Amino Acid Composition of Meat from Smena 9 Broiler Chickens During Ontogeny Under a High Stocking Density and...

Broiler meat is an important source of protein with a balanced essential amino acid profile; however, the environmental stress associated with a high stocking density can reduce its nutritional value. Adaptogen supplementation represents a promising strategy to mitigate this negative impact. This study aimed to evaluate the amino acid composition of the breast and thigh muscles of Smena-9 broiler chickens under a high stocking density and dietary supplementation with an adaptogens complex (dihydroquercetin + vitamins E and C). The experiment was conducted on 120 broilers allocated to four groups: recommended stocking density (negative control), high stocking density (positive control), high stocking density with adaptogens from day 21, and high stocking density with adaptogens from day 1 of the experiment. The stocking density changed as the bird grew. On day 21, the bird stocking density in the S(-)CON group was 38 heads per 1 m², in the other groups it was increased by 10% and amounted to 42 heads per 1 m². Each week, the stocking density changed and amounted to 32 and 35 heads per 1 m² in 28-35 days, 21 and 23 heads per 1 m² in 35-42 days, and 17 and 19 heads per 1 m² in 43 days and until the end of fattening, respectively. The amino acid profile was determined by ion-exchange chromatography with post-column derivatization using ninhydrin. Age was the primary factor influencing the amino acid composition, followed by muscle type and stocking density. Sex-related effects were less pronounced and were observed at 24 days of age. Breast meat exhibited higher amino acid content than thigh meat (82.4-89.9 vs. 65,8-77.8 g/100 g dry matter for total amino acids, respectively). Under a high stocking density, the most notable changes were observed in the thigh muscle at early ages. By day 52, the birds receiving the adaptogen complex from day 1 showed an increase in the sum of essential amino acids in the breast meat (+2.4%, p < 0.05), with the most pronounced improvements observed for methionine (+5.9%, p < 0.001) and lysine (+3.9%, p < 0.05) compared with the recommended-density control group (S(-)CON). Additionally, early adaptogen administration preserved the levels of flavor-related amino acids between days 34 and 52, whereas a decline was observed in other groups, indicating maintained sensory quality with age. Thus, the early administration of the adaptogen complex appears to mitigate for high stocking density negative effects and contributes to preserving the nutritional value of broiler meat, although the underlying mechanisms remain hypothetical and require further.