Respiratory functions and adaptation: an investigation on farm animals bred in tropical environment

To better understand the physiology responses in adapted breed to tropical environment this study evaluated the relationship between responses of adaptation and respiratory functions in ruminants raised in the tropics. Five trials were conducted for different species/breeds (five Nellore beef cattle, 10 Guzerat beef cattle, nine Anglo Nubian goats, 12 Jersey dairy cows, and 12 Morada Nova sheep). An indirect calorimetry system was used with a facial mask adjusted on the muzzle of the animal. Metabolic heat production (qmet, W kg-1), respiratory rate (RR, breaths min-1), ventilation (VE, L min-1), tidal volume (VT, L breath-1), CO2 production (VCO2, L h-1 animal-1), and O2 consumption (VO2, L h-1 animal-1) were measured simultaneously. Environmental data, including air temperature, relative humidity, and solar radiation were recorded from each site. Tidal volume values of 0.01, 0.008, 0.0075, 0.007, and 0.004 L breath^-1 kg^-1 were found for Morada Nova sheep, Anglo Nubian goats, and Jersey, Guzerat, and Nellore cattle, respectively, indicating that tidal volume per unit weight decreased with body weight wherever Morada Nova Sheep present a higher VO₂ consumption per unid of weight. Indeed, all the tropical breeding present a lower respiratory rate consequentially an indication of some adaptation.