Ruminant Nutrition Flashcards

Question

What facilitates calcium absorption? What dietary factors can affect calcium absorption?

Answer 1

Activated Vitamin D, and Parathyroid Hormone. - Phosphorus and magnesium content - High dietary zinc (many times due to formulation error) - Oxalates (can be posionous)

Answer 2

High oxalate plants have potential to be posionous. Rumen can detoxify oxalates but is dependent on bacterial content and can be overwhelmed when large ammounts are ingested. - Forms insoluable salts that precipitate in the kidney causing kidney failure.

Answer 3

- Sheep are most susceptible * Livestock should be adapted to oxalate plants over 4 days incrementally increasing time allowed to graze these plants. * Becomes more resistant to these plants over time.

Answer 4

* More calcium bound to albumin during alkalosis, resulting in slightly lower Ca++ in the blood and ECF * Alkalosis can cause signs of hypocalcemia. * In ruminants normally occurs with diseases that impair abomasal emptying since hcl is trapped in abomasum and forestomachs, metabolic alkalosis.

Answer 5

- Less calcium is bound, causing the release of calcium from the bones. Calcium from bone can also be used as a buffer.

Answer 6

PTH released by chief cells of parathyroid in response to low ionized calcium. This acts to increase Ca2+ in ECF. - PTH promotes bone resorption to provide Ca2+. • Bones of younger animals (12-24 hours) responds more rapidly than older animals(24-48+ hours). • Reabsorption of calcium ion from the glomerular filtrate in the kidney. - Loss of phosphate ion in saliva and urine. - Transformation of inactive vitamin D to active vitamin D

Answer 7

- Released from thyroid C cells in response of excessively high Ca2+ - Promotes deposition of calcium, into bone - Promotes calcium loss in kidneys - Effect: decreases CA2+ in the ECF

Answer 8

Older cows : bone and gut less responsive to pth and calcitriol than heifers. Peripartuant hypocalcemia occurs in 3 progressive stages, and can occur in both dairy and beef cattle.

Answer 9

◦ Stage 1: standing, apprehensive, hypersensitive, tremors. This is loss of dampening on sodium channels. ◦ Stage 2: Loss of Ca2+ influx at motor end plate of the axon causes less acetyl choline to be released per action potential. Decreased calcium ECF. Cows recumbent and too weak to stand, head may be turned to back if too heavy to lift. ◦ Stage 3: Comatose. Death can occur from cardiac/ respiratory failure/ can also cause rumen regurgitation and cause aspiration pneumonia.

Answer 10

- Calcium salts: usually in form of calcium borogluconate, iv slowly ( Rapid iv administration can result in cardiac arrest (stone heart syndrome). Therefore ascult while administering, if heartrate decreases below 60 bpm or you hear severe arrhythmia then stop administration for 20-30 seconds - pad areas, likely to fall and can become injured Prevention: Method 1: 1 month prior to calving, decrease Ca2+ so they could gear up PTH and Vitamin D3 homeostasis early on (this will prevent them from being "blindsided" by drop in calcium). Increasing calcium in feed will have opposite effect and induce milk fever. Method 2: Feed anionic salts for 2 weeks postpartum- inducing mild metabolic acidosis. This will aid calcium absorption in the gut, makes mineral more labile and improves renal activity of 1-alpha hydroxylase ( which activates vitamin D3) Risks: Can cause bone mineral liability, expensive, and may not work.

Answer 11

• Magnesium is important to have in diet at adequate amounts since it is an important cofactor for PTH.

Answer 12

- Cofactor for acetylcholinesterase, the ECF enzyme that cleaves Ach and terminates the stimulatory signal. - Cofactor for release of PTH from parathyroid gland. - Hypomagnesimia ( low mg2+ in ECF) may result in impaired PTH release. - Competes with calcium ( both are 2+ cations) and inhibits its stimulatory activity.

