Malted sorghum as a maize substitute in broiler diets: effect on feed utilisation, growth performance and haemo-biochemical parameters

Abstract

Sorghum is amongst the most drought-tolerant cereals in the driest rain-fed regions of the tropics and its utilisation in sustainable poultry production is limited by presence of phytochemicals. Thus, this study evaluated the effects of malting dietary sorghum on growth performance and haemo-biochemical parameters of Ross 308 broiler chickens. A total of 150 unsexed, 2 weeks-old chicks were evenly distributed into 15 replicated pens which were randomly allocated into three experimental diets and fed in two phase feeding. Three diets were formulated by completely replacing maize grain in commercial grower and finisher diets (CON) with red malted sorghum (RSD) and white malted sorghum (WSD). Broilers fed CON and WSD diets gained more weight compared to those fed RSD in week 3 and 5. The lowest feed conversion ratio (FCR) was observed in CON in week 4 and 6. The protein efficiency ratio was the lowest with broilers fed malted sorghum-based diets (MSD) through out the study. Protein intake was the highest in broilers fed WSD in week 3 and 5, but lowest in week 4 and 5 in broilers fed RSD. Diets affected white blood cells basophils, corpuscular (volume and haemoglobin), corpuscular haemoglobin concentration, creatinine, bilirubin, and enzymes (GTP and GOT). Overall, the results from the present study suggest that maize grains can be replaced with malted white sorghum grains in poultry diets, without any adverse effects on the birds’ growth performance and general health status.

HIGHLIGHTS

• Malting sorghum reduces its phenolic compounds, tannins, and flavonoids that hinder its efficient utilisation in monogastric animal diets.

• Inclusion of malted sorghum to broiler diets did not affect weight gain.

• Biochemical blood parameters of broilers fed malted sorghum-based diets were within normal range of poultry

Keywords:

• Blood chemistry
• growth performance
• malted sorghum
• Ross 308 chicken

Introduction

Maize is the mainstay source of energy in sub Saharan African countries including Botswana, South Africa and Zimbabwe, in commercial broiler rations, and contributes 60% of the ration in diets of monogastric animals (Akinfala et al. 2002). Maize is also a staple feed for most people in sub Saharan Africa and its use as animal feed create a competition that inflate price in the market. As a result, commercial and subsistence poultry farmers encounter high feed costs resulting in unprofitable business. Thus, to reduce feed cost and increase profit margin, formulating feed using cheap and locally available ingredients like sorghum is essential. Sorghum (Sorghum bicolor) is abundant in most parts of sub Saharan Africa and is among the main cereal crops because of its tolerance to harsh climatic conditions. Red/brown sorghum, sometimes called bird-resistant often contain anti-nutritional compounds that render their use in monogastrics feeding limited (Myer et al. 2007). It is known that the red sorghum like Mr Buster contains more phenolic acids and flavonoids (Al-Mashhadani and Al-Rubaie 2021) than the white sorghum.

However, different studies (Emami et al. 2012; Osman and Gassem 2013; Torres et al. 2013; Mohammed et al. 2019) have found that body weight decreased significantly in chickens fed sorghum-based diets. The negative effects of sorghum in animal performance are understood to come from anti-nutritional factors (ANFs) such as tannin, karfirn and phytate that affect efficient nutrients utilisation (Hariprasanna et al. 2015) and metabolism (Hamid et al. 2017). Therefore, it is important to explore processing techniques that can reduce ANFs effects so as to improve feed quality and value. It has been reported by Makokha et al. (2002) that malting improves in vitro digestibility of sorghum grains when porcine pepsin method was used. A study by Legodimo and Madibela (2013) employing rumen fluid as an inoculum, reported improved dry matter (DM) digestibility of malted sorghum grains. Several studies have noted that malting reduces phenolic compounds, tannins, and flavonoids, except for anthocyanins (Khoddami et al. 2017). According to Feyera (2021) and Moses et al. (2022), positive effects on growth performance and carcase traits were observed when chicken were fed diets containing malted red and white sorghum. Therefore, malting may unlock the potential of sorghum as a major ingredient in non-ruminant rations in Southern Africa Development Community (SADC) region. Therefore, the present study aimed at evaluating the growth performance and haemo-biochemical parameters of broilers fed malted sorghum-based diets (MSD) (red and white) in comparison to maize-based diets. It was hypothesised that replacing maize with malted sorghum in Ross 308 broiler diets would have no negative effects on feed utilisation, growth performance and health status of broiler chicken.

Materials and methods

Animal care

The experimental procedures used were reviewed and approved by the Animal Ethics Committee (BUAN AEC # 2020-08) of the Botswana University of Agriculture and Natural Resources (BUAN).

