Midterm - Lecture 8

Question 1

What are the normal phosphorus blood levels?

Answer 1

4-8 mg/dl for most species

Question 2

What can cause low phosphorus blood levels?

Answer 2

vitamin D deficiency or dietary P inadequacy

Question 3

What are plant sources of phosphate usually tied up as?

Answer 3

phytate phosphorus

Question 4

How much of cereals, legumes, and other points are tied up as phytate phosphorus?

Answer 4

60-70 %

Question 5

How well can monogastrics digest phytate phosphorus?

Answer 5

not very well 0-40 %
high in wheat
0% in corn

Question 6

Why can ruminants make use of phytate phosphorus?

Answer 6

because their microbes in the rumen can break it down

Question 7

How does the saliva of ruminants play a role in phosphorus digestion?

Answer 7

the salivary secretions can remove 30-90 g of phosphorus from the extracellular phosphorus pool each day, then the phosphorus secreted is recovered by intestinal resorption

Question 8

What happens when ruminants stop chewing?

Answer 8

lower rumen pH - less bugs (bacteria)- dead cow

Question 9

What happens with downer cows?

Answer 9

when plasma P is below 1.5mg/100 ml
unable to stand
NOT due to dietary phosphorus deficiency

Question 10

What is the cause of rickets?

Answer 10

diet fails to have adequate P to support bone growth

Question 11

What animals usually get rickets?

Answer 11

mostly monogastrics fed plant diets where phosphorus is tied up by phytate

Question 12

What is osteomalacia?

Answer 12

adult rickets, the failure of osteoid to mineralize during bone remodeling

Question 13

What are normal blood magnesium levels?

Answer 13

1.8-2.4 mg/dl

Question 14

How can blood magnesium levels be lowered?

Answer 14

by increasing renal excretion of Mg

Question 15

What are the major functions of magnesium?

Answer 15

• cofactor to activate many enzymes involved in catabolism and anabolism
• extracellular Mg is vital to maintenance of normal nerve and muscle cell stability

Question 16

What is hypomagnesemia?

Answer 16

low blood levels of magnesium that cause tetany

Question 17

What is hypermagnesemia?

Answer 17

high blood levels of magnesium that causes slow reaction time

Question 18

How is magnesium absorbed in monogastrics and young ruminants?

Answer 18

absorbed from ileum and colon by passive absorption

rare to see deficiency

Question 19

How is magnesium absorbed in ruminants?

Answer 19

absorption depends on the Mg concentration in solution in the rumen and the integrity of the rumen Mg active transport mechanism

Question 20

What animals is grass tetany observed in?

Answer 20

lactating beef or dairy animals at pasture

Question 21

What are the ion levels observed in grass tetany?

Answer 21

low levels of Mg and high levels of K, also low levels of Ca

Question 22

What are the side effects of grass tetany?

Answer 22

hyperexcitable nerves- PNS and CNS
muscle tremors
nystagmus
convulsions leading to a coma

Question 23

Is there a role for magnesium in urolithiasis?

Answer 23

too mugh Mg causes struvite stones to form in the bladder and block urethra in male cats