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 females born in Canada since 1970 up to and including registered heifers born in 2021.
Current Inbreeding Level and Change in Average Inbreeding by Breed
Inbreeding for 2021
Average Annual Increase in Average
Among the four major dairy breeds in Canada, the average inbreeding level for heifers born in 2021 is highest for Holstein at 8.86%, followed by Jersey (7.10%), Brown Swiss (7.09%) and Ayrshire (6.73%). In terms of controlling the rate of increase in inbreeding for females born since 2010, the Ayrshire and Jersey breeds are doing the best among these four breeds, averaging +.12% per year, compared to rates of increase of +.15% for Brown Swiss and +.26% per year for Holstein.
Among the breeds with the smallest populations in Canada, Canadienne continues to have the highest average inbreeding, now at 9.53% for females born in 2021, but the average rate of increase since 2010 has been low at +.08% per year. Guernsey heifers born in 2021 average 7.50% inbreeding and the average change since 2010 has been relatively low at +.10% per year. For Milking Shorthorn, heifers born in 2021 average 2.79% inbreeding based on available pedigree data for the breed and the rate of increase has been low at +.06% per year for heifers born since 2010.
Below is a graph showing the inbreeding trend for the four largest dairy breeds based on registered females born in Canada since 1970 as well as a specific graph for the Holstein population alone.
GRAPH 1. Inbreeding Trends in Canadian Dairy Breeds
Graph 2. Inbreeding Trend in Canadian Holsteins