Effects of corn replacement by sorghum in broiler chickens diets on performance, blood chemistry, and meat quality

Abstract

The influence of feeding a new hybrid of sorghum (ES Shamal, orange variety) in broiler chickens on growth, health, meat, and litter quality was evaluated from 1–42 d. A total of 360-day-old male Ross 308 broiler chicks (40.1 ± 2.3 g) were randomly assigned to 3 experimental diets: 100% corn-based diet (S0), partial replacement of corn with 50% sorghum (S50), total replacement of corn with sorghum (S100). All diets were calculated to be isonitrogenous and isocaloric with similar content of total lysine, total sulphur amino acids, calcium, and available phosphorous. The results indicated that partial or total replacement of corn by sorghum is suitable for broiler chicken diets with no adverse effects on growth, and slaughter performance, as well as litter quality over the whole trial period. Moreover, the substitution of corn with sorghum, reduced (p = .007) abdominal fat associated with an increase in breast and thigh meat colour (L* values; p < .001). Also, a significant (p = .002) decrease in plasma triglyceride was found in broilers fed sorghum-based diets. Except for collagen and hardness in the breast and thigh, and gumminess only in the thigh muscle, there were no differences in fundamental physicochemical (pH, protein, fat, moisture) or textural attributes of meat due to dietary treatment. However, sorghum alters the intestinal microflora, resulting in a lower count of E. coli in the caeca. It can thus, be concluded that sorghum (ES Shamal, orange variety) can be included in broiler feeds from hatching to day 42, without any adverse effects on the broiler’s performance.

HIGHLIGHTS

• Climate changes become a threat to the livestock sector and finding novel nutritional solutions for feeding farm animals became a priority.

• New sorghum varieties are valuable in terms of drought-resistant plants.

• Replacement of corn with sorghum in broiler diets maintains growth performances and carcase characteristics.

Keywords:

• Broiler
• sorghum
• performance
• plasma metabolites
• meat traits

Introduction

As a consequence of the consistent development of poultry production, there is an increasing demand for feed ingredients supplying energy and protein for poultry. Corn is the major cereal grain used globally in the poultry feed industry and certainly is the most common feed grain in Romania (Ciurescu et al. 2022a). The price volatility and changing availability of corn due to its use as an alternative fuel in ethanol production has stimulated interest in using other feed ingredients, less popular but upcoming crops such as sorghum grain. Furthermore, for several years, changing climatic (i.e. drought in combination with very high temperatures) conditions observed in European countries, including Romania, are favourable for sorghum development.

Sorghum (Sorghum bicolour L. Moench) is an important crop for food and feed in several regions of the globe, being the fifth most important cereal in the world in terms of volume of production after wheat, rice, corn, and barley (FAOSTAT 2020). The popularity of sorghum occurs due to its drought resistance (Batista et al. 2019; Reddy 2019; Isticioaia et al. 2020; Abreha et al. 2021), high yield potential (Clarke et al. 2019; Thomas et al. 2019), and various industrial applications. This plant provides a wide range of food (Althwab et al. 2015; Trappey et al. 2015; Anunciação et al. 2017), industrial (Dahlberg et al. 2012; Nghiem et al. 2016), and energy applications (Appiah-Nkansah et al. 2019). In comparison to corn, sorghum can withstand a long period without precipitation, often with almost no damage to plants. Plus, the new hybrids of sorghum are developed to be low content of anti-nutritional substances, especially tannins (Osman et al. 2022), and whose amounts in pigs (Pan et al. 2021) and broiler diets (Manyelo et al. 2019; Saleh et al. 2019; Puntigam et al. 2020) may be increased without the risk of a reduction in performance indices. In addition, these new sorghum varieties, especially those known as low-tannin, have good beneficial effects on poultry health due to their phytochemical constituents including phytosterols, anthocyanins, tannins, and phenolic acids (Awika et al. 2005). Moreover, some reports indicated that low concentrations of tannins can improve gut health (Moritz et al. 2023) and digestive performance in broiler chickens (Huang et al. 2018). Nonetheless, poultry farmers are reluctant to use sorghum-based diets, especially during the first week of the broiler’s life. Furthermore, data on the use of sorghum, especially of new hybrids grown in Romania in broiler nutrition, are currently scarce.

In this context, the present study aimed to investigate an appropriate inclusion level of sorghum (Sorghum bicolour L. Moench, ES Shamal hybrid) in broilers’ diet as an alternative to corn and to assess the effects on growth performance, blood plasma profiles, and meat quality.

