# Late gestation metabolizable energy intake is associated with modest differences in adipose tissue insulin responsiveness in antepartum beef cattle

## TL;DR

This study shows that feeding late-pregnant beef cattle higher energy rations slightly reduces their insulin sensitivity before calving, but has limited long-term effects.

## Contribution

The study provides new evidence linking late gestation energy intake to insulin responsiveness in beef cattle adipose tissue.

## Key findings

- HighME cattle had greater rump fat depth and tended to have larger adipocytes compared to LowME cattle.
- HighME feeding was associated with reduced insulin responsiveness, indicated by a lesser decrease in NEFA during an IVGTT.
- Postpartum energy markers like glucose and cholesterol were elevated in HighME cattle compared to LowME.

## Abstract

The objective of this study was to evaluate whether different metabolizable energy (ME) intakes would affect insulin responsiveness in late gestation beef cattle. Primiparous and multiparous cattle were fed rations that supplied 78% (LowME, n = 7 heifers and 12 cows) or 120% (HighME, n = 9 heifers and 10 cows) of predicted ME requirements from day −52 until calving, and then fed a common lactation ration. Body weight and rib and rump fat depth were measured every 2 wk prior to calving and on days 7, 13, 28, and 55 after calving. Plasma and serum were collected on day −3 and 7 relative to calving. Cattle underwent an intravenous glucose tolerance test (IVGTT) and a subcutaneous adipose biopsy on day −7 and −6, respectively. Prepartum body weight was similar (P = 0.62) for LowME and HighME cattle, but HighME cattle had greater (treatment by time: P = 0.01) rump fat depth than LowME at day −10 and −3 relative to calving. Overall, prepartum rib and rump fat depth tended to be greater (P = 0.07 and 0.06, respectively) for HighME vs. LowME. Glucose and insulin were similar (P ≥ 0.19) during the IVGTT and serum NEFA were elevated (P < 0.01) for LowME. The HighME NEFA decrement was lesser (treatment-time: P = 0.03) than that of LowME, indicating reduced insulin responsiveness. Adipocyte area tended to be larger (P = 0.05) for HighME. Antepartum glucose and cholesterol were greater (P < 0.04) and serum NEFA was lower (P < 0.01) for HighME vs. LowME. Postpartum albumin, glucose, and cholesterol were all increased (P ≤ 0.03) on day 7 after calving by feeding HighME before calving. Postpartum body weight was similar (P = 0.19) between treatments while rump fat depth was still less (P = 0.03) for LowME compared to HighME. The HighME cattle tended to have more (P = 0.06) rib fat depth postpartum. As such, HighME provision during late gestation improved markers of energy balance and was associated with modest reductions in antepartum insulin responsiveness, but this had few impacts after calving.

Evidence is presented which suggests that the degree to which late pregnant beef cattle respond to insulin is tied to how well their rations meet their energy requirements before calving. This information can be used to refine nutritional models for late gestation beef cattle.