Study site, ingredients sources and sorghum malting procedures

The study was carried out at the Botswana University of Agriculture and Natural Resources (BUAN), Content Farm (24°36′ 40.90’S and 25° 56′ 13.35’E), Sebele, Gaborone, Botswana. During this time ambient temperatures ranged from ∼12 to 40 °C. Unscreened white and red sorghum grains were purchased from Botswana Agricultural Marketing Board (Gaborone, Botswana), while amino acids and mineral premixes and soybean meal were bought from Optifeeds (PTY) LTD, Gaborone, Botswana. Malting was prepared by soaking sorghum in a plastic container covered with a jute bag for 48 h at room temperature (15 °C), draining excess water and thereafter spreading the sorghum on hessian bags, and allowing for germination over a 7 day period under dark conditions. After germination, the malted grains were sun-dried and ground through a 2 mm sieve, then stored in bags prior to diet formulations.

Diet formulation

Three isonitrogenous and iso-caloric diets in a mash form (Table 1) were formulated by totally replacing maize with malted sorghum meeting the nutritional requirements of Ross 308 broilers’ grower and finisher phases as per Ross recommendations. The formulation of the experimental diets was done with the help of Opti Feeds (PTY) LTD, Botswana following their specifications. The diets were as follows: 1. Control (CON) = commercial grower and finisher diets containing maize only, 2. Red sorghum diet (RSD) = grower and finisher diets in which maize was totally replaced (w/w) with malted red sorghum, 3. White sorghum diet (WSD) = grower and finisher diets in which maize was totally replaced (w/w) with malted white sorghum.

Table 1. Chemical composition of malted and unmalted red and white sorghum grains (g/kg DM, unless stated otherwise).

	Red sorghum		White sorghum		Maize
^1Parameters	Malted	Unmalted	Malted	Unmalted	Yellow	White	^2SEM	^3Significance
GE ^d	16.22	16.34	16.58	16.83	18.43	18.00	1.2	NS
Dry matter	948.0^a	958.4^a	940.5^b	942.9^a	924.4^b	935.5^b	0.3	*
OM	846.7^c	809.9^c	895.6^b	822.9^c	987.3^a	984.3^a	1.1	*
CP	116.4^a	113.2^b	124.0^a	132.5^b	100.8^b	815.0^c	0.3	*
Crude fat	93.4ab	80.9ab	85.1ab	113.3^a	377.0^b	493.3^b	1.3	*
Crude fibre	284.0^b	365.7^b	289.0^b	486.7^a	214.6^c	257.7^c	1.9	*
Ash	153.3^a	190.1ab	104.4^b	177.2^b	126.6^c	156.6^c	1.0	*
Tannin	0.8^a	0.9^a	0.5^b	0.6^b	0.01^c	0.02^c	0.0001	*

^abc Means within a row that do not share a common superscript differ significantly (p ˂ 0.05). ¹Parameters; GE = gross energy; d = MJ/kg, DM = Dry matter, OM = Organic matter, CP = crude protein, ²SEM = standard error of the mean. ³Significance; * = p < 0.05, NS = not significant.

Chemical analysis

Table 1 shows sorghum composition, while the composition of the 3 diets is given in Table 2. Samples of sorghum and diets were milled and analysed in triplicates according to AOAC (2005) methods number 930.15 for dry matter, 924.05 for organic matter, 984.13 for crude protein, 978.10 for crude fibre and 920.39 for crude fat. Gross energy was analysed by combusting about 1.0 g of each sample in a bomb calorimeter (Model-IKA C2000, IKA®-Werke GmbH & Company, Hamburg, Germany). Condensed tannins were determined using the Butanol-HCL method and expressed as leucocyanidin equivalent (% DM) (Makkar, 2000).

Table 2. Gross ingredients and nutrients composition of grower and finisher diets fed to ross 308 broilers during the experimental periods.

	Grower diets (14-28 days)			Finisher diets (29-42 days)
	Control	WSD	RSD	Control	WSD	RSD
Ingredients (g/kg, as fed basis)
Soybean oil cake	104.7	104.7	104.7	145.6	145.6	145.6
Full fat soya	180.0	180.0	180.0	90.4	90.4	90.4
Malted sorghum grains	–	642.7	642.7	–	730.2	730.2
Maize grains	642.7	–	–	730.2	–	–
*Amino acids and mineral premix	39.3	39.3	39.3	33.8	33.8	33.8
Nutrients composition (g/kg DM, unless stated otherwise)
Energy (MJ/Kg)	18.4	18.3	18.3	18.5	18.5	18.6
Dry matter	938.1	936.1	934.1	934.7	928.1	932.0
Organic matter	920.6	928.3	910.8	930.4	903.2.	915.4
Crude protein	229.9	230.0	229.2	218.9	219.2	221.1
Crude fat	75.2	87.8	77.9	78.5	80.6	73.5
Crude fibre	133.1	132.3	144.	136.2	137.4	148.7
Condensed tannin	0.5	0.6	0.6	0.5	0.5	0.7

¹ Experimental diets: Control = a standard commercial grower and finisher diet without malted sorghum; WSD = grower and finisher diets in which maize were totally replaced with malted white sorghum; RSD = grower and finisher diets in which maize were totally replaced with malted white sorghum. *= Company confidential information.