Materials and methods

Birds, experimental design, and diets

A total of 360-day-old male Ross 308 broiler chicks with an average body weight (BW) of 40.1 ± 2.3 g, were purchased from a local commercial hatchery. Chicks were randomly assigned to a completely randomised design with three dietary treatments replicated 6 times having 20 birds per replicate. The trial lasted for 6 weeks. Chickens were reared in pens on a litter floor (wood shavings, 10 cm height) and placed in a climate-controlled room according to Ross Broiler Guide recommendations. The ambient temperature was maintained at thermoneutrality in compliance with bird age. Lighting was provided for 23 h/d from 1D to 7D, and from 8D, the light decreased by 1 h a day until 20 h, in conformity with EU legislation (EU Council Directive 2007/43/EC). Broilers were vaccinated only at the hatch for Marek’s, Newcastle, and Infectious Bronchitis Diseases.

Feed (in mash form) was offered ad libitum as follows: starter-grower (d 1 to 24), and finisher (d 25 to 42) feeding phases. The feeding trial was designed to partially (S50) or completely (S100) substitute corn with sorghum as an energy-yielding source. Dietary treatment S0 served as a control and contained a 100% corn-based diet without sorghum. The sorghum used in this experiment (ES Shamal, orange grain hybrid), was obtained from a plant breeding station (Research and Development Station for Plant Culture on Sandy Soils, Dăbuleni, DJ, Romania), and had low tannin content (0.72% catechin equivalent, according to the manufacturer’s specification).

Diets were formulated to be isonitrogenous, isocaloric, with similar content of total lysine, total sulphur amino acids (TSAA; Table 1), calcium, and available phosphorous, and to meet or exceed breeder guidelines (Ross 308, Aviagen Ltd., Midlothian, UK). Phytase (Axtra PHY 5,000 L, Danisco Animal Nutrition, Marlborough, UK) as exogenous enzymes were included in premixes of all diets. Metabolisable energy was calculated based on chemical analyses using the formula and digestion coefficients according to European tables of energy values of feeds for poultry (WPSA, 1989).

Table 1. Ingredients and nutrient composition of experimental diets (as-fed basis).

Diets	Starter-grower (1–24 days)			Finisher (25–42 days)
	Sorghum levels as a substitute for corn (%)
	S0	S50	S100	S0	S50	S100
Ingredients, %
Corn	57.98	30.50	0.00	64.09	33.40	0.00
Sorghum	0.00	30.50	61.00	0.00	33.40	69.75
Soybean meal, 45.6% CP	31.00	28.56	28.56	25.20	22.34	19.40
Corn gluten meal, 62% CP	4.00	4.00	4.00	3.50	3.50	3.50
Soy oil	2.00	1.30	1.30	2.60	2.70	2.60
Monocalcium phosphate	1.67	1.65	1.65	1.45	1.37	1.37
Calcium carbonate	1.45	1.49	1.49	1.27	1.32	1.30
Salt	0.28	0.28	0.28	0.28	0.28	0.28
L-lysine, 78%	0.29	0.35	0.35	0.28	0.33	0.41
Dl-methionine, 99%	0.25	0.29	0.29	0.25	0.28	0.31
Choline chloride	0.08	0.08	0.08	0.08	0.08	0.08
Premix^a	1.00	1.00	1.00	1.00	1.00	1.00
Calculated composition, %
ME, MJ/kg	12.70	12.70	12.68	13.33	13.33	13.34
Crude protein (CP)	22.0	22.0	22.0	19.5	19.5	19.5
Lysine, total	1.33	1.33	1.33	1.16	1.16	1.16
Lysine, digestible	1.20	1.25	1.25	1.05	1.07	1.07
TSAA	0.99	0.99	0.99	0.91	0.91	0.91
TSAA, digestible	0.90	0.90	0.91	0.83	0.84	0.85
Calcium	0.90	0.91	0.91	0.79	0.79	0.79
Av. phosphorous	0.45	0.45	0.45	0.40	0.40	0.40
Crude fat	4.92	4.52	4.51	5.63	5.72	5.80
Crude fibre	2.80	2.88	3.03	2.61	2.70	2.79
Analysed composition, %
Dry matter	89.77	89.93	90.04	89.82	89.98	90.03
Crude protein	22.09	21.94	22.05	19.52	19.50	19.51
Crude fat	4.94	4.68	4.62	5.72	5.80	5.92
Crude fibre	2.95	3.03	3.15	2.67	2.79	3.11

ME: metabolisable energy; TSAA: total sulphur amino acids. ^aSupplied per kg diet: 12,000 IU vitamin A, 5000 IU vitamin D3, 75 mg vitamin E, 3 mg vitamin K_3, 3 mg vitamin B₁, 8 mg vitamin B₂, 5 mg vitamin B₆, 0.016 mg vitamin B₁₂, 13 mg pantothenic acid, 55 mg nicotinic acid, 2 mg folic acid, 0.2 mg biotin, 120 mg Mn, 100 mg Zn, 40 mg Fe, 16 mg Cu, 1.25 mg I and 0.3 mg Se, 70 mg Monteban G100, 0.2 g Axtra PHY 5000 L (1000 FTU).

