Methods of increasing rates of genetic gain from selection in New Zealand dual - purpose sheep breeds: A dissertation submitted in partial fulfilment of the requirements for the Diploma in Farm Management at Lincoln University

Abstract

The objective of a breeding programme is to improve the mean performance of a flock in successive years. Selection is main the breeding method. Difficulties with selection occur because most traits of importance are controlled by many genes and individual genes are hard to distinguish. Furthermore environmental effects mask genotypes of individuals and the expression of these traits. With the changing economics of meat and wool products and continual advancement in the knowledge and technology of breeding methods , the methods , criteria and objectives of breeding and selection require frequent reviews and assessment. This dissertation will give an overview of selection methods and establish the most useful for breeding purposes . This will include finding practices needed to acquire the fastest rates of genetic gain as well as to establish the uses of recorded data and interpret the economic benefits of record based selection. An analysis was done to investigate selection decisions based on a combination of visual and/or performance factors. The traits looked at were three important dual-purpose sheep breed traits : number of lambs , weaning weight and wool weight. The aim of the study was to evaluate the genetic and financial gain of each selected group.