1. Introduction

Broiler birds have been sources of quality protein supplies and other nutrients needed for growth and development in man [1,2]. They are also potential means of income generation and employment whether in a small and large-scale production productions [3]. Besides, other considerations for broiler production border on their short generation intervals, faster growth rate, lower age at maturity, high meat yield at slaughter and absence of cultural barriers or taboos to consumption [4, 5]. According to Wattanachant [6], broilers are also rated and appreciated for their low cholesterol level, abundance of minerals and vitamins than red meat.

As an efficient management practice, Oluyemi and Roberts [7] reported that the choice and adoption of litter can optimize birds performance and cost of production. According to Ritz et al [8], litters are bedding materials spread on the floor of the broiler pens to absorb birds droppings. In the same view, Fanimo [9] also reported on the importance of litters as they provide insulation from cold and protective cushion between the birds and the floor. Several studies on litters as absorbents for faecal droppings and spilled water from drinkers had been cited by Algers and Severberg [10]. Although in the earlier study on litters, Austic and Nesheim [11] suggested that an effective litter material must be readily available, absorbent, lightweight and non-toxic. Whereas David [12] noted that where high temperature and humidity prevail, litter has been known to favour the proliferation of pathogens and parasites. He also concluded that the effect of different litter materials is dependent on the physic-chemical characteristics of the materials, much the same way that geographic locations determine the types of litter selected for broiler production. Broiler birds can be managed under extensive, semi-intensive and intensive systems but in this experiment, they are reared in the deep litter system where the use of litter is applicable. It is the most common method of raising broilers and the droppings are good source of organic fertilizer on degraded soil.

Soil is often degraded due to constant use and there is need to replenish either by the use of organic matter or chemical fertilizer [13]. Due to increase in Nigerian population shifting cultivation method of farming is no longer sustainable, hence chemical fertilizers often produce plants products quickly and in large quantities. But over time, they become less and less effective and eventually leave the soil arid with some xenobiotic chemicals and the soil depleted of essential nutrients [14]. Consequently, attention is now shifting towards organic manures as soil amendment for crop production on soils [15]. Soil therefore acts as a long-term sink for nutrients and heavy metals which have residence times ranging from hundreds to thousands of years, depending on the element (s) and properties of the soil. The effects on soil nutrients quality on the germination of cowpea bean were used as a model in this study, since seeds are well protected against various stresses which soon after imbibitions and subsequent vegetative developmental processes become stress-sensitive in general.

In the present study, the effects of different litter levels on the physiological parameters of birds and the quality of poultry droppings on soil productivity and percent germination of cowpea seeds were assessed.

2. Materials and Methods

2.1. Experimental Sites

The research was conducted at the poultry unit of the Teaching and Research Farm, of the Faculty of Agriculture, University of Uyo, Nigeria. The area lies between latitudes 4⁰ 52¹ and 5⁰ 3¹N and longitudes 7⁰ 51¹ and 8⁰ 20¹ E and latitude 65 m from the sea level. The area is divided into two distinct seasons, the wet and dry seasons. The wet or rainy season begins from April and lasts till October. It is characterized by heavy rainfall of about 2500-4000 mm per annum [16].

2.2. Birds’ Management

A total of 96 Top Notch day old chicks weighing 40 g were obtained from an accredited farm. These chicks were brooded and managed for 4 weeks under deep litter system using wood shavings. Adequate quantity of weighted pelletized vital starter mash and drinking water were provided adlibitum and the needed warmth was supplied from electricity. The birds were also administered with appropriate medications which included newcastle vaccines, lasota, coccidiostats and word expellers. At 5^th week, the birds were transferred from brooding house to finisher pens where weight pelletized vital finisher mash, sufficient drinking water and other management practices were maintained till the experiment was terminated at 8^th week.

The poultry experiment had 4 treatments and with three replicates each. Treatments were different litter levels, with the following combination: 2.5kg litter of wood shavings for T₁ were labeled as T₁R₁, T₁R₂, T₁R₃; 2.0kg litter (T₂) were T₂R₁, T₂R₂, T₂R₃, T₂R₄; 1.5kg litter (T₃) as T₃R₁, T₃R₂, T₃R₃, T₃R₄ and T₄ without litter (control).