Feed chemical analyses

Samples of ingredients and feeds were analysed in duplicate for DM, CP, EE, CF, and ash content, using standard procedures by the methods of the European Commission Regulation (EC) no. 152 (OJEU, 2009). Nitrogen-free extract (NFE) content was calculated as follows: NFE (%) = dry matter % – (crude protein % + crude fat % + crude ash % + crude fibre %).

The content of dietary fibre fraction: neutral detergent fibre (NDF), acid detergent fibre (ADF), and acid detergent lignin (ADL) was determined with the classical semi-automatic Fibertec method (FOSS, Tecator AB, Höganäs, Sweden) as previously described by Ciurescu et al. (2018).

Growth performance and carcass measurements

The broilers’ body weight (BW, g) was measured at 1, 24, and 42 d of age. Feed intake (FI, g/bird) was recorded for the starter-grower (1–24 d), finisher (25–42 d), and the entire feeding period (1–42 d of age). Mortality was registered daily to calculate body weight gain (BWG, g/bird) and feed conversion ratio (FCR, g feed/g gain). Litter quality was visually scored on a 1 to 10-point scale of 24 and 42 d of age by 1 person. Litter quality was scored into 10 categories from 0 (dry and friable litter) to 10 (wet and 100% caked litter). The European production efficiency factor (EPEF) was calculated, as suggested by Huff et al. (2013), using the following formula: body weight (kg) x % viability × 100/feed-conversion ratio × trial duration in days.

At the end of the trial (d 42), six birds from each treatment (one per replicate pen with BW close to the average) were slaughtered and eviscerated, after fasting for 12 h. The relative weights of the breast, legs, abdominal fat, liver, gizzard, heart, spleen, thymus, and bursa of Fabricius as well as the gastrointestinal tract (GIT) were expressed as a percentage of the cold carcase weight. The length of the GIT (duodenum, jejunum, ileum, and caeca) was also measured and recorded.

Blood chemistry

Blood was collected from the wing vein into 5 mL heparinised tubes for plasma biochemistry assay. The biochemical profile of the plasma consisted of measurements of glucose (Glu), total cholesterol (T-Cho), triglycerides (TG), total protein (T-Pro), albumin (Alb), urea (BUN), total bilirubin (T-Bil), creatinine (Cre), uric acid (UA), calcium (Ca), magnesium (Mg), iron (Fe), alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyl-transferase (GGT), alkaline phosphatase (ALP), and lactate dehydrogenase (LDH). They were analysed using an automated dry chemistry system (model SP- 4430, Spotchem EZ, Arkray Global Business Inc., Kyoto, Japan) with a commercial kit from Arkray-diagnostic according to the manufacturer’s instructions.

Meat quality

Meat quality was evaluated using a Minolta CR-410 (Konica Minolta Co, Osaka, Japan) chromameter by measuring breast and thigh muscle colour parameters of lightness (L*), redness (a*), and yellowness (b*). The instrument was calibrated with a white tile and colour was expressed in CIE (2007) colour space. Simultaneously, duplicate pH values for each sample were measured after 24 h cold storage at 4 °C, using a portable pH-meter (model HI 99163, Hanna Instruments, Romania) equipped with a glass electrode and metal thermometer probe inserted 1 cm into the superior portion of the left breast and thigh muscles. Afterwards, samples were frozen at −20 °C until further analysis (proximate chemical composition and texture profile analysis).

Meat chemical composition, including moisture, protein, fat, and collagen was determinate as previously described by Ciurescu et al. (2022b), using a NIR (near-infrared reflectance) spectroscopy analyser (model DA6200, PerkinElmer, Inc, MA, USA). Texture profile analysis (TPA) of meat samples was performed using a texture analyser (model CT3, BROOKFIELD Engineering Laboratories Inc. MA, USA), equipped with a 50 kg load cell, and a cylinder probe of 76.2 × 10 mm to compress the samples and a fixture base table. The probe moved towards the sample at a constant speed of 2.0 mm s-1 (pre-test), 1.0 mm s-1 (test), and 2.0 mm s-1 (post-test). The data regarding hardness, gumminess, chewiness, springiness, adhesiveness, resilience, and cohesiveness were collected using Texture Pro CT Software. To minimise sampling error, samples were set in duplicates, and each duplicate was measured twice.

