F ounded in 1986, National Sheep Improvement Program (NSIP) is committed to helping U.S. sheep producers improve profitability through the use of genetic information. NSIP provides predictable, economically important genetic evaluation information to enrolled flocks by converting performance records into relevant decision-making tools. This allows NSIP members to combine this genetic evaluation along with visual assessments when selecting breeding stock for purebred and commercial flocks. NSIP is the only U.S. organization to offer sheep producers a proven genetic selection system by which to improve flock productivity and quality. Genotype vs. Phenotype For sheep, quantitative genetics are described through Estimated Breeding Values (EBVs). To have the best understanding of quantitative genetics, it is essential to understand phenotype and genotype. PHENOTYPE: An animal’s phenotype (how it looks, how it performs) is a combination of genetics and environment. PHENOTYPE = GENETICS + ENVIRONMENTAL INFLUENCE GENOTYPE: The genetic makeup of an animal, usually derived from a DNA test or a genetic evaluation. Example of Phenotypes: • Structural correctness • Actual weaning weight and yearling weight
Examples of Genotypes • RR at codon 171 • NN for spider lamb syndrome • EBV Why Use EBVs? Genetics are passed from parent to offspring but environment is not. Even the most highly heritable traits (like growth and carcass traits) are in the 25-45% heritability range, which means 55-75% of what you see with visual appraisal alone is due to environmental factors, and not genetics. Genetic evaluation programs like NSIP weed out the environmental influences and help breeders identify animals with superior genetics. ESTIMATED BREEDING VALUES EBVs are science-based, industry-tested measurements of heritable traits that can be tracked and measured. NSIP develops Estimated Breeding Values (EBVs) which sheep producers can use to select animals for important traits, including productivity, quality and flock health. EBVs are used to measure the genetic merit of individual animals for those traits financially important to commercial sheep production. HERITABILITY is the percentage of an animal’s observed or measured phenotype due to genetics. This varies by trait. Even in the more highly heritable traits, most of the observed or measured difference in individual animal performance is due to environment.
• Birth weight 16% • Weaning weight (60 days of age) 15%
• Post Weaning Weight (120 days of age) 28% • Mature body weight 40%
• Multiple births 10% • Milk production 10% • Loin eye area 35% • Fat thickness over loin eye area 30%
• Loin eye area • Type of birth • Body condition score
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