Inbreeding Among Canadian Dairy Breeds

Friday, August 15th, 2014

Each year, based on official animal registration and pedigree information within its database, Canadian Dairy Network (CDN) computes current statistics related to the level of inbreeding within the Canadian cow population of each dairy breed.

In this way, the average level of inbreeding for animals born in the most recent complete calendar year as well as trends in the level of inbreeding over time can easily be monitored. The following table is based on animals born since 1970 up to and including registered animals born in 2013.

Current Inbreeding Level and Change in Average Inbreeding by Breed
Breed	Average % Inbreeding for 2013	Average Annual Increase in Average Inbreeding Percentage by Time Period
Breed	Average % Inbreeding for 2013	1970- 1980	1980- 1990	1990- 2000	2000- 2010	2010- 2013
Ayrshire	6.11	.25	.19	.10	-.02	.17
Brown Swiss	6.76	.02	.23	.13	.14	.14
Canadienne	8.75	.08	.28	.18	.21	.17
Guernsey	7.36	.05	.10	.21	.16	.19
Holstein	6.56	.12	.07	.27	.07	.21
Jersey	6.00	.14	.05	.16	.06	.04
Milking Shorthorn	2.60	.03	.00	.26	-.10	.09

Among the four major dairy breeds in Canada, all have an average inbreeding level between 6.00% (Jersey) and 6.76% (Brown Swiss) for heifers born in 2013. The Ayrshire breed has well controlled the rate of increase in inbreeding from 2000 to 2010 with an average change of -.02 percentage points per year. In this regard, Jersey and Holstein are also doing reasonably well at +.06% and +.07% per year, respectively. More recently, however, the Jersey trend has been quite stable whereas all other breeds are experiencing a steady increase for animals born since 2010. Among the breeds with the smallest populations in Canada, Canadienne continues to have the highest average inbreeding, now at 8.75% for females born in 2013. Guernsey heifers born in 2013 average 7.36% inbreeding and the average rate of increase during the past few years has also been relatively high at +.19% per year. For Milking Shorthorn, heifers born in 2013 average 2.60% inbreeding based on available pedigree data for the breed but the rate of increase has been slowly on the rise over the past two years.

Below is a graph showing the inbreeding trend for animals of the four largest dairy breeds born in Canada since 1970 as well as a specific graph for the Holstein population alone. For further information, please feel free to contact Canadian Dairy Network (CDN).