Class 12-science NCERT Solutions Biology Chapter 9 - Strategies for Enhancement in Food Production

Animal husbandry deals with the feeding, breeding and health care of animal livestock for getting maximum benefits. It comprises cattle farming, poultry, fisheries, apiculture etc., which provide various food products such as meat, egg, milk, honey, wool etc. to the growing population. Animal husbandry provides income and employment to millions of people. The animal breeding through interspecific hybridisation, artificial insemination and by multiple ovulation embryo transfer technology has improved the genotypes of livestock so that they become more useful to humans.

The following measures would be undertaken to improve the quality and quantity of milk production:

i. Dairy animals would be of good breeds.

ii. There would be clean and hygienic conditions in milking and handling of milk products.

iii. A balanced diet would be given to animals.

iv. Regular visits by a veterinary doctor would be ensured.

v. Farm animals would be kept in a well-ventilated house with adequate water supply and maintained in a disease-free environment.

A group of animals related by descent and similar in most characters such as general appearance, features, size etc. is termed breed.

The main objectives of animal breeding are

i. Improved growth rate.

ii. Increased production of milk, meat, egg, wool, silk etc. with superior quality.

iii. Superior quality of milk, meat, eggs, wool etc.

iv. Improved resistance to various diseases.

v. Increased productive life and acceptable reproductive rate.

The methods employed in animal breeding are

i. Inbreeding

ii. Out-crossing

iii. Cross-breeding

iv. Interspecific hybridisation

v. Artificial insemination

vi. Multiple ovulation embryo transfer technology (MOET)

Cross-breeding is one of the best methods because desirable qualities of two different breeds are combined. It results in the production of new animal breeds, which prove better resistance to diseases and are high yielding.

Apiculture: Rearing of honey bees for the commercial production of honey and beeswax.

Uses:

i. It is a food of high nutritive value and has its use in medicine.

ii. Honeybees produce beeswax which is used in the preparation of cosmetics and polishes of various kinds.

iii. It has become an income-generating industry due to an increased demand of honey.

A fishery has an immense role in the enhancement of food production. A large section of the Indian population eats fish and other aquatic animals such as crabs, lobsters, prawns etc. as food. Fish serve as a cheap source of protein, has very little fat, carries a good amount of minerals, vitamins and iodine.

Aquaculture and pisciculture have increased the production of aquatic plants and animals both fresh water and marine. Indoor hatcheries and nurseries have been developed for rearing and stocking of fish. Fish eggs are introduced into nurseries where young ones hatched from the eggs are fed, nursed and harvested when fully grown. This has led to the development and flourishing of the fishery industry in the country.

Steps in plant breeding:

(i) Collection of variability: Collection and preservation of all the different wild varieties, species and relatives of the cultivated species is a pre-requisite for effective exploitation of natural genes available in the population. The entire collection (of plants/seeds) with all the diverse alleles for all genes in a given crop is called germplasm collection.

(ii) Evaluation and selection of parents: The germplasm is evaluated so as to identify plants with a desirable combination of characters. The selected plants are multiplied and used in the process of hybridisation. Pure lines are created wherever desirable and possible.

(iii) Cross-hybridisation among the selected parents: The desired characters have very often to be combined from two different plants (parents). For example, high protein quality of one parent may need to be combined with disease resistance from another parent. This is possible by cross-hybridising the two parents to produce hybrids which genetically combine the desired characters in one plant.

(iv) Selection and testing of superior recombinants: This step consists of selecting among the progeny of hybrids those plants which have the desired character combination. The selection process is crucial to the success of the breeding objective and requires careful scientific evaluation of the progeny. This step yields plants which are superior to both of the parents. These are self-pollinated for several generations till they reach a state of uniformity (homozygosity), so that the characters will not segregate in the progeny.

(v) Testing, release and commercialisation of new cultivars: The newly selected lines are evaluated for their yield and other agronomic traits of quality, disease resistance etc. This evaluation is done by growing these lines in research fields and recording their performance under ideal fertiliser application, irrigation and other crop management practices. The evaluation in research fields is followed by testing the materials in farmers' fields for at least three growing seasons at several locations in the country, representing all the agroclimatic zones where the crop is usually grown. The material is evaluated in comparison to the best available local crop.

Biofortification: Breeding crops with higher levels of vitamins and minerals, or higher protein and healthier fats is called biofortification. For example, the wheat variety Atlas 66 with high protein content has been used as a donor for improving cultivated wheat. Biofortification is done with improvement of public health as the primary goal.

The apical and axillary meristems are the best-suited parts of the plant for the production of virus-free plants. These parts are generally free from viruses because of the absence of vascular tissue through which viruses are transported.

i. A large number of plants can be raised from a single individual plant within a relatively short period and limited space.

ii. Virus-free healthy plants can be produced from the shoot apical meristem.

iii. It overcomes the dormancy of seeds and helps in producing viable plants.

iv. It is used to derive and multiply disease-free stocks.

v. It is used to multiply sexually derived sterile hybrids as well as haploid plants.

The major components of the medium are water, inorganic salts, sucrose (source of carbon and energy), vitamins, amino acids and growth hormones such as auxins, cytokinins etc.

Other compounds such as casein, coconut milk, yeast extract etc. may be added for specific purposes. If required, a gelling agent agar is added to the liquid medium for its solidification.

The five hybrid varieties of crop plants which have been developed in India are as follows: