Carcass characteristics and meat quality of adult Sahelian does fed a basal diet of Brachiaria decumbens grass supplemented with probiotics and concentrates

Abstract

A 14-week feeding trial was conducted to evaluate the effects of supplementing probiotics and concentrates on carcass characteristics and meat quality of Sahelian does fed a basal diet of Brachiaria decumbens grass. Twenty-four does weighing averagely 13.3 ± 1.16 kg and aged averagely 12 months were randomly allocated to four treatments of six does each in a Completely Randomised Design with 2 × 2 factorial arrangement. The factors were levels of probiotics (0 and 100 g per 100 kg of concentrate) and concentrate (500 g and 1000 g per day). On the last day of the feeding trial, three goats per treatment were slaughtered by severing the jugular veins of the throat and trachea without stunning. Carcass characteristics were determined, and meat samples from longissimus lumborum were taken for analysis of the proximate composition and evaluation of fatty acid profile. The results showed that supplementing higher levels of concentrate and probiotics led to improved dressing percentage without any deleterious effect on the weights of internal organs, increased crude protein content and reduced crude fat content of the meat. The results further showed reductions in saturated fatty acid concentrations and increases in unsaturated fatty acid concentrations. It was concluded that the probiotics could be incorporated at 100 g per 100 kg of the concentrate and fed at 1000 g/d for improved carcass quality.

Keywords:

• Carcass
• probiotics
• concentrates
• fatty acids

1. Introduction

Animal production aims to produce good quality animal protein through the provision of eggs, milk and meat for human consumption. To this end, good nutrition in terms of both quality and quantity is a prerequisite for realising this objective. According to Okai et al. (2005), research over the years has highlighted the general scarcity in the supply of protein of animal origin in the tropics. This scarcity could partly be due to fluctuations in the quantity and nutritive value of natural forages attributable to seasonal variations. In effect, ruminant livestock production in Ghana is dependent on the availability of natural pastures, which in turn is rainfall-dependent. This trend eventually results in the yearly cycle of ruminant livestock gaining weight during the wet season and losing it during the dry season (Ocheja et al., 2016). Integrating agro-industrial by-products into ruminant diets as supplements can go a long way to alleviate the shortfall in feed supply and its attendant high cost, particularly during the dry season. This is particularly important as the demand for goat meat usually surges during festive occasions like Easter and Christmas in Ghana.

Goat meat is reportedly lean and rich in nutrients, meeting the requirement of the modern-day health-conscious consumers. Nonetheless, several factors such as genetic make-up, breed, age, sex and type of feed all bring about variations in the composition of goat meat (Casey et al., 2003; Dhanda et al., 2003; Goetsch et al., 2011). Goat meat is a rich source of animal protein (19.95% − 20.55%) and essential amino acids (Ivanovic et al., 2016) that meet dietary protein requirements. Fat levels in goat meat range from 47–54%, less than those of mutton and beef (Lima et al., 2018). The contents of desirable fatty acids are also higher than those for mutton and beef (Rhee, 1992). One of the cardinal objectives of ruminant nutrition studies is to produce healthy animal products like milk and meat. Such healthy products should have, for instance, fat deposits that are higher in unsaturated fatty acids (UFAs) but lower in saturated fatty acids (SFAs), according to Oliveira, Faria, et al. (2015, b). This is notable as meat higher in UFA lessens the danger of atherogenic plaque in the arteries, thereby preventing cardiovascular and metabolic diseases (Kaberia et al., 2003). Fatty acids (FAs), according to Maleki et al. (2015), are key to appropriate cellular function and health and are vital for the breakdown and absorption of the fat-soluble vitamins A, D, E and K from the diet.

Increasing concern for physical welfare coupled with good health has heightened the need for information regarding the intake of healthy foods of animal origin (Lima et al., 2018) of which goat meat is no exception. Research has proven that feeding regime is an important factor in the growth performance and meat quality of farm animals (Liu et al., 2022). Probiotics are noted for features that promote health (Nocek et al., 2002) and could be valuable for improving meat quality. They also help to boost the efficiency with which nutrients are utilized (Khalid et al., 2011). The productivity potential of goats could also be enhanced through supplementation (Alih et al., 2021; Paula et al., 2020). The use of concentrate supplementation for goats on grass basal diet has been reported by Gama et al. (2022) to lead to higher carcass weight and yield. D. C. Silva et al. (2016) have also reported increases in feed intake and dry matter digestibility resulting in higher average daily gains. Soares et al. (2016) found goats supplemented with protein-energy concentrate to perform better in terms of weight gain as well as hot and cold carcass weights. Concentrate supplementation has also been utilized as vital nutritional management tool to boost productivity and improve the health of livestock (Yousuf et al., 2014) as it can impact positively on the immune system.

Despite the numerous benefits of supplementing probiotics and concentrates, how probiotics and locally formulated concentrates from agro-industrial by-products influence carcass characteristics and meat quality of intensively managed does is unavailable in Ghana. It is against this background that this experiment sought to assess the effects of probiotics and home-made protein-energy concentrates (compounded from millet mash residue and wheat bran) as supplements on carcass characteristics and meat quality (proximate components and fatty acids) of Sahelian does fed Brachiaria decumbens grass as basal diet.

2. Materials and methods

2.1. Experimental location

This trial was conducted at the Livestock Section’s Meat Processing Unit, Department of Animal Science, KNUST. The experimental location can be found between Latitude 06°43”N and Longitude 1°36”W. The area lies inside the humid semi-deciduous forest belt with a bimodal rainfall distribution. The average annual rainfall for the site is around 1194 mm. The mean maximum and minimum temperatures for the location are 32.0°C and 22.1°C (Weather Spark, 2022). The proximate analyses of the meat samples were conducted at the Nutrition Laboratory of the same Department, while the fatty acid analyses (SFA and UFA) were done at the Instrumentation Laboratory, Department of Chemistry, KNUST.

2.2. Sources of experimental feed and probiotics

The basal diet used for the study was B. decumbens regrowth at 60 days after sprouting. Harvesting of the regrowth continued till the termination of the study. The grass was harvested fresh each morning, chopped to a length of 10-15 cm and fed individually to the goats. The analysed chemical composition of B. decumbens is given in Table 1

Table 1. Chemical composition of air-dried B. decumbens on dry matter basis

Chemical component	Value
Dry matter (g/kg)	929.5
Crude protein (g/kgDM)	77.9
Ether extract (g/kgDM)	72
Ash (g/kgDM)	76
Nitrogen free extract (g/kgDM)	289.1
NDF (g/kgDM)	644.0
ADF (g/kgDM)	316.4
Cellulose (g/kgDM)	261.4
Hemicellulose (g/kgDM)	327.6
ADL (g/kgDM)	55
*Metabolizable energy (Kcal/kg)	1887.92

Notes: *Estimated according to Pauzenga (1985): ME (kcal/kg) = (35 x percentage crude protein) + (81.8 x per cent ether extract) + (35.5 x percentage nitrogen free extract)

The concentrate was compounded from millet mash residue (obtained from Hausa “Koko” preparation from Koko sellers within the Kumasi Metropolis), wheat bran, oyster shell, salt, and vitamin-mineral premix, all acquired from local suppliers. Millet mash residue is a by-product of obtained from the preparation of “Hausa Koko” (millet porridge) and millet beer. Dried millet mash residue alone is usually too powdery for ruminants. Mixing it with wheat bran (as used in this study) gave it the right texture and boosted its nutritive value as a protein and energy concentrate. The details of all ingredients used in formulating the concentrate are shown in Table 2.

Table 2. Percentage inclusion of dietary ingredients and chemical composition of concentrate

Ingredient	Percentage inclusion
Millet mash residue (g/kg)	485.0
Wheat bran (g/kg)	485.0
Vitamin Mineral Premix^1 (g/kg)	10.0
Oyster shell (g/kg)	10.0
Common salt (g/kg)	10.0
Total	1000
Analysed Composition (%)
Dry matter (g/kg)	854.0
Crude protein (g/kgDM)	155.7
Crude fibre (g/kgDM)	110.4
Ether extract (g/kgDM)	13.6
Ash (g/kgDM)	94.3
Nitrogen free extracts (g/kgDM)	480.0
Neutral detergent fibre (g/kgDM)	370.0
Acid detergent fibre (g/kgDM)	130.0
Cellulose (g/kgDM)	100.0
Hemicellulose (g/kgDM)	240.0
Acid detergent lignin (g/kgDM)	30.0
*Metabolizable energy (Kcal/kg)	2364.75

Notes: ¹Vitamin-mineral premix: contains the following/kg diet: vitamin A − 8000 IU; vitamin D − 3000 IU; vitamin E − 8 IU; vitamin K− 2 mg; vitamin B1–1 mg; vitamin B 2–2.5 mg; vitamin B 12–15 mcg; niacin − 10 mg; pantothenic − 5 mg; antioxidant − 6 mg; folic acid − 0.5 mg; choline −150 mg; iron −20 mg; manganese − 80 mg; copper − 8 mg; zinc − 50 mg; cobalt − 0.225 mg; iodine − 2 mg; selenium − 0.1 mg.

*Estimated according to Pauzenga (1985): ME (kcal/kg) = (35 x percentage crude protein) + (81.8 x per cent ether extract) + (35.5 x percentage nitrogen free extract)

Vicbinzy Powder Probiotics (multi-strain), a commercial product purchased from a local veterinary store at Amakom in Kumasi, was used as the source of probiotic supplementation. Vicbinzy Powder, supplied by Hebei Weierli Pharmaceutical Group Co., Ltd., China, is composed of Clostridium butyricum (≥5.0 × 10⁷), Bacillus subtilis (1 × 10⁹cfu/g) and Lactobacillus delbrueckii subsp (1.8×10⁹cfu/g).

2.3. Experimental design and treatments

Twenty-four Sahelian does weighing averagely 13.3 ± 1.16 kg and aged 12–15 months were randomly allotted to a 2 × 2 factorial in a Completely Randomised Design (CRD) with six replications for the 98-day feeding period, preceded by a 14-day period of adaptation. The factors were levels of probiotics (0 and 100 g per 100 kg of concentrate) and concentrate (500 g and 1000 g per day). The four treatments imposed were designated P₀C₅₀₀ for ‘no probiotics with lower level (500 g/d) of concentrate supplementation, P₀C₁₀₀₀ for “no probiotics with higher level (1000 g/d) of concentrate supplementation”, P₁₀₀C₅₀₀ for “probiotics (100 g/100 kg of concentrate) with lower level (500 g/d) of concentrate supplementation” and P₁₀₀C₁₀₀₀ for ‘probiotics (100 g/100 kg of concentrate) with higher level (1000 g/d) of concentrate supplementation. All treatments were fed B. decumbens grass as basal diet. Thus, the sources of variability were the levels of supplementation of the concentrate and probiotics.

2.4. Slaughter procedure

At the completion of the 98-day feeding and growth trial, three does from each treatment group, totalling 12 does, were randomly selected and moved from the pens on the farm to the lairage at the Meat Science Section, Department of Animal Science, where pre-slaughter live weight was recorded after twelve hours of fasting but with water available. The live weights of the does were determined using an electronic crane scale (Model OCS−300, Ningbo Lianchung Scale Co., Ltd). The does were then moved to the slaughter area. The does were euthanised according to the traditional Halal method, which does not involve pre-stunning the animal. In this method, no mechanical restraint or stunning equipment were utilized; instead, the does were manually positioned in a prone position, and sticking was performed by an adult Muslim, by severing the carotid artery, jugular vein, trachea and oesophagus in a single swift motion, without lifting the knife from the animal’s throat following the procedure by Kiran et al. (2019). Blood from each slaughtered doe was collected and weighed during exsanguination.

2.5. Evisceration of carcasses and carcass evaluation

The slaughtered does were singed after bleeding using liquefied petroleum gas flame and thoroughly washed with tap water before evisceration and evaluation of carcasses. The feet and head were detached and weighed separately.

The gastrointestinal tract was taken out and weighed full and empty to get the “gut fill” weight. The heart, kidney, liver, lungs, trachea, and spleen were separated and weighed individually and expressed as percentages of slaughter weights. The hot carcass weight of each animal was recorded approximately one hour post-mortem using an electronic crane scale (Model OCS−300, Ningbo Lianchung Scale Co., Ltd.), and the dressing percentage was determined by calculating the ratio of the carcass weight to the animal’s pre-slaughter live weight. The carcass was chilled for twenty-four hours at 3°C−4°C using deep freezers and reweighed to obtain the chilled carcass weight.

2.6. Animal care and welfare

All the necessary standard operating procedures outlined by the Animal Research Ethics Committee (AREC, 2018) of the Quality Assurance and Planning Unit of the Kwame Nkrumah University of Science and Technology, Kumasi were followed.

2.7. Proximate composition of meat samples

The carcasses were cut, and the longissimus lumborum muscle was used to assess the meat quality based on the proximate components. The following parameters were determined; moisture, dry matter, crude protein (CP), crude fibre (CF), crude fat and ash according to the procedure of AOAC (2005).Nitrogen-free extract (NFE) was calculated with the following formula:

$\mathrm{\%}\mathrm{N}\mathrm{F}\mathrm{E}=100-\left(\mathrm{\%}\mathrm{M}\mathrm{o}\mathrm{i}\mathrm{s}\mathrm{t}\mathrm{u}\mathrm{r}\mathrm{e}+\mathrm{\%}\mathrm{C}\mathrm{F}+\mathrm{\%}\mathrm{C}\mathrm{P}+\mathrm{\%}\mathrm{F}\mathrm{a}\mathrm{t}+\mathrm{\%}\mathrm{A}\mathrm{s}\mathrm{h}\right).$

2.8. Extraction procedure and derivatization of fatty acids

Five millilitres (5 ml) of chloroform methanol (2:1) mixture solution was mixed with 1 g of the homogenized meat sample and shaken for 5 minutes for oil extraction. Afterwards, the resulting mixture was centrifuged (Ohaus Centrifuge, Model: FC5706, Germany) at 4000 rpm for 5 minutes. Two millilitres (2 ml) of the extract were taken and dried. One millilitre (1 ml) of 2 M methanolic, potassium hydroxide (KOH) and five millilitres (5 ml) of hexane were added to the extracted oil and shaken for 5 minutes. It was then allowed to stand for about 10 mins, and an aliquot of the hexane layer was taken for Fatty Acid Methyl Esters (FAME) analysis.

2.9. Instrumentation

The FAMEs oils contents were spotted qualitatively and quantitatively with the Shimadzu GC−2010 plus Gas Chromatograph (Shimadzu Corporation, Tokyo, Japan) along with an Auto-Injector (AOC−20i) and an Auto-Sampler (AOC−20s). A capillary column VF−5 ms (5% phenyl, 95% dimethylpolysiloxane) of 30 m length, 0.25 mm internal diameter, and 0.25 mm film thickness was installed in the GC apparatus. A 1 μL aliquot of the sample was introduced into the GC. The injector temperature was set at 250°C with a split mode at a split ratio of 1:10. As a carrier gas, nitrogen gas (99.9%) was employed at a constant flow rate of 1 mL/min. The temperature of the flame ionization detector (FID) was adjusted to 280°C. The column was programmed with an initial temperature set at 100°C (hold time 1 min), increased at a rate of 25°C/min to 200°C (hold time, 1 min), then to 250°C at a rate of 5°C/min (hold time, 7 mins) and finally to 270°C at a rate of 5°C/min (hold time 3 mins) during the analysis. By comparing the retention times to a reference standard (C8 –C24 FAMEs Mixture, SUPELCO, Bellefonte, PA, USA), the individual FAMEs were identified.

2.10. Statistical analysis

The data obtained from the proximate composition, carcass characteristics and fatty acid profile were analysed as a 2 × 2 factorial in a Completely Randomised Design (CRD) using Analysis of Variance (ANOVA) of Minitab Statistical package Version 18.1 (2017). The means were separated by Bonferroni pairwise comparison. Differences between means were deemed significant at P < 0.05.

