eChapters

Individuality tells us what an animal seems to be; his pedigree tells us what he ought to be, but the performance of his progeny tells us what he is
Effectiveness of selection depends on ability to recognize those animals, which possess superior inheritance. Those superior animals must be mated together for the production of offspring. The aids available to estimate the breeding value of an animal is through the phenotype of an animal or its relatives.

The response to selection is the change produced in the population mean through selection. This is achieved through selecting as parents of the next generation, individuals with highest genetic merit and whose progeny will, as a group, have the highest possible genetic merit for the trait in question. 

Selection is an important tool for changing gene frequencies to better fit individuals for a particular purpose. It may be defined as a process in which certain individuals in a population are preferred to others for the production of the next generation. Selection is of two kinds

In genetic studies it is necessary to distinguish two causes of correlation; is chiefly pleiotropy, though linkage is a cause of transient correlation, particularly in populations derived from crosses between divergent strains. Pleiotropy is simply the property of a gene whereby it affects two or more characters, so that if the gene is segregating it causes simultaneous variation in the characters as affects. For example, genes that increase growth rate increase both stature and weight, so that they tend to cause correlation between these two characters. The degree of correlation arising from pleiotropy expresses the extent to which two characters are influenced by the same genes. But the correlation resulting from pleiotropy is the overall, or net, effect of all the segregating genes that affect both characters. Some genes may increase both characters, while others increase one and reduce the other the former tend to cause a positive correlation the latter a negative one. So pleiotropy does not necessarily cause a detectable correlation. The correlation resulting from environmental causes is the overall effect of all the environmental factors that vary; some may tend to cause a positive correlation, others a negative one.

Estimates of heritability use statistical analyses to help to identify the causes of differences between individuals. Because heritability is concerned with variance, it is necessarily an account of the differences between individuals in a population. Heritability can be univariate–examining a single trait – or multivariate – examining the genetic and environmental associations between multiple traits at once. This allows a test of the genetic overlap between different phenotypes: for instance hair colour and eye colour. Environment and genetics may also interact, and heritability analyses can test for and examine these interactions (GxE models).

The concept of value, expressible in the metric units by which the character is  measured. The value observed when the character is measured on an individual is the phenotypic value of that individual. All observations of means, variance, or covariances, must clearly be based on measurements of phenotypic values. In order to analyse the genetic properties of the population we have to divide the phenotypic value into two componants. 
The first division of phenotypic value is into components attributable to the influence of genotypic and environment. The genotype is the particular assemblage of genes possessed by the individual, and the environment is all the non-genetic circumstances under the term ‘environment’ means that the genotype and the environment are by definition the only determinants of phenotypic value. The two components of value associated with genotypic value and the environmental deviation. 

The amount of variation is measured and expressed as the variance. When values are expressed as deviations from the population mean the variance is simple the mean of the squared values. For example, the genotypic variance is the variance of genotypic values and the environmental variance is the variance of environmental deviations. The total variance is the phenotypic variance of the variance of phenotypic values, and is the sum of the separate components. 

Gene Frequency

A population, in the genetic sense, is not just a group of individuals, but a breeding group and the genetics of a population is concerned not only with the genetic constitution of the individuals but also with the transmission of the genes from one generation to the next. In the transmission the genotypes of the parents are broken-down and a newest of genotypes is constituted in the progeny, from the genes transmitted in the gametes. The genes carried by the population thus have continuity from generation to generation, but the genotypes in which they appear do not. The genetic constitution of a population, referring to the genes it carries, is described by the array of gene frequencies, that is, by specification of the alleles present at every locus and the numbers of proportions of the different alleles at each locus. If for example, A1 is an allele at the A locus, then the frequency of A1, is the proportion or percentage of all genes at this locus that are the A1 allele. The frequencies of all the allele at any one locus must add up to unity, or 100 percent. 

Quantitative Versus Qualitative Inheritance

There is a continuum of traits being inherited as a Mendelian trait with simple inheritance and traits having quantitative inheritance without well separated classes and with many genes involved.
Classification of traits in relation to mode of inheritance and environmental tolerance are shown in Figure 1.2. First there are the well known traits with simple Mendelian mode of inheritance. The trait with quantitative genetic inheritance is caused by segregation of many gene pairs, each with small effect. At the same time the trait is influenced by a lot of minor environmental effects.
Diseases will often be ‘either/or traits’ as the simple Mendelian traits. Cases in which the severity of the disease has a normal distribution can also be found. In many production diseases the disease only occurs when a genetically prone individual is exposed to adverse environmental effects. Figure 1. Classification  of traits in relation to mode of inheritance  and environmental tolerance. 
 

Introduction
Statistics is a field of mathematics that pertains to data analysis. Statistical methods and equations can be applied to a data set in order to analyze and interpret results, explain variations in the data, or predict future data. A few examples of statistical information we can calculate are:
Average value (mean)

There are certain inherited traits (characters) in various species of livestock which are economically important. These traits have to be improved for increased production like milk, meat, egg, wool, etc.

Definition of Breed

A breed is a group of animal’s related similar characters like general appearance, size, features and configuration etc. A group of individual which have certain common characteristicsthat distinguish them from other groups of individuals is known as Species.