Microbiological analyses

The same slaughtered broilers were used for digesta microbial counts. The caecum was aseptically removed and placed in sterile plastic bags on ice. Then, in the lab, caecal digesta was homogenised with 7 mL of Brain Heart Infusion broth (Oxoid Basingstoke, Hampshire, UK) supplemented with 2 mL of glycerol and frozen at −20 °C until the analysis. After defrosting, decimal dilutions in phosphate-buffered saline (Dulbecco A; Oxoid Livingstone Ltd., London, England) were done. The samples were assessed for the total number of lactic acid bacteria (LAB) in Man Rogosa and Sharpe agar (MRS, Oxoid CM0361); coliforms in MacConkey agar (Oxoid CM0007); and Clostridium spp. in Reinforced Clostridial Agar (Oxoid CM0151). Escherichia coli (E. coli; biotype β-hemolytic) was determinate using the technique described by Dumitru et al. (2018). Salmonella spp. were enumerated on Salmonella–Shigella agar (Oxoid CM0099). Each sample had three replicates. The microflora level was expressed as colony-forming units (log₁₀ CFU g⁻¹) caecal content.

Statistical analysis

All data were subjected to Shapiro–Wilk and Kolmogorov–Smirnov normality tests; outliers were identified by the ROUT method (Q = 1%) and eliminated from the raw data. Afterward, the effects of the dietary treatments were analysed using the General Linear Model (GLM) method of the SPSS software (SPSS Statistics for Windows, Version 25, IBM). Post-hoc comparisons between treatments were investigated by Tukey’s test. The graphs were made in GraphPad Prism software, version 9 (GraphPad Software, La Jolla, CA, USA). The pen (replicate) was the experimental unit for the performance parameters evaluation. For carcase measurements, blood biochemistry, caecal microflora, and meat quality, each broiler was the experimental unit. The values were expressed as means and standard error of mean (SEM). The results were considered to be significant when p < .05 and tendency at .05 > p < .10.

Results and discussion

Nutrient composition of sorghum

The basic nutrients and fibre fractions of the ES Shamal sorghum hybrid used for this study are shown in Table 2. Several reports showed that sorghum had a similar chemical composition to corn (Mabelebele et al. 2015; Sekhon et al. 2016; Masenya et al. 2021). The protein content in the evaluated sorghum grain was slightly lower than that determined for the same hybrid studied by Croitoru et al. (2018) or by Manyelo et al. (2019) and was considerably higher than those observed by Mabelebele et al. (2015), who reported contents ranging from 81.1 to 95.4 g/kg DM. The fat content (38.7 g kg DM) measured in the current study was higher than other values reported in the literature. Manyelo et al. (2019) found a content of 26.7 g kg DM, similar to those reported by Mabelebele et al. (2015) for four sorghum varieties studied (ranging from 27 to 37 g/kg DM).

Table 2. Chemical composition of ES Shamal hybrid of sorghum.

Item	Nutrient content (g/kg DM)
Dry matter	898.7 ± 1.1
Crude protein	125.6 ± 3.9
Crude fat	38.7 ± 0.7
Ash	17.8 ± 1.1
Crude fibre	28.4 ± 2.6
NFE	789.5 ± 0.4
ME, MJ	14.7 ± 0.7
Fibre fractions
NDF	163.9 ± 0.7
ADF	55.1 ± 0.5
ADL	11.6 ± 0.2
CEL = ADF - ADL	43.5 ± 0.2
HCEL = NDF - ADF	127.3 ± 0.3
Calcium	0.7 ± 0.1
Phosphorus	3.9 ± 0.8

NFE: nitrogen-free extract; ME: metabolisable energy; NDF: neutral detergent fibre; ADF: acid detergent fibre; ADL: acid detergent lignin; CEL: cellulose; HCEL: hemicellulose.

Fibre components are one of the most important nutritional and technological factors of cereal grain. In the present study, the NDF fraction was higher than the values (117 to 148 g/kg DM) found by Mabelebele et al. (2015). The determined content of ADF fraction, which contains cellulose and lignin, fell within the range of 47.4 − 81.9 g/kg DM, as also reported by Mabelebele et al. (2015). The content of cellulose and hemicellulose was a result of the above-mentioned fractions. The variations in proximate chemical composition could be due to geographical, seasonal, climatic conditions, and soil characteristics.

