eChapters

Bacteriophage is the term applied to bacterial viruses. Bacteriophage having the ability to lyse certain sensitive living cells. Phages are small particles, which can only be seen in the electron microscope after the application of suitable staining techniques. All phages have a head and most have a tail. The head may be isometric or prelate with a hexagonal outline.

There are two types of phages virulent and temperate which enter a different relationship with the host, the lytic and lysogenic cycles respectively.

Milk fermentation is process by which a change is produced in milk through the activity of microorganism. As milk leaves the udder it serves as a medium for the growth of many species and accordingly undergoes a series of changes, the processes producing these changes constitute the milk fermentation.

Fermentation of organic compounds, especially in the lack of oxygen leads to the rapid break-down of ‘biopolymers’ to produce ‘anaerobic food chains’.

Starters are selected strains of micro-organisms deliberately added to milk during conversion into cheese, dahi, yoghurt and other fermented dairy products to bring about specific changes in the appearance, body, texture and flavour characteristics of the desired final products.

Functions of Starters

The primary function of almost all starter culture is to develop acid in the product. The secondary effects of acid production include coagulation, expulsion of moisture, texture formation and initiation of flavour production. In addition to these, the starters also help in imparting pleasant acid taste, conferring protection against potential pathogens and providing a longer shelf life to the product. These bacteria convert 1% of lactose in milk approximately to lactic acid with very little by-products such as acetic acid, ethanol, CO2 and normally with no substances causing taints and hence leading to a clean and wholesome milk souring.

In India, the collection, transport and distribution of raw milk involves a number of agencies and persons at rural and urban level – village producers, milk collectors, halwais (Sweet-makers), milk vendors, dairies, producer-retailers and wholesale or retail markets.

1. Collection

Usually, the milk collectors approach the small village producers to collect milk and the same is sold directly or indirectly (through agents) to a dairy (milk procurement centres) or halwais or city milk vendors or consumers. The producer – retailers themselves, in some cases, supply the milk to the above said parties. The production of milk in small, scattered holdings in village causes problems during its collection. It involves visits to many villages, some of which are not easily accessible for the purpose.

The Concept of ‘Clean Milk’ Production

Although milk is nature’s most ideal and perfect single food both for the newborn and the mature human beings, the possibility of it being a source of biological and chemical hazards cannot be excluded. In view of the immense dietary importance of milk, the need for production of safe, clean and wholesome milk is emphasized. The term ‘clean milk’ does not mean milk in which all visible dirt is absent or milk from which it has been removed; rather it does denote raw milk from healthy animals, that has been produced and handled under hygienic conditions; that contains only small number of harmless bacteria and that possesses a good keeping quality without being treated by heat. In other words, the unhygienic production of milk may lead to inferior keeping quality as a result of rapid microbial multiplication under favourable storage conditions apart from serving as a potential health hazard. These microorganisms cause the milk to sour quickly, putrefy and develop undesirable flavours, colour defects, ropiness and bitterness. On the other hand, the pathogenic microorganisms, which may gain entry through various sources, may cause many diseases to the consumers.

The sources of contamination of milk on the farm can broadly be categorized as

    a)    Interior of the Udder
    b)    Exterior of the Udder.
The interior reflects the health of the animal, while the exterior depends on the farm condition, equipment, persons, water etc.

a) Interior of the Udder
The animal by itself is one of the most significant contributors of microorganism in milk. The bacteria in the udder usually enter from the teat opening and get distributed internally by their own growth and physical movement. In the normal healthy udder, the types encountered in milk are most predominantly Micrococci, followed by Streptococci, Corynebacterium and others. Most of the bacteria are excreted in fore milk.