Domestication of Livestock

Domestication (from Latin domesticus) is the process whereby a  population  of  animals  or plants is changed at the genetic level through a process of selection, in order to accentuate traits that benefit humans. It differs from taming in that a change in the phenotypical expression and genotype of the animal occurs, whereas taming is simply the process by which animals become accustomed to human presence. In the Convention on Biological Diversity, a domesticated species is defined as a “species in which the evolutionary process has been influenced by humans to meet their needs.” Therefore, a defining characteristic of domestication is artificial selection by humans. Humans have brought these populations under their control and care for a wide range of reasons: to produce food or valuable commodities (such as wool, cotton, or silk), for types of work (such as transportation, protection, and warfare), scientific research, or simply to enjoy as companions or ornaments. Plants domesticated primarily for aesthetic enjoyment in and around the home are usually called house plants or ornamentals, while those domesticated for large-scale food production are generally called crops. A distinction can be made between those domesticated plants that have been deliberately altered or selected for special desirable characteristics and those plants that are used for human benefit, but are essentially no different from the wild populations of the species. Animals domesticated for home companionship are usually called pets while those domesticated for food or work are called livestock or farm animals.

Introduction

From the very early days human beings depend on animals and animal products for food and other requirements. In dairy and poultry farms high yielding animals are reared. These high yielding animals are produced by hybridization experiments. Previously the animals were developed basing on unscientific methods. Before the discovery of principles of heredity human beings have selected the animals with required characters and learned to develop the plants having the selected characters. This phenomenon is called Artificial selection. However, an increased knowledge of biology, especially genetics, has helped in improving the quality of animals and animal products as per the human requirements.

6.1 PROCESSES IN THE DOMESTICATION TECHNOLOGY

6.1.1 Introduction

The world Agroforestry centre Former international Centre for Research in Agro – forestry (ICRAF) and other home base orgainsation in their programme Africa Humid Tropics Regional programmed are the leader in the science and practice of integrating working trees on small farms and in rural landscapes. In this programme trees that ensure security in food nutrition income, health, shelter and energy and a regenerated environment are domesticated. The mission of this is to increase; diversify and stabilize income, food and health strategies from practicing agroforestry approaches in general domesticating indigenous trees and their products particular.

Definition of Agroforestry

Basically agro forestry is the integration of agriculture forestry and sometimes animal production. This is a measure to maintain soil fertility, stop desertification and soil degradation. Foresters and agriculturalist have long recognized the important of these approached which have been incorporated into forestry law of severe countries. This does not only involve the planting of certain trees in farms but also the protection of certain trees species which are not to be felled or damaged during farming.

5.1 PRODUCTION METHODS OR DIFFERENT TYPES OF PLANTS PRODUCED IN THE NURSERY

The different types of plants produced in the nursery include plants in plastic bags, bare-root plants, stumps, pseudo estacas, root trainers, copper coated trainers and jiffy pellets.

The most common production techniques may not always be the best. Bare-root plants and pseudo estacas are easy to transport to the field, but their survival and growth are usually very poor. Plastic bags are cheap and easily available, but they result in coiled roots and are heavy to carry to the field. Root trainers, copper coated trainers and jiffy pellets are alternative systems which may have higher initial costs for the nursery. However, the farmer will receive the benefit of fast growth and high survival in the field

4.1 THE NURSERY
We distinguish several types of nurseries among which we have Permanent nursery and Temporal or Seasonal nursery.
4.1.1 Permanent nursery
Permanent nursery is a large nursery destined to produce large number of plants for several years or in other words, the place is used for several years even if the plantation center is far. It is also called the central or industrial nursery. For example, the Cameroon Development Corporation [CDC] with head quarter in Limbe has its central nursery in Bota – Limbe. Here oil palm seedlings are being transported from the nursery in Limbe to the Bomboko area in Idenau Subdivision and Illoani in Ndian Division. A special management practices is being carried out in this type of nursery notably:
• Access road for vehicles accessible in all seasons ;
• Forecast annual rotation of surface area and annual production of plants;
• Forecast species with permanent shelter to serve for the protection of pots;
• Anticipated area for irrigation systems;
• Construct a shade, store, office and a guard’s room;
• Forecast methods of plant preservation for plants destined to be transported to far stations.

3.0 INTRODUCTION

There are two main types of plant reproduction / multiplication that are used and these include sexual reproduction known as seed propagation / multiplication and the asexual reproduction known as vegetative propagation / multiplication. Propagation is most often by seeds produced by plants or by plant parts like vines, roots, tubers, suckers, etc. Propagation is the natural mechanism by which plants regenerate. Seed is the organ of reproduction in flowering plants.

3.1 SEXUAL REPRODUCTION OR SEED PROPAGATION TECHNIQUES

Seed is the organ of reproduction in flowering plants. Sexual reproduction is propagation by seeds. This is the main method by which plants reproduced in nature as most plants produce seeds except in species that have separate male and female plants; e.g. Njansang (Ricinodendron heudelotii) and Black fruit (Canarium schweinfurthii)

Seed multiplication seems to be the most practicable technique by the farmers. Example Agroforestry Species that are mostly propagated by seeds are Sweet Bush mango [Irvingia garbonensis], Bitter Bush mango [Irvingia wombolo], Bitter kola, Kola nitida, Kola acuminata, Njansang [Ricinodendron heudelotii].

2.1. GERMPLASM COLLECTION
a. Propagation techniques
There are four main propagation techniques that are used in plant reproduction for most plants, viz;
• Seed
• Cuttings
• Marcotting
• Grafting
Note: That not all plants can be propagated by all the four methods mention above.

1.1 DEFINITIONS
1. Forest
Forest is the homeland of trees. Because man must protect and maintain the life of the forest and because of this;  certain natural
calamities  and  bad  use  of  the  forest  constitute  severe danger to  the forest  and the  environment at large.  In  other to divert from these difficulties, man was bound to cultivate trees. This is silviculture. Silviculture then became a science and art.