Effect of amaranth leaf meal on performance, meat and bone characteristics of Boschveld indigenous chickens

Abstract

This study aimed to determine the effect of amaranth leaf meal inclusion on the performance, meat, and bone characteristics of indigenous Boschveld chickens. A total of 200, day-old, indigenous Boschveld chicks were randomly allocated to five dietary treatment levels in a completely randomised design, with each treatment having four replicates and each replicate having ten chicks. Amaranth leaf meal (ALM) inclusion levels used in this study were 0, 5, 10, 15, and 20%. Bodyweight and feed intake were measured weekly to calculate the feed conversion ratio. Meat and bone characteristics were measured, and the general linear model of statistical analysis software was used to analyse collected data. Chickens which were offered diets with 0 and 10% ALM inclusion levels had higher (p < .05) breast meat weights than those which were offered diets with 5, 15, and 20%. Chickens that were offered diets with 15% ALM levels had higher (p < .05) abdominal fats weights than those offered diets with 0, 5, 10, and 20%. Chickens which were offered 20% ALM in their diets, had higher (p < .05) meat tenderness than those offered 0, 5, 10, and 15%. Chickens which were offered diets with 15% ALM had a lighter and redder (p < .05) breast meat colour than those offered 0, 5, 10, and 15% ALM inclusion levels. At the age of 21 and 42 days, chickens which were offered diets containing 5, 15, and 20% ALM had higher (p < .05) tibia calcium and phosphorus contents than those on diets having 0, and 10% ALM inclusion levels.

Highlights

• Amaranth leaf meal inclusion in diets has no adverse effect on indigenous Boschveld chickens performance

• Amaranth leaf meal inclusion in diets increase meat tenderness and shear force of chickens

• Amaranth leaf meal showed to favour bone physical characteristics and more bone minerals deposition of indigenous Boschveld chickens.

Keywords:

• Indigenous chickens
• meat quality
• minerals
• tibia bone
• amaranth

Introduction

The poultry industry in developing countries such as Africa is facing major challenges, with feed cost being the bigger challenge due to the high prices of protein and energy sources (Abbas 2013). Currently, vegetable leaves have gained the attention of being processed as leaf meals to be used in poultry diets. Plant leaves such as moringa oleifera, Anacardium occidentale, Psidium guajava, bitter leaf, etc. and several medicinal plants i.e. garlic, onion, thyme, spearmint, pepper, yucca, black cumin and ginger have been extensively used in poultry feeding (Selim et al. 2021). The plant materials used in poultry feeding has been reported to be phytogenics with pharmacological effects and widely used monogastric animals feeding. In poultry nutrition, the effects of a wide range of phytogenics on feed efficiency, antimicrobial, coccidiostatic, anthelmintic, and immune-stimulating have been done (Saleh et al. 2014; Abou-Elkhair et al. 2018; Saleh et al. 2018).

According to Saleh et al. (2018) medicinal herbs and phytogenics such as spearmint, thyme, and yucca; seeds of pepper and black cumin; roots of ginger; and developing bulb part of onion and garlic has pharmaceutical activities for antioxidant, antimicrobial, and antiallergic; and a combination of garlic and ginger prevents high blood pressure, high cholesterol level, and cholesterol oxidation which are the primary causes of atherosclerosis, the precursor of cardiovascular diseases. Studies showed that medicinal herbs and phytogenics have several bioactive compounds, including carotenoids, saponins, phenolics, alkaloids, and flavonoids (Selim et al. 2021), which have been shown to increase appetite, carcase yield, enhance digestive enzyme secretion, and stimulate an immune response, and encourage anti-bacterial and antioxidant properties (Abou-Elkhair et al. 2018; Mahfuz and Piao 2019; Su and Chen 2020).

Currently, amaranth leaf meal is being focussed widely as another probable leaf meal in poultry feeding (Manyelo et al. 2020). Amaranth is a drought-tolerant crop rich in nutrients such as protein and minerals (Jimoh et al. 2019; Sarker and Oba 2019; Manyelo et al. 2020). For many years amaranth plants have not been studied by researchers but recently they have gained attention due to their nutritional value and also being a fast grower plant.

Normally high meat yield is one of the desirable traits which are being considered (Hafeez et al. 2014), though with its high yield chickens tend to have leg problems which might result in locomotion difficulties (Sgavioli et al. 2016). Bone minerals are regarded as good indicators of bone health (Ziaie et al. 2011), which in turn depend on their mineral contents, especially calcium and phosphorus (Hafeez et al. 2014). Amaranth has an appreciable amount of minerals that can contribute to improved bone mineral deposition in chickens. However, there is no evidence in the literature on the influence of amaranth leaf meal inclusion on performance, meat quality, and bone characteristics of indigenous Boschveld chickens. Therefore, there is a need to explore the amaranth leaf meal inclusion level on performance and meat quality, and bone characteristics of indigenous Boschveld chickens.

Materials and methods

Study site

The study was conducted at the University of Limpopo Animal unit (latitude of 27.55°S and longitude of 24.77°E). The ambient temperature at the study site ranges between 20 and 36 °C in the summer months (November - January) and between 5 and 25 °C in the winter months (May – July). Mean annual rainfall ranges between 446.8 and 468.44 mm. This study was conducted during the winter period (May-July).

