Correlation of Magnesium contents from soil, forages and small ruminants in Punjab, Pakistan

The study was aimed to investigate magnesium level in soil samples, forages grown in that soil and plasma of grazers (goat and sheep) taken from District Bhakkar, Mianwali and Sargodha. The present study was carried out during 2016. The findings unveiled that the mean magnes ium concentrations in soil of District Sargodha, Mianwali and Bhakhar varied from 40.49 to 50.14, 48.83 to 54.53 and 54 to 59.68 magnesium/kg sequentially. The highest Magnesium content was found in Bhakkar soil. The mean concentrations of Magnesium in forage samples were found between 32.75-39.13, 40.24-42.24 and 49.55-50.35 mg/kg for Sargodha, Mianwali and Bhakhar, independently. The average Magnesium contents in the blood plasma of goats fed on these forages were between 31.4-34.79 magnesium/L in Sargodha, 29.93-33.19 magnesium/L in Mianwali, and 20.76-30.85 mg/L from Bhakkar. In sheep blood samples, Magnesium levels in Sargodha, Mianwali and Bhakhar extended from 25.81 to 32.727, 25.14 to 31.43 and 15.93 to 17.76 mg/L, respectively, indicating that there is no need for magnesium supplementa t ion for small grazers of this area.


Introduction
The health, growth and production rate of livestock rely on quality of forages [1,2]. Forages are source of essential nutrients for grazing livestock. Plants also possess nutritional requirements for their growth that are meant to be delivered by soil [3]. The results of minerals deficiency in soils are retarded growth of plants and lower yields [4]. The level of minerals impacts on soil pH which ultimately affects plants [5,6]. Mineral elements are required by the ruminants to fulfill the metabolic and growth need of the body. Forages contain adequate macro and microelements to meet these requirements [7,8]. There is no information about the effect of season on the natural pastures and its mineral content, protein and fiber components. The adequacy and availability of minera l element from pastures affects the health and performance of grazing livestock. The forage required by the goat and sheep must be replete with various nutrient so that it can help maintain better health of rumina nts [9]. The extent up to which the nutrients of the forages are available for livestock depends upon the quantity and bioavailability of nutrient found in the forage. It is often noticed that the nutrie nt found in the forage does not enter the animal body due to some reasons [10]. Magnesium, being involved in several metabolic pathways, is pivotal to the metabolism of plants [11,12]. The chlorophyll molecules contain Magnesium in the center which plays a significant role in the formation of different product such as fats, carbohydrates and its products and play role in enzymes functioning in forages. The deficiency of Magnesium may cause the chlorotic patches and yellow color appears in the vein of older leaves and leaves become whirled. To overcome the deficiency of metal, its foliar spray prepared in water is applied to the plants [13,14]. This research was aimed to find out the Magnesium residues in forages, soil samples and blood plasma of rumina nts (Goat and Sheep) to evaluate the bioaccumulation and the relation of the well-being of animals to ingestion of forages having the mineral ( Figure 1).

Materials and methods
Bhakkar, Mianwali and Sargodha districts were selected for the present investigatio n. Samples were taken from 10 sites in each district. These samples were thoroughly mixed to get composite samples in triplicate. Soil samples were taken with stainless-steel auger, 1.0 to 1.5 ft deep and stored in plastic bag. Forages such as Bajra (Pennisetum glaucum), Barsem (Trifolium alexanderium) and Oat (Avena sativa) were collected and sun-dried. From jugular vein, blood samples of five goats and sheep of each site were taken in heparinized tubes; plasma separated and was frozen at -20 o C. Soil and forages samples were sun dried and then kept in the oven to dry for three days at 72 o C. After drying, these samples (1g each) and blood plasma (1mL each) were digested by following standard wet digestion procedure [15] and then diluted to 50 mL and filtered. Samples were stored in tagged bottles for further process. To evaluate the magnesium concentratio n samples, Atomic Absorption Spectrophotometer (Model No. AA-6300, Shimadzu, Japan) was deployed [16]. Data were statistically processed using Minitab 16 software. One-way ANOVA (Analys is of Variance) and LSD (Least Signific a nt Difference) were used as advised by Steel and Torrie [17].
Pollution Load Index (PLI) was measured by the formula proposed by Liu  Current research values for Magnesium were higher than those found by Stojković et al. [28]. Correlation A significant correlation was noticed between soil-forage, between soil-blood plasma of selected grazers in Districts Sargodha and Mianwali. A signific a nt correlation was found between forageblood plasma and negative correlation between soil-forages and soil-blood plasma of goat and sheep in Bhakkar (Table 2).

Bio-concentration factor (BCF)
BCF of magnesium in forage was greater in Bhakkar and Mianwali as compared to Sargodha. The lowest BCF was observed in Sargodha while the maximum BCF was seen in Bhakkar. BCF of blood plasma of goats in Sargodha was greater as compared to that of Bhakkar. Similarly, BCF of blood plasma of sheep of Sargodha and Mianwali sampling was greater as compared to Bhakkar (Table 3). Bio-concentra tio n factor serves as a pivotal element for determination of exposure to heavy metals moving along the food chain. The values of BCF ˃ 1 indicate the capacity of plant for metal accumulation while BCF ˂1 conveys the idea of metal absorption without accumulation [29]. BCF for magnesium at Bhakkar, Sargodha and Mianwali sites was ˂ 1.

Pollution Load Index (PLI)
The PLI for magnesium was higher in Bhakkar soil samples as compared to Sargodha and Mianwali. The pollutio n level or contamination factor of magnes ium was ˃1 and the soil is designated as contaminated ( Table 4). The degree of pollution can be assessed using PLI. Soil is considered to be polluted if PLI>1, while the soil is considered to be noncontaminated if PLI<1 [30]. The pollutio n level of magnesium greater than 1 indicated contamination of soil.