HerefordSire
Well-known member
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"Over 20 million parentage records of Hereford cattle were used to evaluate inbreeding levels and rates of change from 1900 to 2001. Inbreeding levels increased on an annual basis until 1966, where a maximum level of 11.5% was calculated. During the 1970s and 1980s inbreeding levels decreased and by the 1990's inbreeding was increasing and reached a level of 9.8% by 2001. The reported decrease in inbreeding is unusual since the Hereford population is relatively closed. Additional analysis suggested that there were two potential causes for the decreased inbreeding levels. These were a shift to types or lines of Herefords that were not as popular before 1966 and/or the importation of genetic resources from Canada. While one or both of these causes led to a reduction in inbreeding that reduction was transient, as inbreeding increased again in the 1990s. From 1990 to 2001 the effective population size of the breed was calculated and found to be 85 animals. The study provides a benchmark of current genetic diversity in Herefords and can be used in monitoring future changes and if need be developing conservation strategies."
http://www.ars.usda.gov/research/public ... 115=173558
(1) Any comments about the following sentence?
The reported decrease in inbreeding is unusual since the Hereford population is relatively closed.
(2) Does ayone see a pattern in the dates of the trend reversal in 1966 and the trend reversal in 1990?
"Over 20 million parentage records of Hereford cattle were used to evaluate inbreeding levels and rates of change from 1900 to 2001. Inbreeding levels increased on an annual basis until 1966, where a maximum level of 11.5% was calculated. During the 1970s and 1980s inbreeding levels decreased and by the 1990's inbreeding was increasing and reached a level of 9.8% by 2001. The reported decrease in inbreeding is unusual since the Hereford population is relatively closed. Additional analysis suggested that there were two potential causes for the decreased inbreeding levels. These were a shift to types or lines of Herefords that were not as popular before 1966 and/or the importation of genetic resources from Canada. While one or both of these causes led to a reduction in inbreeding that reduction was transient, as inbreeding increased again in the 1990s. From 1990 to 2001 the effective population size of the breed was calculated and found to be 85 animals. The study provides a benchmark of current genetic diversity in Herefords and can be used in monitoring future changes and if need be developing conservation strategies."
http://www.ars.usda.gov/research/public ... 115=173558
(1) Any comments about the following sentence?
The reported decrease in inbreeding is unusual since the Hereford population is relatively closed.
(2) Does ayone see a pattern in the dates of the trend reversal in 1966 and the trend reversal in 1990?