Previous Year Questions(Solved) | Animal Husbandry & Veterinary Science Optional for UPSC PDF Download

Q1: Discuss in detail about feed supplements, additives and antibiotics in broiler and layer ration. (CSE 2000)
Ans: Feed Supplements and Additives
A large number of ingredients are used in animal and poultry feeds, and care must be taken to have these rations balanced to supply all required nutrients. A feed or a feed mixture used with another to improve the nutritive value or balance it is referred to as a supplement. A supplement is a semi-concentrated source of one or more nutrients used to enhance the nutritional adequacy of a daily ration or a complete ration mixture.

Supplements are intended to be:

1. Fed undiluted as a supplement to other feeds.
2. Offered as free choice with other parts of the ration separately available.
3. Further diluted and mixed to produce a complete feed, e.g., protein supplements, mineral and vitamin supplements, calcium supplements, coloring supplements, etc.

Protein supplements: Feeds rich in carbohydrates usually make up about 70 percent of the total ration and contribute only an insignificant amount of protein in the diet. Hence, the use of protein supplements becomes necessary to increase the protein content of the rations to the desired level. Protein supplements or feedstuffs commonly used in livestock and poultry feeds may conveniently be divided according to their source of origin, namely animal or plant protein supplements.

Animal protein supplements are better balanced in essential amino acid composition than plant proteins and therefore are of higher nutritive value. Examples of animal protein supplements include Fish meal, Meat meal, Tankage, and Blood meal.

Plant protein supplements are either the residues of oil seeds remaining after expeller or solvent extraction or products of wet milling of maize in starch-making process. Examples include Soyabean meal, Groundnut meal, Sesame meal, Cottonseed meal, Linsced meal, Maize gluten meal, and Mustard cake.

Fats and oils: Fats and oils are 2.25 times richer in energy compared to carbohydrates or proteins. They are a concentrated source of energy and may be used in rations up to 5 percent level, provided it is cost-effective. Examples include animal fats like tallow, lard, and vegetable oils such as Soyabean oil, Corn oil, and Sunflower oil.

Mineral Supplements: Grit, oyster shell, bone meal, trace mineral premix, and mineral mixtures are various mineral supplements used in animal nutrition. Grit and oyster shell are useful as sources of calcium, particularly useful to provide additional calcium in layers. Bone meal is useful as a source of calcium and phosphorous. A trace mineral premix is used as a source of various trace minerals. A mineral mixture may supply both major minerals like calcium, phosphorous, etc., and trace elements such as iron, copper, cobalt, manganese, etc.

Supplementation of Salt: Farm livestock should be provided with supplemental salt under almost all circumstances. This may be provided in the form of block salt or loose salt or as part of a mineral mixture. These salt supplements may be trace minerals as well.

Vitamin Supplements: Vitamin premix should be prepared containing at least vitamins A, D, riboflavin, and choline. In addition, any other vitamin that may require supplementation under specified conditions of feeding and management should be included. Antioxidants may have to be added to the premix to protect from oxidative damages.

Coloring Supplements: Dried alfalfa meal, dried grass meal, dried marigold flowers are some of the coloring supplements used to enhance the color of egg yolks and broiler meat.

Additives: An additive is an ingredient or a combination of ingredients added, usually in small quantities, to a basic feed mix for the purposes of fortifying the basic mix with certain essential nutrients, medicines, coloring agents, etc.

Additives may be broadly classified into two categories:

1. Intentional additives: Substances added on purpose to perform specific functions, e.g., Antioxidants, salt, etc.
2. Incidental additives: Substances that have no function in the finished product but become part of a feed or ration through some phase of production, processing, or storage, e.g., chemicals applied to crops.

Additives may also be classified as Nutritive and Non-nutritive feed additives.

Nutritive additives include vitamins, minerals, amino acids, and other substances having specific nutrient functions. Non-nutritive additives include medicines, antibiotics, flavoring compounds, anticaking agents, and other substances that are not having any specific nutrient function but may help to improve the acceptability, nutrient utilization, market quality, shelf life, etc.

Non-nutrient feed additives are listed below:

1. Antibiotics.
2. Arsenicals.
3. Various coccidiostats, deworming agents, and others for controlling specific diseases.
4. Antioxidants.
5. Hormones and hormone-like preparations.
6. Beta-agonists.
7. Enzymes.
8. Antifungals.
9. Flavouring agents.
10. Pellet binders.
11. Pigments.
12. Methane Inhibitors.
13. Probiotics.