Housing and management of chickens

A total of 200, day-old, male indigenous Boschveld chicks were brought from a local hatchery. The chickens were housed in an open-sided structure and, the long axis was situated along an east-west direction for proper ventilation in 1 m² pens constructed using wire mesh. Moreover, the house was a controlled house with temperatures maintained at 30 to 33 °C and 23 to 25 °C during the starter and grower phases, respectively. Paraformaldehyde was used to disinfect the poultry house two weeks before the start of the experiment. Wood shaved sawdust was used as bedding for the chickens and it was changed on weekly basis. Feeders and drinkers were washed with disinfectants on daily basis. Drinkers and feeders were cleaned daily in the morning before being used. The experimental period lasted for 91 days. Ground feed and water were provided ad libitum throughout the experimental period and a continuous lighting regimen of 23 h lighting and 4-h darkness was provided using 175watt infra-red ruby lamps.

2.3. Experimental diets, design, and procedures

The chicks, had an initial live weight of 42 ± 8 g/bird, were received from a local hatchery and randomly allocated to five dietary treatment levels in a complete randomised design, with each treatment group having four replicates and each replicate having ten chicks. Amaranth leaf meal inclusion levels were at 0, 5, 10, 15, and 20%. Amaranth cruentus (L) leaves, which were used in the present study, were grown under a controlled field trial in the North-West Province, South Africa. The mean temperatures around the area are above 22°C in summer and below 20°C in winter and lie at a latitude of 25.6200°S and longitude of 27.9800°E. The aforementioned variety was grown in September 2019, under dryland conditions, which receives a mean annual rainfall of less than 250 mm. Amaranth leaves were hand-harvested. Thereafter, harvested leaves were independently dried in a well-ventilated laboratory to obtain a constant weight and milled through a 1 mm sieve into powder, by using a hammer mill, before being subjected to the analysis and formulated diets (Tables 1, 2 and 3).

Table 1. Proximate composition (g/100g), gross energy (kcal/g), and amino acids composition (%) of Amaranthus cruentus leaf meal.

Composition (g/100g)	ACLM
DM	92.65
CP	23.23
CF	17.14
NDF	15.40
ADF	7.14
ADL	1.95
GE	14.50
EE	1.12
Starch	0.38
Ash	21.18
Amino acids
Histidine	0.29
Arginine	0.90
Threonine	0.85
Lysine	1.73
Tyrosine	0.52
Methionine	0.34
Valine	1.51
Leucine	1.55
Serine	0.90
Glycine	0.94
Aspartic acid	2.16
Glutamine	2.94
Alanine	1.27
Proline	0.87
Isoleucine	0.83
Phenylalanine	0.66

Values are means of duplicate analysed amaranth leaves samples. DM: Dry Matter; CP: Crude Protein; CF: Crude Fibre; NDF, Neutral Detergent Fibre,; ADF: Acid Detergent Fibre; ADL: Acid Detergent Lignin; GE: Gross Energy; EE: Ether Extracts.

Table 2. Ingredients and calculated analysis of experimental starter diet.

Amaranth leaf meal (ALM) inclusion levels (%)
Ingredients	0	5	10	15	20
Maize (11.0% CP)	50.70	46.70	44.70	41.70	37.70
Groundnut cake (45.0% CP)	33.00	32.00	29.00	27.00	26.00
Soya bean meal (45.0% CP)	10.00	10.00	10.00	10.00	10.00
Fish meal (68.0% CP)	2.00	2.00	2.00	2.00	2.00
Bone meal (%)	2.50	2.50	2.50	2.50	2.50
Limestone (%)	0.50	0.50	0.50	0.50	0.50
Salt (Nacl) (%)	0.50	0.50	0.50	0.50	0.50
DL-methionine (%)	0.15	0.15	0.15	0.15	0.15
DL-Lysine (%)	0.15	0.15	0.15	0.15	0.15
Premix^a (%)	0.50	0.50	0.50	0.50	0.50
ALM	0.00	5.00	10.00	15.00	20.00
Total	100.00	100.00	100.00	100.00	100.00
Calculated analysis
Crude protein (%)	23.42	23.41	23.39	23.41	23.40
Crude fibre (%)	4.31	4.42	4.71	4.70	4.85
Ether extract (%)	7.21	6.41	6.40	6.71	6.51
GE(kcal/100g)	462.4	462.3	462.1	461.5	461.7

^a The ingredients contained in the vitamin–mineral premix were as follows (per kg of diet): vitamin A 12000 IU, vitamin D3 3500 IU, vitamin E 30.0 mg, vitamin K 3 2.0 mg, thiamine 2 mg, riboflavin 6 mg, pyridoxine 5 mg, vitamin B12 0.02 mg, niacin 50 mg, pantothenate 12 mg, biotin 0.01 mg, folic acid 2 mg, Fe 60 mg, Zn 60 mg, Mn 80 mg, Cu 8 mg, Se 0.1 mg, Mo 1 mg, Co 0.3 mg, I 1 mg. ALM: Amaranth Leaf Meal.

Table 3. Ingredients and calculated analysis of experimental grower diet.

