# Supplementation of Rosemary Extract Improves Lactation Performance and Rumen Function in Dairy Buffaloes Under Hot Weather

## TL;DR

Adding rosemary extract to dairy buffalo feed improves milk production and health during hot weather by enhancing the rumen environment and reducing inflammation.

## Contribution

This study demonstrates that rosemary extract can mitigate heat stress effects in dairy buffaloes by improving lactation and rumen function.

## Key findings

- Rosemary extract increased milk production and improved milk composition, including higher protein and lactose levels.
- The extract enhanced antioxidant and immune functions while reducing pro-inflammatory cytokines in heat-stressed buffaloes.
- RE improved rumen fermentation and increased the diversity of beneficial ruminal microorganisms.

## Abstract

In the hot and humid summer, dairy buffaloes are prone to heat stress, characterized by reduced lactation performance, impaired immune function, and ruminal microbial imbalance, severely restricting the efficient and sustainable development of the dairy buffalo breeding industry. Rosemary extract (RE), a natural substance with antibacterial, antioxidative, and anti-inflammatory activities, has been extensively applied in cosmetics, food, and feed manufacturing. However, whether RE regulates heat-stressed buffaloes remains unclear. The experiment aimed to evaluate the effect of dietary RE supplementation on the lactation performance and rumen function of dairy buffaloes in hot weather. Results showed that RE supplementation slightly reduced the body surface temperature of buffaloes. More importantly, it increased milk production and beneficial components, such as milk protein and lactose, and optimized the milk fatty acid profile. In terms of health, RE enhanced the antioxidant capacity and immunity function of buffaloes and reduced inflammatory substances in the blood. It also enhanced rumen fermentation capacity and elevated the diversity of beneficial ruminal microorganisms. This study highlights RE’s potential as a natural feed supplement to boost the productivity of heat-stressed dairy buffaloes over the short term by optimizing the rumen environment and enhancing body health, providing practical value for hot-climate dairy buffalo farming.

Rosemary extract (RE), rich in carnosic and rosmarinic acid, which have antibacterial/antioxidant/anti-inflammatory effects, is a potential natural feed supplement for heat-stressed dairy buffaloes. This study systematically evaluated dietary RE effects on dairy buffaloes during hot weather. Twenty Mediterranean dairy buffaloes were randomly allocated into two groups for a 35-day trial: the control (CON) group receiving a basal diet, and the RE group receiving the same basal diet supplemented with 20 g/d of RE. Results showed RE tended to reduce buffalo body surface temperature; increased milk production, 4% fat-corrected milk, milk protein, lactose, and solids-not-fat; and optimized milk fatty acid profiles. In regard to blood, the RE group exhibited higher catalase activity, total antioxidant capacity, and concentrations of immunoglobulin A and M, together with lower concentrations of the pro-inflammatory cytokines interleukin-1β and tumor necrosis factor-α. Additionally, RE markedly elevated concentrations of total volatile fatty acid, acetate, propionate, and butyrate; improved microbial α-diversity indices (Sobs and Ace); and increased the abundances of Rikenellaceae_RC9_gut_group and Butyrivibrio spp., as well as the enrichment of multiple genera belonging to the family Lachnospiraceae. In conclusion, supplementing the diet of heat-stressed dairy buffaloes with 20 g/d of RE improves milk production and composition-related performance by optimizing the rumen ecosystem and enhancing systemic health status, with these effects observed as short-term responses under the conditions of the present study.