# Effects of Aspergillus niger and Its Compound Preparations on Methane Emissions and Gastrointestinal Microbiota in Heat-Stressed Holstein Bulls

## TL;DR

Adding Aspergillus niger to cattle feed reduces methane emissions and helps animals cope with heat stress by improving digestion and antioxidant defenses.

## Contribution

This study demonstrates that Aspergillus niger and its compound preparation can simultaneously reduce methane emissions and alleviate heat stress in Holstein bulls.

## Key findings

- Aspergillus niger and its compound preparation significantly reduced methane emissions in Holstein bulls.
- The supplements lowered rectal temperatures and improved antioxidant capacity in heat-stressed bulls.
- The additives increased beneficial rumen fermentation products like volatile fatty acids and acetate.

## Abstract

In livestock farming, cattle produce methane—a potent greenhouse gas—during digestion, which contributes to climate change. At the same time, hot weather causes heat stress in animals, harming their health and well-being. In this study, we investigated whether adding the natural microorganism Aspergillus niger or a compound preparation containing it to the diet of Holstein bulls could help solve these two problems at once. Our results showed that these supplements significantly reduced the methane emissions from the animals. They also helped the bulls cope with heat stress by lowering their body temperature and improving their antioxidant capacity. Furthermore, the additives promoted beneficial digestive processes in the rumen. We conclude that Aspergillus niger and its compound preparation are promising, natural feed additives that can make cattle farming more environmentally friendly and help animals better withstand hot summers.

The livestock sector is a major source of methane, a potent greenhouse gas, while heat stress impairs ruminant health. This study evaluated the efficacy of Aspergillus niger (AN) and its compound preparation (CP) as feed additives to mitigate methane emissions and heat stress in Holstein bulls. Twenty-four bulls were assigned to a control group (CON), a group supplemented with 6 g/d of AN, and a group with 20 g/d of CP. Methane emissions were measured using the SF6 tracer technique. Blood and ruminal fermentation parameters were also analyzed. Results showed that both AN and CP significantly reduced total methane emissions, emissions per unit of body weight, and per unit of dry matter intake compared to CON. Supplemented groups had significantly lower rectal temperatures and higher superoxide dismutase activity, with AN also increasing total antioxidant capacity. AN groups showed increased total volatile fatty acids, acetate, and propionate. Microbiota analysis revealed significant beta-diversity shifts with differential taxon enrichment. In conclusion, Aspergillus niger and its compound preparation effectively reduce enteric methane and alleviate heat stress by boosting antioxidant defenses and modulating rumen function, offering a dual-benefit strategy for sustainable ruminant production.