17 Dairy Cattle Breeding
17.1 Overview
This chapter provides a deep dive into dairy cattle breeding, focusing on the transition to genomic selection.
17.2 Learning Objectives
By the end of this chapter, you should be able to:
- Describe the structure of the dairy breeding industry
- Explain how genomic selection transformed dairy cattle breeding
- Identify key traits and genetic parameters in dairy cattle
- Interpret selection indices (Net Merit, Cheese Merit)
- Understand antagonistic genetic correlations affecting breeding objectives
17.3 Global Dairy Industry Structure
Chapter Status
This chapter is currently under development. Content will cover:
- Major breeds (Holstein, Jersey, Brown Swiss)
- AI organizations (Select Sires, ABS Global, CRV, Semex, Alta Genetics)
- Genomic testing companies
- International semen trade
17.4 Key Traits and Heritabilities
17.4.1 Production Traits
- Milk yield: h² = 0.25-0.40
- Fat yield: h² = 0.25-0.40
- Protein yield: h² = 0.25-0.40
17.4.2 Fertility and Reproduction
- Daughter pregnancy rate: h² = 0.05-0.10
- Calving ease: h² = 0.05-0.10
17.4.3 Health Traits
- Mastitis resistance: h² = 0.05-0.15
- Lameness: h² = 0.05-0.15
17.5 Genetic Correlations
- Milk yield vs. fertility: r_A ≈ -0.3 to -0.4 (antagonistic)
- Milk yield vs. health: r_A ≈ -0.2 to -0.3 (antagonistic)
17.6 Selection Indices
Content to be developed covering:
- Net Merit (NM$)
- Cheese Merit (CM$)
- Fluid Merit (FM$)
17.7 Genomic Selection Revolution
Content to be developed covering:
- Implementation timeline (~2009 in US)
- Doubled rate of genetic gain
- Reduced generation interval from 6-7 years to 2-3 years
17.8 Summary
Dairy cattle breeding was revolutionized by genomic selection, which increased accuracy while reducing generation interval.
17.9 Key Points
- Genomic selection increased accuracy while reducing generation interval
- Balancing production with fertility and health is critical
- Economic indices guide selection decisions