Amaranth leaf meal (ALM) inclusion levels (%)
Ingredients	0	5	10	15	20
Maize (%)	40.00	40.00	40.00	40.00	40.00
Groundnut oil cake (45.0% CP)	20.00	18.00	15.00	12.00	10.00
Soya bean meal (45.0% CP)	8.00	8.00	8.00	8.00	8.00
Fish meal (%)	2.00	2.00	2.00	2.00	2.00
Wheat offals (%)	25.70	22.70	20.70	18.70	15.70
Bone meal (%)	2.50	2.50	2.50	2.50	2.50
Limestone (%)	0.50	0.50	0.50	0.50	0.50
Salt (NaCl) (%)	0.50	0.50	0.50	0.50	0.50
Dl-Methionine (%)	0.15	0.15	0.15	0.15	0.15
L-Lysine (%)	0.15	0.15	0.15	0.15	0.15
Vit/Min Premix^a (%)	0.50	0.50	0.50	0.50	0.50
ALM	0.00	5.00	10.00	15.00	20.00
Total	100.00	100.00	100.00	100.00	100.00
Calculated analysis
Crude protein (%)	20.00	20.00	20.00	20.00	20.00
Crude fibre (%)	4.52	4.57	4.71	4.70	4.73
Ether extract (%)	7.21	6.41	6.40	6.71	6.51
GE (kcal/100g)	462.40	462.30	462.10	461.50	461.70

^a The ingredients contained in the vitamin–mineral premix were as follows (per kg of diet): vitamin A 12000 IU, vitamin D3 3500 IU, vitamin E 30.0 mg, vitamin K 3 2.0 mg, thiamine 2 mg, riboflavin 6 mg, pyridoxine 5 mg, vitamin B12 0.02 mg, niacin 50 mg, pantothenate 12 mg, biotin 0.01 mg, folic acid 2 mg, Fe 60 mg, Zn 60 mg, Mn 80 mg, Cu 8 mg, Se 0.1 mg, Mo 1 mg, Co 0.3 mg, I 1 mg. ALM: Amaranth Leaf Meal.

Data collection

Growth performance

The live weight of each chicken was determined at the start of the experiment, thereafter, weekly weights were taken. The daily feed intake was determined by subtracting the weight of feed leftover from the total weight of the feed that was given to chickens daily and the difference was divided by the total number of chickens in each replicate for 13 weeks. The feed conversion ratio was then calculated using the following formulae: $$\text{Feed Conversion Ratio }\left(\mathrm{FCR}\right)=\frac{\text{Feed intake }\left(\mathrm{g}\right)}{\mathrm{Bodyweight}\mathrm{ }\left(\mathrm{g}\right)}$$

Meat characteristics

At the age of 42 and 91 days, three chickens per pen were slaughtered using the cervical dislocation method, following the recommendations of the University of Limpopo and the University of South Africa’s ethical guidelines. The birds were immersed in hot water to remove the feathers. Thereafter, carcase and meat parts’ weights were measured using an electronic weighing scale (Model: RADWAG AS 220/C/2). Meat parts’ pH was measured using the digital pH metre (Crison, Basic 20 pH Metre). Whereas, meat colour was measured using the HunterLab test (L*, a*, b*) system where L* is the lightness, a* is the redness, and b* is the yellowness. For sensory attributes, breast meat samples were frozen at −20 °C and later allowed to be defrosted for 24 hours in a cooler room. A preheated oven was set to 160 °C and was used to cook the breast meat. The meat sample of 1.5 cm thickness, was boiled for approximately 50 minutes and turned over every 25 minutes. Tongs were used for turning to avoid piercing the meat, which could lead to moisture escaping. A taste panel of 25 consumer assessors evaluated the meat for tenderness, juiciness, flavour, and overall acceptability by using a 5-point scale (Table 4). The shear force was done using Warner-Bratzler Shear Force procedures (Novakovi and Tomaševi 2017). For cooking loss, the chicken breast meats were weighed before and after roasting, and the percentage cooking loss was calculated as follows: $$\%\text{Cooking Loss}=\left[\left(\text{W}0-\text{W1}\right)/\text{W}0\right]\text{x1}00$$

Table 4. Evaluation score used by the sensory panel.

	Breast meat
Score	Tenderness	Juiciness	Flavour	Overall acceptability
1	Too tough	Much too dry	Very bad flavour	Strongly dislike
2	Tough	Dry	Poor Flavour	Dislike
3	Neither tough nor tender	Neither dry nor juicy	Neither bad nor good flavour	Neither dislike nor like
4	Tender	Juicy	Good flavour	Like
5	Too tender	Too juicy	Very good flavour	Strongly like

where W0 and W1 are the weights before and after cooking, respectively.

Furthermore, the tibia bone samples were cleaned from remnants and stored in isotonic saline at a temperature of -25⁰C. The geometric characteristics of the tibia bones were assessed by using the method of Muszyński et al. (2017). The content of minerals Calcium and Phosphorus were determined using the method of atomic absorption spectrometry (AOAC. 2012).

Statistical analysis

The statistical analysis was performed using the general linear model (GLM) procedure of SAS (2010). Where there were significant differences (p < .05), the treatment means were separated using the Duncan test at a 5% level of probability. Furthermore, collected data was evaluated for linear and quadratic effects using polynomial contrasts.

The quadratic models were fitted to the experimental data by using the procedure of SPSS (2017). The response in optimum feed intake, body weight, meat and bone characteristics of the Boschveld indigenous chickens, due to the inclusion of amaranth meal, were modelled using the following quadratic equation: $$\text{Y}=\text{a}+{\text{b}}_{\text{1}}\text{x}+{\text{b}}_{\text{2}}{\text{x}}^{\text{2}}$$

where y = optimum, a = intercept; b = coefficients of the quadratic equation; x = amaranth meal inclusion level and -b₁/2b₁ =x value for optimum response. The quadratic equation was the preferred model as it gives the optimum fit.

