# Calcium Nitrate Supplementation Improves Meat Quality in Hu Sheep via Microbial and Transcriptomic Regulation

## TL;DR

Adding calcium nitrate to Hu sheep feed improves meat quality by changing gut microbes and gene activity.

## Contribution

This study reveals how calcium nitrate enhances meat quality in Hu sheep through microbial and genetic regulation.

## Key findings

- Calcium nitrate reduces water loss in muscle and increases meat brightness and polyunsaturated fatty acids.
- It decreases methane-producing microbes and boosts energy metabolism-related genes and short-chain fatty acids.
- The treatment alters gut microbial populations and improves intramuscular lipid profiles.

## Abstract

Calcium nitrate holds great promise as a feed additive for ruminants. This study aimed to investigate the role and mechanism by which calcium nitrate regulates microbial and genetic pathways to enhance slaughter performance and meat quality in Hu sheep. The results indicate that adding 3% calcium nitrate to the diet improved meat quality and increased slaughter performance through microbial and transcriptomic pathways, providing a promising research direction for enhancing Hu sheep meat quality.

Research has demonstrated that incorporating nitrate into animal feed can effectively decrease methane production in ruminants, though its impact on carcass characteristics and meat attributes in Hu sheep requires further investigation. This experiment examined how a dietary inclusion of 3% calcium nitrate (CN) influenced slaughter parameters, meat properties, gut microbial populations, and host gene regulation in Hu sheep. The study involved sixty healthy male Hu sheep aged 120 days with comparable body weights (31.11 ± 3.39 kg), randomly allocated into two groups: a control group receiving standard feed (CON) and a CN-supplemented group. The trial lasted 60 days, including a 15-day adaptation period and a 45-day formal trial period. They were housed individually and fed twice daily (at 8:00 and 18:00). The findings revealed that CN supplementation notably reduced the water loss rate in the longissimus dorsi muscle (LD), elevated meat color brightness, and enhanced the proportion of polyunsaturated fatty acids (PUFA), particularly n-6 PUFA, along with the n-3/n-6 PUFA ratio. Conversely, it reduced the levels of saturated fatty acids such as myristic acid (C14:0) and oleic acid (C18:1n9t). Additionally, the treatment boosted ruminal Ammoniacal nitrogen content and total short-chain fatty acid production, thereby contributing to energy metabolism in the animals. Microbiological examination demonstrated that CN supplementation led to a decrease in Fibrobacterota and Methanobrevibacter populations within the ruminal environment, while promoting the growth of Proteobacteria in the duodenal region. The gene expression profiling of digestive tract tissues showed an increased activity in nitrogen processing genes (including CA4) and oxidative phosphorylation pathways (such as ATP6), indicating an improved metabolic efficiency and acid–base homeostasis in the host animals. These findings demonstrate that CN-enriched diets enhance the carcass characteristics of Hu sheep by modifying intramuscular lipid profiles through gastrointestinal microbial community restructuring and metabolic pathway adjustments. Such modifications affect energy utilization and acid–base equilibrium, ultimately impacting muscle characteristics and adipose tissue distribution, presenting viable approaches for eco-friendly livestock farming practices.