Assessment of Glucose Homeostasis in Crossbred Steer Progeny Sired By Brahman Bulls That Experienced Prenatal Transportation Stress

The objective of this experiment was to assess glucose homeostasis of crossbred male progeny whose Brahman sires experienced prenatal transportation stress (PS) in utero. Sixteen steers (PNS group) sired by 3 PS bulls gestating dams were transported for 2 h at 60, 80, 100, 120, and 140 ± 5 d of gestation) and 16 steers sired by 3 control bulls (gestating dams were maintained in the same environment as stressed dams but not transported) were evaluated. Fifty-six days after weaning, pen score (PS; 1=calm and 5=excitable), exit velocity (EV; m/sec) and temperament score [TS; (PS+EV)/2] were recorded. Sixty days after weaning (d -5 relative to the challenge day), the 32 steers were transported in December from Raymond, MS to Lubbock, TX. Four days later (d -1) steers were fitted with rectal temperature (RT) probes and jugular cannulas, and subsequently placed in individual stanchions. Steers had access to ad libitum water for the full duration of the experiment, but feed was removed 12 h prior to collection of the first blood sample. On collection day (d 0), steers received an i.v. bolus dose of 50% dextrose solution (0.5 mL/kg BW), and serum samples were collected at -60, -45, -30, -15, 0, 10, 20, 30, 45, 60, 90, 120, and 150 min relative to glucose administration (0 min = administration) to assess insulin response. Data were analyzed with a fixed model specific for repeated measures and TS as a covariate. Glucose changed (P<0.01) over time during the hour prior to glucose administration (pre-glucose) and control steers tended to have greater glucose concentrations than PNS steers (P=0.10). There was a pre-glucose treatment by time interaction (P=0.03), with PNS steers having greater insulin concentrations 45 min before glucose administration compared to controls. The pre-glucose insulin:glucose (I:G) ratio changed (P<0.01) over time and PNS steers tended (P=0.06) to have a greater I:G ratio than controls. There was no difference (P>0.1) in circulating concentrations of glucose or insulin in the 150 min period following glucose administration (post-glucose). As expected, there was a post-glucose effect (P<0.01) of time in response to glucose administration for glucose, insulin, and I:G ratio. This appears to be the initial assessment of paternal transgenerational influence of such a prenatal stressor on glucose homeostasis in cattle. Prenatal transportation stress of bulls resulted in altered basal glucose and insulin homeostasis but no effect on insulin response to exogenous glucose in their steer calf progeny.