258. Evaluating Insulin Resistance and Sensitivity Values in Beef Steers from Birth to Weaning.

Abstract Although insulin status is known to affect growth and metabolic performance, it is unclear whether maternal insulin status directly affects calf insulin status at birth. Insulin resistance has been evaluated for animal performance in the feedlot but has limited research in pre-weaning calves. Additionally, there has been limited research on how dam insulin resistance relates to calf insulin resistance and performance. The objective of this study was to determine if dam insulin resistance and sensitivity values correspond to offspring insulin resistance and sensitivity values as well as performance characteristics. Steers (n = 43) and their respective dams were evaluated for insulin-related measures at the KSU Agricultural Research Center located in Hays, KS. Dam blood samples were collected after a 12 hour fast, 2 weeks before their expected calving date. Steer blood samples were collected 24 hours post birth. All blood samples were processed to obtain plasma. Individual animal was used for the experimental unit. Weights were collected both at birth (35 ± 4.2 kg) and weaning (183 ± 26.7 kg). Plasma was analyzed for insulin and glucose concentrations with corresponding values utilized to calculate the dam and steer Homeostatic Model Assessment for Insulin Resistance (HOMA-IR; 3.13 ±3.432, 4.90 ±4.077) and Quantitative Insulin Sensitivity Check Index (QUICKI; 0.36 ±0.062, 0.32±0.030) indices. Relationships between variables were assessed with Pearson correlation coefficients in R Studio (R-4.5.1.pkg) Effects were considered significant at P ≤ 0.05 and considered tendency when 0.05 < P ≤ 0.10. Dam QUICKI was positively correlated with steer QUICKI (r = 0.46, P = 0.002) indicating dam insulin sensitivity values may influence calf insulin sensitivity values at birth. Steer QUICKI was negatively correlated with weaning gain (r = -0.60, P < 0.001) indicating steers with lower gain had lower insulin sensitivity. Steer HOMA-IR was positively correlated with weaning gain (r = 0.52, P < 0.001) showing that steers with higher insulin resistance values had higher weaning weight gain. Dam QUICKI was negatively correlated to weaning gain (r = -0.38, P = 0.01) and tended to be negatively correlated with birth weight (r = -0.28, P = 0.07). Both indicating greater maternal insulin sensitivity is related to reduced offspring weaning gain. Dam insulin sensitivity values may be associated with calf insulin sensitivity values at birth, but they are negatively correlated with birth weight and weaning gains. Higher insulin resistance values may be associated with higher weaning gains and birth weight. These dynamics assist in explaining the key endocrine foundation that cattle may carry throughout their production. Further research is needed to determine if dam insulin sensitivity and insulin resistance values are related to steer insulin sensitivity, insulin resistance, and performance later in their production, both in backgrounding and in the feedlot.