THE EFFECT OF SUPPLEMENTAL SELENIUM AND DIFFERENT FORMS OF CHROMIUM IN FEEDLOT CATTLE – EXPERIMENT

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GENERAL CONSIDERATIONS

Scientific advances in beef production were affected by the Bovine Spongiform Encephalopathy (BSE) scare of 1997. Meat and bone meal has been used to reduce feed costs, diminishing raw material supply needs, which have been incriminated as carriers of BSE (Gadd, 1995; Lyons, 1997). Meat and bone meals have been banned from cattle feed inclusions in many countries and concerns about the use of antibiotic digestive enhancers (formerly called growth promoters) are increasing. It appears that the supplementation of domestic animal feeds, both pet and food animals, with products of animal origin is raising concern. `Today’s consumers monitor carefully what scientists are developing.
The globalisation of the world has made new information readily available. In the meantime, those involved in meat production have to solve the dilemma of meeting the consumer’s needs for this perishable and relatively costly product with regard to price, safety, and quality (Gadd, 1995) if they have to survive in the business. Traditional tools such as hygiene, vaccination programmes, and nutritional manipulations have been used to improve livestock production. Due to increased pressure upon available resources, new ways and means of animal husbandry are to be investigated. This research focuses on nutritional manipulation of growth using the trace minerals, selenium (Se) and chromium (Cr) in inorganic and organic forms. Chromium and selenium are two essential micronutrients for animal production and health (NRC, 1980; NRC, 1997). Their individual and interaction effects on stress alleviation, growth performance, carcass quality, and mineral status of feedlot beef cattle have been examined in this research. The issue of the superiority of organic forms of these minerals was investigated. The inorganic Cr form as Cr sulphate has been introduced in feedlot cattle feeding.
The organic forms of Se and Cr have been investigated alone or in combination with the inorganic forms. As pointed out by Lee et al. (1999), there is a dearth of scientific data on the advantages of using the so-called organic trace mineral supplements. However, Mahan (1999) considers that organic Se may be one of the important nutritional keys to improved human and animal health of the 21st century. It is well known that feedloting is a business where the margin of profit is very small. In order to survive, the feedlot industry must be competitive and responsive to changes arising as a result of the globalisation process, the rapid development of the information technology, and subsequently the new demands of the market. Macro and micro minerals could become very important feed additives in the replacement of traditional antibiotic additives for which consumer resistance has increasingly developed. More importantly, the trace minerals are expected to interact with one another, with the potential of causing a toxicity or deficiency symptoms. Excessive levels of the nutrients may be easily diagnosed and prevented, but in contrast, deficiencies are frequently subtle, and difficult to control or to anticipate because an element may have a variety of functional roles.
It cannot be assumed, therefore that the most significant consequence of deficiency is necessarily that it will produce the most obvious clinical signs of deficiency. Mills (1983) has observed that there are no reliable data available from which to assess the economic losses due to metabolic diseases caused by trace mineral deficiency diseases. Essentially, impaired productivity, or clinical manifestations of deficiency, may often not be evident when widely accepted criteria for assessing the trace mineral status of diets or animal tissues suggest the existence of deficiency. Selenium and Cr are important nutrients of cattle, and this study sought to evaluate their beneficial effects in the absence of their deficiency. Their interactions with other minerals and trace minerals were also investigated in detail. Stress related conditions in the feedlot are common, and the bovine respiratory complex diseases which constitute close to 70 percent of the clinical cases in bovines are the main consequences. The discovery of factors such as disease resistance, which are adversely affected by trace mineral deficiencies, adds emphasis to the need to prevent deficiencies from occurring (Suttle, 1983). Induced stress occurs from weaning, transportation to the saleyard and feedlot, to the adaptation to the new environment, crowding, management and most importantly in adaptation to the high-energy diet. Management of stress in the feedlot involves primarily the management of the environment (the stressor) and, secondly, management of the quantified changes seen in the animal (Grandin, 1997).
Weaning is an unavoidable stress. Management techniques such as preweaning and preconditioning which have been cited as measures to alleviate stress, e.g. at entry in the feedlot, are however, not cost effective (Pritchard and Mendez, 1990). Feed and water deprivation during transportation may limit nutrient absorption not only in the adaptation phase but also during the whole feedlot period. Determination of stress detectors such as blood cortisol and glucose levels was undertaken and it constitutes an important phase of this study. Beef quality, especially freshness, can be assessed by its colour. This is the main factor affecting beef product acceptability at retail points of purchase (Liu et al. 1996a). The appearance of the meat surface depends on the quantity of the myoglobin, the type, its chemical state and the chemical and physical condition of other components in the meat (Laurie, 1985). Vitamin E can prevent meat discoloration through the prevention of lipid oxidation and limitation of production of metmyoglobin (Liu et al. 1996b). As vitamin E was believed to act as a biological antioxidant preventing lipid peroxidation, it was felt that selenium would function in a similar way (MacPherson, 1994). Chromium is involved in carbohydrate metabolism (Burton et al. 1993; Depew et al. 1998) and it allows better storage of glycogen in muscle. It has been established that adequate residual muscle glycogen allows muscle to reach an adequate ultimate pH (Laurie, 1985). Under these conditions meat discoloration might be prevented. This study will also attempt to assess the effect of supplemental selenium and chromium on meat colour. Moreover, the preparation of animal products, rich in selenium and chromium may impact on human requirements for these minerals. According to Pawlowicz et al. (1991), selenium has anticancer properties. Low blood or serum Se levels have been found in patients with various types of cancer. This finding suggests that Se exerts its effect on the molecular level in different ways such as a protective effect against the oxidative damage through decreasing the amount of free radicals and increasing the synthesis of glutathione peroxidase. It is assumed that animal products that are rich in Cr may have an effect in preventing diabetes because of the effect of Cr on insulin sensitivity (Amoikon, 1995). Supplemental Cr has also been associated with less body fat (leanness) and increased muscling in monogastrics (Lindemann et al. 1995). For that reason it has been included in different sport products. An example of such sport products is the Citri-Chromium PlusND (California Pharmaceutics, SA) which is a combination of chromium picolinate (500 mg), carnitine, hydroxy-citric acid and many vitamins, antioxidants and all the amino acids. It is clear that even though these minerals might not affect some animal performance criteria dramatically as used in this study, its inclusion in diets may have indirect application in human nutrition.

