Effects of Ambient Temperature on the Performance and Thermoregulatory Responses of Commercial and Crossbred (Brazilian Piau Purebred Sires × Commercial Dams) Growing-Finishing Pigs.

The study aimed at evaluating the effects of high ambient temperature (HT: 30 °C) on the thermoregulatory responses and performance of commercial and Piau crossbred (Brazilian Piau breed sires × commercial genotype dams) growing pigs. Commercial and Piau crossbred pigs were reared under thermoneutral (TN: 22 °C) or HT conditions during a 14-day experimental period. Feeding (daily) and animals (beginning and end) were weighted to obtain performance parameters. Skin and rectal temperatures, respiratory rate, and blood parameters were also measured. At the end of the trial (day 15), the animal's backfat thickness (BF) and loin eye area (LEA) were measured. No interaction (p > 0.05) between the genetic group and ambient temperature was observed for any performance trait. Irrespective of ambient temperature, Piau crossbred pigs had a similar feed intake (ADFI, 2615 g/day, on average; p > 0.05), lower daily weight gain (ADG, -234 g/day; p < 0.01), and a higher feed conversion ratio (FCR, +0.675 g/g; p < 0.01). There was interaction (p = 0.01) between genotype and ambient temperature for the LEA that decreased significantly in response to HT in commercial pigs (-6.88 cm2) and did not differ in response to ambient temperature in Piau crossbred pigs (29.14 cm2, on average; p > 0.05). Piau crossbred pigs had greater BF (+7.2 mm; p < 0.01) than commercial pigs. Regardless of the genetic group, exposure of pigs to HT resulted in decreased ADFI (-372 g/day; p < 0.01), ADG (-185 g/day; p < 0.01), and a higher FCR (+0.48 g/g; p = 0.01). Ambient temperature did not affect lipid deposition. Pigs at HT had an increased respiratory rate (+38 bpm; p < 0.01) and a long-lasting increase in skin and rectal temperatures compared to TN pigs. Total concentrations of triiodothyronine (T3) and thyroxine (T4) were not affected by ambient temperature in commercial pigs, whereas Piau crossbred pigs kept at 30 °C had a transient decrease in both hormones at day 2 (p < 0.01). Serum cortisol concentrations were not affected (p > 0.05) by genotype nor ambient temperature. In summary, Piau crossbred pigs had lower efficiency using nutrients for growth in association with increased lipid deposition when compared to commercial pigs. In response to HT, commercial pigs had a decreased LEA, whereas no effect was observed for Piau crossbred pigs. Apart from that, commercial and Piau crossbred pigs had a similar magnitude of thermoregulatory responses activation in response to HT, evidencing their innate survival-oriented function.

Effects of heat stress on performance and thermoregulatory responses of Piau purebred growing pigs.

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.

Interaction of space allowance and diet on growth performance and physiological responses of piglets raised in tropical conditions.

Intensification of pig production in developing countries has resulted in increased number of animals per unit area leading to welfare and growth performance issues. This study was then performed to evaluate the effects of space allowance and dietary energy and amino acid content on growth performance and physiological parameters of piglets reared under tropical conditions. A total of 1280 piglets (castrated males and females) with initial body weight of 5.9 ± 0.4 kg were used. Animals were distributed in a 2 × 2 factorial arrangement composed by two space allowances (0.30 and 0.22 m2/animal) and two diets during 43 to 63 days of age (control and experimental diet with increased ME and AA content). The experimental period lasted 42 days subdivided into four phases according to the growth stage of the animals: pre-initial I (21 to 27 days of age), pre-initial II (28 to 34 days), initial I (35 to 42 days), and initial II (43 to 63 days). During pre-initial I and II, and initial I phases, pigs housed at a space allowance of 0.30 and 22 m2/animal had similar (P > 0.05) feed intake, weight gain, and feed conversion. During initial phase II, space allowance did not affect (P > 0.05) feed intake nor weight gain of the animals. Whereas, pigs fed the experimental diet had greater weight gain when compared to the control group (530 vs. 515 g/day, P = 0.03). According to our results, reducing space allowance from 0.30 to 22 m2/animal during the nursery phase (21 to 63 days of age) had negligible effects on piglet feed intake and weight gain, whereas feeding piglets with diets containing higher energy and amino levels resulted in greater weight gain.