Assessment of mineral status during pregnancy in crossbred cattle

Abstract

Twenty, healthy crossbred heifers stationed at Kerala Agricultural University - Cattle Breeding Farm, Thumburrnuzhi, were utilized for the study. The parameters estimated in the experimental animals comprise of serum profile of certain macro and microelements as calcium, phosphorus, magnesium, sodium, .potassium, iron, copper, zinc and haematological parameters like red blood cells count, haemoglobin content, volume of packed red cells and erythrocyte indices before conception and at different stages of pregnancy viz., from third month to ninth month at monthly intervals and first month of lactation. The serum calcium level showed significant variations during the period of study, which decreased from the control level till fifth month of pregnancy and then increased from sixth month of gestation and reached the highest level by ninth month of gestation thereafter, decreased during first month of lactation (table 1). The increased serum calcium level from sixth month of pregnancy and early lactation could be due to an increased demand of this element for the formation of fetal skeleton and organogenesis as well as for drainage into the milk Serum inorganic phosphorus concentration was increased from third month of pregnancy and the highest level was attained by fifth month of pregnancy. Later the level of serum inorganic phosphorus gradually declined from sixth month to ninth month of pregnancy. These fluctuations in serum phosphorus during pregnancy might be due to the mobilisation of calcium and phosphorus from the dam's skeleton or due to an increased G.I tract absorption during the period.

Besides the utilisation of calcium for fetal growth, calcium and phosphorus play a vital role in the action of hormones and enzymes at subcellular levels in an integrated fashion in reproduction of young heifers. During first month of early lactation still lower content of serum inorganic phosphorus was observed which could be due to its drainage into milk. There was an increase in the serum magnesium concentration from the preconception level during different stages of pregnancy and the same was significantly higher from sixth to ninth month of pregnancy which later dropped a little during first month of lactation as observed in the case of serum calcium. The increased magnesium level during the period of gestation could be due to the increased gut absorption in order to meet increased metabolic demands of this mineral, as many of the enzymes of glycolysis and citric acid cycle require magnesium as a cofactor. The serum concentration of sodium' showed an increasing tendency whereas that of potassium showed a decreasing tendency from third to ninth month of pregnancy. However the values of sodium encountered during third to sixth month and that of potassium from third to eighth month of pregnancy were lower than pre conception values which might be due to an increased permeation of these electrolytes into the uterus and fmally drainage into the fetoplacentary unit. The serum sodium and potassium level reached highest values during ninth month of pregnancy which further decreased during first month of lactation due to an increased transfer of these electrolytes into milk .. An increasing trend was observed for serum levels of iron and copper from third to fifth month of pregnancy. The increased level of serum iron during the first half of pregnancy might be due to an increased absorption

from the gastrointestinal tract. It was observed that both these minerals reach their peak serum level by fifth month of pregnancy and towards late pregnancy the iron level decreased which might be either due to its incorporation into the fetus or an increase in plasma volume so that haemoglobin content of blood also got apparently decreased. Serum copper concentration which decreased during the period of sixth to eighth month of pregnancy might be due to an increased blood volume and further increase in serum copper level during the ninth month of pregnancy might be due to the increase in estrogen level during that period as estrogen induce denovo synthesis of ceruloplasmin and thereby increased serum copper value during this period. During the first month of postpartum, serum iron level was found decreased while copper concentration increased. As far as serum zinc levels was concerned it was noticed that throughout the pregnancy its level increased when compared to control value. This could be due to an increased concentration of several enzymes involved in steroidgenesis and carbonic anhydrase, a zinc containing enzyme encountered during pregnancy. Eventhough serum zinc content exhibited a decreasing trend from third to eighth month of gestation, eventually it got increased during ninth month which might be due to higher levels of circulating prostaglandins during this period as zinc is required for their transport. A further increase in serum zinc level was noticed during first month of lactation.