Page 41 - Earnscleugh 2021 Catalogue eBook

COMPOSITE

EARNSCLEUGH COMPOSITES BREEDING PROGRAM
To maintain a minimum of 70% of maximum hybrid vigour we must continue to introduce purebred genetics at regular
intervals.
It is very important that those purebred animals are top performers within their breed or the benefits of hybrid vigor could be
lost due to lower production in the base breeds.
Top cows from our Hereford and Angus studs are used for ET. For breeds we don’t have on site we lease and flush eggs
from breed leading donor cows.

Crossbreeding beef cattle offer two primary advantages relative to the use of only one breed: 1) crossbred animals
exhibit heterosis (hybrid vigour), and 2) crossbred animals combine the strengths of the various breeds used to form the
cross. The goal of a well-designed, systematic crossbreeding program is to simultaneously optimize these advantages of
heterosis and breed complementarity.
The amount of heterosis expressed for a given trait is inversely related to the heritability of the trait. Heritability is the
proportion of the measurable difference observed between animals for a given trait that is due to genetics (and can be
passed to the next generation). Reproductive traits are generally low in heritability (less than 10%), and therefore respond
very slowly to selection pressure since a very small percentage of the differences observed among animals is due to
genetic differences (a large proportion is due to environmental factors). The amount of heterosis is largest for traits that
have low heritabilities. This has significance for commercial breeding systems, as crossbreeding can be used to enhance
reproductive efficiency. To date, the ability to select for reproduction is limited (ie. there are no EPDs for reproduction). COMPOSITE

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