Influence of the Stage of Dairy Cow Reproduction Cycle on Some Clinico-biochemical Parameter

Abstract

The influence of the reproduction cycle stage on selected parameters ofthe mineral metabolism levels has been investigated on 55 clinically healthy dairy cows of the Bohemian Spotted breed, 3-8 years old, the nutrition of which met standard requirements (starch units, digestible nitrogen compounds, Ca and P). The animals were divided into three groups according to the reproduction stage (daily performance) and were followed during the winter feeding period (December -April).The selected clinico-biochemical characteristics of blood (pH, base excees, pC02), blood plasma (Ca, inorg. P) and urine (Ca, inorg. P) have not been found to differ from reference values. The values obtained by chemical analysis of tuber coxae biopsy samples have shown a significant decrease in the concentration of PIg of fat-free dry matter in post parturient dairy cows when compared with the dry ones. Otherwise, the reproduction cycle stage has not significantly influenced the ash content and Ca weight per 1 g of fat-free dry matter and the ash, Ca and P weight expressed per 1 cm3 of cancellous bone tissue.Dairy cows, reproduction stage, blood, blood plasma, urine, cancellous bone tissue, fat-free dry matter, ash, calcium, inorganic phosphorus, acid-base balance.The requirements for maintaining homeostasis of calcium and.phosphorus increase with the augmented milk production and with the advancement of pregnancy. Diimrich (1970), SiSkov and Zelenskaja (1978) rank the milk efficiency and pregnancy among endogenous factors connected with the induction of diseases of skeleton; Later stage oflactation plays a more significant role in the development of skeletal diseases than that of gravidity (Stober 1970). In the period of late lactation the calcium balance is negative, this being connected with bone demineralization (Duckworth and Hill 1953). The skeleton demineralization occurs particularly at the onset of lactation (Illek et al. 1977). If the Ca and P losses are not adequately compensated for, hypocalcaemia and hypophosphataemia develop, inducing thus the parathyroid hypersecretion. The increased level of parathormone exerts its effect in its target organs (bone, intestine, kidney), the result being the adjustement of calcaemia.In contrast to Ca, the mechanism of phosphate homeostasis has not been fully elucidated. Rasmussen and Bordier (1974) have repeatedly shown that the phosphate depression leads to the changes in bone, intestine and kidney cells which stimulate an increased transfer of phosphates into extracellular fluid. With the decrease of serum phosphates the tubular reabsorption in kidney increases together with phosphate absorption in intestine. The shortage of phosphates leads to the stimulation of vitamin D conversion in kidney to 1,25 dihydroxycholeca1ciferol, promoting the enteral absorption of Ca and P.The aim of the present paper was to evaluate the influence of the reproduction stage on chemical composition of skeleton of clinically healthy and optimally fed cows.