IntroductionTop

Commercial layer enterprise is a common subsection within Nigeria poultry industry. The productive performance of commercial layers to a great extent depends on health management during their growing phase (Olawumi, 2011). Pullets raised in proper health condition tends to reach and maintain optimal productive performance during their laying phase while pullets raised with health challenges may be inconsistent in production or become unproductive at the laying phase (Olawumi, 2011). Many health challenges encountered in poultry production arise from bacteria and coccidial infections (Adene, 1996).

Bacterial infection is of great economic importance in poultry production. Many poultry diseases result from colonization of the gut by harmful bacteria which are often characterized by high bacteria load (Albazaz & Buyukunal Bal, 2014). Coccidiosis is a crucial and common disease in poultry production (Ola-Fadunsin & Ademola, 2014). It is characterized by invasion of the gut by Eimeria parasites leading to tissues damage, haemorrhage, weight loss and death (Ola-Fadunsin & Ademola, 2014; Eke et al., 2016). Bacterial infections and coccidiosis significantly increase cost of production and causes huge economic loss in poultry industry (Ganguly & Praveen, 2016; Lawal et al., 2016). Overtime, these diseases have been prevented by the use of various conventional antibiotic and anticoccidial drugs (Aarestrup & Jenser, 2007; Thangarasu et al., 2016).

Emergence of drug resistant bacteria and harmful drug residue in animal products has led to restriction in use of conventional drugs (Diarra & Malouin, 2014; Dhama et al., 2015; Gonzalez-Ronquillo & Angeles-Hernandez, 2017). Moreover, there is increasing public awareness on harmful drug residue in animal products and necessity for food safety, leading to increase in demand for organic-based products (Biswas et al., 2010). These developments necessitate search for viable substitutes to conventional drugs for growth promotion, prophylactic, therapeutic and immune enhancement purposes, readily available at low cost without detrimental effects.

An alternative gaining considerable recognition is the use of medicinal plants which are residue-free, readily available and potent against diseases (Diaz-Sanchez et al., 2015). Several herbal materials have been studied for their prospective benefit as growth-promoting, prophylactic, therapeutic and immune-enhancing agents. Many of these studies have reported positive and promising results (Molan & Faraj, 2015; Nghonjuyi, 2015; Attia et al., 2017a,b; Navidshad et al., 2018). However, the use of medicinal plants in poultry production has not been fully established and investigation on herbal materials is still in progress in order to fully explore the benefits of available medicinal plants to the poultry industry.

Petiveria alliacea L. is a potent herb whose medicinal benefits to the poultry industry have not been explored. P. alliacea belongs to the family Phytolaccaceae, the herb is native to North, Central and Southern America and the Caribbean with wide spread introduced population in Nigeria (Schmelzer & Gurib-Fakim, 2008; USDA-ARS, 2020). The plant has been used successfully in folk medicine to treat various ailments and conditions (Brown, 1995; Randle et al., 2018). Scientific investigations showed that the plant possess antibiotic, anti-oxidant, anti-carcinogenic, anti-cancerous, anti-inflammatory and immuno-modulatory properties (Kim et al., 2006; Williams et al., 2007; Santander et al., 2012; Pacheco et al., 2013; Ekunseitan et al., 2016; Oluwa et al., 2017). Some researchers (Sobayo et al., 2017, 2018a,b; Muhammad et al., 2019; Odetola et al., 2019) have investigated the growth and performance enhancement abilities of P. alliacea on poultry species. However, there is no substantial information on therapeutic benefits of the plant to poultry species. Hence, this study investigated the antimicrobial, immunomodulatory and hepatomodulatory effects of aqueous extracts of P. alliacea root and leaf on growing pullets.

Material and methodsTop

This experiment was carried out according to animal welfare guidelines of Animal Welfare Committee, Colle ge of Animal Science and Livestock Production, Federal University of Agriculture Abeokuta, Nigeria. The study was carried out at the research unit of Livelihoods Support and Development Centre (SLIDEN AFRICA), Abeokuta, Ogun State, Nigeria.

Extraction of Petiveria alliacea root and leaf

Aqueous extraction was carried out according to the method outlined by Nodu et al. (2016). Fresh roots and leaves of P. alliacea were sourced from Kotopo area of Abeokuta, Ogun State, Nigeria. The roots and leaves were rinsed in clean water to remove adhering dirt. Using a sensitive weighing scale, 15, 30 and 45 ɡ samples of fresh roots and leaves were taken and each sample was blended separately in 1-L of clean water. Each blended mixture was separated by filtration using 0.1 mm sieve screen. The root and leaf particles were discarded while filtrate from each mixture was presented to experimental birds as drinking water according treatment.

