Sustainable livestock production is a critical component of global food security and environmental stewardship. Agricultural crop residues, such as cereal straws, stovers, and hulls, as well as agro-industrial by-products, including oilseed meals, distillery wastes, and fruit/vegetable processing residues, are generated in large quantities worldwide, and these residues can be used in the diet of the animals to reduce the feed production cost and sustainability. In this review, we found that the use of treated crop residues in the diet of animals increased the production performance without causing any side effects on their health. Additionally, we also noticed that using these crop residues also mitigates the methane production in ruminants and feed costs, particularly for harvesting the feed crops. Traditionally, these materials have often been underutilized or even disposed of improperly, leading to wastage of valuable nutrients and potential environmental pollution. By incorporating these materials into animal feed formulations, livestock producers can benefit from several key advantages. The review further discusses the challenges and considerations involved in the effective utilization of these alternative feed resources, such as variability in nutrient composition, anti-nutritional factors, and the need for appropriate preprocessing and formulation strategies. Emerging technologies and innovative approaches to optimize the integration of crop residues and by-products into sustainable livestock production systems and also reduce global warming, particularly methane, CO₂ and other particles that affect the environment after burning these crop residues, are also highlighted. By synthesizing the current knowledge and exploring the multifaceted benefits, this review underscores the vital roles that agricultural crop residues and agro-industrial by-products can play in fostering the sustainability and resilience of livestock production, ultimately contributing to global food security and environmental stewardship.

Palm fruits are produced extensively in tropical and subtropical regions and consumed worldwide. However, over 20% of the total yield is discarded due to inferior quality, resulting in significant agricultural waste and economic loss. To mitigate this challenge and enable the safe valorization of discarded dates (DD) in animal feeding systems, this study employed solid-state fermentation (SSF) to upgrade the nutritional quality of DD and evaluated its potential as a functional feed ingredient for goats. Twenty-four male goats (6 months old; initial body weight 25.86 ± 0.25 kg) were randomly assigned to one of three dietary treatments: a basal diet (control), a diet containing 10% raw DD (D1), and a diet containing 10% solid-state fermented DD (D2). Inclusion of DD in the diet significantly increased average daily gain (ADG), final body weight (BW), and feed efficiency, with the highest values recorded for D2 (p < 0.05). Feeding of DD altered (p < 0.001) all measured rumen fermentation parameters, except pH, with higher levels (p < 0.05) of total volatile fatty acids, propionate, microbial crude protein, and ammonia nitrogen recorded for D1 and D2, as compared to control. Similarly, blood biochemistry revealed elevated total protein, albumin, and globulin in both supplemented groups (p < 0.05), whereas higher glucose and cholesterol levels were recorded for the D1 group (p < 0.05). Notably, systemic antioxidant status improved with the inclusion of SSF fermented DD, as evidenced by increased superoxide dismutase, glutathione peroxidase, and catalase activities, alongside reduced malondialdehyde levels (p < 0.05). The inclusion of DD in the diet decreased cooking and drip losses, and decreased shear force (indicating enhanced tenderness) and water-holding capacity (p < 0.05), with better values recorded for D2. Carcass protein and fat contents increased with the inclusion of DD in the diet, with higher values recorded for D2 (p < 0.05). Fatty acid analysis revealed higher (p < 0.05) contents of rumenic acid and octadecenoic acid in D2, as compared to D1 and control. The concentrations of lysine, methionine, threonine, leucine, and valine in meat were also higher in D2-fed goats (p < 0.05). In conclusion, incorporating solid-state-fermented discarded dates into goat diets represents a promising and sustainable strategy to valorize agricultural waste while concurrently improving growth performance, antioxidant status, meat quality, and selected nutrient profiles of goat meat. These preliminary findings warrant validation in larger-scale production.