AGR2AN Practice Exam Questions 2024 PDF

# AGR2AN Practise Exam Questions 2024 ## Section A – Multiple Choice Questions **Answer ALL questions (Each question is worth 1 mark).** 1) Which of the following is **not** a role of proteins in the body? a. The main energy source for cells b. Synthesis of enzymes c. Source of amino...

# AGR2AN Practise Exam Questions 2024 ## Section A – Multiple Choice Questions **Answer ALL questions (Each question is worth 1 mark).** 1) Which of the following is **not** a role of proteins in the body? a. The main energy source for cells b. Synthesis of enzymes c. Source of amino acids d. Components of the cell membrane **Answer:** a. The main energy source for cells **Explanation:** Proteins are not primarily used as an energy source for cells; instead, carbohydrates and fats serve as the primary energy sources. Proteins are primarily involved in synthesizing enzymes, providing amino acids, and forming structural components like those in cell membranes. 2) Which of the following statements is **incorrect** regarding gluconeogenesis in ruminants? a. It is the formation of glucose from a non-carbohydrate substrate b. It relies on the fermentation of cellulose by rumen bacteria c. It uses propionate as the initial substrate d. It involves the conversion of glucose to pyruvate **Answer:** d. It involves the conversion of glucose to pyruvate **Explanation:** This statement is incorrect because gluconeogenesis is the process of forming glucose from non-carbohydrate substrates, not the conversion of glucose to pyruvate. In ruminants, gluconeogenesis often relies on propionate as a key substrate to generate glucose, especially since they have limited glucose intake from carbohydrates. 3) Which of the following statements is **incorrect**? a. Vitamin E causes a ‘sparing effect' on selenium b. Phytates can bind calcium, preventing absorption c. Excess iron is non-toxic in animals d. Vitamin D stimulates intestinal calcium reabsorption **Answer: **c. Excess iron is non-toxic in animals **Explanation:** This statement is incorrect because excess iron can be toxic in animals. High levels of iron can lead to iron toxicity, causing oxidative stress, damage to organs and other health issues. 4) Which of the following statements is **incorrect**? a. Proximate analysis measures the specific minerals present in a food. b. Proximate analysis is a widely accepted method. c. Protein is overestimated by proximate analysis. d. Ash is determined by burning a food sample. **Answer:** a. Proximate analysis measures the specific minerals present in a food. **Explanation:** This statement is incorrect because proximate analysis does not measure specific minerals. Instead, it provides a general breakdown of a food’s components, including moisture, ash, crude protein, crude fat and crude fibre. It does not identify individual minerals. 5) What is the role of stretch receptors in the rumen wall? a. Signal that the rumen is full and induce satiety. b. Expand the rumen to allow for increased food intake. c. Absorb volatile fatty acids from fermentation. d. Stimulate an increase in appetite as a response to low blood glucose. **Answer:** a. Signal that the rumen is full and induce satiety. **Explanation:** Stretch receptors in the rumen wall detect the degree of filling in the rumen and send signals to the brain to indicate fullness, helping to regulate feed intake and induce satiety. They do not directly absorb volatile fatty acids or stimulate appetite in response to low blood glucose. 6) Which of the following statements is **correct** for dairy cows in late lactation? a. Cows increase feed intake and enter negative energy balance. b. Cows increase feed intake and remain in positive energy balance. c. Cows decrease feed intake and enter positive energy balance. d. Cows decrease feed intake but remain in neutral energy balance. **Answer:** b. Cows increase feed intake and remain in positive energy balance. **Explanation:** In late lactation, dairy cows typically increase their feed intake and shift to a positive energy balance, as their energy requirements for milk production decrease. 7) What does the gross energy (GE) of a food indicate? a. Fraction of energy lost in the faeces, urine and gasses. b. Total energy available in a food. c. Total energy available to the animal after digestion. d. Fraction of energy measured by proximate analysis. **Answer:** b. Total energy available in a food. **Explanation:** Gross energy (GE) represents the total energy content of food, measured by the burning the food in a bomb calorimeter. It does not account for energy losses in feces, urine, and gases or reflect the energy actually available to the animal after digestion (which is known as metabolizable energy). 