Author
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Macneil, Michael |
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Submitted to: Beef Improvement Federation Proceedings
Publication Type: Proceedings Publication Acceptance Date: 12/10/2003 Publication Date: 5/21/2004 Citation: Macneil, M.D. 2004. Multiple sire mating: an experimental perspective. Beef Improvement Federation Proceedings p. 59-62. Available at: www.beefimprovement.org/gpw-proceedings May212004.pdf. Interpretive Summary: In the contexts of research and seedstock production, reproductive management options may be limited by the need to maintain accurate records of paternity. Paternity testing using DNA markers opens up the possibility of multiple-sire mating and previous research suggests potentially enhanced reproductive performance. Data reported here result from implementing the practice of using two bulls in each breeding herd of the Line 1 Hereford population maintained at Miles City, Montana beginning in 1997. Data from the preceding 7 yr are used for the purpose of comparison. Average annual pregnancy rates were 81.9 and 84.3 % for the periods 1990 to 1996 and 1997 to 2002, respectively. Risk, in terms of variation in pregnancy rates, was virtually unchanged in the two time periods. Variance in paternal half-sib family size was 54.3 and 172.0 for the periods 1990 to 1996 and 1997 to 2002, respectively. As a consequence, inbreeding is expected to accumulate 2.8 times more rapidly when using two bulls per breeding herd. Collectively these results illustrate the trade-off between a small increment in reproductively rate and an increase in inbreeding resulting from the increased variance in family size. These factors are important considerations in implementation of in situ genetic conservation programs. Technical Abstract: In the contexts of research and seedstock production, reproductive management options may be limited by the need to maintain accurate records of paternity. Paternity testing using DNA markers opens up the possibility of multiple-sire mating and previous research suggests potentially enhanced reproductive performance. Data reported here result from implementing the practice of using two bulls in each breeding herd of the Line 1 Hereford population maintained at Miles City, Montana beginning in 1997. Data from the preceding 7 yr are used for the purpose of comparison. Average annual pregnancy rates were 81.9 and 84.3 % for the periods 1990 to 1996 and 1997 to 2002, respectively. Risk, in terms of variation in pregnancy rates, was virtually unchanged in the two time periods. Variance in paternal half-sib family size was 54.3 and 172.0 for the periods 1990 to 1996 and 1997 to 2002, respectively. As a consequence, inbreeding is expected to accumulate 2.8 times more rapidly when using two bulls per breeding herd. Collectively these results illustrate the trade-off between a small increment in reproductively rate and an increase in inbreeding resulting from the increased variance in family size. These factors are important considerations in implementation of in situ genetic conservation programs. |
