Addition of fermented and unfermented grape skin in broilers' diets: effect on digestion, growth performance, intestinal microbiota and oxidative stability of meat.

Grape skin is a source of polyphenols with antioxidant and antimicrobial properties. Little information is available regarding its application in animal feeding. The present study investigated the effect of inclusion of fermented (FS) and unfermented (UFS) grape skin at two different doses (30 g/kg, FS30 and UFS30, and 60 g/kg, FS60 and UFS60) and 200 mg/kg vitamin E (α-tocopheryl acetate) in a corn-soybean diet on growth performance, ileal protein digestibility, ileal and excreta total extractable polyphenols content and digestibility, intestinal microbiota and thigh meat oxidation in broiler chickens. Growth performance was depressed in chickens fed UFS and FS diets. A reduction in ileal protein digestibility was also observed in birds fed UFS, being this effect more pronounced in those fed 60 g/kg. The dietary inclusion of grape skin increased both ileal and excreta polyphenols contents, being higher in birds fed UFS than in those fed FS. Excreta moisture content increased in birds fed UFS and FS diets. No effect of dietary inclusion of grape skin was observed on ileal counts of lactic-acid bacteria and Clostridium, but UFS inclusion in the diet reduced ileal count of Escherichia coli as compared with FS dietary inclusion. After 7 days of refrigerated storage, values of thiobarbituric acid reactive substances (TBARS) were lower in chicken meat when grape skin was added in the diet at 60 g/kg instead of 30 g/kg, and meat from birds fed 60 g/kg of grape skin reached TBARS values similar to those of birds supplemented with vitamin E. In conclusion, high doses of grape skin polyphenols depressed growth performance and protein digestibility, and increased excreta moisture content. Unfermented grape skin contained more polyphenols than FS, and its inclusion in the diet led to higher ileal and excreta polyphenols contents and to a lower ileal count of E. coli. Furthermore, the antioxidant potential of the polyphenols present in grape skin was observed after 7 days of meat storage, with the dose of 60 g/kg of grape skin being as effective as vitamin E supplementation in maintaining oxidative stability of meat.

Addition of exogenous enzymes to diets containing grape pomace: Effects on intestinal utilization of catechins and antioxidant status of chickens.

Grape pomace (GP) is a rich source of polyphenols with antioxidant capacity. An experiment was conducted to study the effect of GP phenolic compounds included at 5 and 10%, and the addition (individually or combined) of hydrolyzing enzymes (carbohydrase enzyme complex and tannase at 500ppm) on intestinal utilization of catechins and antioxidant status in broiler chickens. A diet supplemented with 200ppm of α-tocopheryl acetate was also used. Our findings demonstrate the capacity of chickens to digest the monomeric (catechin, epicatechin, gallic acid, and epicatechin-O-gallate) and dimeric (procyanidin B1 and procyanidin B2) catechins present in grape pomace. The addition of enzymes (mainly tannase) hydrolyzed the polymeric structures into smaller catechins, but also promoted a lower digestibility of the monomeric and dimeric catechins suggesting that polymeric structures might favour the intestinal utilization of these catechins. The intestinal accumulation of phenolic compounds generated with tannase and with 10% GP reversed the antimicrobial effect against Clostridium perfringens observed with 5% of GP. Grape pomace improved the antioxidant status of the bird, increasing the α-tocopherol and reducing the iron content on plasma, not affecting the plasma gluthatione. Enzymes modified the intestinal utilization of catechins but not additional protective effect was detected on any of the parameters analyzed to evaluate the antioxidant status.

Effects of dietary grape seed extract on growth performance, amino acid digestibility and plasma lipids and mineral content in broiler chicks.

