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

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 (<i>Sus scrofa domesticus</i>). 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 (<i>p</i> < 0.001) and lactate (<i>p</i> < 0.001) concentrations, both peaking at 5 min post-injection. Iberian pigs showed higher plasma lactate (1.26 vs. 1.03 mM; <i>p</i> = 0.002), triglycerides (0.34 vs. 0.27 mM; <i>p</i> < 0.001), and non-esterified fatty acids (NEFA; 0.38 vs. 0.29 mM; <i>p</i> = 0.021), but lower glucose (4.80 vs. 5.03 mM; <i>p</i> = 0.010) than Landrace pigs, while cholesterol remained unaffected (<i>p</i> > 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.