Grape (Vitis Vinifera) Pomace Flour as Pigment Agent of Quail Eggs

Grape Pomace: Agrifood By-Product with Potential to Enhance Performance, Yolk Quality, Antioxidant Capacity, and Eggshell Ultrastructure in Laying Hens

Grape pomace (GP) is an industrial by-product of grape juice making and is commonly discarded as a waste product, even with its large quantity of phytochemicals. Thus, the objectives of this trial were to examine the effects of graded dietary GP on laying rate, egg quality, yolk lipid profile, oxidative stability, shell quality and ultrastructure, and serum biochemistry. Two hundred 35-week-old laying hens were allocated to four dietary treatments with ten replicates each. Four diets were formulated by mixing a standard basal diet with GP at 0 g/kg (control), 30 g/kg (GP_3%), 60 g/kg (GP_6%), and 90 g/kg (GP_9%). Egg production percent, egg weight, and egg mass were linearly improved (p < 0.01) due to adding GP to the diets of laying hens. Eggs obtained from laying hens fed with GP diets had (p < 0.01; linear, p < 0.01) greater Haugh units, yolk color, albumen index, and yolk index than those of the control. The GP_9% group had the greatest values (p < 0.05) for shell weight, thickness, and breaking strength. Electron microscopy scanning of eggshells indicated that the incremental dietary level of GP linearly augmented the thickness of the palisade layer but reduced both the mammillary layer and mammillary knob width (p < 0.01). Improved tibia-breaking strength and ash content were shown (p < 0.05) in the GP-fed laying hens. The dietary addition of GP by up to 90 g/kg linearly (p < 0.01) mitigated lipid oxidation and improved the antioxidant capacity in both the serum and stored eggs. A reduction in the percentages of saturated fatty acids was observed, while the contents of monounsaturated fatty acids, polyunsaturated fatty acids, and n-3 fatty acids were augmented because of increasing dietary GP levels (p < 0.001). Additionally, the eggs obtained from laying hens fed on the GP_6% and GP_9% had lower yolk cholesterol content (p < 0.001); this effect was confirmed by linear and quadratic responses (p < 0.001). Laying hens on GP diets had lower (p < 0.01) serum hepatic enzymes, cholesterol, triglycerides, and low-density lipoprotein but greater high-density lipoprotein compared to the control. To sum up, the addition of GP in the layers' diets by up to 90 g/kg increased laying performance, enriched the yolk with beneficial fatty acids, enhanced antioxidant potential in yolk lipids, and improved shell quality and ultrastructure.

Grape By-Products as Feedstuff for Pig and Poultry Production

Grape by-products are exceptional options for replacement of conventional and unsustainable feed sources, since large amounts are generated every year from the winery industry. However, the majority is wasted with severe environmental and economic consequences. The present review aimed to evaluate the effects of grape by-products on pig and poultry growth performance. The most recent literature was reviewed using ScienceDirect and PubMed databases and the results of a total of 16 and 38 papers for pigs and poultry, respectively, were assessed. Fewer studies are documented for pig, but the incorporation of grape by-products up to 9% feed led to an improvement in growth performance with an increase in average daily gain. Conversely, lower levels (<3% feed) are needed to achieve these results in poultry. The beneficial effects of grape by-products on animal performance are mainly due to their antioxidant, antimicrobial, and gut morphology modulator properties, but their high level of cell wall lignification and content of polyphenolic compounds (e.g., tannin) limits nutrient digestion and absorption by monogastric animals. The use of exogenous enzymes or mechanical/chemical processes can provide additional nutritional value to these products by improving nutrient bioavailability. Overall, the valorization of grape by-products is imperative to use them as feed alternatives and intestinal health promoters, thereby contributing to boost circular agricultural economy.

Productive Performance, Egg Quality and Yolk Lipid Oxidation in Laying Hens Fed Diets including Grape Pomace or Grape Extract

An experiment was conducted to assess in laying hens the effect of including grape pomace (GP, at 30 or 60 g/kg) or grape extract (GE, at 0.5 or 1.0 g/kg) on egg production, feed conversion ratio, protein and polyphenol digestibility, egg weight, egg quality, yolk fatty acid profile and oxidative stability of yolk lipids. No differences were detected among diets for egg production (83.8%, on average) or egg mass (56.8 g/d, on average). However, the average egg weight was lower (p = 0.004) for dietary treatments GP 30, GP 60 and GE 0.5 (67.5 g, on average) than for control hens (68.5 g). Accordingly, in hens fed the GP diets the proportion of XL eggs was lower (p = 0.008) than in control hens, while the proportion of M eggs was higher (p < 0.001) in hens fed the diets GP 30, GP 60 and GE 0.5 than in the control group. The dietary inclusion of both GP and GE decreased daily feed intake (120.9 vs. 125.3 g/d, p < 0.001) and the feed conversion ratio (2.09 vs. 2.18, p = 0.01). Feeding GP at 60 g/kg or GE reduced excreta protein digestibility (54.7 vs. 62.8%, p < 0.001), whereas all GP and GE diets showed higher excreta polyphenol digestibility than the control treatment (57.2 vs. 41.0%, p < 0.001). While yolk colour score was increased with all grape diets (8.12 vs. 7.34, p < 0.001), the dietary inclusion of GP, either at 30 or 60 g/kg, and that of GE at 1.0 g/kg increased the Haugh units of the albumen (80.8 vs. 76.4 Haugh units, p = 0.001). Shell thickness remained unaffected by dietary treatments (365.2 μm, on average). When included in the diet at 60 g/kg, GP reduced the proportion of saturated fatty acids in the yolk (31.6 vs. 32.9%, p = 0.001) and that of monounsaturated fatty acids (39.5 vs. 41.4%, p < 0.001), while it increased the percentage of polyunsaturated fatty acids (28.9 vs. 25.7%, p < 0.001). In fresh eggs, no significant differences were found for the malondialdehyde (MDA) concentration (0.146 mg/kg, on average). In stored eggs, the MDA amount was lower in the eggs of the laying hens fed GP at 60 g/kg than in the eggs of the control hens (1.14 vs. 1.64 mg/kg, p = 0.025). In conclusion, the inclusion of grape pomace, either at 30 or 60 g/kg, and grape extract at 1.0 g/kg in the diet of laying hens improved some egg quality traits, but feeding grape pomace resulted in a lower average weight of eggs. Nevertheless, feeding laying hens with diets containing grape pomace resulted in a higher antioxidant potential in egg yolk than dietary inclusion of grape extract.