# Effects of Myrtus (Myrtus communis L.) Extract Supplementation in the Diet on Metabolic, Immune, and Performance Parameters of Dairy Cows During the Transition Period

## TL;DR

Adding Myrtus extract to dairy cows' diets during the transition period improves feed intake, milk production, and reduces metabolic stress, while also lowering ovarian cysts.

## Contribution

This study demonstrates the novel use of Myrtus communis L. extract as a natural supplement to support dairy cows during the transition period.

## Key findings

- Myrtus extract increased feed intake and milk yield in Holstein cows during the transition period.
- Supplemented cows had lower NEFA and BHBA levels, indicating reduced metabolic stress.
- Treated cows developed fewer ovarian cysts, suggesting improved reproductive health.

## Abstract

Dairy cows experience physiological and metabolic challenges during the transition period which can reduce feed intake, milk production, reproductive performance and metabolic homeostasis. The dietary interventions supporting metabolism and feed intake could have beneficial effects on improving milk yield, reproduction and the immune system. This study investigated the effects of dietary Myrtus communis extract supplementation on the performance, immune and metabolic parameters of Holstein cows during the transition period. Myrtus communis L. extract supplementation increased the feed intake and milk yield and improved the energy balance. Although some immune responses were more active around calving in supplemented cows, the overall health status was not negatively affected. Reproductive efficiency was similar between groups; however, cows supplemented with Myrtus communis L. extract developed fewer ovarian cysts. These findings suggest that Myrtus communis L. extract may help dairy cows by reducing the stress of calving, improving milk production, and supporting reproductive health.

This study evaluated the effects of dietary Myrtus communis L. extract on the production performance, immune functions, and metabolic and health status of Holstein cows throughout the transition period. Forty cows were assigned to either a control group (n = 20) or a treatment group (n = 20) receiving Myrtus communis L. extract at 1.5 mL/kg body weight per day. Milk yield and feed intake were recorded daily, whereas blood samples were collected weekly. Reproductive performance and health status were monitored. Myrtus communis L. supplementation increased dry matter intake during prepartum and early and mid-lactation and elevated prepartum glucose levels. Treated cows produced more milk in early (44.56 vs. 40.72 kg/day) (p < 0.0001), and mid-to-late lactation (42.57 vs. 37.19 kg/day) (p < 0.0001). NEFA and BHBA concentrations were lower in the treatment group (p = 0.015 and 0.019, respectively), whereas cortisol and ALT were higher around calving (p < 0.001). Despite similar prepartum inflammatory profiles, treated cows demonstrated higher TNF-α concentrations at calving (p = 0.006). The days open and insemination number per pregnancy did not differ; however, the number of ovarian cysts were less in treated cows. Overall, Myrtus communis L. extract offered at a dose of 1.5 mL/kg body weight during the transition period improved feed intake, enhanced milk production, and reduced metabolic stress, suggesting its potential as a natural additive to support energy balance and reproductive performance in cows. However, it increased the blood cortisol and ALT concentrations, which requires further investigation.