It is appropriate to first define the term “population”, as used in this learning module. First, it is a group. A population may be small or it may be large. In the case of meat goats it is generally a herd or a breed, or goats owned by members of a particular breed association. The larger the population, the more rapid progress can be made. The basic tools for making improvement in future generations (the current generation is already genetically fixed) require making decisions. The two tools which are available include:

• Selection
  • Deciding which individuals become parents.
  • Deciding how many offspring they may produce.
  • Determining how long individuals will remain in the breeding population.
• Mating plans
  • Deciding which of the selected bucks will be bred to which of the does we have selected.
  • Bucks and does may have come for our own herd or from another population.

Selection

Although “natural selection” fuels the significant evolutionary force that brings about genetic change in all living things, but “artificial selection”, which is selection under human control, is the tool which can be applied to our populations. Artificial selection has two components:

• Replacement selection
  • Deciding which does or bucks become parents for the first time.
  • Selecting new animals to replace parents that have been culled.
  • Usually, replacements are young animals but if you decide to use for the first time a well-known older buck via artificial insemination that would be replacement selection. The buck is not young but is being used in your herd for the first time
• Culling
  • Deciding which parents (does or bucks) will no longer remain parents.

Replacement selection and culling are in a sense two sides of the same coin. They involve different sets of animals but their purpose is the same — to determine which animals reproduce.

What traits?

When we describe meat goats, we usually characterize them either in terms of appearance, or performance, or some combination of both. Regardless, the term “trait” needs to be defined here so there is a common understanding. A trait is any observable or measurable characteristic of an individual goat.

• Observable traits might include color, color pattern, set of jaw, size, set of legs, head shape, degree of muscling, and the like.
• Measurable traits include those to which reference would be made in describing how an animal has performed. Examples include weaning weight, milk yield in dairy goats, postweaning daily gain, prolificacy, feed utilization efficiency, loin-eye area and the like.

There can be many discrete (single) and composite (combinations) traits of interest in meat goat breeding. The more traits included in a selection program, the slower will be the change in any particular one. All traits have an underlying genetic base. The expression of genes is called the phenotype. Phenotype is influenced by one of several kinds of gene action at the cellular level.

Lay breeders tend to use the word phenotype when referring to an animal’s appearance, often giving the impression that “phenotype” means appearance only. Actually a goat has as many phenotypes as there are traits to be observed or measured.

Before continuing further on the details of selection and mating systems, it will be worthwhile to pause and review some of the fundamentals of genetics so that all people continuing through this module will be at the same level of understanding in the basics.

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