Experimental design and bird’s management

A total of 150 broiler chicks were acquired from Ross Breeder hatchery (Gaborone, Botswana), and were reared using commercial starter crumbles of Optifeeds Pty Ltd (Gaborone, Botswana) for the first 13 days. During brooding (day old to 12 days), the chicks were offered vitamins and electrolytes supplements (3 days) via drinking water in the brooding units of 33 °C for the first day and reduced by 1 °C for every three days. Infra-red electric bulbs were used as a source of heat in the brooding unit and the house was bedded with sunflower husk. At day 13, the chicks were individually weighed, balanced, and allocated to 15 replicated pens (2.3 × 1.24 m) in an open-sided type of house. Each pen (experimental units) was holding 10 unsexed chicks with a feeder and drinker in the middle. The 3 dietary treatments were then randomly allocated to the 15 experimental units in a completely randomised design where feed and clean fresh water were given at ad-libitum. Broilers were exposed to 23 hr light from d13 to d42. Whilst, measurements were then taken from day 14 to 28 and day 29–42 for the grower and finisher phases, respectively.

Measurement of feed intake and growth performance

At day 14, the chicks were weighed for the balancing of the weight within the treatment groups and were re-weighed again for initial weight (1036. 2$\pm$234.6 g) in the pen and subsequently on a weekly basis using an electronic scale of sensitivity 0.001 g (Adam 6020 model, Adam, Gauteng Province, South Africa). Average weekly weight gain (AWWG) was then computed by calculating interim weights and divided by the number of days. Feed was weighed and given to the broilers in the morning, and before feeding the next day, refusal feed was collected and weighed. Feed intake (FI) was then calculated as refusal collected subtracted from feed offered.

Average weekly feed conversion ratio (FCR) was calculated by dividing FI by weight gain of the broilers for 7 days. Protein intake (PI) was determined as a product of crude protein concentration in the diet and FI. Protein efficiency ratio (PER) was calculated as a proportion of body weight gain to PI. The FI, AWWG, FCR, PI and PER were calculated as described by Manyeula et al. (2019).

Blood collection, haematology and serum biochemical analysis

At 6 weeks of age, blood samples were collected from the brachial vein of 2 broilers (10 broilers/treatment) which were randomly selected from each pen in the morning before feeding using 23-gauge needles and 5 mL syringes. The blood was then transported to Clinipath Laboratory (PTY) LTD, Molepolole, Botswana for haematology and serum analysis. Blood for haematological parameters (white blood cell (WBC), lymphocytes, neutrophils, monocytes, eosinophils, basophils, red blood cells, haemoglobin, haematocrit, mean corpuscular volume (MCV) and haemoglobin (MCH), and platelets) were collected in ethylene diaminetetra-acetic acid coated vacutainer and analysed using automated Idexx Laser Cyte Haematology analyser (IDEXX Laboratories, Inc.). Whereas, for serum biochemical parameters (albumin, creatinine, total protein, triglycerides, bilirubin, urea, glutamic-pyruvic transaminase (GPT), glutamic oxaloacetic transaminase (GOT) and minerals (potassium, sodium, calcium, magnesium, and chloride) anti-coagulant-free vacutainer tubes were used and serum analysed using an automated Idexx Vex Test Chemistry Analyser (IDEXX Laboratories, Inc).

Statistical analysis

Chemical analyses for white and red sorghum grains (Unmalted and malted) and maize (yellow and white) were done using three subsamples (pseudo replicates) and, thereafter, the data were simply reported as means of the three subsamples without any statistical analysis. Weekly FI, AWG, FCR, PI and PER data were analysed using repeated measures procedure of SAS (2010) to determine the interaction effects between diet and time (in weeks) according to the following general linear model: $${\gamma }_{\mathit{\text{ijk}}}=\mu +D_i+W_j+({\mathit{\text{DW}})}_{\mathit{\text{ij}}}+{\epsilon }_{\mathit{\text{ijk}}}$$

Where ${\gamma }_{\mathit{\text{IJK}}}$ = response variable, $\mu$ = overall mean, $D_I$= fixed effects of diet, W_j = effects of week (age of chicken), $({\mathit{\text{DW}})}_{\mathit{\text{IJ}}}$= effects of interaction between diets and week and ${\epsilon }_{\mathit{\text{IJK}}}$ = random error associated with observation ijk = assumed to be normally and independently distributed.