8) Which of the following foods has the highest biological value (BV)? a. Milk b. Fish meal c. Corn d. Lucerne hay **Answer:** a. Milk **Explanation:** Milk has a high biological value (BV) because it contains a well-balanced profile of essential amino acids that are efficiently used by the body. Foods with high BV provide a greater proportion of absorbed protein that is utilized for growth and maintenance. Fish meal also has a high BV, but milk generally ranks higher than plant-based sources like corn and lucerne hay. 9) Which of the following statements is **correct**? a. Zinc plays an important role in metabolism of DNA and RNA. b. Selenium deficiency is mostly observed in grazing ruminants. c. Excess copper is non-toxic to animals. d. When Vitamin E is in excess, the selenium requirement increases. **Answer:** a. Zinc plays an important role in metabolism of DNA and RNA. **Explanation:** Zinc is essential for DNA and RNA metabolism, as it acts as a cofactor for enzymes involved in nucleic acid synthesis and repair. 10) In the following equation, what does **km** stand for? ME = NEm/km + NEg /kg + NEc/kc + NE₁/k a. The efficiency of use of ME for maintenance b. The distance walked during grazing in kilometers c. The efficiency of milk production d. The digestion of a milk diet in young animals **Answer:** a. The efficiency of use of ME for maintenance **Explanation:** In the equation, km represents the efficiency with which metabolizable energy (ME) is used for maintenance. Similarly, kg, kc, and kl represent the efficiency of ME use for growth, pregnancy and lactation. 11) A deficiency of which vitamin affects eye sight and may cause night blindness? a. Vitamin A b. Vitamin E c. Vitamin D d. Cyanocobalamin **Answer:** a. Vitamin A **Explanation:** Vitamin A is essential for vision because it is key component of rhodopsin, a protein in the retina that absorbs light and supports low light (night) vision. Without enough vitamin A, the production of rhodopsin is impaired, making in difficult for the eyes to adjust to dim lighting, which can result in night blindness. 12) Which of the following is not a source of protein for ruminants? a. NP b. MCP c. ADPLS d. RDP **Answer:** c. ADPLS (Amino Acid Digestible Protein for Lambs) **Explanation:** This is a protein measure used for monogastrics, while ruminants use RDP (Rumen Degradable Protein) and UDP (Undegraded Dietary Protein) measures. ## Section B – Short Answer Questions **Answer ALL questions (Each question is worth 3 marks).** 1) Using the Table below, explain the reason for differences in the relative capacity of a ruminant stomach compared to a hind gut fermenter. (3 marks) | Animal species | Stomach (%) | Small intestine (%) | Cecum (%) | Colon-rectum (%) | | --- | --- | --- | --- | --- | | Cattle | 71 | 18 | 3 | 8 | | Sheep | 67 | 21 | 2 | 10 | | Horse | 9 | 30 | 16 | 45 | | Swine | 29 | 33 | 6 | 32 | | Dog | 63 | 23 | 1 | 13 | | Cat | 69 | 15 | 1 | 16 | | Human | 17 | 67 | 1 | 16 | **Explanation:** The differences in relative capacity of the digestive tract are due to the different methods of digesting food used by ruminants and hindgut fermenters. - **Ruminants:** Their stomachs are much larger than those of hindgut fermenters because they have a complex four-chambered stomach that allows for extensive microbial fermentation. The enlargement of the rumen allows for fermentation and regurgitation to thoroughly break down food - VFA's from microbial fermentation as an energy source. - **Hindgut fermenters:** Their large intestines are larger than those of ruminants because they rely on microbial fermentation to break down fiber after it has passed through the small intestine. The enlargement of the caecum and large intestine allows for fermentation of fibre after digestion of simple carbohydrates, as an energy source. 2) Using the provided Guaranteed Analysis (as fed) for a wet cat food, calculate the % of dry matter (DM) and then use this value to determine the amount of protein and fat on a dry matter basis. Provide the answers for total % DM, protein as % DM and fat as % DM in your response. **Guaranteed Analysis** | Component | | | | --- | --- | --- | | Crude Protein | Min | 6% | 60 g/kg | | Crude Fat | Min| 2.5% | 25 g/kg | | Crude Fiber | Max | 1% | 10 g/kg | | Moisture| Max | 85% | 850 g/kg | **Calculations:** - **DM:** 100% (Total) - 85% (Moisture) = 15% DM - **Protein as %DM:** 6% (Protein as fed) / 15% (DM) = 40% protein as %DM - **Fat as %DM:** 2.5% (Fat as fed) / 15% (DM) = 16.67% fat as %DM **Answers:** - Total % DM: 15% - Protein as %DM: 40% - Fat as %DM: 16.67% 3) Briefly explain how sheep obtain sources of vitamin C from the diet. Include any precursors or cofactors, and whether the active form of vitamin C is produced by plants, bacteria or animals. **Explanation:** Sheep, like most ruminants, are able to synthesize their own Vitamin C (ascorbic acid) in their rumen through the action of the bacteria that live there. This means they don't need to rely on their diet to get it, unlike monogastric animals like humans. 4) What are phytates and how do they affect dietary nutrients? Give an example of a nutrient affected. **Explanation:** Phytates are compounds found in plants, mainly in the seeds and grains. They bind to certain minerals, making them unavailable to animal digestion. One example is calcium: Phytates can bind to calcium, reducing its absorption and potentially leading to a deficiency. 