Determination of serum insulin concentration during intravenous glucose tolerance testing of healthy bulls

Prognostic judgment at post-surgery by biochemical parameters in beef cattle with left displaced abomasum

We examined whether the postoperative prognosis of beef cattle with left displaced abomasum (LDA) can be estimated from changes in laboratory parameters. Preoperatively, beef cattle with LDA showed increases in plasma glucose with decreased serum insulin in the glucose tolerance test compared to non-LDA cattle. Postoperatively, the cattle with LDA were retrospectively divided into two groups, good and bad prognoses. Although plasma glucose concentrations significantly increased either pre- or postoperatively, no difference was noted between the good and bad prognosis groups. Serum insulin concentrations in the bad prognosis group significantly decreased, compared to those in the good prognosis group. These findings suggest that beef cattle with LDA elicit disturbed glucose metabolite pre- and postoperatively, and serum insulin levels may predict their prognoses after surgery.

Evaluation of glucose tolerance and insulin sensitivity in Ilama crias

OBJECTIVE

To investigate glucose tolerance and insulin sensitivity in llama crias.

ANIMALS

7 llamas (age range, 14 to 30 days).

PROCEDURE

On each of 2 sequential days, crias were administered glucose (0.5 g/kg) via rapid i.v. injection. On 1 day (randomly determined for each cria), regular insulin (0.2 U/kg) or 0.9% NaCl solution (0.002 mL/kg) was administered i.v. 15 minutes after glucose administration. Blood samples were collected before (baseline) and at 5, 15, 30, 45, 60, 90, 120, 180, and 240 minutes after glucose administration for determination of plasma glucose and insulin concentrations; fractional turnover rates and plasma half-life of glucose were calculated. The data were compared over time and between days (ie, between glucose treatments with and without insulin administration).

RESULTS

A peak plasma glucose concentration of 342 +/- 47 mg/dL was detected at 5 minutes after glucose administration and llamas cleared glucose from plasma within 60 minutes; at 15 minutes, plasma insulin concentration attained a peak value of 33 +/- 13 microU/mL (ie, triple the baseline value). During the 15- to 45-minute interval, fractional turnover rate of glucose was 1.10 +/- 0.24%/min and plasma half-life was 65.7 +/- 13.4 minutes. Insulin significantly increased glucose turnover and resulted in hypoglycemia within 75 minutes of administration.

CONCLUSIONS AND CLINICAL RELEVANCE

Healthy immature llamas have glucose tolerance and insulin sensitivity superior to that of adults. However, whether sick crias retain the pancreatic sufficiency and tissue responsiveness that are likely responsible for the rapid glucose clearance in healthy individuals is not known.

Glucose tolerance testing in llamas and alpacas

OBJECTIVE

To determine blood glucose clearance in 2 species of New World camelids after IV challenge and to examine mechanisms of this clearance.

ANIMALS

5 adult female llamas and 5 adult gelded alpacas.

PROCEDURE

After food was withheld for 12 hours, camelids received 0.5 g of glucose/kg of body weight by rapid IV infusion. Serum concentrations of glucose, nonesterified fatty acids, cortisol, and insulin, and plasma concentrations of lactate were determined before and 0, 1, 2, 3, 4, 5, 15, 30, 60, 90, 120, 180, and 240 minutes after infusion. Ratios of insulin to glucose and insulin to cortisol were calculated for each time point.

RESULTS

Postinfusion glucose concentrations were significantly higher in llamas than alpacas for the first 15 minutes and remained significantly higher than baseline values in both species for 180 minutes. Lactate and cortisol concentrations did not change significantly; nonesterified fatty acid concentrations decreased in both species 30 minutes after infusion. Baseline insulin concentrations were < 6 microU/ml in both species and increased only to 10.1 +/- 0.7 microU/ml in llamas. Insulin concentrations did not change significantly in alpacas.

CONCLUSIONS AND CLINICAL RELEVANCE

Llamas and alpacas clear glucose more slowly than other domestic species after challenge, mainly because of a weak insulin response and slow cellular uptake. This response may impair the assimilation of exogenous glucose as well as make llamas and alpacas prone to diabetes-like disorders when an abundance of endogenous or exogenous glucogenic agents are present.