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Selection for Improvement in Heritable Traits through Genetic Evaluation

For the past 40+ years, the beef and dairy cattle industries have benefited from accelerated improvement in desired heritable traits though use of genetic analysis and EPDs. US dairy cattle are producing 60% more milk from 30% less cows than in 1967 - each cow produces 2 and a half times as much milk as 50 years ago. Use of EPDs (along with widespread use of AI) played a large part in this increase in effciency.

The National Sheep Improvement Program (NSIP) provides a similar genetic analysis to American sheep producers in the form of estimated breeding values (EBVs).


NSIP converts producer's collected data, such as birth weight, weaning weight, fecal egg counts, and loin muscle depth, into a numerical value - the EBV. The EBV value is a measure of the individual's genetic merit for that trait as compared to other individuals of the breed. Therefore, superior individuals can be selected from the population.

For example, if a ram has a weaning weight EBV of +5.0, he is expected to be 5kg (11lbs) heavier than the average lamb at weaning He will pass on half his genes to his lambs, so you can expect his lambs to weigh 2.5kg (5.5lbs) more than average at weaning based on genetics alone. If he sires 100 lambs, that is 550 additional pounds of lamb!

More detailed information about EBVs is available on the NSIP website.

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