Agrivoltaic systems in a tropical region: Influence on thermal environment, vaginal temperature, and behavior of dairy heifers.

This study aimed to evaluate the influence of different agrivoltaic system configurations on the thermal environment, vaginal temperature, and behavior of dairy heifers raised on pasture in a tropical climate. The study was carried out between July and August 2025, covering the winter season in the Southern Hemisphere. Microclimatic variables were measured, and the black globe-humidity index (BGHI) was calculated to determine thermal comfort. Additionally, vaginal temperature and behavior of 21 dairy heifers were measured in a crossover experimental design and compared among 3 treatments: an agrivoltaic system with panels installed in a vertical position (AGRIver), an agrivoltaic system with panels installed in a horizontal position (AGRIhor), and an open pasture system (OPS). All data were analyzed by mixed generalized linear models, and the results are presented using as estimated marginal means (emmeans ± SE). Both agrivoltaic systems (AGRIver and AGRIhor) showed lower values for the microclimatic variables and BGHI compared with the OPS, except for relative humidity. Treatments did not influence the heifers' vaginal temperature (AGRIver: 38.5°C ± 0.046°C; AGRIhor: 38.67°C ± 0.045°C; OPS: 38.71°C ± 0.046°C). Animals were observed more frequently standing ruminating in the OPS, and were observed most frequently lying in the agrivoltaic systems (AGRIver: lying rumination; AGRIhor: lying idle). Heifers visited the water trough more frequently in the AGRIhor system (emmeans ± SE; 20.2 ± 4.35 events/h) and tended to visit it less frequently in the AGRIver system (14.7 ± 3.19 events/h) compared with the OPS (16.5 ± 3.57 events/h). In OPS, heifers engaged more frequently in affiliative behaviors (3.92 ± 0.40 events/h) compared with agrivoltaic systems (AGRIver: 2.91 ± 0.32 events/h; AGRIhor: 3.15 ± 0.34 events/h). Furthermore, heifers interacted more frequently with photovoltaic panel structures in AGRIhor (4.02 ± 0.91 events/h) than in AGRIver (2.41 ± 0.56 events/h). In conclusion, agrivoltaic systems provided a better thermal environment for dairy heifers and influenced lying behaviors (rumination and idle) compared with the open pasture. Additionally, heifers used the photovoltaic panel structures as environmental enrichment.