OBJECT AND SCOPE OF THIS STUDY

The most obvious function of macro-minerals and trace-minerals, as components of body organs and tissues, is to provide structural support for the body, in addition to their role as catalysts in both enzyme and hormone systems (Close, 1998). Selenium is widely used in different human medicines for its anti-oxidant activity. It is also approved in the Republic of South Africa (RSA) for use in livestock production as a feed additive (Act 36 of 1947). However, it is not used routinely because its inclusion in diets is seldom considered (Van Ryssen, 1996). This is probably due to the fact that typical Se deficiency or toxicity symptoms are rarely observed or reported in RSA. Its deficiency is however expected in South Africa (Cloete et al. 1994; Marnewick, 1995; Van Niekerk et al. 1995; Van Ryssen, 1996). Results of liver mineral concentration in feedlot beef cattle content compiled in nutritional laboratories (Medunsa and Onderstepoort) over six years for diverse farms (Table 2.2) confirm that. It is therefore important to undertake investigations that may contribute to the understanding of its properties and possible use.

TABLE OF CONTENTS :

• DECLARATION
• LIST OF TABLE
• LIST OF FIGURES
• LIST OF APPENDICES
• SUMMARY
• SAMEVATTING
• CHAPTER 1. INTRODUCTION
  • 1.1. GENERAL CONSIDERATIONS
  • 1.2. OBJECT AND SCOPE OF THIS STUDY
  • 1.3. HYPOTHESIS
  • CHAPITER 2. LITERATURE REVIEW
  • 2.1. SOUTH AFRICAN LIVESTOCK AND MEAT INDUSTRIES
  • 2.2.1. FEEDSTUFFS, DIETS AND LIVER MINERAL COMPOSITION
  • 2.2.2. CHEMICAL FORMS OF MINERALS
  • 2.2.3. MINERAL STATUS AND INTERACTIONS
  • 2.2.4. TRACE MINERALS PROPERTIES, METABOLISM AND EFFECTS
    • 2.2.4.1. COPPER
    • 2.2.4.2. IRON
    • 2.2.5.3. COBALT
    • 2.2.4.4. MANGANESE
    • 2.2.4.5. ZINC
    • 2.2.5.6. SELENIUM
    • 2.2.5.7. CHROMIUM
  • 2.3. STRESS PHYSIOLOGY
  • 2.4. MEAT COLOUR
• CHAPTER 3. MATERIALS AND METHODS
  • 3.1. EXPERIMENTAL ANIMALS
  • 3.2. FEED AND FEEDING MANAGEMENT
  • 3.3. PERFORMANCE MONITORING AND SLAUGHTERING
  • 3.4. SAMPLE PREPARATIONS AND ANALYTICAL PROCEDURES
  • 3.4.1. BLOOD SAMPLES
  • 3.4.2. LIVER SAMPLES
    • 3.4.2.1. LIVER PREPARATION FOR MINERALS DETERMINATION
    • 3.4.2.2. FEED PREPARATION FOR MINERAL DETERMINATION
  • 3.4.3. FEED AND LIVER PREPARATIONS FOR SELENIUM DETERMINATION
  • 3.4.4. ANALYTICAL METHODS FOR FEED AND LIVER SAMPLES
  • 3.5. STATISTICAL ANALYSIS
  • CHAPITER 4: SELENIUM AND CHROMIUM INTERACTION EFFECT IN STRESS ALLEVIATION, PERFORMANCE AND CARCASS CHARACTERISTICS OF FEEDLOT CATTLE – EXPERIMENT
  • 4.1. INTRODUCTION AND AIM
  • 4.2. HYPOTHESIS
  • 4.3. MATERIALS AND METHODS
  • 4.3.1. ANIMALS AND EXPERIMENTAL DESIGN
  • 4.3.2. PERFORMANCE AND CARCASS PARAMETERS