Experimental managementf

A total of 288 eight-weeks-old Isa brown pullets were used for this study which lasted for 10 weeks. The pullets were arranged in a 2×4 factorial experimental layout in a completely randomised design. There were eight experimental treatments replicated three times with 12 birds per replicate. The treatments consisted in birds administered aqueous extract of P. alliacea root at 0 ɡ/L (control), 15 ɡ/L, 30 ɡ/L and 45 ɡ/L concentrations and leaf at 0 ɡ/L (control), 15 ɡ/L, 30 ɡ/L and 45 ɡ/L concentrations. The extracts were presented to pullets via drinking water on two consecutive days per week throughout the experiment. Extracts presented met and exceeded daily water requirement of the birds on all occasions of administration. Experimental birds were raised in a deep litter system and fed grower mash diet formulated according to National Research Council recommendation (Table 1). Pullets in all treatments were free of antibiotic and anticoccidial drugs throughout the experiment.

Data collection

Fourteen days prior to the end of the experiment, four birds were randomly selected from each replicate of all treatments. These birds were housed in a separate cage on treatment and replicate basis and administered Newcastle Disease Vaccine (NDV) lasota strain via drinking water for future serum antibody test. Routine administration of P. alliacea extracts was maintained.

Table 1. Composition of the experimental diet

CP: crude protein. ^[1] Premix (composition per kg diet): Vita-mins B1, B2, B6, 0.02 g; Vitamin K3, 3 g; Vitamin E, 30 g; biotin, 0.05 g; folic acid, 1.5 g; choline chloride, 250 g; nicotinic acid, 30 g; Ca-pantothenate, 15 g; Co, 0.4 g; Cu, 8 g; Fe, 32 g; I, 0.8 g; Zn, 40 g; Mn, 64 g; Se, 0.16 g; butylated hydroxytoluene, 50 g.

Faecal Eimeria oocyst count

Anticoccidial effect was estimated by Eimeria oocyst counts in faeces of experimental birds. At the end of the experiment (18 weeks of age), dropping trays covered with aluminium foil were placed on the floor of each rea-ring unit. Fresh faecal droppings were picked from each replicate of all treatments into separate labelled sterile bottles using sterile forceps. The bottles were placed in ice and transported to the laboratory for egg count analysis using McMaster egg counting technique as described by Zajac & Conboy (2012).

Intestinal total bacteria count

Antibacterial effect was estimated by evaluating intestinal total bacteria count in experimental birds. At the end of the experiment, live bodyweights of birds selected earlier were determined after which they were slaughtered. Small intestines of the slaughtered birds were carefully isolated from the carcass and placed in separate labelled sterile bottles. The bottles were placed in ice and trans-ported to the laboratory for bacterial count. Total bacteria count was carried out on mixed digesta from the small in-testine using viable count method as described by Bassiri (2013). The colony-forming units (cfu) were expressed as logarithm to base 10.

Lymphoid organ weight and serum antibody against Newcastle disease vaccine

Immunomodulatory effect was estimated by evaluating weight of lymphoid organs and serum antibody titre against NDV.

Lymphoid organs (bursa, thymus and spleen) were carefully isolated from the carcass of slaughtered birds, weighed using a sensitive weighing scale and expressed as percentage of live bodyweight.

Serum antibody titre against NDV was determined by haemagglutination inhibition (HI) test. Blood (2 mL) was collected aseptically from each slaughtered bird into labelled plain bottles. The blood samples were allowed to clot and the sera separated into different labelled sterile bottles. The samples were transported to the laboratory for HI test using the method described by OIE (2008). The HI titre values were expressed as logarithm to base two.

Liver weight and histopathological examination

Hepatomodulatory effect was evaluated by liver weight and histopathological examination. Livers of slaughtered birds were weighed using a sensitive weighing scale and expressed as percentage of live bodyweight. The livers were fixed in 10 % formalin solution and processed for histopathological examination according to Slaoui & Fiette (2011). Hepatic changes were viewed with a BA410E Elite Research Compound Microscope and photomicrograph taken with aid of an Amscope MU900 digital camera.

Statistical analysis

The experiment was arranged in a 2×4 factorial ex-perimental layout in a completely randomized design. Data collected were subjected to 2-way Analysis of Variance, significant (p<0.05) differences between treatment means were determined using Duncan Multiple Range Test as contained in Statistical Analysis Software (SAS, 2010) package.

The model of the study was:

where Y_ijk = output parameter, µ = overall mean, T_i = ith effect of plant part (i = root, leaf), L_j = jth effect of con-centration of extraction (j = 0 ɡ L^-1, 15 ɡ L^-1, 30 ɡ L^-1, 45 ɡ L^-1), (TL)_ij = the interactive effect of plant part and con-centration of extraction, k = k_th observation in a treatment (i, j), and ε ijk = residual error.