Performance and litter quality

Performances and visual scores of the litter quality are presented in Table 3. There was no effect of the dietary treatments on growth performance (GP; BWG, FI, and FCR). The results show that broilers fed diets containing sorghum had comparable BWG, FI, and FCR to those fed corn-based diet, during the starter (1–24 d), finisher (25–42 d), as well as the overall (1–42 d) study period (p >.05). Litter quality at d 24 and d 42 was not affected by the dietary treatments. These findings are similar to several other studies (Torres et al. 2013; Manyelo et al. 2019) which concluded that partial or total replacement of corn by low-tannin sorghum did not affect performance measurements (FI, BWG, and FCR) at 1–21 days old. Additionally, Garcia et al. (2013) and Tandiang et al. (2014) also, did not find any differences in FI, BWG, or feed conversion when evaluating the growth performance at any rearing phase of broiler-fed low-tannin sorghum-based diets. Moreover, Saleh et al. (2019) noted that corn replacement with low-tannin sorghum at a ratio of 100% in broiler diets from 15 to 27 days of age increased significantly BWG and FI, and consequently improved FCR. Earlier studies by Pour-Reza and Edriss (1997) noted that tannins did not significantly affect broiler performances when dietary tannin concentration did not exceed 2.6 g/kg. Our results demonstrated that a total replacement of corn with a modern hybrid of sorghum grain (ES Shamal) is feasible without negative effects on GP, especially in young birds (from one day old).

Table 3. Effects of dietary treatments on performance variables (mean values^a) of broiler chickens^b.

Parameters	Dietary treatment			SEM^c	p-value
	S0	S50	S100
BWG, g
1–24 d	1059	1048	1061	17.805	0.711
25–42 d	1617	1654	1622	41.089	0.951
1–42 d	2676	2702	2680	36.916	0.945
Feed intake, g
1–24 d	1539	1525	1545	7.838	0.797
25–42 d	3044	3070	3055	21.585	0.534
1–42 d	4583	4594	4591	24.363	0.793
FCR, g/g
1–24 d	1.45	1.46	1.46	0.007	0.998
25–42 d	1.88	1.86	1.88	0.019	0.577
1–42 d	1.71	1.70	1.71	0.008	0.787
Litter quality^d
24 d	7.6	7.5	7.5	0.062	0.645
42 d	7.8	7.6	7.5	0.061	0.503
EPEF^e (1–42 d)	371.76	378.15	373.16	9.245	0.829

BWG: bodyweight gain; FCR: feed conversion ratio. ^aData are means of 6 replicate pens with 20 birds per pen. ^bSurvival rate =100%. ^cSEM, standard error of the mean. ^dLitter quality score ranged from 0 (wet and 100% caked to 10 (dry and friable litter). ^eEPEF, European Production Efficiency Factor.

Carcase traits

The results showed that the partial or total replacement of corn with sorghum did not affect (p >.05) the carcase, breast, and legs’ yield of birds, at 42 d, but it altered the abdominal fat (p = .007; Table 4). No effects of different sorghum inclusion on gizzard, liver, and heart weights, as well as lymphoid organs (i.e. spleen, thymus, and bursa) as a percentage of carcase at slaughter, were found. These findings are in line with Puntigam et al. (2020) who concluded that the partial or total replacement of corn by ground or whole grain low-tannin sorghum in broiler diets did not influence the zootechnical or slaughter performance parameters when the nutrients were balanced. Other previous studies (Garcia et al. 2013; Torres et al. 2013; Tandiang et al. 2014; Gheorghe et al. 2017; Saleh et al. 2019) also, reported that partial or total replacement of corn by low-tannin or tannin-free grain sorghum did not affect carcase and carcase parts. Van Krimpen et al. (2015) noted that the edible organ weights (i.e. liver) were also not affected by the cereal type. Contrary, in the study by Córdova-Noboa et al. (2018), results showed that broilers fed sorghum diets expressed less dressing and breast meat yield, than broilers fed corn diets. These adverse effects were explained by the impact of high tannin contents on amino acid bioavailability.

Table 4. Effects of dietary treatments on results of slaughter analysis (mean values^a) of broiler chickens.

Parameters	Dietary treatment			SEM^b	p-value
	S0	S50	S100
Carcass^c	76.14	76.33	76.39	0.887	0.508
Breast^d	38.97	39.32	39.55	0.683	0.065
Leg^d	27.82	27.78	27.63	0.519	0.103
Abdominal fat^d	1.07^a	0.62^b	0.87^ab	0.085	0.007
Gizzard^d	1.88	1.93	1.74	0.123	0.474
Liver^d	2.79	2.87	2.96	0.059	0.149
Heart^d	0.59	0.57	0.59	0.038	0.480
Lymphoid organs^d
Spleen	0.13	0.14	0.14	0.007	0.589
Thymus	0.22	0.24	0.22	0.003	0.967
Bursa of Fabricius	0.14	0.13	0.15	0.002	0.510
GITW^d
Duodenum	0.75	0.68	0.72	0.031	0.264
Jejunum	1.38	1.33	1.36	0.057	0.746
Ileum	1.24	1.17	1.19	0.072	0.446
Caeca	0.31	0.32	0.32	0.016	0.978
GITL^e
Duodenum	1.74	1.72	1.78	0.044	0.778
Jejunum	4.29	4.39	4.33	0.095	0.242
Ileum	4.25	4.27	4.37	0.080	0.511
Caeca	1.84	1.67	1.75	0.074	0.231

