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United States Department of Agriculture

Agricultural Research Service

Research Project: Alleviating Rate Limiting Factors that Compromise Beef Production Efficiency

Location: Livestock and Range Research Laboratory (LARRL)

Title: Index-in-retrospect and breeding objectives characterizing genetic improvement programs for South African Nguni cattle

Authors
item Matjuda, L -
item Macneil, M -
item Maiwashe, A -
item Leesburg, Vicki
item Malatje, M -

Submitted to: South African Journal of Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 13, 2014
Publication Date: June 14, 2014
Repository URL: http://handle.nal.usda.gov/10113/59337
Citation: Matjuda, L.E., Macneil, M.D., Maiwashe, A., Leesburg, V.L., Malatje, M. 2014. Index-in-retrospect and breeding objectives characterizing genetic improvement programs for South African Nguni cattle. South African Journal of Science. 44 Online.

Interpretive Summary: In order to know where to begin in the process of transferring technology for genetic improvement to emerging farmers, it is important to understand the selection applied to their cattle in the past. Thus, we applied index-in-retrospect methods to data originating from Nguni cattle recorded in the National Beef Cattle Improvement Scheme. Breeding values (EBV) were estimated for animals born during the period 1973 to 2006. The EBV were then used to calculate genetic selection differentials and genetic trends. Relatively little directional selection has been applied to the performance traits recorded for the Nguni breed as the standardized selection differentials were consistently less than 0.1 SD. Approximately 6.4 times more selection was applied to males than to females. However, a greater degree of natural selection was applied to females as opposed to males. Breeder imposed selection seemed opposed by natural selection in females but not in males. Selection applied to males and females appeared to be virtually independent. Overall, the cumulative selection differentials tended to be small and without clear direction. The lack of clear emphases in selection was manifest by a lack of significant genetic trends in the performance traits and by absence of any consensus breeding objective for Nguni in South Africa.

Technical Abstract: The objective of the current study was to describe the historical selection applied to Nguni cattle in South Africa. Index-in-retrospect methods were applied to data originating from the National Beef Cattle Improvement Scheme. Data used were estimated breeding values (EBV) for animals born during the period 1973 to 2006. The EBV were used to calculate genetic selection differentials and genetic trends. Relatively little directional selection has been applied to the performance traits recorded for the Nguni breed as the standardized selection differentials were consistently less than 0.1 SD. Approximately 6.4 times more selection was applied to males than to females. However, a greater degree of natural selection was applied to females as opposed to males. Breeder imposed selection seemed opposed by natural selection in females but not in males. Selection applied to males and females appeared to be virtually independent. Overall, the cumulative selection differentials tended to be small and without clear direction. The lack of clear emphases in selection was manifest by a lack of significant genetic trends in the performance traits and by absence of any consensus breeding objective for Nguni in South Africa.

Last Modified: 7/28/2014
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