Immunity+ is built on High Immune Response (HIR) technology, originally developed by the University of Guelph over 30 years
ago. Immunity+ measures an animal’s ability to mount an effective immune response to bacterial, viral, and mycobacterial infections. Animals with a stronger immune response are genetically better equipped to resist infections and pathogens.
Immunity+ bulls’ daughters experience 30% fewer overall diseases compared to their herd mates, including:
• 30% less Mastitis
• 31% less Lameness
• 25% less Retained Placenta
• 42% less Ketosis
• 15% less Displaced Abomasum
• 6% less Metritis
• 24% less treatment necessity for Bird Flu
Other disease traits are low heritability traits that only manage symptoms. Immunity+ is more than just a single trait; it is a broader, highly heritable trait that strengthens an animal’s immune system genetically. Cows sired by Immunity+ bulls produce higher quality colostrum, and Immunity+ sired calves are stronger from day one, more resistant to common diseases, and respond better to
vaccines.
Yes! Immunity+ has been used worldwide for nearly 15 years. Data from over 35 commercial herds and tens of thousands of animals show 5–20% reductions in major diseases in Immunity+-sired cows compared to others in the same herds. Producers report lower treatment rates for calves, reduced mortality, and higher colostrum quality, with some herds seeing fourfold lower treatment rates in calves from Immunity+ sired animals. These are field-level observations, not just theoretical predictions, and they reflect outcomes seen in typical commercial settings, not only controlled research herds.
Recently, the Journal of Dairy Science Communications published an article about Immunity+ and bird flu. This article, titled “High immune responder cows have lower treatment risk and reduced milk loss during highly pathogenic avian influenza H5N1 outbreaks,”w as so highly regarded that it is included in JDS Communications’ Editor’s Choice Collection. The study evaluated whether genetic selection for improved immune response, using Immunity+ GEBVs, can increase resilience to HPAI H5N1 in commercial dairy herds.
Treatment records and daily milk yield data were obtained from herd management software for six large commercial dairy herds in the United States with confirmed HPAI H5N1 outbreaks.
The study found that cows with high Immunity+ GEBVs were 24% less likely to require supportive treatment than those with low Immunity+ GEBVs. Cows with high immunity also experienced significantly less milk loss during the post-treatment fluctuation period compared to low immunity cows.
No. Immunity+ sires and female testing are exclusive to Semex.
Semex tests all bulls for their immune response through phenotypic and genomic testing, with significant contributions from Antibody-Mediated Immune Response (AMIR) and Cell-Mediated Immune Response (CMIR) testing. The antibody part targets bacterial infections outside cells, such as mastitis, metritis, and digital dermatitis. The cellular part addresses viral and mycobacterial infections inside cells, such as viral pneumonia, retained placenta, and Johne’s disease. Together, they work to fight disease.
In 2022, Semex utilized these testing results and added disease traits from CDCB, Lactanet, and Zoetis. Including these traits with Immunity guarantees that animals develop a robust overall immune response and can identify pathogens that cause major dairy farm diseases.
All Semex sires, including Immunity+ sires, are chosen using the same rigorous standards for production, fertility, and type. There is no genetic trade-off with Immunity+.
What are the Immunity Index and the Calf Immunity Index? The Immunity Index appears on all proof charts for Semex sires and is available for all females tested with Semex’s Elevate® genomic test. Since diseases in cows differ significantly in cause from those in calves, we also publish a Calf Immunity Index. The Calf Immunity Index combines immune response traits AMIR and CMIR with specific proof data for calves. Both indexes are published with a mean of 100 and a standard deviation of 5, so scores usually range from 85 to115. Immunity+ bulls are considered superior transmitters of high immune response if they have an Immunity Index of 105 or higher and a Calf Immunity Index of 100 or higher. The higher threshold for the Immunity Index compared to the Calf Immunity Index reflects the greater economic importance of cow disease traits relative to calf disease traits.
Colostrum is the most important factor for keeping calves alive. As we know, calves are born without immunity, and most won’t survive without high-quality colostrum. High-immunity females have been shown to produce higher-quality colostrum with higher levels of antibodies, total immunoglobulins, and beta-lactoglobulin. Colostrum from high-immunity cows supports better calf development and growth.
Bulls with an Immunity Index of over 105 and a Calf Immunity of over 100 are designated Immunity+, which means they pass a high immune response to their offspring. Immunity+ sires are listed on Semex’s website, proof charts, and printed materials.
Yes! Semex’s Elevate genomic testing program identifies heifers and cows with high immune responses. This allows dairymen to choose animals with high immunity and plan their matings strategically. Ongoing genomic testing helps dairy farmers track results across multiple generations.