2.3. Determination of Physico- chemical Properties of Soil and Dropping

Particle-size distribution was determined by hydrometer method [17]. Soil pH was measured in distilled water (1:2.5) with the use of glass electrode pH meter. Available phosphorus was determined using bicarbonate extraction, with acid reductant. The exchangeable cations (Calcium, Ca; Magnesium, Mg; Potassium, K; and Sodium, Na) in the soil and dropping were determined by first extracting with 1M NH₄ OAc (ammonium acetate) solution [18]. Organic Carbon (OC) was determined by loss-on-ignition [19]. Nitrogen was determined in form of ammonium (NH₄-N) and nitrate (NO₃-N) by absorbance measurement as described by Nelson [20]. Heavy metals were determined by the perchloric acid digestion method. Two grammes of air-dried soil which had been passed through a 2 mm sieve were weighed into a 150 ml beaker. This was added 20 ml of concentrated HNO₃, followed by 15 ml of HClO₄ after it was allowed to stand for one hour. The mixture was then digested on a hot plate till it turned white. The residue was dissolved in dilute HCl and then filtered. The filtrate was used for the determination of Zn, Cu and Pb by atomic absorption spectrophotometry. Consideration was taken of the dilution factor in concentration calculations.

2.4. Green House Study

Surface soil was collected at a location near the Department of Forestry Teaching and Research Arboretum. The soils were air dried, crushed and sieved through a 2-mm sieve. Sub samples were taken for analysis of some soil parameters i.e. pH, organic C, electrical conductivity (EC₂₅) water holding capacity (WHC), and moisture content were determined using the methods described by Gupta [21]. The soil was filled into poly pots (2 kg / pot) and was amended with 200 g of poultry droppings of different litter levels (2.5, 2.0, 1.5, 0 kg / 1.44 m²). Control was run side by side without any poultry manure amendment. All the tests and control were run in triplicates. In order to determine the effects of different litter levels in poultry manure on germination, cowpea (Vigna unguiculata) seeds were immersed in deionized water to eliminate the exogenous contamination. These seeds were embedded 1.0 cm deep in soil pots (2 kg) amended with different concentration of litter in poultry droppings and seedlings emergence rate was determined.

2.5. Statistical Analysis

Laboratory and field data collected from the treatment sets were subjected statistical analyses of multivariate statistical techniques, ANOVA and Bivariate spearman correlation analysis (separately performed for birds’ physiological and soil parameters) using SPSS for Windows (release Ver. 17. Inc. Chicago). Means were subjected to Duncan Multiple Range Test (DMRT). A significant difference among the parameters was concluded when the probability has a difference by 0.05.

3. Results and Discussion

3.1. Effects of Different Litter Levels on Birds’ Performance

Results of Table 1 showed significant difference (p < 0.05) among the parameters; Bodyweight, Feed Intake and Droppings from broilers raised at different litter levels. Bodyweight varied significantly across the treatments p<0.05 through weeks 5, 6, 7, and 8. Value for week 8 (1.72kg) under T₁ was higher than those of other treatments whereas T₂ at week 5 had shown significant increase (2.11kg) in body weight than other treatments T₁, T₂, T₃ and T₄. This result of litter quality on bodyweight gain and broiler performance is in agreement with the results reported by Ritz et al., that litter quantity and quality management could increase feed intake of broilers and body weight as they grow older. From the view point of cost effectiveness, birds receiving treatments T₂ and T₃ are best for table between weeks 6 and 7, because beyond this period, there is likelihood of weight reduction.

Table 1. Effect of different litter levels on body weight, feed intake and droppings on broilers at 5 to 8 weeks

Besides, broilers in T₁ (2.5 kg), T₂ (2.0kg) and T₃ (1.5 kg) through weeks 5,6,7 and might not expend their metabolic energy to counteract cold from the floor but broilers in T₄ (0.0 kg) without litter might have utilized their metabolic energy towards heat production for warmth instead of growth, thus the observed low bodyweights.

Data on the Table 1 also indicated that the feed consumed by birds in T₂ and T₃ were 1.19 and 1.11 kg respectively at week 8 and were not significantly (p > 0.05), whereas the mean feed intake for birds in treatments T₁ and T₄ varied significantly (p < 0.05) (1.33 kg and 0.97 kg). This same trend in Feed intake was observed across other treatments in weeks preceding week 8 and this could be attributed to comfort and convenience provided from litter while birds in T₄ without litter suffered discomfort and body injuries that adversely affected their feed intake. Birds performance can be optimized through appropriate choice and adoption of litter management that has lent credence to the above development.