Data on overall feed intake, weight gain, feed conversion ratio, protein intake, protein efficiency ratio, haematology and serum biochemistry parameters were analysed using one-way analysis of variance as contained in PROC GLM of SAS (2010) according to the following general linear model: $${\gamma }_{\mathit{\text{IJ}}}=\mu +D_{i }+{\epsilon }_{\mathit{\text{IJ}}}$$

Where ${\gamma }_{\mathit{\text{ij}}}$ = response variable, μ = overall mean, $D_i$= fixed effects of diet, ${ϵ}_{\mathit{\text{ij}}}$ = random error associated with observation $\mathit{\text{ij}}$ = assumed to be normally and independently distributed. The probability of difference (PDIFF) option in the LSMEANS statement of the GLM procedure of SAS (2010) was used to separate means. Statistical significance was declared at p ≤ 0.05.

Results

As it was observed from Table 1, malting did not affect digestible energy (DE), and DE was similar in all sorghum grains. However, dry matter was lower in white malted sorghum and yellow maize than in red (malted and unmalted) sorghums. Organic matter (OM) was higher in maize than in red sorghum. Crude protein was highest in malted red and white sorghum and lowest in white maize. Highest crude fat and fibre were observed in unmalted white sorghum and lowest in both maize and unmalted red sorghum. Highest ash contents were observed in malted red sorghum and lowest in both maize. Tannins were highest in red sorghum (malted and unmalted) and lowest in both maize and white sorghum (malted and unmalted).

In the study, no mortality was recorded. Repeated measures analyses revealed significant diet × week interaction effects on AWWG (p = 0.038), FCR (p = 0.011) and PER (p = 0.0001), PI (p = 0.0002), but not on weekly FI (p = 0.363). Diet did not affect overall FI (p = 0.880) but had an effect on AWWG, FCR, PI and PER (Table 3). In week 3, broilers reared on CON diet had higher (p < 0.05) AWWG than those reared on red sorghum diet (RSD). However, those reared on white sorghum diet (WSD) did not differ (p > 0.05) from those reared on CON diet and RSD for AWWG. In week 4 and 5, CON and WSD diet promoted higher AWWG than RSD. Broilers reared on CON had higher AWWG than those reared on WSD and RSD in week 6. Diets did not affect FCR at week 3 and 5. In week 4, broilers fed RSD had the poorest FCR whereas those fed CON diet had the lowest FCR. However, broilers fed WSD did not differ (p > 0.05) from those fed CON diet and its FCR was also similar to RSD. In week 6, lower FCR was observed in broilers fed CON diet whereas the poorest FCR was observed in those fed WSD. In week 3 and 5, WSD promoted the highest (p < 0.05) PI compared with diet CON. In week 4, RSD promoted the highest (p < 0.05) PI compared with the CON diet. However, WSD had statistically similar (p > 0.05) PI with CON diet and RSD. Diets did not affect PER in week 3 and 5. In week 4, broilers fed RSD had the lowest (p < 0.05) PER whereas those fed diets CON and WSD had the highest and were similar (p > 0.05) to each other. In week 6, broilers fed WSD and RSD had the lowest (p < 0.05) PER while those fed CON diet had the highest. The CON and WSD diets led to the highest overall weight gain (Table 4). However, overall FCR and PI were higher (p < 0.05) in broilers fed MSD (white and red) and the lowest observed in birds fed the CON diet. Malted sorghum-based diets promoted overall PER.

Table 3. Average weekly growth performance and protein utilisation of ross 308 fed diets containing malted sorghum grains as substitute to maize grains (n = 50/dietary treatment).

^1Experimental diets
Age (Week)	Control	WSD	RSD	^2SEM	p-value
Average weekly weight gain (g/bird)
Week 3	50.5^a	48.9ab	46.0^b	1.16	0.048
Week 4	70.6^a	71.2^a	63.9^b	1.43	0.006
Week 5	82.1^a	81.5^a	71.8^b	2.55	0.025
Week 6	53.7^a	47.4^b	48.4^b	1.43	0.019
Average weekly feed conversion ratio
Week 3	1.59	1.66	1.70	0.04	0.09
Week 4	1.74^b	1.82^ab	1.91^a	0.04	0.05
Week 5	1.84	1.87	2.00	0.04	0.07
Week 6	3.00^c	3.48^a	3.35ab	0.05	0.0001
Averagely weekly protein intake (g)
Week 3	1529.8^c	1727.8^a	1678.8^b	15.65	<.0001
Week 4	2332.7^b	2767.9^ab	2870.9^a	44.80	<.0001
Week 5	2601.5^c	3056.3^a	2890.8^b	44.67	<.0001
Week 6	2780.4^b	3302.9^a	3254.0^a	65.73	0.0002
Average weekly protein efficiency ratio
Week 3	0.03	0.03	0.03	0.001	0.40
Week 4	0.03^a	0.03^a	0.02^b	0.000	0.0001
Week 5	0.03	0.03	0.03	0.002	0.10
Week 6	0.02^a	0.01^b	0.01^b	0.001	0.001