GITW: gastrointestinal tract weights; GITL: gastrointestinal tract length. ^aData are means of 6 broilers per dietary treatment. ^bSEM: standard error of the mean. ^cRepresents as eight (g) of without head, neck, feet, and viscera carcase as 100 g of live body weight. ^d,eCalculated as relative weight or length (g and cm) of organs as 100 g carcase.

In the current study, the low percentage of abdominal fat may partly be attributed to the slightly greater fibre concentration of sorghum groups compared to the control group, but also could be related to phytogenic formulations in broiler diets (Abdel-Wareth et al. 2019). These findings are similar to those of Cherian et al. (2002) who found less accumulation of abdominal fat in broiler chickens fed diets containing high levels of sorghum, or to those of Saleh and Alzawqari (2021) when an olive cake meal was used as energy byproduct to corn replacement. Lower carcase fat content would also be beneficial to consumer health.

As shown in Table 4 the weight and length of the GIT (i.e. duodenum, jejunum, ileum, and caeca) of 42-d-old broilers, we’re not significantly affected by corn and dietary sorghum treatments (p > .05). This finding is in line with a study by Silva et al. (2015), who compared ground maize, sorghum, and whole-grain sorghum in broilers and found similar small intestine (SI) and caeca across the treatment diets. Similarly, the graded level of white sorghum meal did not result in any difference in the weights of the liver or intestine, or the intestinal length when included in the broiler chicken diets to replace maize (Ibe and Makinde 2014). Recently, Manyelo et al. (2019) reported that the absolute and relative weights of the SI and large intestine were not affected by the sorghum replacement level. Generally, chicks might require a minimal amount of fibre in the diet to stimulate the development of the upper GIT. Our results indicate a similarity in the nutritive value of diets based on corn or low-tannin sorghum to broilers.

Plasma blood parameters

Blood biochemistry is a labile biochemical system that can reflect the condition of the organism and the changes happening to it under the influence of internal and external factors. Data for the biochemical components of blood plasma show no significant impact of diet type on plasma biochemical constituents (Glu, T-Cho, T-Pro, Alb, BUN, T-Bil, Cre, UA, Ca, Mg, and Fe; Table 5). However, TG levels of the broilers fed sorghum diets (S50 and S100) were statistically lower (p = .002). This finding is in line with a study by Saleh et al. (2019), who noted that feeding low-tannin sorghum decreased plasma triglycerides and total cholesterol concentration in broilers. Sorghum contains phytosterols (or plant sterols) which are cholesterol-like composition and involved in the structural components of all plant cell membranes. In recent years, there is a large interest in these phytosterols due to their advancement of human and animal health like cardiovascular health, especially out of their cholesterol-lowering properties (Poli et al. 2021). Phenolic compounds and proanthocyanidins in sorghum were explained as having modest cholesterol-lowering ability in animal and human studies (Santos-Buelga et al. 2019). Plasma glucose level also tends to be decreased by sorghum substitutions, and this may be due to the polyphenolic content in sorghum (Krueger et al. 2003).

Table 5. Effects of dietary treatments on blood biochemical parameters (mean values¹) of broiler chickens.

Parameters	Dietary treatment			SEM^2	p-value
	S0	S50	S100
Plasma energy profile
Glu, mg/dL	220.10	208.19	203.67	8.00	0.540
T-Cho, mg/dL	108.17	98.33	106.86	7.03	0.506
TG, mg/dL	49.97^a	29.83^b	30.83^b	4.66	0.002
Plasma protein profile
T-Pro, g/dL	2.70	2.67	2.63	0.12	0.463
Alb, g/dL	0.95	0.88	0.92	0.05	0.871
BUN, mg/dL	2.90	3.00	2.83	0.14	0.574
T-Bil, mg/dL	0.10	0.13	0.10	0.02	0.162
Cre, mg/dL	0.05	0.08	0.07	0.02	0.092
UA, mg/dL	4.68	3.32	3.02	0.82	0.337
Plasma mineral profile
Ca, mg/dL	8.27	10.87	10.42	0.83	0.101
Mg, mg/dL	1.92	2.06	2.08	0.09	0.123
Fe, μg/dL	4.95	5.62	5.95	0.29	0.082
Plasma enzyme profile
ALT, U/L	15.17	10.50	11.50	2.29	0.317
AST, U/L	287.17	309.67	303.00	86.30	0.323
ALP, U/L	2441.50	1383.67	3037.17	612.25	0.188
GGT, U/L	49.00	47.83	47.17	4.98	0.345
LDH, U/L	2609.33	3239.83	3279.00	511.37	0.594

