CALCIUM AND MAGNESIUM LEVELS IN THE OVARIAN CYCLE OF THE LAYING HEN Akrum Hamdy Animal Production Department, Faculty of Agriculture, Minia University

Minerals Inorganic elemental atoms that are essential nutrients. Not changed by digestion or metabolism. Functions of Minerals 1- Some participate with enzymes in metabolic processes (cofactors) 2- Some have structural functions (Ca, P in bone and egg shell; S in keratin) 3- Acid-base and water balance (Na, K, Cl) Nerve & muscle function (Ca, Na, K)

Bioavailability, & Regulation of Major Minerals Bioavailability Influenced by genetics, aging, nutritional status, production level & other food compounds Absorption Small intestine & large intestine Regulation Kidneys & small intestine

Classification Macro or Major minerals Sodium, potassium, magnesium, calcium, phosphorus, sulfur, chloride Present in body tissues at concentrations >50 mg/kg (50 ppm) Micro or Trace minerals (body needs relatively less) Chromium, manganese, iron, cobalt, molybdenum, copper, zinc, fluoride, iodine, selenium, silicon, arsenic, nickel … Present in body tissues at concentrations <50 mg/kg (50 ppm)

Calcium homeostasis: Parathyroid Hormone, Calcitonin and Vitamin D3 Calcium metabolism Calcium metabolism physiologic functions : 1.blood coagulation. 2.muscle contraction. 2.muscle contraction. 3.neuromuscular transmission. 3.neuromuscular transmission. 4.Skeletal growth & Mineralization & Egg Shell Ionized Ca is physiologically important.

Calcium Most abundant mineral in animal tissues 99% Ca in skeleton Present in: Blood & other tissues Lots of functions Bone structure Egg Shell Nerve function Blood clotting Muscle contraction Cellular metabolism

Calcium & Phosphorus: 1- The recommended ratio P:Ca in diet of poultry is 1:1.2 (range 1:1 to 1:1.5) 2- For laying hen 1:4 ( Ca important for bone & shell formation) 2- For laying hen 1:4 ( Ca important for bone & shell formation)  Ca in diet  utilization of Mg, Mn & Zn.  Inorganic P have a higher availability than organic P  All P from animal origin & 40% from plant origin (wheat bran & rice bran) is available.

Hormonal control of Ca2+ Three principal hormones regulate Ca ++ and three organs that function in Ca ++ homeostasis. Parathyroid hormone (PTH), 1,25- dihydroxy Vitamin D3 (Vitamin D3), and Calcitonin, regulate Ca ++ resorption, reabsorption, absorption and excretion from the bone, kidney and intestine. In addition, many other hormones effect bone formation and resorption.

Vitamin D action The main action of 1,25-(OH) 2 -D is to stimulate absorption of Ca 2+ from the intestine. 1,25-(OH) 2 -D induces the production of calcium binding proteins which sequester Ca 2+, buffer high Ca 2+ concentrations that arise during initial absorption and allow Ca 2+ to be absorbed against a high Ca 2+ gradient

Vitamin D promotes intestinal calcium absorption Vitamin D acts via steroid hormone like receptor to increase transcriptional and translational activity One gene product is calcium-binding protein (CaBP) CaBP facilitates calcium uptake by intestinal cells

Regulation of PTH The dominant regulator of PTH is plasma Ca 2+. Secretion of PTH is inversely related to [Ca 2+ ]. Maximum secretion of PTH occurs at plasma Ca 2+ below 3.5 mg/dL. At Ca 2+ above 5.5 mg/dL, PTH secretion is maximally inhibited.

Reproductive Cycle

Calcium: Laying birds need large amounts of Ca because egg shells composed entirely of CaCo3  Ca in laying ration   egg production & soft or weak egg shell. Bird stored Ca for about days before the first egg was laid in the marrow of long bone. Bird stored Ca for about days before the first egg was laid in the marrow of long bone.

Outside Chorion or Chorioallantois

Feeding and nutrition of young layers: young layers should not receive a diet with calcium levels above 2%, => start of lay would begin too early, when body weight is too low => especially in alternative housing systems this is the time for a “pre-lay-diet” with 2% of calcium, which allows the birds to grow and prevents premature onset of egg laying with nearly 5% rate of lay a start lay-diet must be fed, with high nutrient density in this phase the hen need support to reach enough feed intake of ca g/day

Example of phase feeding in Germany:

Deficiencies Calcium Deficiencies Rickets in growing birds. Osteomalacia (osteoporosis) in adult birds. Shell less in laying hens.

Calcium Toxicity Deposition in soft tissue Impaired kidney function Interference of other nutrient absorption Iron & zinc

Magnesium Functions Associated with Ca and P 70% of Mg in skeleton Enzyme activation (e.g., pyruvate dehydrogenase) Deficiency Hypomagnesemic tetany poor nervous and muscular control

Magnesium Magnesium is a mineral, so therefore just like calcium, magnesium must be absorbed through dietary intake. Hypomagnesemia, resulting in low blood calcium levels, muscle cramps, nausea, weakness, irritability and confusion Early signs of magnesium deficiency include loss of appetite, nausea,vomiting,fatigue,and weakness

How it functions in body metabolism How it functions in body metabolism Approximately 50% of total body magnesium is found in bone. The other half is found predominantly inside cells of body tissues and organs. Only 1% of magnesium is found in blood, but the body works very hard to keep blood levels of magnesium constant. Only 1% of magnesium is found in blood, but the body works very hard to keep blood levels of magnesium constant.

Magnesium helps regulate blood sugar levels, promotes normal blood pressure, and is known to be involve in energy metabolism and protein synthesis. Magnesium is excreted through the kidneys. Magnesium is needed for more than 300 biochemical reactions in the body. Helps maintain normal muscle and nerve function, keeps heart rhythm steady, supports a healthy immune system, and keeps bones strong

Magnesium (Mg): Dietary Sources & Bioavailability Green leafy vegetables, seafood, legumes, nuts, dairy products, chocolate, brown rice, whole grains Bioavailability influenced by: CalciumPhosphorus

Metabolism & Regulation of Magnesium in the Body Stabilizes enzymes Neutralizes negatively charged ions Energy metabolism Cofactor for over 300 enzymes DNA & RNA metabolism Nerve & muscle function

Magnesium Deficiency & Toxicity Deficiencies Abnormal nerve & muscle function increase risk for type 2 diabetes Toxicity Large dose supplements Intestinal distress, alterations in heart beat

Some examples of feeding mistakes: unbalanced diets, for example deficiency of amino acids diets with too low nutrient density (use fat and oil!) structure not correct: too fine, not homogeneous, limestone of too fine structure amount of feed (and water) intake is unknown misunderstanding of phase feeding rearing pullets with too low body weight

With this chart beyond the “most important nutrient” I want to finish this presentation of CALCIUM AND MAGNESIUM Thank your for your attention