Biochemical status and productive parameters of pigs (Sus scrofa domesticus) in modeling stress and its correction

A peculiarity of living organisms is the internal constancy maintained by self-regulation mechanisms. In higher animals, the functions of control and regulation of biochemical reactions are performed by the neuro-endocrine system. With its help the organism perceives various influences of external and internal environment and reacts to them by means of hormones. In this regard, biomarkers of stress level are primarily the content of hormones, as well as blood concentrations of metabolites and their correlation. The use of dihydroquercetin, vitamins C and E in nutrition can help to reduce the negative effects of stress. In the present work we have established for the first time the positive influence of additional feeding of antioxidant complex on the adaptation of pigs under stress by hormonal regulation and strengthening of antioxidant status of the organism. The aim of the work was to evaluate the effect of feeding a complex of adaptogens DHQEC (dihydroquercetin and vitamins E, C) on the biochemical status and productive qualities of pigs under stress modelling. Fattening experiments were performed on 34 pigs ( Sus scrofa domesticus ) F2 [(Large White ½ Landrace) ½ Duroc] (Ernst Federal Research Center for Animal Husbandry, 2022-2023). Body weight (BW) of piglets aged 99 days at the beginning of the experiment was 40.7-41.0 kg. The duration of the fattening period was 90 days. During the preliminary period, piglets were distributed into four groups by the paired-analogues method: I control (С-, without dietary DHQEC) (9 animals), II control (C+, with dietary DHQEC) (9 animals), III experimental (Е-, without dietary DHQEC) (8 animals), IV experimental (E+, with dietary DHQEC) (8 animals). Each stall sized 2.4½2.25 m (5.4 m2) with 1.05 m feeding front. That is, with four pigs per stall (groups Е- and E+) instead of 3 pigs per stall (groups С- and C+), there was a decrease in the stall area per pig from 1.8 to 1.35 m2, and the feeding front from 0.35 to 0.26 m (according to GOST 28839-2017, the norm is at least 0.3 m per pig). DHQEC contained DHQ (Ecostimul-2, AO Ametis, Russia; DHQ 72-73 %, 32 mg/kg of feed), vitamin E (INNOVIT E60, MEGAMIX, Russia, 10 mg/kg of feed), and vitamin C (Tiger C 35, Anhui Tiger Biotech Co., Ltd., China, 35 mg/kg of feed). Animals from groups C+ and E+ received dietary DHQEC (0.025 % by weight of mixed fodder) throughout the whole period of the tests. Young animals were weighed individually every decade. To assess the clinical, physiological and metabolic status of the organism at the end of the growing period, as well as during transfer to final fattening and before slaughter, blood samples were taken from the jugular vein in the morning before feeding. Calcium, phosphorus, magnesium, aspartate aminotransferase, alanine aminotransferase activity, alkaline phosphatase, total bilirubin, creatinine, cholesterol, glucose, total protein, albumin, chloride and urea were determined in blood serum. To assess antioxidant status, the total amount of free water-soluble antioxidants was determined amperometrically in serum samples. The serum concentrations of total and free thyroxine (T4t and T4f) and triiodothyronine (T3t and T3f), as well as thyroid hormone, cortisol, adrenaline, insulin-like growth factor-1, and melatonin were also determined by solid-phase enzyme-linked immunosorbent assay. BW of pigs after starvation was evaluated immediately before slaughter. After slaughter, the carcass was weighed, the slaughter yield, thickness of the skin, muscle eye area, and pH were determined 45 min after slaughter and after 24 h of storage. It was found that with increased competition for feed table, DHQEC provides a significant decrease in cortisol (p = 0.014) and adrenaline (p = 0.09) in piglets during the final fattening. Due to competition for feed, the melatonin concentration decreased (p = 0.01), while DHQEC in E+ group normalized the melatonin level to the values for the 1st and 2nd blood draws. Stress had a negative effect on some metabolic processes indicators of which are biochemical blood parameters (blood concentration of triglycerides, cholesterol, bilirubin, AsAT). At final fattening, there were significant shifts in the animal hormonal status. In piglets in groups C compared to E, the concentration of T4t (p = 0.02), T3t (p = 0.05), T3f (p = 0.004) decreased together with an increase in the thyroid hormone (TTG) production (p = 0.05). Dietary DHQEC somewhat smoothed the negative influence of the modelled factor. The lowest values of T4t, T4f, T3t, T3f were rebealed in the E+ group. It should be noted that the TTG content and integral thyroid index (ITI) in the E+ group decreased to 0.46 mME/l and 69.7 units vs. 0.51 mME/l and 263.8 units in the Е- group, while the conversion of T4f to T3f decreased 1.73 times.