The popularity of plant-based feed additives in livestock production has increased significantly in the last decade. Polyphenols are secondary plant metabolites which contain bioactive components and deliver positive effects for humans and animals. They are renowned for their anti-inflammatory, immunomodulatory and anti-mutagenic effects. Polyphenols have antioxidant properties, and they minimize the negative consequences of oxidative stress. Their antioxidant capacity is comparable to that of the major biological antioxidants: vitamins E and C. Despite those advantages, polyphenols are characterized by low bioavailability, and further research is needed to harness their full potential in livestock farming. This article presents a review of findings from recent studies investigating the efficacy of polyphenols in monogastric nutrition, with special emphasis on their antioxidant properties.

Losses of crude protein during ensiling of herbages, in contrast to carbohydrates, do not affect the reduction of its content; their form is changed into greater solubility non-protein compounds and also highly degraded forms, which lower the efficiency of the microbial protein synthesis in the rumen. These processes are accompanied by a change of amino acid composition of herbage protein and decrease in intestinal digestibility of protein from feeds as a result of the formation of indigestible complexes with carbohydrates (ADIN). Reduction of protein degradation in silages is achieved by accelerated acidity through addition of acids or dominance of homofermentative bacteria. The positive effects of fermentation inhibitors or sorbents use, as well as the wilting of raw material on the level and rate of protein degradation were demonstrated by many researchers. A greater contribution of protein nitrogen and reduction of deamination in silages can also be obtained by using bacteria inoculants. Increasing the proportion of protein nitrogen is accompanied by the improved efficiency of microbial protein synthesis.

The aim of this study was to determine the effect of a polyphenol product (PP) (Proviox) and vitamin E on the antioxidant status and meat quality of broiler chickens exposed to high temperature. The experimental materials comprised 120 ROSS 308 broilers (6 treatments, 10 replications, 2 birds per replication). Dietary supplementation with vitamin E and PP was applied in the following experimental design: group I (negative control) – without supplementation; group II (positive control) – without supplementation; group III – supplementation with 100 mg vitamin E/kg; group IV – 200 mg vitamin E/kg; group V – 100 mg vitamin E/kg and 100 mg PP/kg; group VI – 200 mg PP/kg. In groups II–VI, broiler chickens aged 21–35 d were exposed to increased temperature (34°C for 10 h daily). In chickens exposed to high temperature, dietary supplementation with antioxidants, mostly PP, improved growth performance parameters, including body weight, body weight gain and feed intake until 28 d of age. Vitamin E added to broiler chicken diets at 200 mg/kg and vitamin E combined with PP was most effective in improving the total antioxidant status of birds, enhancing blood antioxidant enzyme activities and increasing vitamin E concentrations in the liver and breast muscles. Broilers fed diets supplemented with 200 mg/kg of vitamin E alone and vitamin E in combination with PP were characterised by a higher percentage content of breast muscles in the carcass. Dietary supplementation with antioxidants improved the water-holding capacity of meat, reduced natural drip loss and increased the crude ash content of meat. The breast muscles of chickens fed diets supplemented with PP had a lower contribution of yellowness. The breast muscles of chickens receiving diets with 100 mg vitamin E/kg(group III) and diets supplemented with PP (groups V and VI) were characterised by the highest concentrations of polyunsaturated fatty acids. The PP can be a valuable component of diets for broiler chickens exposed to high temperature.

The aim of this study was to determine the effect of herbal feed additive on growth performance, carcass characteristics, the chemical composition of breast muscles and selected meat quality parameters in broiler chickens. The experiment was performed on 1080 Ross 308 chickens, which were randomly divided into six groups with six replicates per group. In experimental groups, dietary energy concentration was reduced by 0.10 or 0.25 MJ kg⁻¹, and the diets were or were not supplemented with the Superliv herbal formula at 500 g t⁻¹ of diet. A statistical analysis revealed that Superliv had a beneficial influence on the final body weights (BWs) of birds, average daily gain (ADG), feed conversion ratio (FCR), European Efficiency Index (EEI) and the proportion of heart relative to total carcass weight. However, meat acidity measured 15 min post mortem was higher in experimental groups. A decrease in dietary energy concentration contributed to a highly significant increase in the water-holding capacity (WHC) of meat and natural drip loss, an increase in pH₁₅, an increase in color lightness, a decrease in redness, an increase in the fat content of meat, and a decrease in malondialdehyde (MDA) concentration.

This study aimed to determine the efficacy of sodium butyrate (SB), coated sodium butyrate (CSB), and butyric acid glycerides (BAG) in turkey nutrition based on an analysis of nutrient digestibility, gastrointestinal function, and fecal bacterial populations. A total of 400 1-day-old female BIG 6 turkeys were divided into 4 groups, with 5 replicates per group and 20 birds per replicate, to determine the effects exerted by various forms of butyric acid (SB, CSB, and BAG). The addition of CSB and BAG to turkey diets improved the feed conversion ratio (FCR, p < 0.05), increased the values of the European Efficiency Index (EEI, p < 0.01) and duodenal villus height (p < 0.05), and decreased the fecal populations of Escherichia coli and Clostridium perfringens (p < 0.05). Dietary supplementation with BAG increased protein digestibility (p < 0.05). The analyzed forms of butyrate added to turkey diets increased the butyric acid concentration in the cecal digesta (p < 0.01). The results of this study indicate that protected forms of butyric acid can be valuable feed additives in turkey nutrition.

The aim of this study was to determine the effect of a polyphenol product (PP) (Proviox) and vitamin E on the antioxidant status and meat quality of broiler chickens fed diets contaminated with ochratoxin A (OTA). One hundred and twenty ROSS 308 broiler chickens were randomly divided into six groups (10 replications, 2 birds per replication). Group I received an uncontaminated and unsupplemented diet, diets of groups II to VI were contaminated with OTA at 172 µg and 200 µg/kg for the starter and grower period, respectively. Furthermore, diets of groups III, IV and V were supplemented with vitamin E at 100, 200 and 100 mg, respectively, and to diets of groups V and VI additionally 100 and 2200 mg PP was added, respectively. Supplementation with PP and vitamin E had no significant effects on the growth performance, dressing percentage or carcass trait parameters of broiler chickens. In chickens exposed to stress, dietary supplementation with vitamin E and/or PP improved the total antioxidant status (p ≤ 0.05), enhanced the blood activity of antioxidant enzymes (p ≤ 0.01) and increased the concentrations of non-enzymatic antioxidants (p ≤ 0.01) in the liver and breast muscles. Regardless of the administered antioxidants, chickens fed diets contaminated with OTA were characterised by lower dressing percentage (p ≤ 0.01), a higher proportion of the liver in the carcass (p ≤ 0.01), lower carcass fat content (p ≤ 0.01), and longer small intestines (p ≤ 0.01) and caeca (p ≤ 0.01). Dietary supplementation with PP improved the water-holding capacity of meat (p ≤ 0.01). The breast muscles of chickens fed diets supplemented with PP and vitamin E were characterised by higher (p ≤ 0.05) concentrations of eicosapentaenoic acid (C_20:5). It was concluded that PP can be an insufficient component of diets for broiler chickens to improve growth performance and mitigate the negative effects of high dose of OTA in diets.