Genetics – Trait Selection An S 426 Fall 2007

Genetics – Trait Selection Has led to development of Economically Relevant Traits (ERT) and Indicator Trait (IT) Has led to development of Economically Relevant Traits (ERT) and Indicator Trait (IT) Distinguish between two by asking question about the trait of interest: if that trait changes one unit, either up or down with no changes in other traits, will there be a direct effect on income or expense Distinguish between two by asking question about the trait of interest: if that trait changes one unit, either up or down with no changes in other traits, will there be a direct effect on income or expense

Genetics – Trait Selection 1.Birth weight and calving ease: does a 1 lb. change in birth weight directly influence expense or income a. May or may not result in increased /decreased calving difficulty b. Calving ease, a 1% decrease (meaning one extra animal assisted for every 100 calving) has a direct impact on profitability c. Thus birth weight is an IT and calving ease is an ERT and thus select for calving ease

Genetics – Trait Selection 2.Instances where traits can be both an IT and ERT a. Cow mature weight; selling cull cows – a 1 lb. change in mature weight directly influences income b. Mature weight also influences maintenance feed requirements; a mature weight increases of 1 lb. may not increase maintenance requirements c. Thus mature weight when selling cull cows is an ERT and when considering maintenance is an IT

Genetics – Trait Selection Why EPD for IT:

Genetics – Trait Selection Guidelines for using ERT and IT Guidelines for using ERT and IT 1. Many ERT still being developed by breed associations 2. Suggested procedure: a. Identify ERT for your production and marketing system b. Make selection decisions based on EPD with the following order of preference

Genetics – Trait Selection b. Make selection decisions based on EPD with the following order of preference 1.)Select using EPD for the ERT when available 2.)Select using EPD for the IT when ERT are unavailable When phenotypic information is available, but not EPD: 3.)Select from within a herd on phenotype or ratios for the ERT 4.)Select from within a herd on phenotype or ratios for the IT

Sire Selection An S 426 Fall 2007

Sire Selection Represents the greatest opportunity for making genetic improvement

Sire Selection Example: 100 cow herd 5 year generation interval – 5 year generation interval – 90% conception rate – 80% conception rate in heifers – 1 bull saved per year 1 bull saved per year

Sire Selection AI permits more rapid genetic improvement – AI permits more rapid genetic improvement – Selection of bulls is more accurate Selection of bulls is more accurate Genetic improvement is slow and depends on h2, but it is permanent Genetic improvement is slow and depends on h2, but it is permanent Management decisions can be changed rapidly and are not permanent