5) Environmental temperature plays a role in influencing feed intake in animals. Briefly explain the why feed intake changes with temperature in livestock. **Explanation:** Animals use food for energy, and the conversion of food into energy generates heat. The amount of heat generated depends on factors like the animal's body size and activity level. So, how animals adjust their feed intake depends on environmental temperature: - **Cold Temperatures:** Animals experience a higher rate of heat loss. To compensate, they increase their feed intake to generate more heat, keeping their body temperature stable. - **Hot Temperatures:** Animals experience a higher rate of heat gain. To avoid overheating, they may reduce their feed intake, minimizing the amount of heat being produced by their bodies. 6) The generalised equation for determining metabolic energy at maintenance in ruminants is: MEm (MJ/d) = (K.S.M. (0.28W0.75 exp(-0.03A))/km + 0.1 MEp + MEgraze + Ecold Define what __K__, __km__ and __Ecold__ refer to in this equation **Definitions:** - **K:** Refers to the species factor. This value is a constant that is defined by the species of the animal. It takes into account the animal's specific metabolic rate and energy requirements. - **km:** Stands for the net efficiency of metabolizable energy (ME) used for maintenance. It represents how efficiently the animal uses ME for the basic functions needed to maintain body weight and stay alive, without any growth or production. - **Ecold:** Represents the additional energy expenditure required by the animal to maintain a stable core body temperature in a cold environment. This is the energy needed to replace the heat lost due to cold conditions. It takes into account factors like insulation and body size. 7) Environmental temperture plays a role in influencing feed intake in animals. Briefly explain the why feed intake changes with temperture in livestock **Explanation:** The relationship between environmental temperature and feed intake is driven by the animal's need to regulate body temperature, primarily to maintain an internal core temperature for optimal function. - **Lower Critical Limit:** When the environmental temperature drops below the lower critical limit, animals increase their feed intake. This is because they need to increase their metabolic rate to produce heat and counter the heat loss, maintaining their core temperature. - **Upper Critical Limit:** As the environmental temperature rises above the upper critical limit, animals typically decrease their feed intake. This is because the body produces heat as a byproduct of metabolism, so increasing feed intake in warm temperatures would further raise body temperature, increasing the risk of overheating. - **Comfort Zone:** Between the lower and upper critical limits lies the "comfort zone." This is where the animal requires minimal adjustment to their normal feed intake to maintain a steady body temperature. They can comfortably maintain their energy balance without significant changes to their feeding behaviour. 8) Briefly explain the difference between foregut fermenters and hindgut fermenters. **Explanation:** Foregut fermenters and hindgut fermenters are distinguished by the location of their primary microbial fermentation: - **Foregut Fermenters:** The primary fermentation happens in the foregut, which is the front part of the digestive tract. This includes the rumen in ruminants. These animals digest complex carbohydrates like cellulose through microbial action in the rumen before the food moves to the stomach and small intestine for further breakdown and absorption. - **Hindgut Fermenters:** These animals have their main microbial digestion occurring in the hindgut, which includes the cecum and large intestine. This is where the breakdown of cellulose and other complex carbohydrates occurs. Examples include horses, rabbits, and some other herbivores. 9) Briefly explain how animals adjust their diets during different life stages. **Explanation:** Animals adjust their diets in their different life stages due to varying needs for specific nutrients for growth, development, reproduction, and lactation. - **Growth Stage:** Young animals require higher amounts of energy and protein to support their rapid growth and development. - **Pregnancy:** Pregnant animals have increased energy requirements to support the development of the fetus. They also need additional nutrients, such as calcium, for bone development. - **Lactation:** Animals that are lactating, such as dairy cows, require significantly higher energy and protein to produce milk. - **Mature Adults:** Mature adults have reduced growth requirements and their energy needs also decrease. However, specific nutrients are still important for maintaining overall health and immune function. 