Rabbit barns are of economic importance in central Mexico, where rabbit breeders use rustic buildings for production. In such barns, climate conditioning is mostly based on natural ventilation (NV) where the lack of a well-designed NV system may be a limiting factor. In this study, computational fluid dynamics was used to analyse the performance of the NV system in a 24 x 4 x 4.8 m typical Central Mexico rabbit barn with a density of 20 rabbits m^-2 of cage. The barn included both side vents at 1.2 m in height from the ground. Results indicated exchange rates of 0.052 and 2.9 x 10^-4 m³ m^-2 s^-1 when the wind direction was simulated as orthogonal and parallel to the side vents, respectively, suggesting the orthogonal direction favoured the exchange rate. However, such conditions produced an accumulation of ammonia underneath the rabbit cages. Thus, a design modification including a lower inlet vent was analysed. Such modification substantially decreased the concentration gradients of temperature and ammonia.

The concentration of ammonia (NH₃) and the temperature of the air surrounding the rabbit habitat in the farm condition basic health processes such as breathing and feeding. The indoor climate in a rabbit farm is largely conditioned by the ventilation system (air conditioning). The objective of this study was to build a numerical model based on computational fluid dynamics (CFD) in order to evaluate, by numerical simulations, the air dynamics of a rustic farm. After the validation of the computational model, the thermal gradient and ammonia concentration were analyzed under three wind incidence angles (0°, 45°, and 90° with respect to the horizontal Z axis of the facility). The results of the simulations showed that, in the area occupied by the rabbits (AOR), the concentration of ammonia with respect to the source was reduced by 37.3% in the most favorable case (wind direction at 45°), and 21.2% in the least favorable case (wind direction at 0°), and the indoor temperature presented a maximum difference of 2 °C with respect to the outside temperature. Climate control is a more expensive cost in rabbit farm exploitation; dynamics modulation can serve as an auxiliary tool for reducing health risks in rabbits. The use of models based on fluid dynamics allowed us to understand the efficiency of the ventilation system, which must be increased to reduce the found temperature gradient. Through numerical simulation it will be possible to find alternatives to increase the ventilation rate.