Effects of Concentrate Supplementation on Skin Quality Attributes in Crossbred Sheep

Abstract

This study examined the effects of concentrate supplementation levels on skin quality in crossbred sheep (Awassi X Bonga; AB, Awassi X Washera; AW, and Dorper X Menz; DM). The lambs (44 in total) were randomly assigned to different breed and supplementation groups. They grazed on natural pasture and received 300, 600, or 900 grams of concentrate feed with 21% crude protein and 14 MJ/kg metabolizable energy. After 90 days, the animals were culled, and their skins were assessed. Higher concentrate supplementation (900 g) significantly improved skin weight, size, thickness, and tear load (p < 0.05). Moisture content, fat content, and hide substance percentage were not significantly affected by the supplementation level (p > 0.05). DM breed showed higher thickness, tear load, and moisture content for raw skin compared to AB and AW (p < 0.05). Skins from DM with 900 g supplementation exhibited superior quality. The study concluded that skins from different breeds with concentrate supplementation (300 to 900 g) showed improved leather production within acceptable standards. Further research is recommended for indigenous sheep breeds in different regions, considering crossbreeding levels.

1. Introduction

Ethiopia is home to a diverse population of livestock, including a substantial sheep population, making it the second-largest in Africa with approximately 30.7 million heads [1]. In the study conducted by Galal [2], the sheep breeds in the country were classified into four primary groups based on their tail type. These groups consist of short fat-tailed, long fat-tailed, thin-tailed, and fat-rumped sheep.

Another researcher [3] expanded on this classification and identified fourteen sheep breeds in Ethiopia. Among them, Washera, Bonga, and Menz sheep are specifically adapted to the Western, Southwestern, and Northern regions of the country, respectively.

Small ruminants, such as sheep and goats, possess unique characteristics, including efficient reproduction cycles, faster growth rates, and adaptability to diverse environments, making them an important source of protein and income for farmers in the tropics and subtropics [4]. However, the productivity of Ethiopian sheep breeds remains low, with most sheep breeds yielding less than 10 kg of carcass weight at 1 year of age [5]. Factors contributing to this low productivity include limited availability of quality feed throughout the year, inadequate management practices, limited veterinary services, and slow growth rates in indigenous sheep breeds.

The main emphasis in Ethiopia has been on enhancing the meat production of indigenous sheep breeds, with efforts directed towards improving productivity. Crossbreeding programs, involving the introduction of improved exotic sheep breeds, have been implemented to enhance the growth traits of indigenous sheep breeds [6, 7]. However, the impact of crossbreeding on the quality of sheep skins, particularly for leather production, remains a concern. Skins obtained from crossbred sheep in Ethiopia have often received lower acceptance and lower market prices, or have been rejected entirely [6, 7].

The international trade of raw and manufactured hides, skins, and leather has experienced significant growth, reaching around US$53.8 billion with an annual average increase of 12% over the past 30 years [8]. As trade patterns have evolved, the evaluation and classification of skins have become essential [9]. Therefore, it is crucial to understand the quality attributes of skins from crossbred sheep, particularly those subjected to different levels of concentrate supplementation, to optimize the benefits of crossbreeding programs in Ethiopia.

The aim of this study was to investigate the quality attributes of skins from F₁ crossbred sheep with varying levels of concentrate supplementation, in addition to grazing, to inform the design of crossbreeding programs and enhance leather production in the country.

2. The materials and methods used in this study are as follows

2.1 Study site description

The study was conducted at the Debre Berhan Agricultural Research Center, situated in the central highlands of Ethiopia. The center is positioned approximately 120 km northeast of Addis Ababa, at an elevation of 2780 m above sea level. Its geographical coordinates are 39° E longitude and 10° N latitude. The grazing area within the research site is characterized by natural vegetation, primarily dominated by Andropogon longipes grass. Additionally, the area contains varying proportions of Pennisetum and Festuca species, along with the legume Trifolium species. The climate of the study area exhibits distinct seasonal patterns. It experiences a long rainy season from June to September, accounting for 75% of the total annual rainfall. There is also a short rainy season from February/March to April/May, followed by a dry season from October to January. The average annual rainfall recorded at the research center is approximately 920 mm. The monthly minimum air temperatures, measured at a height of 0.5 m above the ground, range from 2°C in November to 8°C in August. Correspondingly, the monthly maximum temperatures range from 18°C in September to 23°C in June.

