# Effects of Dietary Grape Branch and Leaf Silage on Growth Performance, Serum Biochemical Parameters, Gut Microbiota, and Metabolism in Kazakh Rams

## TL;DR

Feeding grape branch and leaf silage to Kazakh rams improved their growth, reduced fat, and boosted health by altering gut microbes and metabolism.

## Contribution

This study is the first to systematically evaluate grape branch and leaf silage as a feed alternative in rams, linking its effects to microbiota and metabolic changes.

## Key findings

- Replacing corn silage with grape branch and leaf silage increased dressing percentage and reduced tail fat in rams.
- The silage improved immune and antioxidant markers while lowering inflammation and oxidative stress.
- It altered gut microbiota and enriched metabolic pathways like bile acid biosynthesis and glycerophospholipid metabolism.

## Abstract

This study explored the use of grape branch and leaf silage as a feed ingredient in the diet of Kazakh rams. Sixty rams were divided into three groups: one fed Whole-crop Corn Silage, and the others with 50% or 100% replacement by grape branch and leaf silage over a 120-day feeding period. The results showed that replacing Whole-crop Corn Silage with grape branch and leaf silage improved slaughter performance by increasing dressing percentage and reducing tail fat deposition. It also enhanced immune function and antioxidant capacity while lowering inflammation and oxidative stress markers. Additionally, the grape branch and leaf silage positively influenced gut microbiota composition and metabolic pathways. These findings suggest that grape branch and leaf silage can be a beneficial feed alternative, supporting both production performance and health in sheep.

With the continuous development of the livestock industry, the availability of high-quality roughage is becoming increasingly constrained. Therefore, the exploitation of unconventional feed resources is crucial for the sustainable development of the sector. Grape branches and leaves are a major by-product of viticulture, abundant in supply but currently underutilised. Their ensilage presents potential feed value and ecological benefits. This study aimed to systematically evaluate the effects of dietary supplementation with grape branch and leaf silage on the growth performance, serum biochemical parameters, gut microbiota, and metabolomic profiles of Kazakh rams. Sixty Kazakh rams aged 6.0 ± 0.5 months with similar initial body weight (34.21 ± 2.13 kg) were randomly allocated to three dietary treatment groups: the control group (CG) fed whole-crop corn silage, the EG50 group where grape branch and leaf silage replaced 50% of the whole-crop corn silage, and the EG100 group where grape branch and leaf silage entirely replaced the whole-crop corn silage. Each treatment comprised four replicates with five rams per replicate. Following a 7-day adaptation period, a formal feeding trial was conducted for 120 days, after which relevant parameters were measured. Results: (1) Compared with the CG, the dressing percentage was significantly increased in the EG100 group (p < 0.05), while tail fat weight and tail fat percentage were both markedly decreased (p < 0.01). (2) Serum immunoglobulin (IgA, IgG) levels and antioxidant enzyme (SOD, CAT) activities were significantly elevated in the EG100 group (p < 0.05), accompanied by enhanced total antioxidant capacity. Concurrently, levels of inflammatory cytokines (IL-1β, TNF-α) and the oxidative damage marker malondialdehyde (MDA) were significantly reduced (p < 0.05). (3) Based on slaughter performance, jejunal microbiota analysis was performed for the CG and EG100 groups. The relative abundance of the phylum Firmicutes increased in the EG100 group, with beneficial genera such as Ruminococcus and Lactobacillus becoming predominant. (4) Metabolomic analysis revealed significant enrichment of pathways including primary bile acid biosynthesis and glycerophospholipid metabolism in the EG100 group, with 20 key differential metabolites identified. Dietary supplementation with grape branch and leaf silage may improve slaughter performance and reduce fat deposition in Kazakh rams, potentially by modulating the gut microbiota structure and its metabolic functions, thereby synergistically enhancing nutrient utilisation, anti-inflammatory capacity, and antioxidant status. This study provides a theoretical basis for the feed-oriented and value-added utilisation of grape processing by-products. Future research should further elucidate the molecular mechanisms underlying the interaction between its active components and host metabolism.