3. Results and discussion

3.1. Effects of probiotic and concentrate supplementation on slaughter live weight and carcass characteristics of does

Effects that the treatments imposed had on carcass characteristics are presented in Table 3. Interaction between probiotic and concentrate was significantly present (P < 0.05) for all parameters except for slaughter body weight, blood weight and chilling loss. Marques et al. (2014) and Souza et al. (2015) have also earlier reported improvements in carcass traits due to supplementation. Values recorded for the exceptions observed were alike (P > 0.05) for the various dietary treatments. The exceptions observed could be due to age, nutrition, sex, pre-slaughter weight and gut fill (Vergara et al., 1999).

Table 3. Effects of probiotic and concentrate supplementation on slaughter live weight and carcass characteristics of does on treatment diets

Prob. level	Treatments				SEM	Significance
	0		100			P values
Conc. level	500 P0C500	1000 P0C1000	500 P100C500	1000 P100C1000		Prob.	Conc.	Prob.* Conc.
Parameter
Slaughter body weight (kg)	18.50	19.30	20.47	21.10	0.396	0.017	0.259	0.889
Hot carcass weight (kg)	9.40^b	10.11^ab	10.69^ab	11.42^a	0.255	0.005	0.053	0.019
Cold carcass weight (kg)	9.14^b	9.85^ab	10.40^ab	11.13^a	0.250	0.005	0.051	0.019
Empty body weight (kg)	11.91^b	12.69^ab	13.37^ab	14.10^a	0.291	0.010	0.098	0.019
Chilling loss (%)	2.80	2.63	2.70	2.57	0.045	0.401	0.155	0.863
Dressing percentage	50.81^b	52.38^ab	52.22^ab	54.12^a	0.647	0.044	0.026	0.028
*Blood weight	8.70	8.67	8.90	8.77	0.069	0.414	0.643	0.780
*Head weight	7.67^a	7.60^ab	7.33^ab	7.13^b	0.113	0.007	0.283	0.016
*Feet weight	5.90^a	5.73^ab	5.80^ab	5.57^b	0.046	0.040	0.008	0.016

Note: * Percentage of slaughter body weight. Prob.: Probiotic, Conc.: Concentrate, SEM: Standard error of the mean ^a,b,c, Mean values with different superscripts on the same row differ significantly (p < 0.05).

The significant (P < 0.05) probiotic and concentrate interaction observed for cold and hot carcass weights was due to higher levels of both probiotics and concentrate. The values of hot and cold carcass weights appreciated linearly with increased levels of probiotic and concentrate supplementation. This observation is in tandem with the report of Gama et al. (2022) who also reported increases in hot and cold carcass weights attributable to protein/energy concentrate supplementation. Concentrate supplementation led to increased nutrients intake which probably had an additive effect on intake culminating in the positive effect on carcass weights.

However, interaction (P < 0.05) for empty body weight, which also linearly improved (P < 0.05), was due to probiotic supplementation.

The dietary treatments imposed did not influence chilling loss (P > 0.05). The values recorded ranged from 2.57% in treatment P₁₀₀C₁₀₀₀ to 2.80% in treatment P₀C₅₀₀. The current values were lower than the 4.81% and 4.03% reported for Boer and indigenous South African goats, correspondingly (Pophiwa et al., 2017). Overall, the chilling losses for the various treatment groups were all marginally lower than the 3% frequently projected for the carcasses of goats (Simela et al., 2011; Webb et al., 2005).

It can also be seen from Table 3 that higher levels of probiotics and concentrates offered accounted for the significant interaction (P < 0.05) observed for dressing percentage, which refers to the fraction of the animal’s live weight that is transformed into carcass (Warmington & Kirton, 1990). The dressing percentage increased linearly with increased levels of probiotic and concentrate supplementation. This trend disagreed with the findings of M. Solomon et al. (2008), who did not find any differences in dressing percentage with increasing daily levels (200 g, 300 g and 400 g) of concentrate supplementation. The current range of dressing percentage was higher than 43.80% − 47.30% recounted by Ukanwoko et al. (2009) when West African Dwarf goats were fed cassava peel meal-based diets. However, the current values were all within the 40.0% − 56.0% reported by Casey et al. (2003) for goats and lesser than the 55% obtained by Safari et al. (2009) for small East African goats on a diet of low-quality grass hay. These variations in dressing percentages reported from different studies are attributable to differences in breed, nutrition (Fasae et al., 2007), body weight, dressing method (Okpanachi et al., 2016), the weight of hide and hair, size of the gastrointestinal tract and gut fill, method of slaughtering and partitioning of body fat (Cassey and Van Niekerk (1988). The differences in head and feet weights could partly account for the variations observed in dressing percentage in this work.

Significant interactions (P < 0.05) in head and feet weights were also detected, attributable to higher levels of probiotics and concentrates, respectively. The weights of the head and feet were both influenced by treatment effects. Head weight ranged from 7.13% to 7.67% of slaughter body weight while that of the feet ranged from 5.57% to 5.90%. Both parameters decreased linearly with increased levels of probiotics and concentrate supplementation. It can also be observed from Table 3 that the weights of the head and feet decreased as the slaughter weights and carcass weights increased across the various treatments. This observation aligned with the findings of Omojola and Attah (2006) and Okpanachi et al. (2016).