The term growth as applied to higher organisms such as animals commonly is concerned with increase in protoplasmic mass and does apply to reproduction or to increase in number. In microbiology the term refers to increase in the number of organisms. Bacteria increase in number by a process of simple binary fission. Each cell increase in size and redivide into two similar cells. Each of the divide cells may in turn divide to become two cells. Each division produces what is termed as new generation of cells, theoretically there are 2,4,8,16,32,64,128,256 cells in the 2,3,4,5,6,7,8,& 9th generation, this is known as logarithmic growth – the population doubles with each successive generation. Under favourable conditions, bacteria produce generation within 15min. Under unfavourable conditions 24 hours of more may be needed for each generation. Generation time for E.coli is 17 to 20 minutes.

Life forms are composed of one of two basic cell types : Eukaryotic or Prokaryotic. Generally, eukaryotic cells are larger and more complex than the prokaryotic cells and possess a membrane-enclosed nucleus; eukaryotic means ‘true nucleus’ (eu=true; karyon = nucleus). All plants, animals, fungi, protozoa and algae are composed of eukaryotic cells. Only the microorganisms classes as bacteria and the archaea are prokaryotic cells. Prokaryotic cells have no nuclear membrane and therefore lack a true nucleus. The latin prefix pro means ‘early’ and in this instance suggests the somewhat primitive nuclear structure found in bacterial cells. Eukaryotic microorganism are sometimes simply referred to as eukaryotes, and the prokaryotic microbes as prokaryotes.

Veterinary public health deals with the contributions of veterinary medicine to public health. It is concerned, in the first instance, with the control and elimination of zoonoses and also with the following areas of activity:
    ·    Food hygiene (production, processing and distribution of foods of animal origin)
    ·    Environmental contamination and degradation by animal wastes and animal products
    ·    Comparative medicine (eg. Studies in animals on naturally appearing cancer, cardiovascular disease, metabolic and other disorders encountered in humans)
    ·    Laboratory animal medicine
    ·    Education and training in VPH and communication with the public
    ·    Reproduction biology
    ·    Aspects of mental and societal health
    ·    Emergency veterinary functions in natural disasters and other catastrophes.

Important by-products from rabbits are meat, wool, planner and skin. It can be made highly profitable if products are wasted because people do not have enough knowledge about their processing.

11.1. Slaughtering and Dressing

    1.    Rabbits are killed by one of two methods. The preferred method is dislocation of the neck. The rabbit is held firmly by the rear legs and head; it is stretched full length. Then with a hard, sharp pull, the head is bent backward to dislocate the neck. The rabbit can also be struck a hard, quick blow to the skull behind the ears. A blunt stick or side of the hand is commonly used to incapacitate the rabbit. Both methods quickly render the rabbit unconscious.

Behaviour have an influence on rabbit housing. Since the domestication of the rabbit is recent in terms of species evolution (200 to 300 generations at most) the behaviour of the domestic rabbit is still much like that of the wild rabbit. The reactions of wild rabbits will often provide explanations for the problems of housing domestic rabbits and suggest ways of solving them. Common behaviours observed in rabbits are:
    1.    Territorial behavior.
    2.    Social behavior.
    3.    Sexual behavior.
    4.    Maternal behavior.
    5.    Feeding behavior.
    6.    Aggressive behavior.

9.1. Handling

Rabbits must be handled very carefully. Although they are generally docile they are apt to struggle when picked up, with potentially harmful consequences. All rabbits are prone to vertebral fractures, and this risk is greatest in hutch rabbits or in those on an unbalanced diet that may have concurrent osteoporosis. It is extremely important to support the back and hindquarters whenever a rabbit is handled.
 
A rabbit should never be picked up by the ears. It can be lifted gently by the scruff of the neck with one hand whilst the other hand supports its bottom (Fig. 9.1), or alternatively lifted with one hand under the chest, and one supporting its hindquarters (Fig. 9.2). The rabbit should be carried against the body to minimize struggling. It is advisable to place the rabbit’s carrying box on the floor so that if it does jump as it is picked up it does not hurt itself. Similarly it is usually easier to return the rabbit to the box on the floor at the end of the examination.