Glu, glucose; T-Cho, total cholesterol; TG, triglyceride; T-Pro, total protein; Alb, albumin; BUN, urea; T-Bil, total bilirubin; Cre, creatinine; UA, uric acid; Ca, calcium; Mg, magnesium; Fe, iron; ALT, AST, ALP, alkaline phosphatase; GGT, LDH. ^a,bMeans in the same row without the same superscript differ significantly (p < .05).^cData are means of 6 broilers per dietary treatment. ^dSEM: standard error of the mean.

Plasma ALT, AST, ALP, GGT, and LDH are parameters for liver damage assessment, and diagnosis of these enzymes is frequently used for hepatic function evaluation. In the present study, the total replacement of corn with sorghum did not affect the activity of these plasma enzymes, indicating that the energy source or level did not affect liver health. Similarly, Saleh et al. (2019) noted that feeding sorghum to broiler chicks did not significantly affect blood GOT and total protein contents.

Meat quality

Consumers consider the safety and high quality of products to be essential aspects of poultry consumption. Diet is the most frequent environmental factor that directly influences meat quality. Generally, meat quality is characterised by such parameters as pH, colour, and texture attributes and along with meat’s chemical composition (crude protein, fat, and water content) are one of the major features that translate to meat value.

The effect of diets on the physicochemical composition of breast and thigh muscles of broiler chickens is presented in Table 6. There were no differences in fundamental components (i.e. protein, fat, moisture) of breast and thigh muscles due to dietary treatment. However, the source of variability in diets influenced total collagen amounts. The breast and thigh muscles collected from broilers under the sorghum treatments (S50 and S100) registered a higher collagen content (p < .0001) than the S0 treatment.

Table 6. Effects of dietary treatments on physicochemical parameters of breast, and thigh muscle (mean values^d) of broiler chickens.

Parameters	Dietary treatment			SEM^e	P-value
	S0	S50	S100
Breast muscle
Moisture, %	76.60	76.50	76.55	0.30	0.969
Protein, %	21.18	21.22	21.12	0.31	0.977
Fat, %	1.46	1.51	1.60	0.10	0.639
Collagen, %	0.69^c	0.85^b	0.91^a	0.01	0.000
pH24	6.10	6.05	6.07	0.08	0.362
L*	55.44^c	60.62^a	58.98^b	0.70	0.001
a*	10.87	11.18	10.93	0.44	0.564
b*	12.27	12.22	12.34	0.52	0.771
Thigh muscle
Moisture, %	75.96	75.93	75.98	0.21	0.988
Protein, %	18.10	18.07	18.03	0.08	0.872
Fat, %	5.79	5.89	5.92	0.10	0.654
Collagen, %	1.02^c	1.13^b	1.26^a	0.01	0.000
pH24	6.15	6.14	6.11	0.02	0.120
L*	55.65^b	60.28^a	60.70^a	0.57	0.001
a*	11.40	11.32	11.44	0.53	0.673
b*	9.28	9.16	9.23	0.67	0.515

pH_24, pH 24 h after slaughter; L*, lightness; a*, redness; b*, yellowness. ^a,b,c Means in the same row without the same superscript differ significantly (p < .05); ^dData are means of 6 broilers per dietary treatment. ^eSEM, standard error of the mean;

Since it is directly perceived by the consumer, meat colour is an essential quality parameter. In our study, the colour of broiler meat was slightly affected by the total replacement of corn with sorghum (Table 6). Broilers fed sorghum diets (S50 and S100) had significantly (p < .001) lighter colour breast and thigh meat (higher L* values), compared with the meat from broilers fed the corn diet. Meat redness (a* value) and yellowness (b* value) of breast and thigh samples did not differ significantly (p > .05) among treatments. This effect is probably due to the presence of pigment that this sorghum hybrid (orange grain, ES Shamal variety) contains it. In our study, it is not surprising that meat from sorghum birds may have a higher lightness value. Lightness (L*) is a good indicator of the freshness of meat and has a direct influence on the final purchase decision of consumers (Mancini and Hunt, 2005). An opposite response for lightness was observed by Garcia et al. (2013) and Córdova-Noboa et al. (2018) where no differences (p > .05) between treatments were detected in breast meat due to grain type. When meat quality is assessed, objective criteria such as pH, skin, and meat colour are taken into account. In our study, even if the breast or thigh samples showed a higher lightness, the pH value was within a normal range (5.5-6.5) for broilers (Ao et al. 2008), suggesting that the inclusion of sorghum in a broiler diet did not affect glycogen levels. The pH range is an indication of how much glycogen was in the breast or thigh muscle before slaughter, and how rapidly the remaining glycogen was converted to lactic acid after slaughter. The pH 24 h after the slaughter, obtained in the present study can be considered normal and ranged between 6.05 and 6.10 for breast and between 6.11 and 6.15 for thigh meat.

