The X Factor: What It Is & How to Find It: The Relationship Between Inherited Heart Size and Racing Performance [Paperback]

Marianna Haun (Author)

Book Description

Publication Date: January 1, 1997

Scientists have known for years that superior human athletes have hearts that are substantially larger than those of non-athletes. Human athletes can increase the size of their hearts through proper conditioning. Scientific research shows that superior racehorses, both Thoroughbreds and Standardbreds, also have hearts substantially larger than those of average horses. Unlike humans, the size of equine hearts is an inherited trait. Large racehorse hearts are passed from generation to generation along the X chromosome, through the mare. The challenge faced by breeders and buyers is learning how to capitalize on this important research. Marianna Haun was part of the U.S. team that conducted this ground-breaking research. In her book, The X Factor: The Relationship Between Inherited Heart Size and Racing Performance, she explains the significance of Thoroughbred and Standardbred heart scores and why those scores should be considered when buying or breeding a racehorse. Haun identifies the large-heart lines in the pedigrees of champion racehorses and shows how to find it in the pedigrees of horses that haven't yet been examined. After reading The X Factor, you will understand how heart size is measured and what the scores mean. You will learn how to trace large hearts through modern-day pedigrees and be able to find these genetic links in the horses you buy or breed. You will also see the body types that are consistent with large-hearted bloodlines that can be recognized and used in the selection of bloodstock. This is information you can use today to give your racing and breeding program the edge.

Editorial Reviews

About the Author

Marianna Haun is a member of the National Turf Writers Association. She has covered the racing industry as a writer and photographer, for the Thoroughbred Times and later the Associated Press, and currently as a freelancer. She is involved in the University of Kentucky project described in The X Factor.

Excerpt. © Reprinted by permission. All rights reserved.

From Chapter 1: Suffering from a severe case of laminitis, Secretariat had been humanely destroyed. As the mighty stallion lay on an autopsy table at the University of Kentucky, a group of research pathologists surrounded him. As the veterinary pathologists began to cut into the stallion, they made a groundbreaking discovery: They uncovered the largest heart ever found in a Thoroughbred racehorse, estimated at 22 pounds. The normal heart size of a Thoroughbred is 8.5 pounds. . . . It was this discovery that would lead to further research on the large heart.

Product Details

• Paperback: 208 pages
• Publisher: Russell Meerdink Co (January 1, 1997)
• Language: English
• ISBN-10: 0929346467
• ISBN-13: 978-0929346465
• Product Dimensions: 9 x 6 x 0.5 inches
• Shipping Weight: 11.8 ounces
• Average Customer Review: 3.8 out of 5 stars  See all reviews (4 customer reviews)
• Amazon Best Sellers Rank: #1,855,777 in Books (See Top 100 in Books)

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Customer Reviews

Most Helpful Customer Reviews

13 of 13 people found the following review helpful:

4.0 out of 5 stars Useful on at least two levels, July 12, 2000

By 

Miles Michelson (Berkeley, CA USA) - See all my reviews
(REAL NAME)   

This review is from: The X Factor: What It Is & How to Find It: The Relationship Between Inherited Heart Size and Racing Performance (Paperback)

I think this book is good on two levels. As a primer for getting to know what the X-Factor is and how take advantage of it when breeding horses, I think book is essential. It also contains an absolute wealth of information that is incredibly valuable and interesting to breeders and pedigree researchers alike.

On the other hand, I found a number of ommisions & contradictions in Mrs. Haun's logic and quite a few problems or errors in the book itself. There are points where the serious researcher will have to make leaps of faith with Mrs. Haun and other points where you'll be left scratching your head wondering what's she's talking about. I found of typos (horse names spelled incorrectly in the book AIR FORBES ONE, ISINGLAS, etc) and the general impression I got was that her work hadn't been checked thoroughly for errors or was rushed to print before it was ready. At one point she mentions that Bend Or and Gainsborough trace their X-Factor genes to the mare Pocahontas which is flat wrong. I could find no such link and was left scratching my head.

While Marianna documents the Princequillo and War Admiral lines fairly well, it seems that there's a lack of documentation of the Mahmoud and Blue Larkspur lines. Whether this is because the author doesn't know the complete story with these lines or not is hard to tell. There also appear to be Omaha and Citation lines which she treats differently than the other lines. Unless you are an astute reader, you'll miss some of information Marianna has to share about these specific lines.

Overall, I found the book great. I was able to replicate and validate most of the connections she made and in many cases extend them by locating additional double copy mares which aren't included in the book.

I look forward to an update of this book with a list of additional X-Factor sires and more complete documentation.

4 of 4 people found the following review helpful:

3.0 out of 5 stars A starting point, June 6, 1998

By A Customer

This review is from: The X Factor: What It Is & How to Find It: The Relationship Between Inherited Heart Size and Racing Performance (Paperback)

Marianna Haun's X-Factor is a starting point of information regarding the subject of the X chromosome, however, I felt the format of text hard to digest because the author's writing style is very broken up. The she wanders and comes back to the subject matter pages, and some times chapters, later. There is at least one pedigree error. Page 105 states Milan Mill is a daughter of Princequillo and the pedigree on page 106, shows her out of Caruso. Also, pedigrees of all listed DC mares would have been extremly informing and the index does not list all horses mentioned in the text. Myself being a researcher, would have liked to have had a bibliography included so I could varify the information presented. My general opinion of this work is that Ms. Haun compiled information from research work that has been done on this subject without a complete understanding of the subject matter herself.

3 of 3 people found the following review helpful:

5.0 out of 5 stars Researching the Large Heart x Factor In Thoroughbred Horses, May 7, 2000

By 

Ivan Inglebaum (United States) - See all my reviews

This review is from: The X Factor: What It Is & How to Find It: The Relationship Between Inherited Heart Size and Racing Performance (Paperback)

The findings of a genetic link to a specific characteristic found in superior race horses is nothing less than spectacular, both in terms of significance to the Thoroughbred industry, and in the sheer volume of information that had to be researched in order to achieve these findings. In a time of genetic emphasis and the biotechnical explosion that is to come in the near future, it is amazing to pinpoint a genetic link that is recessive, yet has found it's way down the gene trail for over 200 years. I applaude Marianna Haun, as I applauded the greatest racehorse ever with the largest heart in history: Secretariat.