# Efficiency of Utilizing Bulls with High Immune Response (HIR) in Terms of Reproductive Traits of PHF Cows

## TL;DR

Breeding cows with sires that have high immune response can improve some reproductive traits but also increases risks like difficult births and twin pregnancies.

## Contribution

This study evaluates the impact of breeding with high immune response sires on reproductive traits in Polish Holstein-Friesian cows.

## Key findings

- Cows related to HIR sires had shorter calving intervals and reduced age at first insemination.
- There was a higher frequency of twin pregnancies and difficult births in cows related to HIR sires.
- The overall impact of HIR sire breeding on reproductive efficiency remains inconclusive.

## Abstract

Simple Summary: This study examines how breeding dairy cows with high immune response (HIR) sires affects their reproductive performance. We looked at factors like calving time, how long they stay open for insemination, and the ease of calving. We found that cows related to HIR sires tended to have shorter intervals between calving, which is good for farm productivity. However, there were also more cases of twin pregnancies and difficult births among these cows. This suggests that while there are some benefits to breeding with HIR sires, there are also potential challenges. Understanding these effects can help farmers make better decisions about breeding strategies, ultimately contributing to the efficiency and success of dairy farming.

Reproductive traits in dairy cattle are crucial for herd productivity and profitability. This study investigates the influence of relatedness to high immune response (HIR) Immunity+ sires on reproductive performance indicators in Polish Holstein-Friesian cows. A total of 5094 cows were analyzed, categorized based on their relatedness to HIR Immunity+ sires, and assessed for various reproductive parameters, including age at first insemination, gestation length, days open, calving interval, and calving ease. The results showed that the level of relatedness to HIR Immunity+ sires influenced certain reproductive traits, such as service period, gestation length, and age at first and second calving. Additionally, cows related to HIR Immunity+ sires exhibited a higher frequency of twin pregnancies and more complicated births. While some benefits were observed in certain reproductive traits among cows related to HIR Immunity+ sires, such as reduced age at first insemination and shortened gestation length, the overall impact on reproductive efficiency remains inconclusive. Further studies are needed to fully elucidate the effects of using semen from HIR Immunity+ sires on reproductive performance in dairy cattle.