Chapter 1 - Cattle genomics: genome projects, current status, and future applications

Abstract

Cattle have been recognized as very useful livestock since prehistoric time due to their contribution through milk, beef, manure, hide, and draft power. Genetic improvement of cattle germplasm has been targeted by the scientific community in different ways. The major challenge for the researchers working in this area is to increase the production performances and disease resistance to ensure higher returns to the dairy and beef industries and cattle farmers. The present chapter discusses the evolution of molecular breeding that actually started from the scrap and eventually flourished into its current form. Preliminary experiments on genomic selection (GS) were reported on simulated data which revealed that GS can practically be implemented in large animals with longer generation intervals. Later, GS has been successfully implemented in a number of domestic animals to associated genome-wide distributed markers with economically important traits (ETL). Various projects that have been undertaken throughout the world to improve the ETL s in cattle have been discussed in this chapter. The reliability of predicted genomic estimated breeding value in dairy cattle has already been evaluated in some countries, like, the United States, Australia, New Zealand, and the Netherlands. In these experiments, reference populations were genotyped for approximately 50,000 genome-wide markers. GS has been successfully applied for a number of important traits, like, the prediction of milk flow traits in Italian Brown Swiss population at the North Carolina State University (United States), female fertility of Holstein-Friesian (HF) cows distributed across countries, tuberculosis susceptibility in HF cattle (using 44,000 single nucleotide polymorphisms), claw disorder in dairy cattle, efficiency of feed utilization (residual feed intake) in multibreed cattle population and occurrence of supernumerary teats in Holstein cows. At present, GS has become the cornerstone to ameliorate the ETL, especially in large animals. Now it is being considered by several developing countries including India and Pakistan. GS has been successfully applied to increase the genetic gain in less time in large animals.