3.2. Effects of probiotic and concentrate supplementation on edible viscera of goats

The effects of the treatments on edible viscera (internal organs) are presented in Table 4. It can be seen that except for empty gut weight, interaction between probiotics and concentrate supplementation was not present (P > 0.05). The significant (P < 0.05) interaction observed for empty gut weight was due to higher probiotic and concentrate supplementation levels. Additionally, probiotic supplementation influenced (P < 0.05) lung and trachea weight which saw a reduction with an increase in the level of supplementation.

Table 4. Effects of probiotic and concentrate supplementation on edible viscera expressed as percentages of slaughter body weight

Prob. level	Treatments				SEM	Significance
	0		100			P values
Conc. level	500 P0C500	1000 P0C1000	500 P100C500	1000 P100C1000		Prob.	Conc.	Prob.* Conc.
Parameter
Heart weight	0.66	0.67	0.69	0.62	0.008	0.612	0.076	0.260
Kidney weight	0.58	0.55	0.58	0.59	0.014	0.520	0.744	0.520
Lung + trachea weight	3.00	3.13	2.85	2.81	0.056	0.022	0.553	0.312
Liver weight	2.40	2.50	2.60	2.20	0.068	0.710	0.286	0.099
Spleen weight	0.23	0.20	0.20	0.20	0.010	0.179	0.245	0.245
Full gut weight	28.67	27.17	27.60	26.73	0.339	0.286	0.116	0.641
Empty gut weight	9.95^b	10.50^ab	10.60^ab	10.80^a	0.096	0.017	0.042	0.027

Notes: Prob.: Probiotic, Conc.: Concentrate, SEM: Standard error of the mean

a,b,c^,Mean values with different superscripts on the same row differ significantly (p<0.05).

The range of heart weights in the current study was more than the ranges of 0.53% to 0.59% and the 0.53% to 0.61% reported respectively by Okpanachi et al. (2016) and Ocheja et al. (2021). The present values were, however, less than the 1.01% to 1.20% reported by Abdelrahman et al. (2017). The similarities in heart weight detected in the current study were inconsistent with the reports of Ozung and Anya (2018) and Odoemedem et al. (2014), who both had differences (P < 0.05) in weights of internal organs in West African dwarf goats which they attributed to treatment effects. The current however was in harmony with the account of Okpanachi et al. (2016) who found heart weights to be similar across various treatments. The absence of differences in heart weights across the various treatments suggest that the treatments imposed did not exert any deleterious effect on the heart.

Kidney weights across treatments were not found to be different (P > 0.05). All values compared well to the 0.57% to 0.63% range that Ocheja et al. (2021) quoted. The combined weight of the lungs and trachea was influenced (P < 0.05) by probiotic supplementation. The values declined linearly with an increased level of probiotic supplementation. Liver weights remained unaffected (P > 0.05) by the dietary treatments used. According to Ngi (2012), internal organs, particularly the liver, will become large if the diet contains substances injurious to the animal. The absence of significant differences in liver weights is indicative of the fact that all diets were safe for the does. The current range of liver weights was comparable to the range of 1.99% to 2.37% obtained by Okpanachi et al. (2016) but much lower than the 4.53% to 5.67% reported by Abdelrahman et al. (2017). Weights of the spleen were also similar (P < 0.05) and comparable to those (0.15% to 0.19%) reported by Okpanachi et al. (2016) but lower than those (0.34% to 0.45%) of Abdelrahman et al. (2017). The range of full gut weight recorded in the current study was lower than the 28.18% to 34.38% reported by Okpanachi et al. (2016). Empty gut weights were however comparable to those (8.99% to 9.33%) of the same authors. The differences in weights of some of the internal organs relative to those of earlier works could be attributed to the breed and slaughter weights of the goats.

3.3. Effects of probiotic and concentrate supplementation on the proximate composition of goat meat

Table 5 shows data on the effects of supplementing probiotics and varying levels of concentrates on the chemical composition of goat meat. A significant interaction (P < 0.05) between probiotic and concentrate supplementation was found for all parameters except ash content. This trend contradicts the results of Rodriguez et al. (2014) and Lee et al. (2008), who reported no differences between the chemical composition of meat from control and supplemented groups when they supplemented a commercial concentrate (18.2% CP) and a concentrate diet consisting predominantly alfalfa meal and yellow corn (18% CP) to goats respectively. The contradiction observed could be attributed to the additional supplementation of probiotics in the current work. However, the trend of differences in meat proximate composition with increased dietary protein concentration was consistent with the findings of Kemp et al. (1976).

Table 5. Effects of probiotic and concentrate supplementation on the proximate composition of goat meat samples

Prob. level	Treatments				SEM	Significance
	0		100			P values
Conc. level	500 P0C500	1000 P0C1000	500 P100C500	1000 P100C1000		Prob.	Conc.	Prob.* Conc.
Parameter (%)
Moisture	74.22^b	74.27^b	75.17^a	75.03^a	0.144	0.000	0.725	0.043
Organic matter	23.66^a	23.67^a	22.56^b	22.73^ab	0.171	0.002	0.650	0.046
Crude protein	20.69^b	21.10^ab	21.02^b	21.74^a	0.123	0.006	0.003	0.024
Crude fat	2.84^a	2.53^a	1.83^b	1.77^b	0.146	0.000	0.135	0.028
Ash	2.12	2.07	2.27	2.23	0.047	0.125	0.622	0.943

Notes: a,b,c^, Mean values with different superscripts on the same row differ significantly (p<0.05).

