Increased dietary Trp, Thr, and Met supplementation improves growth performance and protein deposition of salmonella-challenged growing pigs under poor housing conditions.

Highly intensified rearing conditions and precarious sanitary management predispose pigs to immune system activation, altered amino acid (AA) metabolism, and decreased growth performance. Thus, the main objective of this study was to evaluate the effects of increased dietary tryptophan (Trp), threonine (Thr), and methionine + cysteine (Met + Cys) supplementation on performance, body composition, metabolism, and immune responses of group-housed growing pigs under challenging sanitary conditions. A hundred and twenty pigs (25.4 ± 3.7 kg) were randomly assigned to a 2 × 2 factorial arrangement, consisting of two sanitary conditions (SC, good [GOOD] or salmonella-challenge and poor housing condition [Salmonella Typhimurium (ST) + POOR]) and two diets, control (CN) or supplemented with AA (Trp, Thr, and Met + Cys:Lys ratios 20% higher than those of the CN diet [AA>+]). Pigs were followed during the growing phase (25-50 kg) and the trial lasted 28 d. The ST + POOR SC pigs were challenged with Salmonella Typhimurium and raised in a poor housing condition. The ST + POOR SC increased rectal temperature, fecal score, serum haptoglobin, and urea concentration (P < 0.05) and decreased serum albumin concentration (P < 0.05) compared with GOOD SC. Body weight, average daily feed intake, average daily gain (ADG), feed efficiency (G:F), and protein deposition (PD) were greater in GOOD SC than in ST + POOR SC (P < 0.01). However, pigs housed in ST + POOR SC fed with AA+ diet had lower body temperature (P < 0.05), increased ADG (P < 0.05) and nitrogen efficiency (P < 0.05), and a tendency for improved PD and G:F (P < 0.10) compared with CN diet fed pigs. Regardless of the SC, pigs fed AA+ diet had lower serum albumin (P < 0.05) and tended to decrease serum urea levels (P < 0.10) compared with CN diet. The results of this study suggest that the ratio of Trp, Thr, and Met + Cys to Lys for pigs are modified by sanitary conditions. Furthermore, supplementation of diets with a blend of Trp, Thr, and Met + Cys improves performance, especially under salmonella-challenge and poor housing conditions. Dietary tryptophan, threonine, and methionine supplementation can modulate immune status and influence resilience to sanitary challenges.

Immune system activation alters pigs' physiology and metabolism, increasing maintenance requirements and reducing voluntary feed intake and weight gain. Dietary functional amino acid supplementation (tryptophan, threonine, and methionine) is a strategy to support the immune system activation for immune components production, maintenance of the gut barrier integrity, and reduction of the oxidative status. Additionally, amino acid supplementation may mitigate growth performance losses. In this context, this study was conducted to investigate the effect of diets with or without tryptophan, threonine, and methionine supplementation on the performance and immune system activation of growing pigs under a sanitary challenge. The amino acid supplementation mitigated the immune system activation of challenged growing pigs and improved growth performance when compared to pigs fed diets with no supplementation. The functional amino acid supplementation may be an efficient nutritional strategy to optimize health and growth performance of immune-challenged pigs.

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.