Animal Agrivoltaics combines electric energy generation, animal thermal comfort, and sustainable production at the same time. This model of production can foster the sustainable intensification of dairy production in tropical areas where solar irradiance is high and nearly constant throughout the year. In this study, we propose Animal Agrivoltaics as an alternative practice to reduce the heat load and eCH₄ emissions from dairy heifers in tropical areas. To attest this hypothesis, (1) the meteorological data and the behavioral and physiological responses of the animals were integrated in order to determine the benefits provided by the shade from the solar panels on the thermoregulation of the dairy heifers, and (2) measurements of the enteric methane emissions were taken to determine the potential of the solar panels to offset the GHG. Seven crossbred Holstein heifers (7/8, Holstein × Gyr) with a mean body weight of 242 kg (SD = 53.5) were evaluated in a paddock shaded with ten modules of solar panels. Miniature temperature loggers were used to record the body surface, skin and vaginal temperatures of the heifers every five minutes. The respiratory rate and the shade-use behavior were also monitored by two observers. These measurements were taken from 08:00 to 17:00 h for 18 consecutive days. After completing the field study, the heifers underwent for assessments of the daily oscillations of eCH₄ emission using a flow-through respirometry system. The use of shade by the heifers was progressively increased (p < 0.01) with an increasing level of solar irradiance. Lying and ruminating were more likely (p < 0.01) to occur when the heifers were in the shade, especially when the solar irradiance exceeded 500 W m⁻². Between 10:00 and 14:00 h, the heifers benefited from the shade produced by the solar panels, with a reduction of 40% in the radiant heat load. With an increasing intensity of solar irradiance, body surface temperature, skin temperature and respiratory rate of the heifers in the shade were lower (p < 0.01) compared to when they were exposed to the sun. The heifers had a daily methane emission total of 63.5 g per animal⁻¹ or 1.7 kg of CO_2-eq. Based on this emission rate and the amount of CO_2-eq that was not emitted to the atmosphere due to the electricity generated by solar panels, 4.1 m² of panels per animal (nominal power = 335 W) would be expected to obtain a net-zero eCH₄ emission. Over a period of one year (from September 2018 to August 2019), a set of ten photovoltaic panels used in the study produced 4869.4 kWh of electricity, thereby saving US $970.00 or US $48.00 per m² of solar panel. Based on the results of this study, it can be concluded that use of Animal Agrivoltaics, in addition to producing electricity, has significant potential benefit in providing better thermal comfort to cattle, as well as offsetting the enteric methane emissions released into the environment. In addition, the system would provide extra income to farmers, as well as a potential source of energy micro-generation.

The objective of the current study was to determine the influence of biochar supplementation on steer growth performance, carcass characteristics, and ruminal temperature of calf-fed Angus × Holstein (AXH) crossbred steers versus calf-fed Charolais × Holstein (CXH) crossbred steers fed for over 300 d. Fifty-six AXH crossbred steers (body weight (BW) = 192 ± 12 kg), and 56 CHX steers (BW = 188 ± 13 kg) were blocked by initial BW and assigned randomly to 28 pens. Dietary treatments consisted of a steam-flaked corn-based diet supplemented with 1) no biochar supplementation (control); 2) 0.2% (dry matter (DM) basis) of Biochar. Data were analyzed as a randomized complete block in a 2 × 2 factorial arrangement, using pens as the experimental unit. From 112 to 224 d on feed, dietary supplemental biochar decreased (P = 0.05) cattle average daily gain (ADG). However, there were no other dietary effects (P ≥ 0.11) on steer growth performance or performance-adjusted net energy values. Biochar supplementation tended (P ≥ 0.08) to decrease the marbling score and increase calf morbidity. Biochar had no other effects (P > 0.13) on carcass characteristics. Angus cross steers had a greater (P ≤ 0.05) final live weight and DM intake compared to CXH steers. Moreover, AXH steers tended (P = 0.09) to have overall ADG, and had a 9.4% greater (P = 0.03) overall ADG in the last 78 d compared to CXH. There were no differences (P ≥ 0.44) between breeds for gain efficiency or net energy for maintenance or gain based on growth performance. Charolais cross steers had the lesser (P ≤ 0.04) average ruminal temperature during the months of June, July, August, and November, while there were no ruminal temperature differences in September and October (P > 0.10). Angus cross steers demonstrated an increase (P ≤ 0.04) in kidney, pelvic, and heart fat, backfat thickness, marbling, and yield grade compared to CXH; however, CXH had a larger (P = 0.01) longissimus muscle area. There were no other differences (P ≥ 0.11) in carcass characteristics, health, or liver abscesses between breeds. Results indicate that biochar supplementation at 0.20% (DM basis) did not affect growth performance or carcass characteristics; however, breed (Angus vs. Charolais) used in a beef on dairy cross did affect carcass characteristics, including carcass weight, and muscle and fat deposition; showing the importance of proper breed selection when a beef on dairy crosses production.

Hair sheep dissipate heat mainly through respiratory evaporation, making panting an important physiological response to heat stress. This study evaluated the panting score (PS) as an indicator of heat stress in field-managed hair sheep. Fifty-two non-pregnant, black-coated Santa Inês ewes were kept in paddocks without shade for five consecutive days from 07:00 to 18:00. Respiratory rate (RR) was recorded every 30 min, vaginal temperature (T_VG) was continuously monitored, and PS was assessed every two hours using a 0–4 scale. Meteorological variables were recorded, and the temperature–humidity index (THI) was calculated. Associations were analyzed using Pearson’s correlation, mixed (T_VG), and generalized additive (RR) models. Animals were exposed to severe and, at times, extreme heat stress conditions (THI ≥ 25.6) between 10:00 and 16:00. PS showed a strong correlation with RR (r = 0.74) and moderate associations with air temperature (r = 0.69), THI (r = 0.49), and solar radiation (r = 0.47). Higher PS values (2–3) predominated during peak solar radiation. Increases in PS were associated with elevations in RR and T_VG (~0.66 °C). Broken-line regression identified a THI inflection point at 24.44, above which the T_VG increase was attenuated by 46%. These results establish PS as a valid field indicator of heat stress in hair sheep and provide a THI inflection point (24.44) above which thermoregulatory capacity is engaged, enabling more accurate on-farm heat stress monitoring in tropical extensive systems in the future.