Midterm - Lecture 8 Flashcards
What are the normal phosphorus blood levels?
4-8 mg/dl for most species
What can cause low phosphorus blood levels?
vitamin D deficiency or dietary P inadequacy
What are plant sources of phosphate usually tied up as?
phytate phosphorus
How much of cereals, legumes, and other points are tied up as phytate phosphorus?
60-70 %
How well can monogastrics digest phytate phosphorus?
not very well 0-40 %
high in wheat
0% in corn
Why can ruminants make use of phytate phosphorus?
because their microbes in the rumen can break it down
How does the saliva of ruminants play a role in phosphorus digestion?
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
What happens when ruminants stop chewing?
lower rumen pH - less bugs (bacteria)- dead cow
What happens with downer cows?
when plasma P is below 1.5mg/100 ml
unable to stand
NOT due to dietary phosphorus deficiency
What is the cause of rickets?
diet fails to have adequate P to support bone growth
What animals usually get rickets?
mostly monogastrics fed plant diets where phosphorus is tied up by phytate
What is osteomalacia?
adult rickets, the failure of osteoid to mineralize during bone remodeling
What are normal blood magnesium levels?
1.8-2.4 mg/dl
How can blood magnesium levels be lowered?
by increasing renal excretion of Mg
What are the major functions of magnesium?
- cofactor to activate many enzymes involved in catabolism and anabolism
- extracellular Mg is vital to maintenance of normal nerve and muscle cell stability
What is hypomagnesemia?
low blood levels of magnesium that cause tetany
What is hypermagnesemia?
high blood levels of magnesium that causes slow reaction time
How is magnesium absorbed in monogastrics and young ruminants?
absorbed from ileum and colon by passive absorption
rare to see deficiency
How is magnesium absorbed in ruminants?
absorption depends on the Mg concentration in solution in the rumen and the integrity of the rumen Mg active transport mechanism
What animals is grass tetany observed in?
lactating beef or dairy animals at pasture
What are the ion levels observed in grass tetany?
low levels of Mg and high levels of K, also low levels of Ca
What are the side effects of grass tetany?
hyperexcitable nerves- PNS and CNS
muscle tremors
nystagmus
convulsions leading to a coma
Is there a role for magnesium in urolithiasis?
too mugh Mg causes struvite stones to form in the bladder and block urethra in male cats