^abcMeans within a row that do not share a common superscript differ significantly (P˂0.05). ¹Experimental diets: Control = a standard commercial diet without malted sorghum; WSD = a standard commercial diet in which maize were totally replaced with malted white sorghum; RSD = a standard commercial diet in which maize were totally replaced with malted white sorghum. ²SEM = standard error of the mean.

Table 4. Overall feed intake, weight gain, feed conversion ratio, protein intake and protein efficiency ratio of ross 308 fed malted sorghum-based diets (n = 50/dietary treatment).

	^1Experimental diets
Parameters	Control	WSD	RSD	^2SEM	p-value
Overall feed intake (g/bird)	128.4	131.7	126.5	32.7	0.89
Overall weight gain (g/bird)	64.2^a	62.2^a	57.5^b	1.05	0.002
Overall feed conversion ratio	2.04^b	2.28^a	2.24^a	0.02	<0001
Overall protein intake (g)	2311.1^b	2713.7^a	2673.6^a	29.26	<0001
Overall protein efficiency ratio	0.03^a	0.02^b	0.02^b	0.001	0.0001

^abMeans within a row that do not share a common superscript differ significantly (P˂0.05). ¹Experimental diets: Control = a standard commercial diet without malted sorghum; WSD = a standard commercial diet in which maize were totally replaced with malted white sorghum; RSD = a standard commercial diet in which maize were totally replaced with malted white sorghum. ²SEM = standard error of the mean.

No health issues were encountered throughout the duration of the study. But experimental diets had effects (p ˂ 0.05) on haematological parameters except for lymphocytes, neutrophils, monocytes, eosinophils, red blood cells, haemoglobin, haematocrit, and blood platelets (Table 5). The broilers fed CON diet had higher (p ˂ 0.05) WBC counts compared to those fed WSD which did not differ (p > 0.05) with those fed RSD. Higher (p ˂ 0.05) basophil counts and MCV were recorded from broilers fed WSD compared to those fed CON diet. The MCH was higher (p ˂ 0.05) in broilers fed WSD compared to those fed CON diet. However, broilers fed RSD had similar (p > 0.05) MCH to those fed CON and WSD. The MCHC was highest (p ˂ 0.05) in broilers fed CON followed by those fed WSD and the least was noted from those fed RSD.

Table 5. Effects of substituting maize with malted sorghum grains on haematological parameters of ross 308 broiler chickens (n = 10/dietary treatment).

	^1Experimental diets
^3Parameters	Control	WSD	RSD	^2SEM	p-value
White blood cells (10e)^3/µL	46.8^a	39.2^c	41.8bc	1.44	0.003
Lymphocytes %	47.3	45.9	42.8	2.30	0.39
Neutrophils %	44.8	46.4	50.4	2.21	0.20
Monocytes %	0.17	0.35	0.10	0.16	0.30
Eosinophils %	7.45	6.06	6.39	0.69	0.35
Basophils %	0.33^c	0.57^a	0.56ab	0.06	0.01
Red blood cell (10e)^6/µL	2.6	2.48	2.56	0.06	0.30
Haemoglobin g/dL	13.7	13.4	13.7	0.29	0.77
Haematocrit %	33.7	33.6	35.0	0.72	0.32
Mean corpuscular volume, FI	128.8^c	135.4^b	137.0ab	1.29	0.0003
Mean corpuscular haemoglobin, Pg	52.7^c	53.9^a	53.5abc	0.36	0.05
Mean corpuscular haemoglobin concentration, g/d^-L	40.5^a	39.9^b	39.0^c	0.24	0.0004
Platelets (10e)^3/µL	3.10	3.00	3.60	0.52	0.69

^abcMeans within a row that do not share a common superscript differ significantly (P˂0.05). ¹Experimental diets: Control = a standard commercial diet without malted sorghum; WSD = a standard commercial diet in which maize were totally replaced with malted white sorghum; RSD = a standard commercial diet in which maize were totally replaced with malted white sorghum. ²SEM = standard error of the mean.³Parameters: µL = microliter; %= percentage; g/dL = gram/decilitre; FI = femtolitres; Pg = pictograms.

Experimental diets did not affect (p > 0.05) serum biochemistry parameters except creatinine and plasma enzyme profile (Table 6). The broilers fed CON diet had the lowest (p ˂ 0.05) creatinine content compared to those fed MSD. The enzyme profile (GOT and GPT) was lowest (p > 0.05) in broilers fed WSD and highest in broilers fed the CON and RSD diets.

