Company News

Semex takes breeding for health to the next level with new Immunity Health Index

A decade after the introduction of Immunity+, based on the ground-breaking high immune response technology, Semex is taking the brand’s health-boosting capability to the next generation by rating every sire in the stud with its own Immunity index, and by also introducing a Calf Immunity Index to better facilitate sire choices to improve disease resistance in calves.
The net result will be greater clarity on which bulls are the best at siring daughters with the greatest resistance to disease. Previously only the elite sires for Immunity were badged as being Immunity+. Now, giving full transparency through the stud, every bull will get their own score. This will introduce more intra-bull competition into the programme by effectively ensuring every Immunity+ sire has to requalify for the status at each proof run. This means some sires may lose their Immunity+ rankings as a result, and new ones will qualify, but that is the nature of genetic selection, says Drew Sloan, Vice President, Corporate Development.
“Years of research, based on over 300,000 animals, has culminated in the Immunity Index. For the last decade dairy farmers have - uniquely with Semex - been able to build immunity into their breeding goals by using Immunity+ sires, but now with an easily interpretable index they can take it to the next level, and the true impact of immunity can be better understood”.
The new Immunity Index is generated by a new specially developed machine learning algorithm, developed by Dr Steven Larmer, Semex. The objective of the development has been to take the best available global data on health traits and alongside Immunity+ technology enabling the firm’s geneticists to better predict bulls that will sire daughters with the lowest risk of disease, and the lowest disease cost. The new Calf Immunity Index is calculated with a higher proportion of CMIR [cell-mediated immune response] as opposed to AMIR [antibody-mediated immune response], because CIMR is better for defending against viruses that are more prevalent in calves, allowing more precise selection on calf health for those farmers who need it.
Similar to all bull traits, there will be a fixed base starting with bulls born from 2014-2016 with a base change in line with the next UK changes in 2025. Bulls will receive Immunity+ status when the Immunity Index is equal to or greater than 105, and Calf Immunity Index equal to or greater than 100.
All in all, the culmination of this research means dairy farmers can expect a near 30% reduction in disease from daughters sired by Immunity+ bulls compared to their herd mates, with health lifetime costs reduced by over £100:
Daughters of Immunity+ Sires Vs Whole Herd
Health Index Mast Lame Retp Keto DA Metr TOTAL
Immunity+ -25.6% -31.4% -24.9% -42.4% -15.2% -6.4% -28.6%

“We are incredibly excited about introducing the new Semex Health Index, because we believe it to be the world’s best health index. This next generation of Immunity+, with even greater accuracy, brings the ability to lower disease even faster, and will accelerate improvements in animal health via genetics” concludes Mr Sloan.