Results

Growth performance

The results of the effect of Amaranth leaf meal inclusion on initial weight, final weight, average daily gain, average daily feed intake, and feed conversion ratio of indigenous Boschveld chickens are presented in Table 5. Amaranth leaf meal inclusion level had no influence (p > .05) on final weight, average daily gain, average daily feed intake, and FCR of indigenous Boschveld chickens aged one to 91 days. ALM inclusion levels in the diets showed no linear (p > .05) or quadratic (p > .05) influences on final weight, average daily gain, average daily feed intake, and feed conversion ratio of indigenous Boschveld chickens.

Table 5. Effect of amaranth inclusion leaf meal (AML) on initial weight (IW), final weight (FW), average daily gain (ADG), average daily feed intake (ADFI) and feed conversion ratio of Indigenous Boschveld chicken aged 91 days.

	IW (g)	FW (g)	ADG(g)	ADFI (g)	FCR
AML%
0	32.36	1358.75	14.93	32.79	2.19
5	31.54	1531.71	16.83	31.32	1.86
10	31.96	1498.42	16.47	32.33	1.96
15	31.68	1559.06	17.13	34.76	2.02
20	31.74	1554.30	17.08	35.09	2.05
SEM	0.602	67.555	0.013	1.706	0.104
P-Value
Treatment	0.886	0.564	0.679	0.489	0.318
Linear	0.343	0.104	0.104	0.115	0.802
Quadratic	0.508	0.183	0.181	0.209	0.415

Diets: AML0% = a diet having no amaranth leaf meal inclusion, AML5%= a diet having 5 g/kg of amaranth leaf meal inclusion, AML10% = a diet having 10 g/kg of amaranth leaf meal inclusion. AML15% = a diet having 15 g/kg of amaranth leaf meal inclusion. AML20% = a diet having 20 g/kg of amaranth leaf meal inclusion. SEM: standard error of the mean.

Meat characteristics

Meat part weights of indigenous Boschveld chickens that were fed with ALM inclusion are shown in Table 6. ALM inclusion did not affect (p > .05) the carcase, breast, thigh, drumstick, or abdominal fats of indigenous Boschveld chickens aged 42 days. ALM inclusion had no effect (p > .05) on carcase or thigh weights of indigenous Boschveld chickens aged 91 days. Indigenous Boschveld chickens which were fed with diets containing 0 and 10% ALM inclusion levels, had higher (p < .05) breast meat weights than those fed with diets containing 5, 15, and 20% ALM inclusion levels. Similarly, chickens that were fed with diets having 0 and 10% had the same (p > .05) breast meat weights. Chickens fed diets having 0, 5, 10, and 20% ALM inclusion levels, had higher (p < .05) drumstick weights than those on diets having a 15% ALM inclusion level. Similarly, chickens on diets having 0, 5, 10, and 20% ALM inclusion levels, had the same (p > .05) drumstick weights. Chickens offered diets with a 15% ALM inclusion level, had higher (p < .05) abdominal fat weights than those offered diets with 0, 5, 10, and 20% ALM inclusion levels. ALM inclusion levels in the diets showed no linear (p > .05) or quadratic (p > .05) influences on meat part weights of indigenous Boschveld chickens.

Table 6. Effect of amaranth leaf meal (ALM) inclusion on meat part weights (g) of indigenous Boschveld chickens.

	Parameters
ALM%	Carcase	Breast	Thigh	Drumstick	Abdominal Fats
42 days
0	283.3	69.70	23.00	23.95	0.27
5	307	67.19	22.59	23.56	0.39
10	528.7	158.46	38.35	37.21	1.30
15	278.1	64.96	21.38	22.17	0.32
20	265.8	65.38	21.46	20.92	0.36
SEM	107.657	38.820	7.500	6.291	0.483
P-value
Treatment	0.412	0.385	0.464	0.389	0.545
Linear	0.884	0.947	0.882	0.775	0.949
Quadratic	0.560	0.659	0.653	0.592	0.600
91 days
0	938.17	221.45^a	85.37	83.27	3.92^b
5	877.50	189.37^b	77.60	77.37	3.32^bc
10	906.67	223.02^a	76.65	81.80	4.02^b
15	745.32	180.17^b	68.50	60.42	7.25^a
20	785.15	194.52^b	72.47	73.32	2.20^c
SEM	67.243	14.768	7.361	9.035	1.985
P-value
Treatment	0.063	0.023	0.078	0.091	0.016
Linear	0.072	0.377	0.053	0.248	0.948
Quadratic	0.286	0.724	0.117	0.565	0.974

^a,b,c,Means in the same row not sharing a common superscript are different (p < .05), Diets: ALM0%= a diet having no amaranth leaf meal inclusion, ALM5%= a diet having 5 g/kg of amaranth leaf meal inclusion, ALM10% =a diet having 10 g/kg of amaranth leaf meal inclusion. ALM15%= a diet having 15 g/kg of amaranth leaf meal inclusion. ALM20% = a diet having 20 g/kg of amaranth leaf meal inclusion. SEM: standard error of the mean.