Table 6. Effects of substituting maize with malted sorghum grains on serum biochemical parameters of ross 308 broiler chicken (mean ± SEM) (n = 10/dietary treatment).

	^1Experimental diets
^2Parameters	Control	WSD	RSD	p-value
Plasma protein profile
Albumin (g/L)	6.91 ± 0.95	6.81 ± 0.95	8.01 ± 0.95	0.62
Creatinine (µmol/L)	14.3 ± 1.59^c	23.1 ± 1.59^a	22.6 ± 1.59ab	0.0007
Total protein (g/L)	26.0 ± 2.99	23.6 ± 2.99	28.6 ± 2.99	0.50
Total bilirubin ((µmol/L)	4.54 ± 1.70	7.70 ± 1.61	6.42 ± 1.61	0.41
Urea (mmol/L)	0.62 ± 0.29	0.37 ± 0.26	0.59 ± 0.26	0.77
Plasma energy profile
Triglycerides (mmol/L)	0.41 ± 0.08	0.43 ± 0.08	0.63 ± 0.08	0.14
Plasma enzyme profile (IU/L)
Glutamic-pyruvic transaminase	167.9 ± 18.0^a	84.8 ± 17.1^b	138.6 ± 17.1^a	0.008
Glutamic oxaloacetic transaminase	329.0 ± 35.1^a	165.7 ± 33.3^b	267.6 ± 33.3^a	0.008

^abcMeans within a row that do not share a common superscript differ significantly (P˂0.05); ¹Experimental diets: Control = a standard commercial diet without malted sorghum; WSD = a standard commercial diet in which maize were totally replaced with malted white sorghum; RSD = a standard commercial diet in which maize were totally replaced with malted white sorghum; ²Parameter: µmol/L = micromole/litre; g/L = gram/litre; mmol/L = millimoles/litre; µl = microliter; IU/L = international units per litre.

Diet significantly affected (p ˂ 0.05) serum minerals except potassium and sodium (Table 7). Serum Ca of broilers fed the CON and RSD diets was high (p ˂ 0.05) compared to those fed WSD, but no difference was observed in serum Ca from broilers fed WSD. Serum Mg and Cl were significantly low (p value??) in broilers fed WSD, whilst the highest (p value??) values were observed from those fed CON and RSD diets.

Table 7. Effects of substituting maize with malted sorghum grains on blood minerals (mmol/L) of ross 308 broiler chicken (n = 10/dietary treatment).

	^1Experimental diets
Parameters	Control	WSD	RSD	^2SEM	p- value
Potassium	5.35	5.10	5.46	0.28	0.67
Sodium	147.6	144.1	145.9	1.63	0.33
Calcium	2.16^a	1.60^b	1.89ab	0.18	0.04
Magnesium	1.03^a	0.73^b	0.97^a	0.08	0.03
Chloride	113.1^a	104.7^b	113.0^a	2.16	0.01

^abMeans within a row that do not share a common superscript differ significantly (P˂0.05); ¹Experimental diets: Control = a standard commercial diet without malted sorghum; WSD = a standard commercial diet in which maize were totally replaced with malted white sorghum; RSD = a standard commercial diet in which maize were totally replaced with malted white sorghum; ²SEM = standard error of the mean.

Discussion

In the present study, the concentration of GE in maize grain and in red and white sorghum grains were closer to the average values reported by Thomas et al. (2020) in the similar varieties of sorghums, confirming the nature of sorghum to contain higher amounts of biochemical compounds. The highest dry matter (DM) observed in malted red sorghum than in maize could be due to presence of high complex structure like anti-nutritional factors such as tannin in malted red sorghum which signifies that malting did not breakdown all tannin (Hariprasanna et al. 2015). Indeed higher tannins content was found in sorghum than maize grain (Table 1). The values were higher than the average DM for unmalted sorghum varieties reported by Thomas et al. (2020). The significant increase in OM contents after malting white sorghum grains is in line with the findings by Otutu et al. (2014) who observed an increase in OM content after fermenting sorghum grains for 7 days. In line with the current results, Dewar et al. (1997) reported malting as a treatment that improves protein digestibility and quality characteristics. In the current study, the CP values were significantly higher than the average CP for sorghum varieties reported by Mabelebele et al. (2015) in South Africa and Thomas et al. (2020) in United State of America. Malting reduced fibre content in this study in white sorghum only which disagrees with the results of Laxmi et al. (2015), who found that crude fibre increases significantly during germination as the plant cells synthesise different cellular components (Kim et al. 2012). Processing methods (malting versus germinating) may be causing discrepancies in the results of these two studies. Red sorghum grains (normal and malted) were observed to have high tannin content compared to both malted and unmalted white sorghum and maize grains, and this is in line with the results of Myer et al. (2007) and Thomas et al. (2020), who reported high tannin contents in red sorghum compared to white sorghum and maize grain varieties. In the current study, malting did not affect tannin conten, and this contradicts the findings by Ogbonna et al. (2012) who observed that malting sorghum reduced ANF by 8.45%.

