Rumination or cud chewing consists of regurgitation, remastication, reinsalvation, and reswallowing.

Transcription

1 Nutrition 115 Midterm Exam 2 February 25, 2000 Name Please be sure to put your name at the top of each page. Any page without a name in the appropriate place will not be graded. Read each question carefully, and answer each question thoroughly. As usual, the answer to bonus question is a true. 1. TRUE or FALSE. Indicate on the line to the left of each question whether the statement is True (T) or False (F). (9 pt) Rumination or cud chewing consists of regurgitation, remastication, reinsalvation, and reswallowing. Biological value of a protein is a measure of the proportion of the nitrogen absorbed from the gastrointestinal tract that is available for productive body functions. Cellulose is a polysaccharide consisting of a linear polymer of ß 1,4 linked D-glucose units and is resistant to digestion by mammalian enzymes. The omasum of cattle and sheep functions to regulate particle flow from the rumen to the abomasum and to absorb volatile fatty acids from the digesta. An objective of a premix is to dilute the micro ingredients to facilitate the even distribution of micronutrients in the finished diet. Emulsification of ingested fat in the small intestine by the action of bile salts enhances the hydrolysis of fat by pancreatic lipase. Digestion in the small intestine involves enzymes secreted by the pancreas into the intestine and enzymes associated with the brush border region of the microvilli. Lignin is a carbohydrate found in the cell wall of forage plants that is indigestible in the mammals discussed in class. Eructation of rumen gas in ruminants is a quiet process in contrast to belching in humans which can be a violent, noisy process. 1

2 2. Nutrition professionals provide a valuable service to their clients. In the livestock industries nutritionists formulate diets for their clients using a knowledge of nutrients requirements and composition of feedstuffs. Joe Herndon concluded his lecture by saying that there are three rations on a livestock operation. They were (1) the ration printed on paper, (2) the ration that is fed, and (3) the ration that the animal consumes. What did he mean by saying that there are three rations? (5 pt) 3. The NRC (National Research Council) publications of feeding standards are the foundation for formulating diets for livestock and pets. Explain and describe 2 advantages of feeding standards. (6 pt) Explain and describe 2 disadvantages of feeding standards as they relate specifically to the discussions presented by Joe Herndon? (6 pt) 1

3 4. Nutritionists use feeding standards to formulate diets, which meet the minimum nutrient and energy requirements of an animal for a specific biological function. Feeding standards for protein will include requirements for protein quantity and quality depending on the animal in question. a. The formulation of a diet for a growing pig requires the nutritionist to meet requirements for total protein intake and intake of specific amino acids. Amino acids, which are required in adequate amounts in the diet to promote growth of a growing pig, are called essential or indispensable amino acids. Why do growing pigs have a dietary requirement for specific amino acids? (6 pt) b. List the 10 essential amino acids required for growth of pigs. No abbreviations will be accepted. (5 pt) c. Many natural sources of protein do not have a high biological value for growth. For example feeding either casein or gelatin alone as the source of dietary protein for growing chickens does not support optimum growth. However, a mixture of casein and gelatin provides dietary protein that will promote optimum growth. Why does the mixture of these two proteins promote optimum growth? (5 pt) 2

4 5. Energy utilization in beef cattle is an active area of research. The study of energetics is based on an understanding of the 1st and 2nd laws of thermodynamics. A. Describe energy flow through an animal using a flow chart. Include digestible energy (DE), intake energy (IE) (also called gross energy), metabolizable energy (ME), and net energy (NE) and indicate where along the transfer of energy the losses of energy listed below occur. (8 pt) energy losses: fecal energy, gaseous energy, heat of fermentation, heat of nutrient metabolism, and urinary energy, B. Explain why the DE and ME values for tallow are similar while the DE and ME values for barley (grain) are not the same in the 1996 NRC for beef cattle. (4 pt) DE ME Mcal/kg DM ---- tallow barley

5 6. The rumen environment is a symbiotic relationship between the animal (host) and the microorganisms that inhabit the rumen. a. Describe and explain 4 things that the animal provides for the microbes that contribute to this symbiotic relationship. (8 pt) b. Describe and explain 2 things the microbes provide to the animal that contribute to this symbiotic relationship. (4 pt) c. The fermentation balance in the rumen is complex. Small changes in the diet can alter the end products of microbial digestion. Removing a portion of the carbohydrate that is cellulose and replacing it with a similar amount of carbohydrate that is starch will result in an increase in propionate and a decrease in acetate. Why do the concentrations of volatile fatty acid change? (4 pt) 4

6 7. Carbohydrates contained in plant materials are a major source of energy for animals that consume the plants. a. Compare the pig, the feedlot steer, and the horse in regard to the digestion of starch and cellulose by indicating below (1) the primary site(s) of digestion of each carbohydrate, (2) the end product(s) of digestion for each carbohydrate, and (3) the agents of digestion for each carbohydrate. Consider only the sites within the gastrointestinal tract listed below. (20 pt) Small intestine: starch - cellulose - pig Rumen: feedlot steer starch cellulose - Small intestine: starch - cellulose horse Small intestine: starch - cellulose Large intestine/colon: starch 5

7 cellulose - 6

8 8. Assume that you talk with your friends about the material you are learning in Nutrition 115 and that your friends are fascinated. Answer correctly any 3 out of the 4 questions below your friends have asked you below. You must be specific; the nutrition knowledge of your friends is not as good as your knowledge. a. Why does thoroughly cooking potatoes increase starch digestibility compared to uncooked potato starch? (4 pt) b. Why does the horse digest a higher proportion of the cellulose in alfalfa hay it consumes compared to a rabbit even though both animals are herbivores with hindgut fermentation capabilities? (4 pt) c. Why do the corn flakes stay crunchy when you add milk to them at breakfast time? (4 pt) d. Why is insoluble fiber, e.g. wheat fiber, used in the diet to promote normal bowel function in some humans? (4 pt) 7