Management of Angora rabbit includes important aspects of breeding, feeding, heeding and disease control.

8.1. Reproduction

Angora rabbits of lighter breeds reach breeding age of 6-7 m, medium rabbits at 7-8m and heavier breeds at 8-10 m. Female Angora rabbits do not have a true oestrus cycle with a definite heat period. They may mate at any time of year. Ovulation in does is induced by mating and occurs about 10 -12 hours later to mounting and copulation with the bucks. No doubt there is no definite heat cycle in Angora rabbits, yet during certain periods breeding does are more receptive to bucks than other times of the year. Some of the signs of such receptive period are restlessness, rubbing of chin on the feeding or watering bowls and vulva may be slightly swollen and purplish red.

Health care and preventive hygiene in rabbits are very important for the productivity of the rabbits and economical viability of a farm.

It is always better to prevent the disease rather than to get an animal treated, which is usually quite expensive. As such it is desirable that the rabbits are checked daily. The health and ailment signs can be recognized from the following things:

6.1. The Production Cycle

As ovulation in does is induced by mating and the females are generally kept in different cages from the males, it is the breeder who determines the reproduction rate of the unit. These rates vary from one or two litters a year under the most extensive management to eight to ten litters in an intensive management system. Does are remated either immediately after kindling (intensive system) or about ten days later (semi-intensive). In the semi-intensive system, the does are first presented to the buck at four and a half months. They are then mated 10 to 12 days after the birth of each litter. Weaning takes place at 30 to 35, or even 37 to 38 days. Extensive systems are characterized by a long delay between kindling and mating, and perhaps even until weaning. For example, the young may be weaned at 56 days and the doe mated after weaning.

5.1. Anatomy of the Genitals

5.1.1. Male reproductive system

Testes in the male are oval-shaped present within the scrotum which remain in communication with the abdominal cavity, where they were at birth. The rabbit is actually able to withdraw its testes when frightened or fighting with other males (Fig. 5.1). The testicles descend at about two months. The short, back-slanting penis points forward when erect.

4.1. Digestive System of Rabbit

The digestive system of rabbit includes:
    A.    The digestive tract 
    B.    Its associated glands
The digestive system breaks down the complex molecules into the simpler one so that it is readily absorbed from gastro intestinal mucosa.
 
A. The digestive tract (gastro intestinal tract/ alimentary canal)

The digestive tract is essentially a tubular structure for the ingestion and digestion of food. In an adult (4 to 4.5 kg) or semi-adult (2.5 to 3 kg) rabbit the total length of the alimentary canal is 4.5 to 5 m. It commences from mouth and terminates in anus. G.I.T is divided into following parts:

The success of rabbit farming depends upon the location and design of the rabbit house. Rabbit is a burrowing animal and has sharp reflexes. It is easily disturbed by any new and sudden noise. The farm should be located in a peaceful environment away from the hustle and bustle of human population.  A good housing facility with adequate arrangement of ventilation is the most important factor in rabbit house.

Domestication of the rabbit is relatively recent and most of today’s breeds have been bred by man in the last 200 to 300 years.

The rabbit has been used as an experimental animal in genetics, reproduction and physiology since the beginning of the century, but it was not until 1950 that the first findings on quantitative genetics were published in Venge’s study of maternal influence on rabbit birth weight.

1.1. History and Origins of Rabbits

The existence of rabbit with human being remained from time immemorial. Romans were the first to domesticate wild rabbits in the 5th century by the monks of the Champagne region in France as a readily available food source. Rabbits were introduced to Britain during the 12th Century, and during the Middle Ages, the breeding and farming of rabbits for meat and fur became widespread throughout Europe. Sources suggest that some women among the Medieval gentry even kept rabbits as pets. The selective breeding of European rabbits meant that distinct breeds arose in different regions, and the origins of many old breeds can be traced back several centuries.