10) Explain the importance of protein for production animals. **Explanation:** Protein is a vital nutrient for production animals as it plays a crucial role in several key processes: - **Growth and Development:** Protein is essential for building and maintaining body tissues, including muscle, bone, and organs, during the growth phase. This applies to animals raised for meat, wool, and other products. - **Reproduction:** Protein supports healthy reproductive function in both male and female animals. It plays a role in the development of eggs and sperm, as well as the growth and development of offspring. - **Lactation:** Milk production requires a high level of protein, as it is a rich source of essential amino acids for young animals. - **Maintenance:** Adequate protein intake is crucial for maintaining body functions, repairing tissues, and supporting immune function. 11) Briefly explain the differences in protein requirements for ruminants and monogastrics. **Explanation:** Ruminants and monogastrics differ significantly in their protein metabolism and requirements due to their different digestive systems: - **Ruminants:** These animals rely on microbial protein synthesis in their rumen, which allows them to use non-protein nitrogen (NPN) sources in the diet. This means they can obtain amino acids from protein sources and also from the breakdown of non-protein nitrogen sources – like urea – by microbes in the rumen. It can compensate for lower protein levels in their diet. - **Monogastrics:** These animals lack a rumen and cannot digest non-protein nitrogen. They rely solely on dietary protein to obtain their amino acids, so it’s crucial to ensure their diets contain sufficient protein of high quality. This means monogastrics have a stricter requirement for digestible protein that their bodies can directly absorb. 12) What are the main functions of water-soluble vitamins in animals. **Explanation:** Water-soluble vitamins are essential for various metabolic processes in animals, playing a vital role in energy production, cell division, and growth. Here are some key functions: - **Energy Metabolism:** B vitamins are vital cofactors for enzymes involved in energy production, as well as carbohydrate metabolism, cellular respiration, and fatty acid metabolism. - **Cell Growth and Development:** B vitamins are crucial for DNA synthesis, cell division, and protein synthesis, which are vital for growth and development, especially in young animals. - **Nerve Function:** B vitamins, particularly Vitamin B1 (Thiamine) and B12 (Cobalamin), play a key role in maintaining healthy nerve function. They are essential for nerve impulse transmission and the production of myelin, which is a protective sheath around nerve fibers. - **Immune Function:** Certain B vitamins, like Vitamin B6 and B12, are key for maintaining proper immune function, which helps the body fight off infections and disease. - **Red Blood Cell Production:** Vitamin B12 (Cobalamin) is crucial for the production of red blood cells, which are responsible for carrying oxygen throughout the body. - **Collagen Synthesis:** Vitamin C (ascorbic acid), an antioxidant, is vital for the synthesis of collagen, a protein that provides strength to connective tissues, bones, tendons, and skin. 13) Describe the functions of fat-soluble vitamins and list their deficiencies and sources. **Fat-soluble vitamins:** - **Vitamin A** * **Functions:** Supports vision, immune function, growth, and cell differentiation. * **Deficiencies:** Night blindness, dry eyes, skin problems, immune deficiency. * **Sources:** Leafy green vegetables, carrots, liver, eggs, dairy products, fish oils. - **Vitamin D** * **Functions:** Regulates calcium and phosphorus absorption for bone health, immune function, and cell growth. * **Deficiencies:** Rickets (bone deformities) in children and osteomalacia (bone softening) in adults. * **Sources:** Sunlight exposure, fatty fish, eggs, fortified milk, mushrooms. - **Vitamin E** * **Functions** : Acts as an antioxidant, protecting cells from damage caused by free radicals, supporting muscle function, and reproductive health. * **Deficiencies:** Muscle weakness, reproductive problems. * **Sources:** Vegetable oils (sunflower, soybean, corn), nuts, seeds, leafy green vegetables. - **Vitamin K** * **Functions:** Essential for blood clotting and bone health. * **Deficiencies:** Excessive bleeding and increased risk of fractures. * **Sources:** Green leafy vegetables, some fruits, and some fermented foods. 