The results of the effect of amaranth leaf meal (ALM) inclusion levels on the meat parts pH of indigenous Boschveld chickens are presented in Table 7. Amaranth leaf meal inclusion levels had no effect (p > .05) on breast, thigh, or drumstick pH of indigenous Boschveld chickens aged 42 and 91 days. Furthermore, meat parts pH of indigenous Boschveld chickens which were measured showed no linear (p > .05) or quadratic (p > .05) influences with increasing levels of ALM in their diets.

Table 7. Effect of amaranth leaf meal (ALM) inclusion on meat parts pH of Indigenous Boschveld chickens.

	Parameters
ALM%	Breast	Thigh	Drumstick
42 days
0	5.80	6.37	6.32
5	5.93	6.05	6.55
10	6.01	6.22	5.97
15	5.94	6.25	6.43
20	5.73	6.44	6.36
SEM	0.222	0.230	0.223
P-value
Treatment	0.314	0.412	0.385
Linear	0.771	0.554	0.963
Quadratic	0.069	0.258	0.926
91 days
0	5.75	6.06	6.18
5	5.57	5.96	6.17
10	5.63	6.03	6.15
15	5.63	6.04	6.10
20	5.72	6.24	6.40
SEM	0.087	0.139	0.095
P-value
Treatment	0.657	0.786	0.464
Linear	1.000	0.219	0.386
Quadratic	0.238	0.077	0.283

Diets: ALM0%= a diet having no amaranth leaf meal inclusion, ALM5%= a diet having 5 g/kg of amaranth leaf meal inclusion, ALM10% =a diet having 10 g/kg of amaranth leaf meal inclusion. ALM15%= a diet having 15 g/kg of amaranth leaf meal inclusion. ALM20% = a diet having 20 g/kg of amaranth leaf meal inclusion. SEM: standard error of the mean

The sensory attributes, cooking loss, and shear force values of indigenous Boschveld chickens that were fed with ALM inclusion are shown in Table 8. Amaranth leaf meal inclusion had no effect (p > .05) on juiciness, flavour, overall acceptability, or cooking loss of indigenous Boschveld chickens aged 91 days. Indigenous Boschveld chickens which were fed with a 5% ALM inclusion level in their diets, had higher (p < .05) meat tenderness and shear force values than those fed with diets containing 5, 10, 15, and 20% ALM inclusion levels. Moreover, indigenous Boschveld chickens on 0 and 20% ALM inclusion level diets had higher (p < .05) shear force values than those fed with 5, 10, and 15% ALM inclusion levels. There was a linear (p = .006 and .005) on breast meat juiciness and tenderness and quadratic (p = .044) effect on breast meat juiciness of indigenous Boschveld chickens with increasing levels of ALM in the diets.

Table 8. Effect of amaranth leaf meal (ALM) inclusion on sensory attributes, cooking loss, and shear force values of indigenous Boschveld chickens.

	Breast
ALM%	Juiciness	Flavour	Tenderness	Overall acceptability	Cooking loss	Shear force
0	3.00	3.33	2.33^c	3.00	37.15	17.72^a
5	4.00	3.67	4.00^a	3.67	34.37	15.20^b
10	3.33	3.33	3.00^bc	3.67	33.98	14.28^b
15	3.66	3.67	3.67^ab	3.33	25.14	12.95^c
20	3.33	3.67	3.00^bc	3.33	29.87	17.77^a
SEM	0.258	0.333	0.211	0.298	4.114	0.404
P-value
Treatment	0.147	0.871	0.002	0.512	0.065	0.003
Linear	0.006	0.058	0.005	0.772	0.101	0.798
Quadratic	0.044	0.190	0.053	0.329	0.319	0.172

Diets: ALM0%= a diet having no amaranth leaf meal inclusion, ALM5%= a diet having 5 g/kg of amaranth leaf meal inclusion, ALM10% =a diet having 10 g/kg of amaranth leaf meal inclusion. ALM15%= a diet having 15 g/kg of amaranth leaf meal inclusion. ALM20% = a diet having 20 g/kg of amaranth leaf meal inclusion. SEM: standard error of the mean.

The effects of ALM inclusion on the breast meat colour of indigenous Boschveld chickens are presented in Table 9. Amaranth leaf meal inclusion had an effect (p < .05) on the breast meat colour of indigenous Boschveld chickens aged 91 days. Indigenous Boschveld chickens which were fed with diets with a 15% ALM inclusion level, had higher (p < .05) breast meat lightness, redness, and yellowness than those offered 0, 5, 10, and 20% ALM inclusion levels. However, chickens fed with diets with 0, 5, 15, and 10% had a similar (p > .05) lighter breast meat colour. ALM inclusion levels in the diet showed no linear (p > .05) or quadratic (p > .05) influences on gut organ digesta pH of Ross 308 broiler chickens.

Table 9. Effect of amaranth leaf meal (ALM) inclusion on breast meat colour of Indigenous Boschveld chickens.