Malting improves feed utilisation of feedstuffs containing polyphenols (Medugu et al. 2012). It is known that malting increases alpha-amylase activity leading to increase in digestibility of starch, improved feed quality, and reduced tannin content (Bera et al. 2018). However, limited studies (Bohoua and Yelakan, 2007; Mohammed et al. 2019) have been conducted to evaluate the effects of malted grains on the performance of broiler chickens. In the present study, repeated measure analyses showed week × diets interaction on AWWG, FCR, PI and PER, and this indicates that the capacity of broilers to utilise dietary treatment depends on broiler’s age. Replacing maize with malted sorghum did not affect feed intake, implying that replacing maize with malted sorghum (white and red) did not change the physicochemical capabilities of birds to digest and utilise the diets hence palatability was not affected. Similar results were observed by Torki and Pour (2007) and Al-Mashhadani and Al-Rubaie (2021), who reported lack of significant effects on feed intake when malted high tannin sorghum was fed to broiler chickens. Contrary to results of the current study, Demeke (2007) and Onyimba (2020), respectively reported lower weekly feed intake in broilers fed industrial brewers’ grain and fermented spent sorghum grains. The discrepancies between their studies with the current study could be due to processing methods and type of sorghum used. Furthermore, evaluating the effectiveness of malted sorghum as potential alternative ingredients in broiler diets is essential in determination the growth performance, haematological and biochemical parameters.

This study reported no broiler mortality, and thus confirming that diets did not cause any health and welfare issues and this was supported by normal haematological results (Table 5). The high weekly and overall weight gain observed in broilers fed CON and WSD diets suggest that the substitution of maize with white sorghum did not suppress weight gain, therefore white sorghum could be a good candidate for such replacement. Feeding RSD resulted in the lowest AWWG, further suggesting adverse impact of anti-nutritional factors such as tannin (0.8–0.9 g/kg, Table 1) and kafirin in this type of sorghum. According to Selle et al. (2017) compounds like kafirin, phenolic compounds, and phytate are three main anti-nutritional in sorghum that would contribute to relatively slow and incomplete digestion of starch in poultry. Tannin binds proteins and carbohydrates, while kafirin is reported to be hydrophobic, and all these properties hinder proper utilisation of sorghum in diets of monogastric animals (Taylor et al. 2007). Although kafirin is the dominant protein fraction in sorghum, its anti-nutritional character is derived from the fact that as kafirin proportions of sorghum protein escalate, lysine content declines, and grain endosperm corneousness (vitreosity) ‘hardness’ increases (McCuistion et al. 2019). The present results corroborate the findings by Al-Mashhadani and Al-Rubaie (2021) and Manyelo et al. (2019), where broiler chicks aged 11–24 days had low weight gain when fed with diets in which maize grain had been completely replaced with germinated red sorghum. In the present study Week 6 weight gain decreased while, protein intake was high in MSD, implying that the protein consumed was not utilised by the broilers, perhaps pointing out to the effects of kafirin as discussed above. In addition kafirin protein bodies and starch granules are intimately associated within sorghum endosperm (McCuistion et al. 2019) and such a relationship has been suggested to compromise starch digestibility (Wong et al. 2009). Therefore, it is clear from the present results that feeding RSD significantly depressed performance. In week 3 and 5, replacing maize with malted sorghum (white and red) did not influence FCR suggesting that at this point in time the broilers were efficiently utilising malted sorghum-based diets like those of the CON groups, and this is in agreement with the study by Manyelo et al. (2019). These authors reported lack of significant difference in FCR where maize was totally replced with sorghum in starter diets. However, in week 4 and 6 the overall FCR in the current study was high in broilers fed malted sorghum-based diets (MSD), suggesting that broilers were having difficulties in converting the feed into muscle, which could be due to the presence of fibre and tannins (see in Table 1 for composition) that hinder crude protein digestibility. The FCR was significantly higher than what is described in performance objectives in the Ross 308 manual (1.793) (Aviagen 2022). This could be due to lower protein quality in malted sorghum-based diets, perhaps due to presence of kafirin and varying rearing conditions when compared to those recommended by the Ross manual. Additionally, since higher FCR was observed in week 6, age of maturity, this would lead the feed been converted to fat instead of muscle owing to such high FCR.