Antibiotics: These non-nutrient feed additives are added at very low levels to improve feed efficiency, combat bacterial infections, and act as growth stimulants. Examples include Bacitracin, Chlortetracycline, Oxytetracycline, Procaine Penicillin, Streptomycin, and Flavomycin.

Q2: Discuss the mechanism of action of various growth-promoting agents to enhance the energetic efficiency and nitrogen retention in ruminants. (CSE 2001)
Ans:
The success of animal agriculture, particularly with respect to meat production, depends to a large extent on improved growth promotion due to better feeding, management, and disease control. Additionally, certain growth promoters are used to improve growth and feed conversion efficiency by manipulating metabolic processes within the animal. There are two basic types of these growth-promoting compounds classified by their major sites of action:

1. Antibiotic feed additives, which act within the digestive tract.
2. Hormonal anabolic compounds, which alter partitions of nutrients absorbed from the digestive tract.

Apart from these two, other techniques are being investigated in many laboratories worldwide. These include:

1. Use of probiotics.
2. Use of immune response - i.e., immunization of animals against compounds which inhibit the release of hormones influencing nutrient metabolism, e.g., immunization of animals against somatostatin.
3. Use of transgenic animals.

Anabolic agents: Anabolic compounds improve growth and feed conversion efficiency by manipulating metabolic processes within the animal. These compounds fall under any one of the following categories:
(a) Sex steroids
(b) Growth hormone
(c) Beta-agonists

Sex steroids: The important hormonal compounds used to promote growth in animals, particularly in ruminants, are those having activity similar to the androgenic or estrogenic sex hormones.

Mode of action of anabolic steroids: Steroid hormones exert their biological effects at the target tissue by binding to specific cytosolic hormone receptors. The hormone-receptor complex then interacts with DNA in the cell nucleus, initiating increased RNA synthesis followed by increased protein synthesis and specific hormonal effects.

The actual mechanism by which anabolic agents increase net muscle protein synthesis is not fully understood. Anabolic agents have two possible modes of action:

(a) They enter the muscle cell and have a direct action on protein synthesis and/or degradation. (b) They enter other endocrine organs such as the hypothalamus, anterior pituitary, gonads, pancreas, or thyroids and alter the synthesis, metabolism, or secretion of other hormones. These hormones may then produce the anabolic effect in muscle and affect intermediary metabolism in other parts of the body, including fat and liver.
The administration of anabolic agents has been found to bring about a change in the concentration of circulating endogenous hormones. For example, estradiol injection increases the concentration of circulating plasma growth hormone. In addition, it was found to increase the hepatic binding of growth hormone to both high and low-affinity sites. Similarly, there is a reduction in plasma glucocorticoid concentration, which is consistent with the observed reduction in the rate of both protein synthesis and degradation of muscle protein. The ultimate result is a reduction of muscle protein turnover. The relationships between muscle growth, muscle protein synthesis, muscle protein degradation, and circulating concentrations of insulin and tri-iodothyronine have considerable influence in manipulating the growth of animals. The enhanced growth rate may possibly be due to the combined action of the metabolic changes rather than due to a single metabolic change.

Growth hormone: The potential use of growth hormones as a growth promoter is better since it is not associated with sex steroids. Recent advances in recombinant DNA technology have enabled the production of large quantities of bovine or porcine growth hormone. The use of growth hormone results in an increased rate of lean deposition at the expense of fat and also an increased rate of growth. However, the effect on muscle protein metabolism is in direct contrast to anabolic steroids. With growth hormone, there is a reduction in lipogenesis and an increase in muscle protein deposition. However, the commercial exploitation of growth hormone as a growth promoter is limited because of the difficulties in frequent administration.