2.2 Management of experimental animals

A total of 44 half-bred lambs, comprising male lambs of AW, AB, and DM crossbreeds, were included in the study. The Dorper sheep breed was sourced from South Africa, while the Awassi breed was imported from Israel, respectively, with the aim of improving the productivity of indigenous sheep breeds. These lambs were a subset of animals from a larger experiment focused on evaluating the early finishing ability of crossbreed ram lambs for commercial production.

The experimental sheep were randomly assigned to three treatment groups and three genotypes, taking age and initial live weight into consideration during the stratification process. The treatment groups consisted of grazing supplemented with 300, 600, and 900 g/d of concentrate feed, corresponding to three feeding levels. At the start of the experiment, the average age of the sheep was 7.26 months, and they weighed 23.92 kg. The lambs were slaughtered at approximately 10 months of age. The concentrate feed used in the experiment was purchased from the Kality feed processing plant in Addis Ababa. On a dry matter basis, it contained 49.5% wheat bran, 49.0% Noug cake (Guizotia abyssinica), 1% limestone, and 0.5% salt. This composition provided 21% crude protein and 14 MJ/kg metabolizable energy. The concentration of the commercial concentrate is as follows: Wheat bran - 830.3 g/kg, Noug seed cake - 139.7 g/kg, common salt - 10 g/kg, and limestone - 20 g/kg.

The experiment took place from May to July. The animals were grazed together during the day, and group batches of concentrate feed were provided twice daily at 12:00 am and at night. Fresh skins from the 44 male lambs were obtained which had an average age of 7.26 months and an initial weight of 23.99 kg at the beginning of the experiment, were used to assess the skin/leather quality attributes. The study consisted of a 15-day acclimatization period, followed by a 90-day experimental period. During the experimental period, the animals had unrestricted access to grazing, and watering took place twice daily. Prior to the commencement of the experiment, the animals underwent internal parasite drenching and external parasite deworming, following the established protocol of the research center.

3. Preparation of natural pasture HAH and commercial concentrate

Feed samples were subjected to drying in an air-forced oven at 60°C for 48 hours and then ground to pass through a 1 mm sieve mill. The ground samples were stored in a sealed plastic bag at room temperature until analysis. Analysis of dry matter (DM), ash, crude protein (CP), neutral detergent fiber (NDF), and acid detergent fiber (ADF) followed the methods outlined by AOAC [10] and Van Soest et al. [11]. The nitrogen (N) content was measured using the Kjeldahl method [10], and the crude protein (CP) was calculated as N multiplied by 6.25.

3.1 Skin grading and physical tests

Fresh skins were gathered for analysis and promptly dispatched to the Leather Industry Development Institute (LIDI) on the day of animal slaughter. The weight of the fresh skins was recorded immediately after slaughter. At the Leather Industry Development Institute Testing and Research Laboratory in Ethiopia (LIDI), the measurement of size and the grading of quality for the fresh skins were performed.

Trained technicians at LIDI measured the size of the skins in square inches and classified them into three categories: medium, large, and extra-large.

The wet salting process adhered to the guidelines prescribed by the Ethiopian Standards Authority. Prior to salt application, the skins were cleaned in accordance with the ESA code B.J6.003 (1990). The quantity of salt utilized was equivalent to 50% of the weight of the fresh skin. It is worth mentioning that skins from all breeds underwent identical wet salting conditions. Following the wet salting process, the skins from all breeds underwent curing under identical conditions (wet salted) and were subsequently tanned using the same method (chrome tanned). This ensured that any observed differences in the leather quality among the different groups could be attributed to variations in breed, diet, and properties of the raw materials. Chemical and physico-mechanical characteristics were evaluated to assess the leather quality of the ram lambs. Tensile strength (N/mm²) and percent elongation (%) were measured using the methodology described in ISO 3376-1 [12].