14) Briefly describe the functions of major minerals for animals. **Functions of Major Minerals:** - **Calcium:** Essential for bone and teeth formation, muscle contraction, nerve function, blood clotting, and egg shell formation. It is also important for milk production in lactating animals. - **Phosphorus:** Works with calcium for strong bones, teeth, and overall skeletal health. It is also crucial for energy metabolism and genetic material (DNA/RNA). - **Magnesium:** Important for muscle and nerve function, regulating blood sugar levels, and maintaining a healthy immune system. - **Potassium:** Vital for nerve function, muscle contraction, fluid balance, and maintaining a healthy heart. - **Sodium:** Plays a role in fluid balance, nerve impulses, and muscle function. - **Chlorine:** Helps maintain fluid balance, pH levels, and assists in the digestion of food. - **Iron:** Essential for oxygen transport in the blood through red blood cells (hemoglobin). It is also involved in energy metabolism, cell growth, and immune function. - **Zinc:** Essential for immune function, wound healing, protein synthesis, growth, healthy skin and coat, and reproductive function. - **Copper:** Involved in red blood cell formation, connective tissue synthesis, pigmentation, and immune function. - **Manganese:** Essential for bone health, immune function, and carbohydrate metabolism. - **Iodine:** Important for thyroid hormone production, which is essential for regulating metabolism, growth, and development. - **Selenium:** An antioxidant that protects cells from damage, supporting immune function, and fertility. 15) Briefly explain the difference in digestive processes between ruminants, monogastrics, and hindgut fermenters. **Explanation:** These three digestive systems represent different strategies for breaking down and absorbing nutrients, particularly for those that have a high fiber content. - **Ruminants:** Have a four-chambered stomach - the rumen. The food is digested through microbial fermentation in the rumen. The microbes break down cellulose and other complex carbohydrates that monogastrics cannot handle. The food is then regurgitated as cud and chewed again before moving on to the stomach and small intestine for further digestion and absorption. - **Monogastrics:** These animals have a single stomach. They rely on enzymes to break down food. They generally have a smaller cecum and large intestine, meaning they digest less fiber than ruminants. - **Hindgut Fermenters:** They have a single stomach followed by a large cecum and large intestine. The main fermentation occurs in the cecum and large intestine due to microbes present there. The process is slower as digestion happens after the food passes through the stomach and small intestine. 16) Briefly explain the different energy partitioning concepts; gross energy, digestible energy, metabolizable energy and net energy. **Energy Partitioning Concepts:** - **Gross Energy (GE):** The total energy content of a food or feed. It is measured by burning the food in a bomb calorimeter. However, it doesn't account for losses during digestion. - **Digestible Energy (DE):** The amount of energy that is absorbed from the food in the small intestine. It is calculated by subtracting the amount of energy lost in feces from GE. - **Metabolizable Energy (ME):** It is the energy available for metabolic processes in the body. It is calculated by subtracting the energy lost in urine and gases from DE. - **Net Energy (NE):** The amount of energy that is available for maintenance, growth, production, or activity. It is calculated by subtracting the energy lost as heat from metabolic processes from ME. 17) Explain the concept of the respiratory quotient (RQ) and its importance in animal nutrition. **Respiratory Quotient (RQ):** - **Concept:** The respiratory quotient (RQ) is a measure of the ratio of carbon dioxide (CO2) produced to oxygen (O2) consumed during metabolism. - **Importance:** The RQ provides insights into the type of fuel being utilized by the body for energy production, whether it's primarily carbohydrates, fats, or proteins. * **RQ Values:** - **RQ = 1:** Indicates that the animal is predominantly utilizing carbohydrate as a fuel source. - **RQ > 1:** Usually occurs during periods of high protein use for energy. - **RQ < 1:** Generally signifies that the animal is primarily using fat as a fuel source. - **Applications:** * It helps assess the efficiency of nutrient utilization and can identify situations where the diet is not adequately balanced for the animal's needs. * It can indicate potential health problems like energy imbalances or suggest that certain diets or energy requirements need modification. 18) Briefly explain the three different types of approaches used for determining nutrient requirements. **Determining Nutrient Requirements:** - **Feeding Trials:** An experimental approach where different levels of nutrients are provided in the diet. The animals are monitored for growth, weight gain, and other health parameters. This allows researchers to analyze the relationship between nutrient intake and animal performance. - **Comparative Slaughter:** Two groups of animals are fed different diets. The animals are then slaughtered, and the body composition is analyzed. This approach helps determine the efficiency of different diets and the relationship between diet composition and animal tissue deposition. - **Calorimetry: ** This method directly measures the heat produced by the animal to estimate energy expenditure. It is a highly precise method for determining energy requirements, but it is more expensive and time-consuming.