# Effects of dietary inclusion of blooming Ulva sp. on milk production, methane emitting potential, and physiological parameters in lactating Holstein cows

## TL;DR

This study explores the effects of adding blooming Ulva sp. to the diet of lactating cows, finding no adverse effects on milk production and a potential reduction in methane emissions.

## Contribution

The study introduces Ulva sp., a macroalgae causing green tides, as a potential feed ingredient for ruminants with possible methane-reducing properties.

## Key findings

- Ulva sp. inclusion did not affect methane production but tended to reduce methane intensity from respiration and eructation.
- Milk fat yield and energy-corrected milk increased temporarily in week 2 but not in week 4.
- Ulva sp. had no adverse effects on milk production, blood parameters, or metabolites in lactating cows.

## Abstract

Ulva sp., a blooming macroalgae causing the green tide in Korea, has been suggested as a feed ingredient for ruminant livestock. The objective of this study was to investigate the effects of 3% dry matter inclusion of Ulva sp. in a total mixed ration (TMR) on milk production, methane emitting potential, and physiological parameters in lactating Holstein cows.

A total of 36 cows were allocated into two groups considering milk production, parity, days in milk, and methane production concentration from respiration and eructation, and fed the TMR with or without 3% dry matter inclusion of Ulva sp. for 4 weeks. Methane emitting potential was measured using a laser methane detector in week 4, and feed, milk, and blood were collected every 2 weeks.

Ulva sp. inclusion did not affect methane production concentration from respiration and eructation, but tended to decrease the methane intensity concentration from respiration (p = 0.06) and eructation (p = 0.06). In addition, it increased the milk fat yield, energy-corrected milk, and net energy for lactation in week 2, but this did not persist to week 4, indicating the interaction between treatment and week (p<0.05). Likewise, it increased milk urea nitrogen, blood urea nitrogen, and white blood cell counts in week 2 but not in week 4 (p<0.05). Cortisol concentration in hair tended to decrease with Ulva sp. inclusion (p<0.10), whereas the serum total antioxidant capacity and uric acid were not affected.

It was demonstrated that Ulva sp. can be utilized as a feed ingredient for lactating cows without any adverse effects on milk production, complete blood cell counts, or blood metabolites. The potential methane-reducing property of Ulva sp. should be further investigated in future studies.