Prob.: Probiotic, Conc.: Concentrate, SEM: Standard error of the mean

Probiotic supplementation had a significant effect on the moisture content of the meat, with the moisture levels increasing linearly as the level of probiotic supplementation increased. However, the level of concentrate supplementation did not have an effect (P > 0.05) on moisture content. The study also found that the moisture contents in this study were lower than in previous studies (76.7–79.43%) by (Rodriguez et al., 2014; T. M. Silva et al., 2016) but within the range of 73.33–77.53% reported previously (Islam et al., 2019; Ivanovic et al., 2016) and higher than values (64.2–69.8%) reported by Webb et al. (2005) for different goat breeds.

There was a significant interaction (P < 0.05) between levels of probiotics and concentrate supplementation for CP attributable to the synergy between the two factors. Thus higher levels of both probiotics and concentrate accounted for the significant interaction experienced. The CP contents of meat samples recorded differences (P < 0.05) attributable to treatment effects. The CP contents improved as the levels of probiotics and concentrate were increased. The probiotics supplemented may have regulated and improved upon the properties of the muscle fibres which according to Gagaoua and Picard (2020), are directly related to meat quality. The current CP contents were all higher than the 19.95% and 20.55% reported for Serbian white goats and Balkan goats, respectively, by Ivanovic et al. (2016). The current values were also higher than the ranges of 19.91% to 19.6%, and 17.75% to 19.28% reported respectively by T. M. Silva et al. (2016) and Rodriguez et al. (2014). However, compared to the 22.2% to 24.47% found by Islam et al. (2019), the current range of CP values was lower.

Significant interaction (P < 0.05) was also present for crude fat content due to probiotic supplementation. Thus, the trend observed was in line with the account of De Smet et al. (2004) that feed profoundly influences how intramuscular fat is deposited. Supplementation of B. subtilis in broilers led to a significant decrease in abdominal fat (Tang et al., 2021). In contrast to the crude protein contents, the values for crude fat decreased with an increase in probiotic supplementation (Table 5). However, crude fat content was not influenced by the level of concentrate supplementation. This observation regarding the effect of concentrate supplementation on crude fat contradicts the account of Werdi et al. (2007), who found that supplementation with concentrates lowered fat content in the carcass of grazing goats. The range of values for crude fat was lower than the 3.55% to 3.92%, 3.07% to 3.9%, and the 4.4% to 10.5% recounted by Ivanovic et al. (2016), Rodriguez et al. (2014) and Webb et al. (2005) in that order. According to Taboada et al. (2022) the biological effects of supplementing probiotics is dependent on the strain of microorganisms used, the time of treatment the concentration of the probiotics as well as the health status of the animal. However, the crude fat levels recorded in the present work were similar to the 1.80% to 2.16% stated by Islam et al. (2019) and the 2.02% to 2.58% by T. M. Silva et al. (2016).

Ash levels in meat samples were not different (P > 0.05), ranging from 2.07% in treatment P₀C₁₀₀₀ to 2.27% in treatment P₁₀₀C₅₀₀. The present ash contents were higher compared to the 1.04% to 1.08% and 0.95% to 1.0% by T. M. Silva et al. (2016) and Webb et al. (2005) correspondingly, which might be attributable to the ash content of the concentrate supplement. However, the current values for ash content were comparable to those (1.80% to 2.16%) reported by Islam et al. (2019). The variances observed between the proximate components of the meat in the current study and those of earlier studies are attributable to genetic and environmental influences like breed, growth stage, sex, and nutritional issues (Casey & Webb, 2010; Goetsch et al., 2011).

3.4. Effects of Probiotic and concentrate supplementation on the fatty acid profile of goat meat

The fatty acid (FA) composition of the longissimus lumborum muscle of does on the various dietary treatments is presented in Table 6. The main FAs detected in the meat were palmitic acid (C16:0), stearic acid (C18:0) and oleic acid (C18:1), which constituted 85.67% of overall fatty acids detected. FAs that were most prevalent in the meat samples in the current study were in increasing order oleic acid (C18:1) with 27.73 mg/g, stearic acid (C16:0) with 31.23 mg/g and palmitic acid (C18:0) with 44.61 mg/g. These same FAs have earlier been reported to be the most prevalent in goat meat (Ding et al., 2010; Kim et al., 2014; Pratiwi et al., 2006). Determining meat fatty acid (FA) composition cannot be underestimated as intramuscular fat is usually not trimmable and hence not removed before consumption. Therefore, it would influence the consumer’s health (Aghwan et al., 2014).

