# Selenium-Biofortified Alfalfa Hay Supplemented to Jersey and Holstein Dairy Heifers During the Peripartum Period: Effects on Dams and Their Offspring

## TL;DR

This study found that feeding selenium-biofortified alfalfa hay to pregnant dairy heifers had minimal effects on their performance and the health of their offspring.

## Contribution

The study provides new evidence on the limited effectiveness of selenium-biofortified hay in improving dairy heifer and calf health.

## Key findings

- Supplementation of Se-biofortified hay improved milk yield in Holstein heifers only.
- No significant impact was observed on blood parameters or the liver transcriptome in most cases.
- Feeding Se-biofortified hay did not improve the health of offspring.

## Abstract

The period from pregnancy to lactation and the early phase of life after calving are the most challenging for dairy cows and calves, respectively, due among others to heightened inflammation, dysfunction of the immune system, and oxidative stress that can negatively affect their offspring, Selenium, especially if fed in an organic form, as in the case of biofortified hay, can aid in improving the immune system decreasing inflammation and oxidative stress. To assess this, we fed selenium biofortified alfalfa hay to pregnant dairy Holstein and Jersey heifers and evaluated their performance and, through the analysis of several blood parameters, their physiological status as well as the status of their offspring. Our data indicated that feeding selenium-biofortified alfalfa hay to pregnant Holstein or Jersey heifers had minimal effects on the performance and health status of the dairy cows and their offspring.

The objective of the study was to assess whether supplementing dairy heifers with Se-biofortified hay during the last 40 days of pregnancy and early lactation improves performance, metabolism, oxidative status, and immune response in the dams and their calves. Ten Jersey and eight Holstein pregnant dairy heifers were divided into two groups and supplemented with Se-biofortified or a control alfalfa hay from 40 days before to 2 weeks postpartum. The calves born to the heifers were also monitored during the first month of life. Supplementation of Se-biofortified hay improved milk yield in Holstein heifers only, but had minor effects on blood parameters measured and the liver transcriptome. Similarly, we did not detect any impact of feeding Se-biofortified hay to heifers on their offspring. The data indicated a better immune system and oxidative status in Holstein compared to Jersey heifers. Overall, our data did not support the hypothesis that supplementing Se-biofortified hay to pregnant heifers improves their performance and the health of dams and offspring, at least at the dose we provided.