No significant differences due to the dietary inclusion of sorghum into broilers’ diets were observed for some of the TPA parameters (chewiness, springiness, adhesiveness, resilience, cohesiveness) of breast and thigh muscles (Figures 1 and 2). Only hardness was statistically lower in the breast (p = .041) and thigh muscle (p = .001) of broilers fed sorghum diets, as well as gumminess in the thigh muscles (p = .030), particularly at higher levels (S100) when compared with the corn diet. Unfortunately, to the best of our knowledge, no studies exist investigating instrumental TPA of poultry meat from broilers fed sorghum diets. Hardness refers to the maximum resistance of meat to being bitten by teeth. Gumminess (the combination of hardness and cohesiveness) is explained as the energy required to chew meat products (Xiong et al. 2022). Grashorn (2006) found that nutrient levels did not impact the texture of the broiler breast meat. In our study, the decreased hardness with the inclusion of sorghum grain is desirable because it is an important textural attribute in the determination of acceptable meat.

Figure 1. Textural properties of breast muscle (data are means of 6 broilers per dietary treatment). ^a-bWithin each treatment, means without the same superscript differ significantly (p < .05).

Figure 2. Textural properties of thigh muscle (data are means of 6 broilers per dietary treatment). ^a-bWithin each treatment, means without the same superscript differ significantly (p < .05).

Microflora of caecal digesta

The microbial community in the gut can have either a positive or negative impact on gut health and bird performance. It has been demonstrated that a healthy intestinal tract is important for efficient digestion, nutrient absorption, and consequently, optimal performance (Choct, 2009). Although limited data are available to support the use of tannin-free varieties of grain sorghum as an alternative feed to corn in broiler diets, there are also limited data regarding its effectiveness in inhibiting pathogenic bacteria and therefore improving the growth and health of the chicks. In the current study, although no significant differences were detected among dietary treatments for Coliforms, and LAB, there was a significant decrease (p < .05) in Escherichia coli populations and Clostridium spp. when the sorghum diets were compared with the corn (Figure 3). In a previous study by Gheorghe et al. (2017) a decrease in the E. coli and Enterobacteriaceae population, concomitant with an increase in the lactobacilli counts in the ileum was reported in broilers fed a white grain sorghum diet compared with corn diet. Another study on the replacement of corn with sorghum showed a decrease in Clostridium levels and an increase in the Lactobacillus in the small intestine and caeca in chickens fed sorghum-based diets (Fagundes et al. 2017). Also, Shields et al. (2021) found that lower levels of Clostridium in the small intestine of broilers could be due to the total phenols and tannins concentration in the sorghum grains, associated with efficient antimicrobial activity against C. perfringens or Salmonella enterica.

Figure 3. Microflora evaluation of caecal digesta at d 42. ^a,b Means with different superscripts within the same bacterial species are significantly different at p < 0.05.

Conclusions

The obtained results indicate that modern sorghum grain (ES Shamal variety) could be an alternative energy source for corn-based diets without any detrimental effects on the growth performance of younger chickens from 1-42 days of age. Also, providing sorghum-based diets did not affect the carcase, breast, and legs’ yield as well as organ size. Furthermore, our results indicated that this cereal can modify plasma lipids and improve some meat quality traits in broilers. Results may also allow nutritionists in the commercial poultry industry to consider using the inclusion of sorghum grain as an alternative to corn.

Ethical approval

The birds’ care and use protocol was approved by the Animal Ethics Committee of the National Research-Development Institute for Biology and Animal Nutrition, Balotești, Romania, following the principles of EU Directive 2010/63/EU and Romanian law on Animal Protection.

Disclosure statement

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

Data availability statement

The data presented in this study are available on request from the corresponding author upon reasonable arguments.

Additional information

Funding

This study was financially supported by the Romanian Ministry of Research, Innovation, and Digitisation (project no. PN23-20.04.01 and project no. PFE 8/2021).