Answer 13

- Doesnt have specific hormones to regulate it - Doesnt mobilize bone mineral release. Mg absorption from gi tract is only regulatory mechanism for ECF. Animal must ingest from diet. Magnesium Sources: - Variety of plants, (legumes better than grasses) and nuts. - Animal tissues and liver are sources of mg ( for carnivores)

Answer 14

* GI tract absorption of Magnesium is generally inefficient. * High nitrogen (protein) as well as high dietary K+ will reduce magnesium absorption from the rumen since their will be a change in the electrical gradient. * Rapidly growing grasses have a lot of nitrogen and potassium.

Answer 15

* Graze lush pastures can lead to hypomagnesemia. * Clinical signs: repetitive muscle contractions that are uncontrolled, hyperirritability and convulsions. * Start with muscle tremors and progress to tetany. Clinical signs by stage: Early: Muscle fasiculations, hyperesthesia, stiff goose stepping gait. Animal may be irritable or maybe aggressive. Can be bellowing with an overly alert , nervous expression Later: Recombency and convulsion, paddling motions with limb, extensor rigidity, opisthotonus, death can occur from respiratory/ cardiac arrest.

Answer 16

Low Mg2++ -\> less competition for Ca2++ at axon terminus so more acetylcholine is released, which allows for more vigorous, sustained muscle contracctions. Acetylcholine will not be broken down effectively since magnesium is needed as a cofactor for acetylcholinersterase. Sustained muscle contraction. Same occurs in cholinergic CNS so thats why you can see both tetany and seizures.

Answer 17

• Magnesium SO4 via rectum as well as Calcium/ magnesium salt solution. Wear boots and get ready to run ( Salts can cause diarrhea and the cows can wake up aggressive) IV magnesium slowly Prevention: - one gram elemental magnesium absorbed per head per day.

Answer 18

It is a component of bone mineral and tooth enamel. 85% of total body P in hydroxyapatite Phospholipids in cell and cellular organelle membranes. Energy metabolism: ATP Sources: - Grains - Wheat bran - Supplements - Grasses are low in Phosphorus Phosphorus competes with calcium and can reduce its absorption.

Answer 19

• Can compete with calcium and reduce bone absorption. Low Ca++ and High Phosphorus in blood triggers chronically elevated PTH. Can cause bone resorption and condition called rubber jaw. • Ruminants on high grain diets may develop phosphate based urinary calculi if urine becomes highly concentrated ( i.e struvite ( magnesium ammonium phosphate). Disease termed urolithiasis. In ruminants: Phosphorus is usually excreted in the saliva and gi tract. - Saliva : supplies rumen bacteria with P source for ATP - Allows phosphorus recycling from blood into gut, minimizing urinary losses.

Answer 20

• Low phosphorus in ECF. - relatively uncommon, can occur with milk fever. Clinical presentation: usually alert but show weakness/ and inability to stand. Cows can attempt to rise on multiple occasions pushing part way up on legs and moving around pen on abdomen. "termed creeper cows" Trigger: Lactation triggers heavy ca2+ loss in milk, triggers pth secretion, pth moves alot of phosphate into urine, and persistent weakness is likely due to ATP depletion from muscle cells. Treatment: Blood Samples: Note hemolysis increases blood phosphorus because it leaks from ruptured RBC - IV Monosodium phosphate. Cannot mix Ca++ containing soluion. CaPO4 aggregrates and will precipitate. - Phos supplements - Offer phosphorus rich grains - Consider checking vitamin D status of diet

Answer 21

* More common in young animals. Camelids * More likely occurs in dark finer llamas due to UV not penetrating their darker skin as well. This is problem in pacific northwest and occurs primarily in the winter. Without Vitamin D, inadequate Ca and Phos absorption from gut to mineralize bones. Results in microfractures, wich cause lameness and angular deformities of the long bones. Clinical signs: - Reluctant to play, lethargic, Diagnostic indications: - Widened growth plates and flared metaphyses are hallmark signs - Typically normal serum calcium, low serum phosphorus