  • 4.3.3. PARAMETERS MONITORED
  • 4.3.4. STATISTICAL ANALYSIS
  • 4. 5. RESULTS AND DISCUSSION
  • 4.5.1. STRESS, CORTISOL AND GLUCOSE LEVELS
    • 4.5.1.1. BLOOD CORTISOL CONCENTRATIONS
    • 4.5.1.2. BLOOD GLUCOSE LEVELS
    • 4.5.1.3. STRESS AND PERFORMANCE RELATIONSHIPS
    • 4.5.2.1. LIVE WEIGHT AND AVERAGE DAILY GAIN
    • 4.5.2.2. SELENIUM SUPPLEMENTATION EFFECTS ON PERFORMANCE
    • 4.5.2.3. CHROMIUM SUPPLEMENTATION EFFECTS ON PERFORMANCE
    • 4.5.2.4. FEED INTAKE AND FEED CONVERSION RATIO
  • 4.5.3. CARCASS EVALUATION
    • 4.5.3.1. CARCASS WEIGHT AND DRESSING PERCENTAGE
    • 4.5.3. 2. FAT CODE, CARCASS CONFORMATION AND MEAT YIELD PERCENTAGE
  • 4.5.3.5. MEAT pH
  • 4.5.4. MINERALS AND TRACE MINERALS STATUS
    • 4.5.4.1 LIVER SELENIUM CONCENTRATIONS
    • 4.5.4.2. LIVER CHROMIUM CONCENTRATIONS
    • 4.5.4.2. INTERACTION BETWEEN MINERALS
    • 4.5.4.2.1. SELENIUM INTERACTIONS
    • 4.5.4.2.2. CHROMIUM INTERACTIONS
  • 4.5.4.3. EFFECT OF MINERALS ON PERFORMANCE OF FINISHING CATTLE AND CARCASS
  • CHARACTERISTICS
• CHAPTER 5. THE EFFECT OF DIETARY SUPPLEMENT OF SELENIUM AND CHROMIUM ON MEAT COLOUR OF FEEDLOT CATTLE – EXPERIMENT
  • 5.1. INTRODUCTION AND AIM
  • 5.2. HYPOTHESIS
  • 5.3. MATERIALS AND METHODS
  • 5.3.1. EXPERIMENTAL ANIMALS AND SAMPLING
  • 5.4. PARAMETERS MONITORED
  • 5.5. RESULTS AND DISCUSSION
• CHAPTER 6: THE EFFECT OF SUPPLEMENTAL SELENIUM AND DIFFERENT FORMS OF CHROMIUM IN FEEDLOT CATTLE – EXPERIMENT
  • 6.1. INTRODUCTION AND AIM
  • 6.2. HYPOTHESIS
  • 6.3. PARAMETERS MONITORED
  • 6.4. MATERIALS AND METHODS
  • 6.4.1. ANIMAL AND EXPERIMENTAL DESIGN
  • 6.4.2 FEED AND DIETS
  • 6.5. RESULTS AND DISCUSSION
  • 6.5.1. THE EFFECTS OF STRESS ON BLOOD CORTISOL AND GLUCOSE LEVELS
  • 6.5.3. FEED CONVERSION RATIO
  • 6.5.4. CARCASS PARAMETERS
  • 6.5.5. MINERALS
    • 6.5.5.1. MINERAL STATUS
    • 6.5.5.2. INTERACTION BETWEEN MINERALS
    • 6.5.5.3. INTERACTION BETWEEN MINERALS AND PERFORMANCE
• CHAPTER 7: THE EFFECT OF DIFFERENT COMBINATION OF SELENIUM AND CHROMIUM ON FEEDLOT CATTLE – EXPERIMENT
  • 7.1. INTRODUCTION AND AIM
  • 7.2. HYPOTHESIS
  • 7.3 MATERIALS AND METHODS
  • 7.3.1. ANIMAL AND EXPERIMENTAL DESIGN
  • 7.3.2. DIETS AND FEEDING PATTERNS
  • 7.3.3. ANALYTICAL PROCEDURES
  • 7.3.4. STATISTICAL ANALYSIS
  • 7.4. PARAMETERS MONITORED
  • 7.5. RESULTS AND DISCUSSION
  • 7.5.1. BLOOD CORTISOL AND GLUCOSE
  • 7.5.2. CORRELATION BETWEEN CORTISOL AND GLUCOSE WITH ADG AND P- FCR
  • 7.5.3 PERFORMANCE
  • 7.5.3. CARCASS CHARACTERISTICS
  • 7.5.4. MINERALS
    • 7.5.4.1. MINERAL STATUS
    • 7.5.4.2. MINERAL INTERACTIONS
• CHAPTER 8: GENERAL DISCUSSION
  • REFERENCE LIST
  • APPENDICES

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