# Comparative Metabolic and Stress-Related Responses to Adrenaline in Iberian and Landrace Pigs

## TL;DR

Iberian pigs show stronger metabolic responses to adrenaline compared to Landrace pigs, suggesting greater sensitivity to stress hormones.

## Contribution

The study reveals breed-specific metabolic differences in response to adrenaline, highlighting Iberian pigs' enhanced lipolytic and glycolytic activity.

## Key findings

- Iberian pigs showed higher increases in lactate, triglycerides, and NEFA after adrenaline injection compared to Landrace pigs.
- Adrenaline caused a stronger glycolytic activation in Iberian pigs, as indicated by a larger relative increase in glucose and lactate.
- The results suggest Iberian pigs have greater metabolic flexibility and sensitivity to adrenergic stimulation.

## Abstract

Stress can strongly influence how farm animals use energy and nutrients. Adrenaline is a natural hormone released during stressful situations that helps animals prepare for “fight or flight” by changing how sugars and fats are used in the body. This study compared how two pig breeds with very different characteristics—the traditional, fatty Iberian pig and the modern, lean Landrace pig—respond to an injection of adrenaline. Blood samples taken over time revealed that adrenaline transiently elevated glucose and lactic acid concentrations in both breeds, although the magnitude of these changes was greater in Iberian pigs. Iberian pigs also had higher levels of fat-related substances in plasma, showing a greater release of energy from body fat. These results suggest that Iberian pigs are more sensitive to stress hormones, which may influence how their muscles and fat behave during stressful events. This could help explain differences in growth, fatness, and meat quality between traditional and modern pig breeds. Understanding these differences can help improve animal welfare and product quality in pig farming.

Differences in metabolic traits between traditional and modern pig breeds may influence their physiological responses to stress hormones. This study evaluated the in vivo metabolic effects of an acute adrenaline challenge in Iberian (obese, slow-growing) and Landrace (lean, fast-growing) pigs (Sus scrofa domesticus). Four Iberian and five Landrace barrows (≈50 kg body weight; BW) fitted with a carotid catheter received an injection of adrenaline (3 µg/kg BW), and serial blood samples were collected for 105 min. Adrenaline transiently increased plasma glucose (p < 0.001) and lactate (p < 0.001) concentrations, both peaking at 5 min post-injection. Iberian pigs showed higher plasma lactate (1.26 vs. 1.03 mM; p = 0.002), triglycerides (0.34 vs. 0.27 mM; p < 0.001), and non-esterified fatty acids (NEFA; 0.38 vs. 0.29 mM; p = 0.021), but lower glucose (4.80 vs. 5.03 mM; p = 0.010) than Landrace pigs, while cholesterol remained unaffected (p > 0.10). No breed × time interaction was detected for any metabolite. The relative increase in glucose reached +47% in Iberian and +27% in Landrace pigs, whereas lactate rose +140% and +113%, respectively, indicating stronger glycolytic activation in Iberian pigs. Despite the limited sample size, the results provide physiologically relevant evidence supporting increased metabolic flexibility in Iberian pigs, characterized by a heightened sensitivity to adrenergic stimulation and associated with enhanced lipolytic and glycolytic responses; however, these conclusions should be interpreted within the specific experimental conditions under which the study was conducted. These findings demonstrate that Iberian pigs have higher metabolic sensitivity to adrenergic stimulation, with enhanced lipolytic and glycolytic activity. In conclusion, breed-dependent differences in stress-related metabolism suggest that Iberian pigs are furnished with increased metabolic flexibility to face short-term stress.