Genetic factors affecting fertility, growth, health and longevity in dairy cattle

What is it about?

Inclusion of secondary or ‘ functional ’ traits in breeding objectives began in earnest only in the late 1990, but by 2003, production traits accounted for less than 60% of the indices in most advanced countries. Although there is nearly complete consensus of the economic importance of fertility, health traits and HL, genetic evaluation and inclusion of these traits in selection indices were hindered by diffi culty of measurement and analysis and generally low heritability. Statistical methods have been developed that overcome the problems encountered in the analysis of non-production traits, including discrete distributions, and records that become available only after selection decisions have been made. Current state of the art for genetic analysis of fertility, calving traits, health, growth rate and HL are explained. Genetic parameters and genetic and phenotypic trends for these traits are presented. The advantages and limitations of breeding for disease traits and HL via selection on correlated traits and via cross-breeding are discussed. Finally, we discussed methodologies for detection and analysis of the actual segregating genes that affect functional traits and the current state of the art in the age of genomics.

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Why is it important?

Although there is nearly complete consensus of the economic importance on fertility, health traits and longevity, genetic evaluation and inclusion of these traits in selection indices was hindered by several factors. Despite these problems, the general trend in most countries is still in the direction ofincreasing selection emphasis on non-production traits.

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