Beta-agonists: Beta-agonists are analogs of the natural hormones adrenaline and noradrenaline, the phenylethanolamines which stimulate lipolysis and glycogenolysis in animals. Numerous experiments have clearly demonstrated that these compounds reduce fat retention and increase protein deposition in various species of animals. These phenylethanolamine derivatives appear to act on the sympathetic nerve system through stimulation of beta-adrenergic receptors. Thus they are referred to as sympathomimetics or beta-agonists. They activate the adenylate cyclase system through CAMP resulting in increased activity of triglyceride lipase causing lipolysis. This results in an increase of NEFA and glycerol level in blood. Further, enough evidence is accumulating to the effect that there is inhibition of skeletal muscle proteolysis by Beta-agonists. Clenbuterol and cimeterol are the two beta-adrenergic agonists that are being evaluated for their performance on growth and carcass composition in sheep. Either cimaterol or clenbuterol at levels less than four PPM helped to decrease meat fat while improving weight gain and lean mass. An interaction with sex and dietary supplementation was also observed in some studies. Further, an increase in protein deposition was observed due to clenbuterol supplementation. These pieces of information have come from work done in developed nations, and practically no published data is available from developing countries. Whether the beta-agonists perform at the same level in developing nations where the production level of the animals is much less is not clear. The beneficial effects of beta-agonists would depend upon breed (due to variation in protein retention capacity of the animals), and environmental conditions (particularly temperature). Various breeds differ with respect to their protein retention capacity, due to variations in muscle mass and adipose tissue content among the different breeds. The nutritional efficacy of beta-agonists is most substantial if the body fat content is high. The effects of beta-agonists will be more pronounced in developing countries because of their low protein retention capacity. But because of undernutrition and less fat in the carcass, the efficacy may be impaired in these animals.

It is reported that immunization of animals against somatostatin helped to a 76% increase in the rate of weight gain in lambs. This growth was not confined to weight gain; there was also an increase in bone length, and improvement in feed conversion efficiency. The carcass composition remained unaffected.

In conclusion, it may be said that one major factor to be considered in advocating the use of growth promoters is the availability of feed for the animals since most growth promoters only induce a significant positive response in animals fed an adequate diet. Thus, the use of exogenously applied hormones and their analogs to enhance growth can only be recommended in animals receiving an adequate plane of nutrition. If the availability of feeds and fodder is going to be a major limiting factor, the use of either immune response or transgenic animals deserves greater consideration prior to its acceptance.

Probiotics as Growth Promoters Increasing consumer concern about residues of antibiotics, anabolic agents, and growth hormones in meat products led to the use of biological feed additives in animal feeds. The biological feed additives refer to the use of yeast/bacterial cultures, organic acids, and enzymes to enhance nutrient utilization and growth rate in livestock and poultry.

It is defined as a 'live microbial feed supplement which beneficially affects the host animals by improving its intestinal microbial balance'. These live cultures of natural and beneficial bacilli can be introduced into an animal gut in massive numbers to supplement those already present. The increasing level of beneficial organisms in the gut crowds out the existing pathogens and as they proliferate ensure that there is no room for others to be established.

The probiotic preparations available in the market are generally composed of organisms of lactobacilli and/or streptococci species, few may contain b.fidobacterium and yeast cultures. These products are either non-viable and freeze-dried or viable and microencapsulated, which proliferate and establish in large numbers in the gastrointestinal tract, particularly in the small intestine.

Mode of action: The possible modes of action of probiotics are not clearly understood. The normal gut microflora has a supportive role in disease protection and digestion of food. However, stressful conditions such as introduction to artificial rearing, castration, weaning, parturition, change of diet, and many more may increase gut pH which may favor growth of pathogenic organisms. The probiotics may bring about its beneficial effects as given below:

Neutralization of toxins. Suppression of viable numbers of specific bacteria. Suppression of antibacterial agents. Suppression of competition for adhesion sites. Alteration of microbial metabolism. Stimulation of immunity.

Uses of Probiotics Cattle: The use of probiotics in ration for cattle is of recent origin. The earlier use was primarily in controlling diarrhea in young calves. Some of the recent studies recorded improved weight gain and better feed efficiency due to the inclusion of probiotics in cattle rations. The yeast culture was found to influence rumen metabolism by altering the microbial fermentation rates, the protein turnover of the microbes, the hydrogen ion exchange and metabolism of easily soluble carbohydrates. Thus there is an improvement in the digestibility of structural carbohydrates increasing the energy supply to the microbes, inhibition of methane build-up stimulating formation of propionic acid, increased flow of proteins of microbial origin resulting in better feed conversion for milk yield.