In week 8, significant difference (p < 0.05) occurred in values obtained for droppings in T₁ (2.5kg) and T₄ (0.0 kg) but values 13.60 and 13.79 for T₂ (2.0 kg) and T₃ (1.5 kg) did not differ significantly (p>0.05). Other weeks preceding week 8 also experienced similar trend across their treatments whereby T₁ showed higher values while lower values were recorded for T₄. Significant values for T₁ and T₄ presented in Table 1 has corroborated in the report of Algers and Sverberg that litters absorb faecal droppings in a manner that reduce contact between birds and droppings.

From Table 2, correlation analysis revealed negative correlation between the treatments, feed intake and dropping while positive correction between dropping and feed intake were also observed. This implies that litters in poultry pens enhance feed consumption and vice visa. On the other hand, it also confirmed that increase in feed intake gave rise to the increase in the quantity of dropping.

Table 2. Correlation analysis to show relationship among treatment in feed intake, bodyweight and droppings

3.2. Influence of Litter Levels on Quality of Poultry Droppings as It Affects Soil Nutrients

The soil collected was dark brown, porous with small aggregates, organic C 4.61%, pH 5.1, EC₂₅ 178.5 micro Siemens cm^-1, water holding capacity (WHC) 23% and moisture content of 2.13%. Exchangeable cations were significantly higher in T4, but exponentially decreased with the level of litter inclusion (Table 3). The mineral element originated from soil and poultry droppings dissolved in water for plant roots’ absorption but those required in small quantity for optimum performance are regarded as traced elements. The concentration of these metals can however be increased to become potential pollutants if heavy metals containing in agronomic activities are introduced into the environment [22]. Concern over the presence of heavy metals in an environment arises from the fact that they cannot be broken down into non toxic forms. Thus once aquatic ecosystems are contaminated by heavy metals; they remain a potential threat for many years. The results obtained are presented in Table 3. Clearly indicated that the two treatments (Litter and non-litter droppings) exhibited different concentrations of heavy metals. It is evident that litter inclusion in dropping had high degree of variation of heavy metals level.

Table 3. Some chemical properties and heavy metals of the poultry manure used in the study

3.3. Seed Emergence of Vigna unguiculata in Poultry Dropping Amended Soil

As shown in Fig. 1, delayed germination of the Vigna unguiculata in soil amended with treatment 4 resulted from the relative toxicity of heavy metal concentration. Kelly et al., [23] observed that seed germination was gradually delayed in the presence of increasing concentration of traced elements. Seed emergence results obtained after 10, 15, and 20 days of planting revealed that at lower concentration of heavy metal, little or no harm is done to seed viability but at higher concentration, germination was retarded (Fig. 1). Order of toxicity of these heavy metals was found to be T₄ > T₃ > T₂ > T₁ > un-amended soil (check).

Those seeds emerged in litter’s free dropping (T₄) showed resistance through their delayed germination. Consequences of the presence of toxic metals and organic binding effect lead to delay in germination of seeds that in turn will affect the crop yield. If plant tissues accumulate these heavy metals then it can ultimately affect the human health in the form of poisoning (Lead poisoning). Applications of T₄ in the soil leads to the decreased value of this soil above 80 % with reference to its productivity and ultimately affect the human health.

4. Conclusions

Litter quantity and quality are essential, management factors in broiler production as applicable to deep litter system. This is due to its several advantages that enhance feed intake, body weight gain and minimal faecal droppings, all which also promote growth, good health and performance among broilers as compared with those broilers that were raised without litter.

Heavy metal contamination of soil via litter’s free droppings (poultry manure) application can induce serious problem to the soil, cropping, vegetation and in turn human health. Heavy metal accumulation by plant tissues and its presence in soil persistently is not healthy for the soil environment. So poultry manure containing 2.5 Kg per 1.44 m² floor space (T₁) is most preferred and is recommended because its amendment in soil derived from acid sand parent material is not toxic to plant.

Figure 1. Percent cowpea seed emergence after 10, 15 and 20 days planted in poultry dropping amended soils

ACKNOWLEDGEMENTS

We would like to appreciate Dr Beckley Ikhajiagde and other anonymous reviewers for their constructive suggestions during the review process.