Status and Interrelation of Trace Minerals and Steroid Hormones in Heifers

| The aim of the present study was to evaluate the serum trace mineral and steroid hormone status in heifers and to find interrelation among them. Thirty crossbred heifers (Holstein Friesen X local non-descript) were divided into three groups on the basis of age viz. group A (12-18 months), group B (18-24 months) and group C (24-30 months) and each group was having ten animals (n=10) each. Serum trace minerals were estimated by atomic absorption spectrophotometry and steroid hormones (estrogen and progesterone) by radio immuno assay. Overall mean±SE of copper, iron, zinc and manganese in heifers was found to be 0.59±0.20, 1.32±0.57, 0.93±0.38 and 0.18±0.03 ppm respectively. Most of the trace minerals were in deficient range when compared with critical levels. Overall mean±SE of estrogen and progesterone in heifers was 18.34±2.28 pg/mL and 0.83±0.21 ng/mL respectively. Copper showed non-significant (p>0.05) decrease whereas iron showed non-significant (p>0.05) increase with increase in age. Zinc and manganese showed significant (p<0.05) decrease with age. Serum estrogen significantly (p<0.05) increased with increase in age whereas serum progesterone decreased non-significantly (p>0.05) with increase in age. Positive and significant (p<0.05) correlations were noted between most of the trace minerals and steroid hormones. This may be due to involvement of trace minerals in steroid hormone synthesis through metalloenzymes or cofactors. Hence supplementation of trace minerals can improve animal health and reproductive efficiency by minimizing mineral deficiency and favouring steroid hormone synthesis.


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countries (McDowell et al., 1984;Sharma et al., 2003).For this purpose the present study was under taken to evaluate the trace mineral status and their interrelation with steroid hormones in growing heifers so that the requirement for mineral supplementation in the diet, if any, can be evaluated.

MAtErIAlS And MEthodS
A total of thirty crossbred heifers (Holstein Friesen X local non-descript) were selected randomly from farmers herd in Kashmir Valley and were divided into three groups on the basis of age viz. group A (12-18 months), group B (18-24 months) and group C (24-30 months).Each group was having ten animals (n=10).Blood samples (10 mL) were collected by jugular vein puncture into vials without anticoagulant and serum was harvested.Serum trace minerals were estimated by atomic absorption spectrophotometry after digesting the serum samples by the procedure of Kolmer et al. (1951).Serum estrogen (E 2 ) and progesterone (P 4 ) were determined by radioimmunoassay (RIA) technique using gamma scintillation counter (I 125 calibrated), at Nuclear Research Laboratory, Division of Physiology and Climatology, IVRI, Izatnagar.Estradiol radioimmuno assay kits were obtained from Immunotech, France whereas progesterone radioimmunoassay kit was obtained from Bhabha Atomic Research Centre (BARC), Mumbai, India.Data were analyzed as per the method described by Snedecor and Cochran (1994) for mean, standard error, correlation and analysis of variance (ANOVA).Positive and significant (p<0.05)correlation was noticed between copper (0.55), zinc (0.60), manganese (0.58) and estrogen whereas iron (0.47) showed positive but non-significant (p>0.05)correlation.Similarly copper (0.52) and manganese (0.54) showed positive and significant (p<0.05) with progesterone whereas iron (0.36) showed positive but non-significant (p>0.05)correlation and zinc (-0.33) showed negative and non-significant (p>0.05)correlation.

dIScuSSIon
Lower level of copper and iron observed in group A may be due to the lower level of these minerals in milk (Radostitis et al., 2007) which constitutes the main diet of young animals.Higher levels of iron in group B and C heifers may be due to the presence of adequate amount of iron in fodders (Yatoo et al., 2011).Lower levels of copper, zinc and manganese in group C heifers may be due to the deficiency of these trace minerals in fodders (Yatoo et al., 2013).Lower levels of trace minerals in group C heifers may also be due to the increase in requirements of the trace minerals with increasing age for different developmental processes (NRC, 2001) including reproductive development and hormone synthesis (Smith et al., 2000).Increase in estrogen with age of heifers may be due to activation of reproductive organs or processes in which trace minerals play an important role (Boland, 2003;Ceylan et al., 2008).Decrease in progesterone levels may be due to inhibitory effect of estrogen on progesterone along with increased release of estrogen in adult heifers.Trace minerals play a vital role in estrogen and progesterone synthesis and production.Copper and zinc are involved in regulating progesterone production by luteal cells via involvement of superoxide dismutase (Sugino et al., 1999).Zinc is a component of insulin like growth factors involved in regulation of granulosa cell estradiol production during follicular waves in cattle (Kobayashi et al., 2006).Manganese acts as a cofactor in the synthesis of cholesterol which is precursor of steroids like estrogen and progesterone (Nocek et al., 2006).Correlation between iron and progesterone can be attributed to its role in ovarian activity (Qian et al., 2001).

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Copper, zinc and manganese levels followed same trend as estrogen levels with variation in age suggesting positive interrelation as reflected from positive and significant (p<0.05)correlation.But mere positive and significant correlation cannot interpret the importance of this interrelation because of involvement of many enzyme systems in hormone regulation.As in case of zinc, iron and progesterone though the correlation was either negative or non-significant but the role of zinc and iron in progesterone production or ovarian function is well reported (Sugino et al., 1999;Qian et al., 2001).
From the present study it can be inferred that trace minerals and steroid hormone have important interrelation.Deficiency of former can affect latter and consequently reproductive performance of animals especially in heifers.
Hence maintenance of appropriate serum mineral levels by proper supplementation can boost production and reproductive performance.

AcKnowlEdGMEnt
Authors are thankful to Director Indian Veterinary Research Institute for their kind support in this research.

conflIct of IntErESt
Authors declare that they have no conflict of interest.

table 1 :
Mean±SE of trace minerals in heifers .05)increasewithincrease in age.Zinc and manganese levels showed significant (p<0.05)decrease with increase in age.Copper and iron showed non-significant (p>0.05)difference between different age groups whereas zinc and manganese showed significant difference between group A and group C heifers.Mean±SE of hormones are given in Table2.Serum estrogen significantly (p<0.05)increased with increase in age whereas serum progesterone showed non-significant (p>0.05)decrease with increase in age.
rESultSMean±SE of trace minerals are given in Table1.Lower levels of copper and iron were noted in group A and C heifers than the group B heifers.Lower levels of zinc and manganese were observed in group B and C heifers than the group A heifers.Copper showed non-significant (p>0.05)decrease whereas iron showed non-significant (p>0

table 2 :
Mean±SE of hormones in heifers