and glucose concentrations, were studied in neonatal calves exposed to 0 degree C. Primiparous dams were observed continuously during parturition and if Stage II (labor) was not completed within 2 h after appearance of the allantochorion, delivery was completed with obstetrical assistance. Parturitions were scored (CDS) for difficulty and obstetric assistance required: CDS 1, no assistance (n = 8); CDS 2, minor manual assistance (n = 7); CDS 3, use of a mechanical calf puller (n = 5); CDS 4, cesarean section (n = 6). A blood sample, rectal temperature, and body weight were obtained within 30 min after birth. Calves were then fed 38 degrees C pooled colostrum, muzzled to prevent suckling, and placed back with their dam in a heated (22 degrees C) barn. At 4 h of age an indwelling jugular catheter was inserted. At 5 h of age calves were placed in a 0 degree C room for 140 min and blood samples and rectal temperatures were obtained every 10 or 20 min. A shivering score (1 = no shivering; 2 = moderate shivering; 3 = intense shivering) was assigned at each sampling time. Rectal temperatures were higher (P < 0.01) in CDS 1, 2 and 4 calves (39.0, 39.3, and 39.0 +/- .02 degrees C, respectively) than in calves with CDS 3 (38.3 +/- 0.02 degrees C) and were affected by duration of cold exposure (time; P < 0.01). Shivering was not affected by CDS but was affected by time (P < 0.01). Glucose concentrations were higher (P < 0.01) in CDS 3 calves (110.1 +/- 1.6 mg/dL) than in CDS 1, 2, or 4 calves (77.2, 86.4, and 89.0 +/- 1.3 mg/dL, respectively) and changed over time (P < 0.01). Cortisol concentrations were higher in CDS 1 calves (80.0 +/- 1.7 ng/mL) than in CDS 2, 3 or 4 calves (62.7, 58.2, and 57.7 +/- 2.0 ng/mL, respectively) and were affected by time (P < 0.01). We conclude that severe dystocia (CDS 3) resulted in lower calf rectal temperature, reduced serum cortisol, and increased serum glucose which could affect the ability of the calf to withstand cold stress. Minor dystocia did not cause and timely cesarean delivery prevented, the physiological aberrations encountered in severe dystocia.