Context: Dietary supplementation with trace mineral chromium (Cr) has been shown to enhance the physiological responses of broilers subjected to heat stress (HS), modulate gene expression, and improve performance. Aims: This study aimed to evaluate the impact of chromium–methionine (CrMet) supplementation on growth performance, body temperatures, lymphoid organ weights, hormones, blood parameters, and the expression of heat-shock protein-70 (HSP-70) and insulin-like growth factor-1 (IGF-1) genes in broilers under HS conditions (33°C for 12 h/day). Methods: In the first experiment, 336 22-day-old male broilers were randomly distributed into four blocks with six treatments (0, 0.10, 0.20, 0.40, 0.80, and 1.20 mg/kg CrMet) and eight replicates with seven birds per cage. These broilers were subjected to HS from 22 to 43 days of age. In the second experiment, 24 male broilers, in total, at 43 days of age, previously exposed to HS, were randomly distributed to the same six treatments from the first experiment, with four replicates. Breast samples were collected for the analysis of HSP-70 and IGF-1 expression. Results: A quadratic effect (P < 0.05) was observed on bodyweight gain (BWG) and feed conversion ratio (FCR). The supplementation of 0.71 and 0.68 mg/kg improved BWG and FCR, respectively. At 28 days of age, cloacal and mean body temperatures, corticosterone, and thyroid hormones were quadratically affected (P < 0.05), while at 43 days of age, a linear effect (P < 0.05) was observed on haemoglobin concentration. There was a reduction (P < 0.05) in the expression of HSP-70 and an increase in IGF-1 (P < 0.05) in the breast tissue of broilers supplemented with CrMet. Conclusions: The supplementation with 0.71 mg/kg and 0.68 mg/kg of CrMet improved BWG and FCR, respectively. Additionally, the supplementation with 0.80 mg/kg improved hormones, reduced HSP-70 and increased the expression of IGF-1 in broilers during HS. Implications: These findings suggest that CrMet can be included in the diet of broiler chickens subjected to HS to enhance physiological responses and performance.

Necrotic enteritis (NE) is a disease of worldwide distribution, which affects young broilers and causes economic losses on a scale of 6 billion dollars per year. For decades, NE was controlled in poultry flocks by dietary administration of low doses of antimicrobial growth promoters (AGPs). However, an increase in NE incidence was noted after the AGP ban. This study aimed to compare the effect of an antibiotic (Enramycin) diet to a combination of sodium butyrate, hydrolyzed yeast, and zinc proteinate (Viligen^TM) on broiler diets regarding performance, blood parameters, intestinal permeability, morphology and lesions, and carcass yield of broilers challenged with Eimeria spp. and Clostridium perfringens to simulate subclinical necrotic enteritis. A total of 1,150 one-day-old male broiler chickens with an initial average weight of 43.9 ± 0.65 g were allocated to 50 experimental pens. Animals were divided into 5 groups: Negative control (NC) without additives; Positive control (PC) with 0.12 g/ton of Enramycin (8%); V500, V1000, and V1500 with the addition of 500, 1.000, and 1.500 g/ton of Viligen, respectively. All animals were challenged by Eimeria spp. at 7 d of age and by C. perfringens at 17, 18, and 19 d for induction of subclinical NE. The broilers fed with all concentrations of Viligen showed similar performance, blood parameters, intestinal permeability, and carcass yield compared to PC broilers. However, NC broilers showed higher FCR compared to PC broilers from 1 to 33 d (1.42 vs. 1.39) (P = 0.048) and from 1 to 42 d (1.51 vs. 1.49) (P < 0.001). V1500 broilers had fewer intestinal lesions at 28 d when compared to the PC treatment (P < 0.05) and showed that higher Viligen inclusion resulted in lower intestinal damage. At 21 d, the V500 group showed higher intestinal morphology characteristics (VH:VD 4.9 vs. 3.5) compared to the PC treatment (P < 0.001). Thus, in this study, the dietary addition of Viligen to broilers challenged by an experimental model of subclinical NE resulted in lower intestinal damage and similar performance to that obtained by the addition of Enramycin.

The study investigated guanidinoacetic acid (GAA) supplementation with varying dietary digestible arginine (Arg) and glycine+serine (Gly+Ser) concentrations in the starter phase, exploring respective carry-over effects on growth performance, blood chemistry, incidence of pectoral myopathies and proximate composition in broilers. A total of 2,800 one-day-old male broiler chicks were distributed in a central composite design with 2 factors and double experimental mesh, represented by supplementation or omission of 0.6 g per kg of GAA, with a central point represented by 107% of Arg and 147% of Gly+Ser, 4 factorial points (combinations of Arg/Gly+Ser concentrations: 96.4/132.5%; 117.6/132.5%; 96.4/161.5%, and 117.6/132.5%), and 4 axial points (combinations of axial points estimated for Arg and Gly+Ser, with the central points of 92/147%; 122/147%; 107/126.5, and 107/167.5%), totaling 18 treatments, 4 repetitions to factorial and axial points, 24 replicates to the central point, and 25 birds per pen. Feed conversion ratio (FCR) from d 1 to 10 had a linear response (P = 0.009) for the decreasing Arg content and a quadratic response (P = 0.047) for Gly+Ser concentrations. Broilers supplemented GAA had lower FCR compared with nonsupplemented groups from d 1 to 10 (P = 0.048) and d 1 to 42 (P = 0.026). Aspartate aminotransferase (AST) exhibited increasing and decreasing linear effects as a function of Arg (P = 0.008) and Gly+Ser (P = 0.020) concentrations, respectively. Guanidinoacetic acid decreased serum AST (P = 0.028). Guanidinoacetic acid reduced moderate + severe (P = 0.039) and mild (P = 0.015) Wooden Breast scores. The occurrence of normal White Striping increased (P = 0.002), while severe score was reduced (P = 0.029) with GAA supplementation. In conclusion, increased digestible Arg:Lys and 14% and 6% above the recommendations (107% and 147%), respectively, provided improved FCR during the starter phase. Dietary GAA supplementation (0.6 g per kg) improved FCR, reduced severity of breast myopathies and appears to have reduced muscle damage in broilers fed plant-based diets.