Author
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Roberts, Andrew |
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Submitted to: Meeting Proceedings
Publication Type: Proceedings Publication Acceptance Date: 9/1/2007 Publication Date: 12/10/2007 Citation: Roberts, A.J. 2007. Heifer Development and Economically Important Traits. Meeting Proceedings. CD only. Interpretive Summary: The genetic composition and method used for developing replacement heifers can have major impacts on efficiency and lifetime productivity. Nutritional influences on replacement heifers begin in utero and continue throughout life. Genetic changes in age and weight of puberty achieved over the last several decades may provide opportunities to reduce cost of developing heifers by decreasing the industry guidelines for heifer weights at time of first breeding. Developing heifers on lower levels of nutrient input can also improve efficiency and may alter longevity. Although a large number of traits exist for producers to choose from, reproductive traits have the largest influence on productivity in commercial cow-calf enterprises, as these traits culminate in less open cows, older calves at weaning, increased longevity and decreased replacement rate of younger animals. However, feeding to maximize reproductive performance or any other trait may not equate to the most efficient productivity. In this respect, greater efficiency is probably achieved by matching the genetics to the environment rather than altering the management (increase feed inputs) to support changes resulting from genetic selection. Genetic antagonisms exist between desirable traits for market animals and desirable traits for replacement heifers. Crossbreeding and (or) terminal breeding systems can result in improved reproductive efficiency and (or) allow for differential selection pressure for maternal traits in replacements and growth and carcass traits in market animals. Technical Abstract: The genetic composition and method used for developing replacement heifers can have major impacts on efficiency and lifetime productivity. Nutritional influences on replacement heifers begin in utero and continue throughout life. Genetic changes in age and weight of puberty achieved over the last several decades may provide opportunities to reduce cost of developing heifers by decreasing the industry guidelines for heifer weights at time of first breeding. Developing heifers on lower levels of nutrient input can also improve efficiency and may alter longevity. Although a large number of traits exist for producers to choose from, reproductive traits have the largest influence on productivity in commercial cow-calf enterprises, as these traits culminate in less open cows, older calves at weaning, increased longevity and decreased replacement rate of younger animals. However, feeding to maximize reproductive performance or any other trait may not equate to the most efficient productivity. In this respect, greater efficiency is probably achieved by matching the genetics to the environment rather than altering the management (increase feed inputs) to support changes resulting from genetic selection. Genetic antagonisms exist between desirable traits for market animals and desirable traits for replacement heifers. Crossbreeding and (or) terminal breeding systems can result in improved reproductive efficiency and (or) allow for differential selection pressure for maternal traits in replacements and growth and carcass traits in market animals. |