	Breast
ALM%	L*	a*	b*
0	45.27^b	−0.25^b	8.93^b
5	45.06^b	−0.73^b	9.53^b
10	43.92^b	−1.29^b	10.65^b
15	49.92^a	0.11^a	16.14^a
20	42.60^b	−0.20^b	9.60^b
SEM	1.26	0.960	1.522
P-value
Treatment	0.020	0.017	0.040
Linear	0.965	0.550	0.475
Quadratic	0.882	0.858	0.618

Diets: ALM0%= a diet having no amaranth leaf meal inclusion, ALM5%= a diet having 5 g/kg of amaranth leaf meal inclusion, ALM10% =a diet having 10 g/kg of amaranth leaf meal inclusion. ALM15%= a diet having 15 g/kg of amaranth leaf meal inclusion. ALM20% = a diet having 20 g/kg of amaranth leaf meal inclusion. SEM: standard error of the mean; L* is the lightness; a* is the redness; and b* is the yellowness.

Bone characteristics of indigenous Boschveld chickens fed with ALM inclusion are shown in Table 10. ALM inclusion levels had no effect (p > .05) on the tibia length, weight, or seedor index, nor on the femur length, weight, or seedor index of indigenous Boschveld chickens aged 21 days. Indigenous Boschveld chickens which were fed with diets containing a 5% ALM inclusion level, had a greater (p < .05) tibia diameter than those on diets having 0, 10, 15, and 20% ALM inclusion levels.

Table 10. Effect of amaranth leaf meal (ALM) inclusion on bone characteristics of Indigenous Boschveld chickens.

	Tibia				Femur
	Length	Weight	Diameter	S index	Length	Weight	Diameter	S index
ALM%
21days
0	4.12	0.79	1.57^b	0.19	3.00	0.44	2.26^bc	0.14
5	4.25	0.83	2.07^a	0.19	2.87	0.35	3.06^a	0.12
10	3.87	0.75	1.06^c	0.19	2.87	0.30	1.94 ^cd	0.10
15	4.00	0.64	2.02^a	0.16	2.57	0.27	2.82^ab	0.10
20	4.22	0.69	1.61^b	0.16	2.57	0.24	1.29^d	0.09
SEM	0.168	0.131	0.119	0.028	0.153	0.093	0.228	0.028
P-value
Treatment	0.505	0.854	0.0002	0.278	0.225	0.604	0.0005	0.581
Linear	0.936	0.097	0.985	0.058	0.018	0.007	0.404	0.014
Quadratic	0.657	0.344	0.997	0.190	0.118	0.007	0.509	0.029
42 days
0	7.62	3.59	4.25	0.47	5.47	2.66	5.12	0.48
5	7.73	3.58	4.25	0.46	5.62	2.62	4.62	0.46
10	7.43	3.33	4.00	0.44	5.43	2.66	4.75	0.47
15	7.43	3.19	4.00	0.42	5.43	2.46	4.75	0.45
20	7.30	3.05	3.75	0.41	5.20	2.15	4.50	0.24
SEM	0.133	0.261	0.232	0.028	0.221	0.211	0.218	0.055
P-value
Treatment	0.205	0.529	0.539	0.230	0.079	0.402	0.379	0.512
Linear	0.056	0.004	0.015	0.001	0.130	0.063	0.140	0.132
Quadratic	0.226	0.039	0.082	0.015	0.156	0.034	0.385	0.122
91 days
0	12.67	12.27^a	6.50	0.97^a	8.77^a	8.32	7.75	0.96
5	11.70	8.17^b	7.00	0.69^b	8.50^ab	7.12	7.75	0.84
10	12.70	9.95^b	6.75	0.78^ab	8.47^ab	7.87	7.75	0.92
15	11.97	11.90^a	6.25	0.99^a	7.22^b	6.17	7.00	0.89
20	11.97	10.62^ab	7.00	0.89^ab	8.22^b	7.90	6.75	0.96
SEM	0.397	0.893	0.555	0.073	0.312	0.943	0.428	0.133
P-value
Treatment	0.715	0.032	0.325	0.031	0.024	0.052	0.078	0.061
Linear	0.513	0.947	0.846	0.780	0.258	0.583	0.042	0.803
Quadratic	0.842	0.775	0.975	0.717	0.521	0.600	0.086	0.471

Diets: ALM0%= a diet having no amaranth leaf meal inclusion, ALM5%= a diet having 5 g/kg of amaranth leaf meal inclusion, ALM10% =a diet having 10 g/kg of amaranth leaf meal inclusion. ALM15%= a diet having 15 g/kg of amaranth leaf meal inclusion. ALM20% = a diet having 20 g/kg of amaranth leaf meal inclusion. SEM: standard error of the mean.

S index: Seedor index

Amaranth leaf meal inclusion levels had no effect (p > .05) on the tibia length, weight, diameter, or seedor index, nor on the femur length, weight, diameter, or seedor index of indigenous Boschveld chickens aged 42 days. However, tibia weight and seedor index showed linear (p = .004 and .001) and quadratic (p = .039 and .015) effects with increasing levels of ALM in the diets. Moreover, there was a linear (p = .015) effect on tibia diameter with increasing levels of ALM in the diets. Femur weight showed a quadratic (p = .034) effect with ALM inclusion in the diets.

At the age of 91 days, indigenous Boschveld chickens which were fed with diets having 0% ALM inclusion levels, had higher (p < .05) tibia weights and seedor index than those on diets having 5, 10, 15, and 20% ALM inclusion levels. However, chickens offered diets with 0 and 15% ALM inclusion levels, had the same (p > .05) tibia weights and seedor index. Indigenous Boschveld chickens which were fed with diets having 0% ALM inclusion levels, had longer (p < .05) femur lengths than those on diets having 5, 10, 15, and 20% ALM inclusion levels. However, chickens fed with diets having 0, 5, and 10% ALM inclusion levels, had similar (p > .05) femur lengths. Furthermore, femur diameter showed a linear (p = .042) effect with increasing levels of ALM in the diets.

