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On-farm assessment of insulin sensitivity from glucose responses to insulin infusion in neonatal dairy calves.

N. P. Uzee



On-farm assessment of insulin sensitivity from glucose responses to insulin infusion in neonatal dairy calves.
N. P. Uzee*1, C. C. Williams2, E. L. Oberhaus2, S. J. Blair2, B. S. Whitley1. 1Louisiana State University Baton Rouge, LA, 2LSU AgCenter Baton Rouge, LA.

Six male Holstein calves were used to assess glucose responses to insulin to develop an on-farm method of measuring insulin sensitivity with 4 blood samples. Calves were housed in individual hutches and fed milk replacer twice daily according to manufacturer recommendations. Milk replacer was reduced to one feeding daily on d 42, with weaning on d 49. Calf starter and water were offered free choice beginning on d 3. At 3, 6 and 9 weeks of age, insulin tolerance tests were conducted at 0700 h. Calves were not fed the AM feeding or allowed access to feed for the duration of the test. Insulin (7.5 mU/kg BW, 15 mU/kg BW, 30 mU/kg BW, 45 mU/kg BW, or 60 mU/kg BW) was infused through a jugular catheter (14 gauge, 3.5 in; MILA International, Inc.; Erlanger, KY) at time 0. Insulin concentrations were selected based on calf age, with calves at 3 wk receiving 7.5, 15, and 30 mU/kg and calves at 6 and 9 wk receiving the higher doses. Blood was collected at −10 and 0 min pre-insulin infusion and 10, 20, 30, 40, 50, 60, and 70 min post- insulin infusion and immediately tested for glucose concentrations using an Abbot Precision Xtra meter. The percentage decline in glucose concentrations at 40 and 60 min was calculated and plotted against the natural log (ln) of the insulin dose for each calf. Linear regression analysis was used to calculate the regression equation for each calf, and the ln of the dose of insulin resulting in a 50% decline in glucose concentration [ln(ED50)] was estimated from that equation. The ED50 was calculated by taking the antilog of ln(ED50). These values were used to determine the insulin dose that best predicts insulin sensitivity. Results indicated that mean insulin concentrations of 13, 33, and 36 mU/kg BW at 3, 6, and 9 weeks, respectively, were determined to result in a 50% decline in blood glucose post infusion using only 4 blood samples (−10, 0, 40, and 60 min post insulin). This method for assessing insulin sensitivity with fewer blood samples and no laboratory analyses will benefit researchers in quickly generating research data in dairy calf projects.

Keywords: insulin sensitivity, dairy calves, on-farm assessment.

Biography: Nicholas Uzee is a senior from Port Allen, La, majoring in animal sciences with a concentration in dairy production. He will graduate in May, 2020, and plans to pursue graduate studies in ruminant nutrition. He is the current ADSA-SAD first vice-president and has been very active in the student affiliate divsion of ADSA.