Polyphenols are chemically and biologically active compounds. Grape seed extracts (GSEs) have been widely used as a human food supplement for health promotion and disease prevention. However, there is little information regarding its application in animal feeds. An experiment was conducted to investigate the effect of inclusion of GSE at 0.025, 0.25, 2.5 and 5.0 g/kg in a wheat soya bean control diet on growth performance, protein and amino acid (AA) digestibility and plasma lipid and mineral concentrations in broiler chickens at 21 days of age. Performance was not affected by dietary treatment except in the case of birds fed the diet with the highest GSE concentration, which showed a worsening of weight gain and feed conversion. Apparent ileal digestibility (AID) of protein was significantly reduced in the birds fed the highest concentration of GSE, which also had a reduction on the AID of arginine, histidine, phenylalanine, cystine, glutamic acid and proline compared with those fed control diet. The inclusion of graded concentration of GSE in the chicken diets caused a significant linear decrease in the concentrations of plasma copper, iron and zinc. Plasma cholesterol, triglycerides and lipoproteins (high-density lipoprotein, low-density lipoprotein and very-low-density lipoprotein) concentrations were not affected by dietary GSE. In conclusion, this study demonstrated that incorporation of GSE in chicken diets up to 2.5 g/kg had no adverse effect on growth performance or protein and AA digestibility. Feed conversion was reduced and growth rate was retarded, when chickens were fed 5 g/kg of GSE. This study also indicated that grape polyphenols reduce the free plasma minerals.

Changes in polyphenol and polysaccharide content of grape seed extract and grape pomace after enzymatic treatment.

Grape seed extract and grape pomace are rich sources of polyphenols. The aim of this study was to evaluate the release of polyphenols, the solubilisation of carbohydrate, and the antioxidant capacity of these grape by-products after enzymatic reaction with carbohydrases (cellulolytic and pectinolytic activities) and tannase for 24h. The use of tannase in these by-products, and pectinase in grape pomace changed the galloylated form of catechin to its free form, releasing gallic acid and increasing the antioxidant activity. In grape pomace, cellulase treatment was not efficient for phenolic release and antioxidant activity improvement. The addition of carbohydrases to grape pomace, either alone or in combination, degraded the cell wall polysaccharides, increasing the content of monosaccharides. These results provide relevant data about the potential of pectinase, tannase and combinations of enzymes on the release of polyphenols and monosaccharides from grape by-products, improving the antioxidant capacity and the nutritional value.

Effect of dietary supplementation with glutamine and a combination of glutamine-arginine on intestinal health in twenty-five-day-old weaned rabbits.

The effect of dietary supplementation with 1% l-glutamine and a combination of 1% l-glutamine and 0.5% l-arginine on intestinal health was examined in weaned rabbits. A basal diet was formulated to meet nutrient recommendations. Another 2 diets were formulated by adding 1% (as-fed basis) Gln or a mixture of 1% (as-fed basis) Gln + 0.5% (as-fed basis) Arg (Gln-Arg) to the basal diet. In Exp. 1, a total of 357 rabbits were blocked by litter and assigned at random to the experimental diet to determine mortality (119 per diet) and growth performance (35 per diet; from weaning at 25 to 56 d of age). Rabbits were fed the experimental diets for a 2-wk period and thereafter received a commercial diet. Rabbits weaned at 25 d (blocked by litter and assigned at random to diets) were slaughtered at 35 d and used to determine apparent ileal digestibility of DM, CP, and AA (Exp. 2, a total of 60 rabbits), intestinal morphology, N-aminopeptidase and myeloperoxidase intestinal activity, the expression of PPARgamma at the ileum and kidney, serum immunoglobulin in healthy and sick rabbits (Exp. 3, a total of 24 rabbits), and ileal and cecal microbial composition by PCR-RFLP (Exp. 4, a total of 45 rabbits). Dietary treatment did not affect ADG, ADFI, or G:F, during the entire fattening period. Supplementation with Gln reduced mortality during the first 2 wk and the whole fattening period from 18.5 to 8.4% (P = 0.023) and from 31.9 to 20.2% (P = 0.039), respectively, whereas no effect was detected for Arg supplementation. Among all the variables studied, the reduction on mortality due to Gln was related to a reduced intestinal colonization (Eimeria lesions) and changes on microbial ecosystem in the ileum and cecum, reducing the frequency of detection of Clostridium spp. (from 86.7 to 33.3%, P = 0.003) at the ileum, and Helicobacter spp. at the ileum (from 86.7 to 46.7%, P = 0.003) and at the cecum (from 86.7 to 46.7, P = 0.028), whereas no effect was detected for Arg supplementation. In conclusion, 1% l-Gln supplementation to postweaned rabbit diets decreased fattening mortality and modified the intestinal microbiota (although no consistent effects were observed on mucosal histology or inflammatory and systemic immune response). Diets containing a combination of 1% Gln and 0.5% Arg were of little additional benefit.