The skin processing involved multiple stages, including soaking, liming, washing, fleshing, trimming, deliming, pickling, tanning, basification, slamming, neutralization, re-tanning, drying, and smoothing. Following the tanning process, the leather was conditioned according to ISO 2419 [13], and samples were taken for testing based on the procedure outlined in ISO 2418 [14]. The physical tests were conducted under controlled environmental conditions, with a temperature of 20 ± 2°C and a relative humidity of 65 ± 5%. Samples were collected from both parallel and perpendicular orientations to the backbone of the leather. These physical tests assessed the strength of the leather and its resistance to stretching before the upper grain layers cracked, potentially causing surface damage. Although the specific physical tests conducted at LIDI were not explicitly mentioned, they were performed as part of the evaluation process.

3.2 Tensile strength

Tensile strength quantifies the force necessary to fracture a dumbbell-shaped leather specimen. The sample is firmly secured between two clamps, which gradually separate at a consistent speed of around 100 mm per minute. During this separation, the force required to stretch the leather is automatically recorded. Eventually, the leather sample will rupture. The force at which the sample breaks is known as the tensile strength and is expressed in Newtons (N).

“To determine the tensile strength, samples were taken from both along and across the length of the skin. The samples were cut into a specific size, taking into account the thickness (mm) and width (mm) of the leather. The tensile strength was then calculated by dividing the measured breaking load (N) by the cross-sectional area of the sample, which is the product of the thickness and width of the leather. The result is expressed in units of N/mm². The measurement and calculation of tensile strength were performed following the ISO 3376-1 [12] procedure.

$$\text{Measured breaking load}\left({\text{N}}^2\right)=\frac{\text{Tensile strength}\left(\text{N}/mm\right)}{\left(\text{Thickness}\left(mm\right)\times \text{Width}\left(mm\right)\right)}$$E1

3.3 Elongation at break

During the tensile strength test described earlier, the elongation at break is also measured. As the leather sample stretches under the applied force, it eventually reaches a point where it breaks. At this point, the percentage of stretch the sample underwent before breaking is referred to as the elongation at break.

The elongation at break is calculated by comparing the change in length of the leather sample at the point of breakage to its original length. The difference is expressed as a percentage of the original length, representing the amount of stretch the leather underwent before it broke. This measurement provides valuable information about the ductility and flexibility of the leather. It indicates the extent to which the leather can be stretched before reaching its breaking point.

$$\text{Elongation}at\text{break}\left(\%\right)=\left(\frac{\text{Length}at\text{break}\left(mm\right)-\text{Initial length}\left(mm\right)}{\text{Initial length}\left(mm\right)}\right)\times 100$$E2

3.4 The tear load

The slit tear strength test involves a well-defined procedure using a rectangular leather sample with a small cut or slit. One clamp is fastened to the bottom of the sample, while another clamp is inserted through the slit. The clamps then apply tension to the sample until the slit initiates tearing. The point at which the tear commences is considered the slit tear strength. To facilitate standardized comparison across various leather samples, the slit tear strength is expressed relative to the average thickness of the leather.

To determine the average tear load or arithmetic mean, multiple samples are tested, and the tear load values are averaged. This provides a representative measure of the tear strength of the leather. Tear resistance is another parameter that is determined using the test method specified by the International Organization for Standardization. ISO 3377-2 [15] defines the test method for determining tear resistance, while ISO 3376-1 [12] outlines the test method for slit tear strength.

Samples used for the tests were conditioned according to ISO 2419 [13], which specifies the conditioning procedure for leather samples. The sampling method followed ISO 2418 [14], and the sampling location adhered to ISO 2418 [14]. Additionally, the thickness of the samples was measured in accordance with ISO 2589 [16], which provides guidelines for measuring the thickness of leather. By following these standardized procedures and test methods, the slit tear strength, average tear load, and tear resistance of the leather samples can be accurately determined and compared.

$$\text{Tear resistance}\left(\text{N}/mm\right)=\left(\frac{\text{Force}at\text{tear}\left(\text{N}\right)}{\text{Skin thickness}\left(mm\right)}\right)$$E3

3.5 Double edge tear force (N)

The Double Edge Tear Force is the maximum load at which tearing occurs, as determined by following the ISO 3377-2 [15] procedure.

