# Milk Yield and Quality, Metabolic Profile and Oxidative Status in Lactating Goats, as Affected by Silage Based on Agro-Industrial By-Products

## TL;DR

Feeding lactating goats a silage made from agro-industrial by-products improves milk yield, quality, and animal health while supporting sustainability.

## Contribution

Demonstrates that mixed agro-industrial by-product silage improves goat milk quality and sustainability.

## Key findings

- BPS supplementation increased milk yield and improved fatty acid profiles, including higher polyunsaturated fatty acids and CLA.
- Milk oxidative stability and vitamin E content were enhanced, with reduced cholesterol and TBARS values.
- Goats showed improved metabolic and oxidative status, with increased TAS and vitamin E and reduced ROMs.

## Abstract

The use of agro-industrial wastes such as grape pomace, olive mill wastewater, wheat straw, and cheese whey in animal feed represents a valuable strategy to reduce environmental impact and promote sustainable livestock production within a circular bioeconomy framework. In this study, a mixed silage produced in cylindrical bale silos (50 kg) from these combined raw agro-industrial residues was included in the diet of lactating dairy goats. The supplementation improved milk yield and enhanced several quality traits, including: a more favorable fatty acid profile, characterized by higher levels of polyunsaturated fatty acids and conjugated linoleic acid (CLA), milk oxidative stability, metabolic status and animal health. Overall, the results demonstrate that incorporating agro-industrial by-product silage into goat diets can improve animal performance, enhance the nutritional value of milk, and support sustainability by reusing materials that would otherwise contribute to environmental waste.

Large amounts of agro-industrial residues—such as grape pomace, olive mill wastewater, wheat straw, and cheese whey—pose disposal challenges and generate substantial environmental and economic burdens. Incorporating these by-products into ruminant diets may reduce feeding costs while supporting sustainability within a circular bioeconomy. Two experiments were conducted to evaluate: (i) the characteristics of a mixed raw agro-industrial by-product silage (BPS) in cylindrical bale silos (50 kg) and (ii) its effects as dietary supplementation on metabolic profile, oxidative status, milk yield, and milk quality in lactating goats. The BPS was formulated from raw wheat straw, grape pomace, olive mill wastewater, and cheese whey and tested at a 30% inclusion level (dry-matter basis). The combined by-products produced in 50 kg cylindrical bale silos were positively characterized and exhibited a nutritionally suitable silage with relevant antioxidant potential. Dietary BPS improved oxidative status, as evidenced by increased TAS and vitamin E and reduced ROMs, and positively influenced lipid and immunological blood markers of goats. Milk yield was higher in goats receiving the BPS. Moreover, milk quality was improved through a more favorable fatty acid profile, higher vitamin E content, reduced cholesterol levels, and enhanced oxidative stability, as evidenced by lower TBARS values. Overall, BPS supplementation enhanced animal health indicators and milk nutritional properties, demonstrating that this silage can contribute to more sustainable dairy goat production while offering potential benefits for human nutrition.