Background: Selenium (Se) has been recognized as an essential micronutrient for nearly all forms of life. In recent decades, broiler responses to dietary Se supplemental levels and sources have received considerable attention. On environmental grounds, organic trace mineral utilization in practical broiler feeds has been defended due to its higher bioavailability. In such feeds, trace minerals are provided simultaneously in the same supplement as inorganic salts or organic chelates, a fact commonly ignored in assays conducted to validate organic trace mineral sources. The current assay aimed to investigate growth and biochemical responses, as well as Se retention of growing chicks fed diets supplemented with organic and inorganic Se levels and where the trace minerals (zinc, copper, manganese, and iron) were provided as organic chelates or inorganic salts according to Se source assessed. In so doing, a 2 × 5 factorial arrangement was used to investigate the effects of sodium selenite (SS) and selenium-yeast (SY) supplemented in feeds to provide the levels of 0, 0.08, 0.16, 0.24, and 0.32 mg Se/kg.Results: Chicks fed selenium-yeast diets had body weight (BW), and average daily gain (ADG) maximized at 0.133 and 0.130 mg Se/kg, respectively. Both Se sources linearly increased (P < 0.05) the glutathione peroxidase (GSH-Px) activity in chick blood but higher values were observed in sodium selenite fed chicks (P < 0.05). Both Se sources influenced thyroid hormone serum concentrations (P < 0.05). Chicks fed SY exhibited greater retention of Se in the feathers (P < 0.05). Relative bioavailability of selenium yeast compared with SS for the Se content in carcass, feathers, total and Se retention were, 126, 116, 125 and 125%, respectively. SY supplementation resulted in lower liver Se concentration as Se supplementation increased (P < 0.05).Conclusions: Based on performance traits, the supplemental level of organic Se as SY in organic trace minerals supplement to support the maximal growth of broiler chicks is 0.133 mg Se/kg.

A sanitary challenge was carried out to induce suboptimal herd health while investigating the effect of amino acids supplementation on piglet responses. Weaned piglets of high sanitary status (6.33 ± 0.91 kg of BW) were distributed in a 2 × 2 factorial arrangement into two similar facilities with contrasting sanitary conditions and two different diets. Our results suggest that increased Trp, Thr, and Met dietary supplementation could support the immune systems of piglets under a sanitary challenge. In this manner, AA+ supplementation improved the performance and metabolism of piglets under mixed management and poor sanitary conditions. No major temporal microbiome changes were associated with differences in performance regardless of sanitary conditions or diets. Since piglets often become mixed in multiple-site production systems and facility hygiene is also often neglected, this study suggests that increased Trp, Thr, and Met (AA+) dietary supplementation could contribute to mitigating the side effects of these harmful risk factors in modern pig farms.

Salmonella Typhimurium is the most frequent serovar in pigs and causes infections in humans. However, the dosage used for experimentation is not well defined. The present study aimed to evaluate a dosage for oral inoculation with Salmonella Typhimurium to assess immunological and growth performance alterations in pigs. Gilts were randomly allocated into one of three experimental treatments: no Salmonella Typhimurium inoculation (Basal), or oral inoculation of 1 × 10⁸ or 1.5 × 10⁸ colony-forming units of Salmonella Typhimurium. Growth rate, rectal temperature, and fecal Salmonella shedding were recorded. Blood samples were taken. Inoculated pigs shed the bacteria for up to 7 days, but no differences were observed between the groups. No differences were observed in rectal temperature, body weight, or average daily feed intake. However, reductions in average daily gain (−17 and −22%) and feed efficiency (−14 and −20%) were observed in pigs inoculated with 1 × 10⁸ and 1.5 × 10⁸ colony-forming units, respectively. The hemoglobin and hematocrit concentrations increased in challenged pigs compared to Basal pigs. The oral dosage of 1.5 × 10⁸ colony-forming units of Salmonella Typhimurium is suitable for activating the immune system of pigs and assessing the impact of Salmonella on pig performance.

Sanitary challenges (SCs) may alter the health status, growth performance, and pigs’ welfare. Changes in amino acid (AA) plasma concentrations have been observed in inflammatory-challenged pigs which may be associated with key factors, such as: (1) the synthesis of immune components to support innate and/or adaptive immune responses, (2) the redistribution of nutrients from growth and production functions toward cells and tissues involved in inflammatory and immune responses, and (3) decreased anabolism and/or increased catabolism of skeletal muscle to increase the availability of nutrients, often as a consequence of reduced feed intake. Due to their health-promoting effects, nutritional strategies involving AA may help mitigate the negative impacts of SC. Methionine, tryptophan, and threonine, beyond serving as protein building blocks, are considered functional AA because they support immune system function, enhance intestinal barrier integrity, modulate inflammatory responses, and limit oxidative stress. Additionally, the review highlights the influence of individual variability, such as differences in body weight, on nutritional requirements and responses to AA supplementation for pigs under SC. The integration of nutritional strategies tailored to immune-challenged pigs offers promising avenues to improve productivity and animal welfare in commercial swine production systems with increasing restrictions on antibiotic use.

This study aimed to evaluate the internal predictability of weight gain using an integrated dataset derived from four experiments conducted with growing–finishing pigs subjected to a common Salmonella Typhimurium challenge protocol. Individual-animal data from 230 pigs were harmonized into a database containing growth performance, body composition, serum biochemical measurements, and experiment-level information. Relative weight gain, calculated relative to body weight at the beginning of each evaluation period, was evaluated separately during the acute phase, from days 0 to 7 post-challenge (RWG₇; n = 132), and the chronic phase, from days 7 to 28 post-challenge (RWG_7–28; n = 131). Linear Model, Elastic Net, Random Forest, XGBoost, Generalized Additive Models, and Support Vector Machine were compared using individual-level five-fold cross-validation, in which pigs from the same source experiment could occur in both training and validation folds. Single regression trees were additionally fitted as exploratory tools. During the acute phase, cross-validated R² values ranged from 0.078 to 0.186, indicating that the available baseline variables explained only a limited proportion of the variation in RWG₇. Predictive performance was higher during the chronic phase, particularly for the Linear Model and Elastic Net, which showed essentially equivalent cross-validated performance, with R² values of 0.419 and 0.420, respectively. Random Forest and XGBoost achieved high in-sample performance but substantially lower out-of-fold performance, suggesting overfitting structures within the integrated dataset. Body weight, body composition, biochemical variables, and the source experiment contributed to model predictions, indicating that the predictive signal incorporated information related to both individual physiological status and between-experiment heterogeneity. Overall, acute-phase growth performance was poorly predicted from baseline information, whereas chronic-phase growth showed a stronger internal predictive signal. This comparison reflects differences in the predictor information available at the beginning of each phase, as chronic-phase models additionally incorporated body weight and relative weight gain measured on day 7. These results should be interpreted as exploratory and hypothesis-generating because experiment-held-out or external validation is required before extrapolation to independent experimental or commercial populations.