Animal responses and physiological indicators of stress in late pregnant alpacas on cultivated pastures in the High Peruvian Andes.

This study evaluated the effects of alpaca variety (Huacaya vs. Suri) and period on physiological parameters and stress indicators in late pregnancy, grazed on high-altitude cultivated pastures in Cusco, Peru (4,141 m.a.s.l). Eight Huacaya and six Suri alpacas were monitored in two experimental periods Transition (gestation months 8‒9) and Wet (gestation months 10-11), this last coinciding with the beginning of the rainy season. Data were analysed using a repeated measures model and Pearson correlations were established among selected variables. Regardless of variety, alpacas lost liveweight during the Transition period despite increased feed intake. Suri females displayed lower body temperatures (36.1 vs. 37.5 °C), and heart rates (60 vs. 65 beats/min) compared to Huacaya. No differences were associated either with variety or period in adrenocorticotropic hormone (ACTH) or cortisol in blood serum. The albumin-to-globulin ratio was lower in Suris and increased in Wet period. Differences in pasture crude protein contents between periods may explain increases blood urea nitrogen (BUN; + 1.25 mg/dL) in Wet period, whereas creatinine (CREA) was responsive to both variety and period. Distinct stress responses in Huacaya and Suri alpacas were evidenced by cortisol-ACTH correlations. Huacaya exhibit a stable hormonal feedback loop, whereas Suri are more influenced by period. Both alpaca varieties displayed unexpected negative cortisol-glucose correlations and differed in cortisol-protein metabolism associations. Despite physiological differences, kidney function remained consistent for both varieties. These findings highlight unique metabolic adaptations in alpacas and underscore the need for further research.