Table 6. Effects of probiotics and concentrate supplementation on the fatty acid profile (in mg/g) of the meat samples

	Treatments					Significance
Prob. level	0		100		SEM	P values
Conc. level	500 P0C500	1000 P0C1000	500 P100C500	1000 P100C1000		Prob.	Conc.	Prob* Conc
SFA Profile
C8:0	0.20	0.20	0.20	0.18	0.004	0.091	0.397	0.202
C10:0	0.21	0.22	0.22	0.20	0.004	0.236	0.741	0.134
C12:0	0.71^a	0.62^a	0.41^b	0.39^b	0.045	0.001	0.220	0.043
C14:0	4.72^a	3.65^ab	2.24^bc	1.26^c	0.425	0.001	0.043	0.019
C16:0	31.23^a	28.85^a	18.26^b	11.64^b	2.480	0.000	0.034	0.024
C18:0	44.61^a	37.48^a	24.51^b	14.80^b	3.680	0.000	0.037	0.026
C20:0	0.35^a	0.35^a	0.17^b	0.14^b	0.031	0.000	0.563	0.016
C22:0	0.10^a	0.07^ab	0.06^b	0.05^b	0.006	0.005	0.074	0.015
C24:0	0.091^a	0.091^a	0.071^ab	0.064^b	0.004	0.003	0.480	0.034
ƩSFA	82.22^a	71.53^a	46.12^b	28.71^c	6.510	0.000	0.013	0.043
UFA Profile
C16:1	1.39^b	1.53^b	2.61^a	2.84^a	0.206	0.000	0.339	0.018
C18:1cis 9	27.73^b	36.53^ba	46.68^a	48.02^a	2.840	0.007	0.223	0.013
C18:2 n−6	1.52^b	1.55^b	2.83^ab	3.97^a	0.331	0.001	0.129	0.015
C18:3 n−3	6.87^b	5.12^c	10.61^a	9.90^a	0.693	0.000	0.001	0.005
C22:1	0.17^bc	0.14^c	0.29^ab	0.31^a	0.024	0.003	0.899	0.014
ƩUFA	37.68^b	44.88^b	63.01^a	65.04^a	3.820	0.001	0.285	0.015
MUFA	29.29^b	38.21^ab	49.57^a	51.17^a	3.040	0.005	0.218	0.037
PUFA	8.39^b	6.67^b	13.44^a	13.87^a	0.969	0.000	0.178	0.044
PUFA/SFA	0.10^c	0.09^c	0.29^b	0.49^a	0.051	0.000	0.023	0.016
n6/n3	0.22^b	0.30^ab	0.27^ab	0.40^a	0.025	0.093	0.024	0.048

Notes: Prob.: Probiotic, Conc.: Concentrate, SEM: Standard error of the mean, SFA: Saturated fatty acids, UFA: Unsaturated fatty acids

a,b,c^,Mean values with different superscripts on the same row differ significantly (p<0.05).

In respect of the saturated fatty acids (SFA), Table 6 shows that but for the short chain FAs—caprylic acid (C8:0) and decanoic acid (C10:0), significant interactions (P < 0.05) between levels of probiotics and concentrate supplementation were present for all FAs identified. The observed interactions for lauric acid (C12:0), arachidic acid (C20:0), behenic acid (C22:0) and lignoceric acid (C24:0) were due to a higher level of probiotic supplementation. However, the interactions for myristic acid (C14:0), palmitic acid (C16:0) and stearic acid (C18:0) were attributable to the synergy between probiotics and concentrate, with probiotics having a higher impact.

The concentrations of lauric acid (C12:0), myristic acid (C14:0), palmitic acid (C16:0), stearic acid (C18:0) and behenic acid (C22:0) generally decreased linearly with an increase in levels of probiotic and concentrate supplementation (Table 6). However, the concentrations of arachidic acid (C20:0) and lignoceric acid (C24:0) were influenced by only the probiotic level but not concentrate level. The decreasing trend in the concentrations of SFAs in response to probiotic supplementation agrees with Cimmino et al. (2018), who also found a reduction in SFAs levels when dietary polyphenols were supplemented in Saanen goats, also recounted a reduction in SFA concentrations in the meat when goats were supplemented with fermented Saccharina Japonica and Dendropanax morbifera containing probiotics (Lactobacillus plantarum and Saccharomyces cerevisiae). SFAs are reported to present undesirable impacts on health when consumed excessively, particularly myristic (C14:0) and palmitic (C16:0) acids that intensify the danger of diseases associated with the cardiovascular system (Howes et al., 2015). Thus the decreasing trend in levels of SFAs (from C12:0 to C24:0) seen in the present work is desirable.

The relatively higher percentage of SFAs in muscles of does from treatments P₀C₅₀₀ and P₀C₁₀₀₀ without probiotic supplementation could be due to hydrolyzation and biohydrogenation processes of lipids in the diets within the rumen which resulted in the absorption of SFAs in the gut (Lima et al., 2018). The decrease in the contents of SFAs in treatments P₁₀₀C₅₀₀ and P₁₀₀C₁₀₀₀ that received probiotic supplementation suggests that the probiotics probably modulated rumen fermentation, thereby plummeting the rate of biohydrogenation of fatty acids.

The observed differences in saturated fatty acids (SFAs) could be attributed to the treatments imposed since diet has been reported severally (Aurousseau et al., 2007; De Smet et al., 2004; Díaz et al., 2005; Nuernberg et al., 2008) to have a key influence on the deposition of intramuscular fat as well as on the contents of SFA. However, Johnson et al. (2010) found no difference (P > 0.05) in the percentages of SFAs in goat meat as a result of diet. Reports from other earlier studies (Aurousseau et al., 2007; Díaz et al., 2005; Momen et al., 2016; Nuernberg et al., 2008) have attributed changes in FA concentrations to breed, live weight, fatness, gender and production system. Total SFAs (ƩSFA) decreased (P < 0.05) linearly as levels of probiotics and concentrate increased. Interaction between probiotics and concentrates supplementation levels was present (P < 0.05) for total SFAs. The reduction in SFA content due to treatment effects was desirable because SFAs have been known to increase the cholesterol level and are associated with coronary heart disease (Richard et al., 2009; Ruiz-Núñez et al., 2016).