The higher PI in broilers fed WSD in week 3 and 5 could be influenced by high protein content of the diets. However, weeks 4 and 6 also showed higher PI in broilers fed RSD which could be due to overall high feed intake. Likewise, the overall PI observed on broilers fed MSD was influenced by numerically higher feed intake and high protein content of sorghum grains (See Table 1) Onyimba (2020) observed lower PER in broilers fed spent sorghum which is in line with the current results on overall PER. Lower PER in broilers fed RSD in week 4 and 6 is explained by high protein intake and low weight gain. Compared to red sorghum, white sorghum has less tannin content hence the impact of ANFs on broilers fed WSD was minimal. The overall PER was low in broilers fed MSD (white and red) due to higher PI while protein utilisation was low. Despite higher PI in broilers fed MSD, the overall findings of this study illustrate that MSD reduces PER when used in broiler diets.

It was expected that MSD would not have negative effects on hematological and biochemical parameters due to the processing method (Malting). However, the fact that all values fell within normal ranges (Jain 1993) of a healthy chicken, suggests that indeed there were no negative effects by MSD on the physiological status of the broilers. Similar studies by Kim and Kang (2016) reported lack of significant differences in leukocytes when fermented barley and wheat were included in broiler diets. Higher WBC and MCHC in broilers fed the CON suggests that feeding MSD lowered body defence mechanism while the CON diet were responding to infections. The MSD promoted production of basophils and MCH when compared to the CON, suggesting that broilers fed MSD were protected against infectious and foreign pathogen invasion. Therefore, it can be postulated that malted sorghum grains can substitute maize in broiler diets without having any adverse effects on the health status of the chickens.

Blood parameters are good indicators of physiological, pathological, and nutritional status of an animal (Kim and Kang 2016). The lack of effect on serum albumin, total protein, triglycerides, urea, and total bilirubin in this study, suggests that malted sorghum grains provided sufficient dietary energy for transportation of protein for steroids and thyroid hormones in the blood (Kim and Kang 2016). The higher creatinine in broilers fed MSD indicates production of more waste products from protein metabolism and muscle contraction (Ileke et al. 2014) through the kidneys. Normally high creatinine indicates malfunction of kidneys (Odunitan-Wayas et al. 2018). However, in this study, high creatine level in MSD broilers compared to those fed CON diet could imply lower than optimal functioning of the kidneys. It is known that high levels of liver enzyme above the normal range represent hepatocellular degeneration (Mohammed et al. 2019). Interestingly, broilers fed RSD, or the CON diet had similar and high GOT and GPT values, suggesting hepatoprotective abilities of those diets in reducing free radicals that could have caused liver damage (Hernández et al. 2006). No broilers in the current study showed any form of illness associated with the diets and no mortalities were recorded, which is in line with the proposed hypotheses. Therefore, MSD can be safely used to replace maize grains in broiler diets without any adverse effect on health status of broilers. Thus malting, a process known by local communities especially in beer making (indigenous knowledge) can be employed by local poultry industry to process sorghum and use the processed sorghum to formulate diets for partial or complete replacement of maize.

Phytate and oxalates in sorghum are known to reduce mineral bioavailability (Samtiya et al. 2020), and this could be the reason why broilers fed WSD had lower concentrations of serum magnesium and chlorine, compared to those fed diet CON and RSD. Despite the differences in serum Ca in broilers fed different diets, blood Ca was within the normal range, therefore no hypocalcaemia observed in broilers throughout the study. Lack of significant differences in serum K and Na implies that diets provided enough dietary minerals which were absorbed in the blood for efficient utilisation, hence proper maintenance of bone integrity. The lack of an effect on blood minerals indicates that maize grains can be replaced with malted sorghum grains in broiler diets without any negative effect.

Conclusions and future research

Based on overall weight gain and blood biochemistry which were within the normal range of healthy broilers, it is thus concluded that white sorghum could be used to replace maize in commercial grower and finished diets without compromising the growth performance. The broader application of these results may be limited by the treatment methods used to ameliorate anti-nutritional factors in sorghum. However, this can be overcome by proper application of treatment methods and chemical characterisation of sorghum (Amino acids) before inclusion in the broiler diets. Further research is needed to evaluate sorghum with different processing methods that will reduce anti-nutritional factors, and to study various inclusion levels of processed sorghum on broiler starter, grower and finisher diets.

Ethical approval

The management and care of chickens were performed following the ethical guidelines of BUAN Animal Ethics Committee (BUAN AEC # 2020-08).

Acknowledgements

We are also grateful to Optifeeds (Botswana) for outstanding contribution

Disclosure statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

Data availability statement

Analysed data is available from the corresponding author on reasonable request.

Additional information

Funding

This work was financially supported by Research and Publication Committee (Alternative Poultry Feeds Project–A/C: 1510-1-16-60-46) of Botswana University of Agriculture and Natural Resources