RESUMO
The study of how different breeds adapt to heat stress and the further understanding of mechanisms underlying pigs thermotolerance is of utmost importance to attenuate the negative effects of heat stress on pigs welfare, physiology, and performance. Therefore, this study aimed at evaluating the effects of ambient temperature on performance and thermoregulatory responses of Piau purebred pigs. The Brazilian native pig breed Piau is a fat-type breed characterized by adaptability and resistance to diseases. To achieve our goal, Piau purebred pigs (65 kg initial BW) were allocated to one of the two constant ambient temperature conditions: thermoneutral (22 °C; n = 11) and heat stress (30 °C; n = 11). The experimental period lasted 15 days (days 1 to 15). Pigs were individually weighed at the beginning and end of the experimental period. Body and rectal temperatures, respiratory rate and blood indicators of stress and metabolism were measured throughout the experiment. Piau purebred pigs exposed to 30 °C had lower (p < 0.05) feed intake, body weight gain and final body weight than pigs at 22 °C. Feed conversion rate was not affected (p > 0.05) by ambient temperature. Irrespective of ambient temperature, pigs had similar (p > 0.05) backfat thickness and loin eye area. Piau pigs at 30 °C had increased (p < 0.05) nape, dorsal, flank, and rectal temperatures and increased respiratory rate than their counterparts reared at 22 °C. In summary, our results show that Piau purebred pigs acclimation to 30 °C of ambient temperature is characterized by increased body skin temperature to optimize sensible heat loss to the environment; increased respiratory rate to promote latent heat loss; and by a concomitant reduced voluntary feed intake to reduce heat production associated with digestion and metabolic processes with negative effects on body weight gain.