Significant interactions (P < 0.05) between probiotics and concentrate supplementation were present for all unsaturated fatty acids (UFA) identified as a result of treatment effects (Table 6). The interactions for palmitoleic acid (C16:1), oleic acid (C18:1), linoleic acid (C18:2) and erucic acid (C22:1) were attributed to probiotic supplementation. However, both levels of probiotics and concentrate supplementation accounted for the interaction for linolenic acid (C18:3). Concentrations of palmitoleic acid (C16:1), oleic acid (C18:1), linoleic acid (C18:2) and linolenic acid (C18:3) generally increased linearly with increase in levels of probiotic and concentrate supplementation. However, the concentrations of erucic acid (C22:1) as affected by the level of concentrate were similar (P > 0.05).

Due to probiotic supplementation, significant interactions between probiotics and concentrates can also be seen in Table 6 for ƩUFA, MUFA and PUFA. However, both levels of probiotics and concentrate accounted for the interactions observed for PUFA/SFA and n6/n3. The contents of UFA were greater in the probiotic supplemented treatments than those without probiotic supplementation. This trend was akin to the account of Kim et al. (2014). Conversely, treatments without probiotics had higher concentrations of SFAs than the probiotic supplemented groups. Concentrate supplementation generally led to a fall in the level of SFAs while increasing the levels of UFA and MUFA, similar to the observation made by Kim et al. (2014). These disparities in FA concentrations could be due to modifications in the types and configuration of microbes within the rumen as levels of concentrates (Majdoub-Mathlouthi et al., 2013) and probiotics increased.

Monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs) concentrations were both not influenced (P > 0.05) by the differing levels of concentrate. This trend however disagrees with the results of Rossatti et al. (2019), who found improvements in MUFA and PUFA contents in lamb meat as a result of concentrate supplementation. Probiotic supplementation, on the other hand, influenced (P < 0.05) the concentrations of both MUFA and UFA. The increasing trend of PUFA in response to probiotic supplementation in the current corroborates the results of , who also observed a rise in PUFA concentration after probiotics were supplemented. PUFA has been reported to lower the concentrations of low-density lipoproteins cholesterol and positively impact health (Richard et al., 2009; Ruiz-Núñez et al., 2016).

The PUFA/SFA and n−6/n−3 ratios are indices used to measure the nutritive value of fat or lipid fractions in meat. Fats with high PUFA/SFA ratios with corresponding low n−6/n−3 ratios are considered favourable as they minimize the risk of cholesterolaemia (Santos-Silva et al., 2002). Treatment effects influenced the ranges of PUFA/SFA and n6/n3 ratios in the present work (P < 0.05). PUFA/SFA and n−6/n−3 ratios generally improved (P < 0.05) with increased supplementation of probiotics and concentrates. This trend was attributable to the increasing trends of the UFAs across the various treatments. The increase in PUFA/SFA ratios in the current study due to probiotic supplementation was consistent with the results of , but those of n−6/n−3 ratios were contrary to the findings of the same authors who reported a reduction in n−6/n−3 ratio.

The upsurge in n−6/n−3 ratio with increased levels of both concentrate and probiotic supplementation agreed with the reports of Demirel et al. (2006) and Ryan et al. (2007), who both recorded increases in n−6/n−3 ratios due to feeding high levels of concentrate. Thus the resulting higher n−6/n−3 ratio attributable to higher levels of concentrate and probiotic was a shift in an undesirable direction. The current trend of the n−6/n−3 ratio conflicts with the findings of Brassard et al. (2018), who found that the n−6/n−3 ratio significantly decreased consistently as corn inclusion in the diets of goats increased. also observed a reduction in the n−6/n−3 ratio after probiotics were supplemented in Korean native black goats. The current n−6/n−3 ratios were much lower than the 14.79–18.22 Aghwan et al. (2014) reported for longissimus lumborum when goats were supplemented with inorganic selenium and iodine. PUFA concentration has been said to be influenced by diet or nutritional conditions (Enser et al., 1998; Mandel et al., 1998; M. B. Solomon et al., 1991). The n−6/n−3 ratios obtained in the present work were within the recommended ratio (<4) required to minimize the danger of suffering from coronary disease in humans (Simopoulos, 2008; Wood et al., 2004).

4. Conclusions

The current results suggest that meat obtained from goats supplemented with Vicbinzy powder probiotics (100 g/100 kg of concentrate), and higher levels of concentrate (1000 g/d) had improved nutritional value due to increased crude protein content with reduced crude fat. Higher levels of concentrate and probiotic supplementation also improved carcass weights (hot and cold) and dressing percentage without any deleterious effect on the weights of internal organs.

In addition, supplementing higher levels of concentrate and probiotics in does could ameliorate the nutritional indices of fatty acids in goat meat to enhance good health since it helps decrease SFAs and then increase UFA, MUFA, PUFA indices and the PUFA/SFA ratio. However, the n−6/n−3 ratios obtained were less than the minimum recommended ratio for human health.

Consequently, Vicbinzy powder probiotics used in the current study could be incorporated at 100 g per 100 kg of concentrate into the millet mash-based protein/energy concentrate and fed at 1000 g/d to Sahelian does for improved carcass quality.

Disclosure statement

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