The bone minerals of indigenous Boschveld chickens which were fed with ALM inclusion are shown in Table 11. ALM inclusion levels had an effect (p < .05) on tibia and femur Ca and P of indigenous Boschveld chickens aged 21 and 42 days, respectively.

Table 11. Effect of amaranth leaf meal (ALM) inclusion on bone minerals of indigenous Boschveld chickens.

Tibia			Femur
	Ca	P	Ca	P
ALM%
21days
0	19.34^e	8.37^d	30.00^e	10.89
5	22.38^b	9.63^b	32.71^c	11.09
10	19.91^d	8.38^d	31.53^d	11.06
15	22.91^a	19.34^a	33.24^b	11.44
20	21.93^c	8.43^c	33.80^a	11.42
SEM	0.012	0.014	0.012	0.022
P-value
Treatment	<.0001	<.0001	<.0001	<.0001
Linear	0.313	0.594	0.069	0.024
Quadratic	0.624	0.780	0.264	0.142
42 days
0	28.48^e	9.59^d	29.55^e	8.61^e
5	31.67^d	10.78^b	32.54^c	9.42^c
10	32.57^c	10.62^c	32.54^d	9.25^d
15	33.49^a	11.02^a	34.20^a	10.26^b
20	33.22^b	11.04^a	33.29^b	11.48^a
SEM	0.020	0.022	0.050	0.022
P-value
Treatment	<.0001	<.0001	<.0001	<.0001
Linear	0.049	0.080	0.084	0.017
Quadratic	0.018	0.148	0.094	0.057

Diets: ALM0%= a diet having no amaranth leaf meal inclusion, ALM5%= a diet having 5 g/kg of amaranth leaf meal inclusion, ALM10% =a diet having 10 g/kg of amaranth leaf meal inclusion. ALM15%= a diet having 15 g/kg of amaranth leaf meal inclusion. ALM20% = a diet having 20 g/kg of amaranth leaf meal inclusion. SEM: standard error of the mean

At the age of 21 days, indigenous Boschveld chickens which were fed with diets containing a 15% ALM inclusion level, had higher (p < .05) tibia Ca and P contents than those on diets having 0, 5, 10, and 15% ALM inclusion levels. Indigenous chickens fed with diets having a 20% ALM inclusion level, had higher (p < .05) femur Ca contents than those on diets having 0, 5, 10, and 15% ALM inclusion levels. However, there was a linear (p = .024) effect observed in femur P of indigenous Boschveld chickens with increasing levels of ALM in their diets.

At the age of 42 days, indigenous Boschveld chickens which were fed with diets containing a 15% ALM inclusion level, had higher (p < .05) tibia Ca, phosphorus and femur Ca contents than those on diets having 0, 5, 10, and 20% ALM inclusion levels. There was a linear (p = .049) and quadratic (0. 018.) effect observed on tibia Ca of indigenous Boschveld chickens with increasing levels of ALM in their diets. Moreover, there was a linear (p = .017) effect observed on femur P of indigenous Boschveld chickens with increasing levels of ALM in their diets.

Discussion

The present study demonstrated the potential of amaranth leaf meal as a protein source for inclusion in indigenous Boschveld chicken diets, as well as being of immediate importance for feed production. Amaranth leaf meal inclusion did not affect ADFI, ADG, FCR, and LW of indigenous Boschveld chickens aged one to 91 days. It is possible that the secondary metabolites present in ALM used in the current study were not too high to adversely affect the performance of chickens. To the best of our knowledge, no results were found from the literature to back up the findings of the current study, especially with the kind of breed we used. According to Manyelo et al. (2020) Amaranth cruentus leaves have appreciable amounts of amino acids which reflect protein of good quality raw materials for chickens feed formulation with excellent amino acids profiles. ALM inclusion levels did not affect carcase, breast, thigh, drumstick, or abdominal fats of indigenous Boschveld chickens, aged 42 and 91 days. However, at 91 days, chickens that were fed with diets containing a 15% ALM inclusion level, had higher abdominal fat weights than those offered diets with 0, 5, 10, and 20% ALM inclusion levels. This might be due to natural antioxidants that can act as metal chelators and free radical or oxygen scavengers, which can slow the progression of lipid oxidation whereas lipid oxidation may have negative effects on the quality of meat causing changes in meat colour, texture, odour and flavour and fats. However, the results of the current study are in contrast with the results of Suchý et al. (2002), in which the authors reported that diets with amaranth did not have any effect on percentage yield; the quality of the carcase, or on indicators of the chemical composition of meat. Normally, high meat yield is one of the most desirable traits which is considered (Hafeez et al. 2014). Carcase and meat weights observed in the current study ranged within the recommended values of indigenous chickens. ALM inclusion did not affect the breast, thigh, or drumstick pH of indigenous Boschveld chickens, aged 42 and 91 days. The pH of normal chicken breast meat ranges between 5.7 and 5.96 (Fletcher et al. 2000), and pH values observed in the present study are within the normal values.

ALM inclusion levels did not affect juiciness, flavour, overall acceptability, or cooking loss of indigenous Boschveld chickens, aged 91 days. Indigenous Boschveld chickens which were fed with a 20% ALM inclusion level in their diets, had higher meat tenderness than those fed with 0, 5, 10, and 15% ALM inclusion levels. Sensory attributes of meat, such as tenderness, juiciness, flavour, and overall acceptability, are amongst the most important factors in consumer preferences (Font-i-Furnols and Guerrero 2014). Natural antioxidants which are present in plant leaves, such as ALM, have been reported to improve chicken meat quality attributes such as meat colour, pH, cooking loss and sensory attributes (Velasco and Williams 2011). Several researchers reported that antioxidants from faba beans and clove seeds resulted in an improvement of the flavour of chicken meat, moreover, a reduction in the metallic taste and the overall after taste (Escobedo del Bosque et al. 2020; Suliman et al. 2021). However, in the current study, the differences observed with meat tenderness might be due to the consumer panellists that often fail to detect small differences as a trained panel would have.

ALM inclusion levels affected the breast meat colour of indigenous Boschveld chickens aged 91 days. Indigenous Boschveld chickens which were fed with diets containing a 15% ALM inclusion level, had lighter breast meat colour than those fed with 0, 5, 10, and 15% ALM inclusion levels. Indigenous Boschveld chickens which were fed with diets containing a 15% ALM inclusion level, had higher breast meat redness than those fed with 0, 5, 10, and 15% ALM inclusion levels. López-Pedrouso et al. (2020), states that consumers associate meat colour with a better quality of meat. According to Listrat et al. (2016), animal diets can influence meat colour. However, to the best of our knowledge, there are no results in the literature to back up the findings of the current study. Thus, the explanation of the affected light and red meat colour might be due to the antioxidant activity of ALM, which is well-known for being involved in redox reactions and delaying the meat oxidation processes (Saracila et al. 2021).

ALM inclusion levels did not affect tibia length, weight, or seedor index, nor on femur length, weight, or seedor index of indigenous Boschveld chickens aged 21 days. Indigenous Boschveld chickens which were fed with diets having 5 and 15% ALM inclusion levels, had greater tibia and femur diameters than those on diets having 0, 10, and 20% ALM inclusion levels. To the best of our knowledge, there are no studies available in the literature on the use of ALM on bone characteristics in indigenous Boschveld chickens aged 21 days. ALM inclusion levels did not affect tibia length, weight, diameter, or seedor index, nor on femur length, weight, diameter, or seedor index of indigenous Boschveld chickens aged 42 days. Indigenous Boschveld chickens which were fed with diets having 0 and 15% ALM inclusion levels, had higher tibia weights and tibia seedor index than those on diets having 5, 10, and 20% ALM inclusion levels. Indigenous Boschveld chickens which were fed with diets with 0% ALM inclusion levels, had longer femur lengths than those on diets having 5, 10, 15, and 20% ALM inclusion levels. The heavy and longer bones obtained, in the current study, might have contributed to the high mineral deposition. Bone minerals are regarded as good indicators of bone health (Ziaie et al. 2011). In the current study, at the age of 21 days, indigenous Boschveld chickens which were fed with diets having 5, 15, 20% ALM inclusion levels, had higher tibia Ca and P contents than those on diets having 0, 5, 10, and 15% ALM inclusion levels. Some evidence shows a link among nutrients, antioxidant intake and bone health. Recent data demonstrate the antioxidant properties and their influence on bone metabolism. Antioxidants in the diet, and nutritional approaches to antioxidant strategies, in animals have been suggested to prevent bone mineral loss.At the age of 42 days, indigenous Boschveld chickens which were fed with diets having 15 and 20% ALM inclusion levels, had higher tibia Ca and P contents than those on diets with 0, 5, 10, and 20% ALM inclusion levels. Indigenous Boschveld chickens given 15 and 20% ALM inclusion levels in their diet, had higher femur Ca and P contents than those on diets with 0, 5, 10, and 20% ALM inclusion levels. Bone minerals are regarded as good indicators of bone health (Ziaie et al. 2011), which, in turn, depends on its mineral content, especially calcium (Hafeez et al. 2014). However, amaranth has appreciable amounts of minerals which can contribute to improved bone mineral deposition in chickens.

Conclusion

From the results obtained in this study, it is concluded that various amaranth leaf meal (AML) inclusion levels can be incorporated into the diets of indigenous Boschveld chickens. However, 5, 10, and 15% AML inclusion levels in the diet are recommended as they showed to favour, performance, meat, and bone physical characteristics and more bone minerals deposition of indigenous Boschveld chickens.

Ethical approval

The experimental procedures were conducted following the University of South Africa's (UNISA) Ethics code for the use of live animals in research, ethics reference number: 2019/CAES_AREC/154 and University of Limpopo (UL) Ethics committee, reference number: AREC/12/2020: IR.

Acknowledgments

The authors thank the Agricultural Research Services of the North-West Department of Agriculture and Rural Development for supplying us with Amaranthus cruentus grain produced at the Taung Experimental Farm and the CA LCMS Lab, at the University of Stellenbosch for assistance with the LC-MS analysis.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

Data is available on request from the corresponding author.

Additional information

Funding

The authors thank the National Research Foundation [grant number 118245] and the University of South Africa for their financial support.