3.6 Chemical quality test of skin/leather

3.6.1 The fat content

Fat content is determined using the dichloromethane extraction method, which involves the following formula for the determination of fat and other soluble substances:

$$Fat\text{content}\left(\%\right)=\left[\frac{\left(\text{Weight of extracted}fat\right)}{\left(\text{Weight of the moisture}-\text{free sample}\right)}\right]\times 100$$E4

To calculate the fat content, the weight of the extracted fat is divided by the weight of the moisture-free sample and then multiplied by 100 to express the result as a percentage.

The process for determining the fat content involves the following steps:

The moisture-free samples are subjected to Soxhlet extraction using dichloromethane as the solvent. The extraction process continues for a minimum of 5 hours to ensure complete extraction of the fat.

After the extraction, the solvent is distilled from the flask, leaving behind the extracted materials.

The extracted materials are then dried at a temperature of 102 ± 2°C until a constant weight is achieved. This drying process helps remove any residual solvent and moisture.

If there is a reduction in weight of more than 0.1% compared to the original weight of the sample, the samples are re-dried to ensure accurate measurements.

The total drying time should not exceed 8 hours to prevent over-drying of the sample.

Using the formula and following the specified procedure, the fat content of the moisture-free samples can be accurately determined. This information provides insights into the lipid composition of the leather material.

$$\text{The extractable substance in}\left(\%\right)=\left(\frac{\text{gram extract}}{\text{gram weight of the sample}}\right)\times 100$$E5

3.6.2 Moisture content

The moisture content of the skin samples was assessed as a percentage of mass using the ES 1195 test method [17].

3.6.3 Percent hide substance

The ‘hide substance’ H, is expressed as a percentage by mass, is given by the formula: H = N x 5.62. Where Nitrogen (N) is expressed as a percentage by mass, is given by the formula;

The hide substance (H), which is expressed as a percentage by mass, was calculated using the formula: H = N x 5.62. Here, Nitrogen (N) was also expressed as a percentage by mass and can be calculated using the formula:

$$\text{N}=\left(\text{V}/\text{m}\right)\text{x}0.7$$E6

Where:

V represents the volume, measured in milliliters, of the standard volumetric sulfuric or hydrochloric acid solution (5.5) utilized for the titration. It is adjusted for the blank test (Table 1).

Variable (n)	Age (months)	Initial Weight (kg)	Raw skin weight (kg)	Skin Size, Raw (Sq ft)
Overall (44)	7.26 ± 0.36	23.99 ± 1.39	3.62 ± 0.19	7.75 ± 0.30
Breed and blood level	ns	ns	***	**
Awassi x Bonga 50% (10)	7.1 ± 0.45	26.24 ± 1.70	4.23 ± 0.23^b	8.54 ± 0.36^b
Awassi x Washera 50% (13)	7.6 ± 0.36	24.05 ± 1.39	3.74 ± 0.19^b	8.11 ± 0.30^b
Dorper x Menz 50% (21)	7.2 + 0.29	22.64 ± 1.10	3.14 ± 0.15^a	7.05 ± 0.23^a
Treatment	ns	ns	***	*
Grazing +300 g concentrate (12)	7.6 ± 0.42	23.85 ± 1.60	3.11 ± 0.21^a	7.43 ± 0.34^a
Grazing +600 g concentrate (16)	7.0 ± 0.33	24.27 ± 1.26	3.57 ± 0.17^a	7.74 ± 0.27^a
Grazing +900 g concentrate (16)	7.3 ± 0.33	24.81 ± 1.26	4.43 ± 0.17^b	8.54 ± 0.27^b
CV (%)	18.03	20.91	18.53	13.71

Table 1.

Least squares means (LSM) ± standard error (SE) of initial age (months), initial weight (kg), and raw skin weight (kg) for crossbred lambs under different supplementation levels.

Means with different superscripts for a class within a column differ significantly, ***P < 0.001; **P < 0.01; *P < 0.05, ns - non-significant.

“a” was denoted for lower values and “b” is for the next higher values etc.

3.7 Data recorded and analysis

Each experimental animal’s initial live weight, as well as their weight and body condition scores every fortnight, were meticulously recorded. Body weight measurements were taken at the beginning of the experiment, every 15 days throughout the 90 days, and finally at the end. To analyze the live weights and body condition scores, a general linear model from SAS (2004) was employed. The model included the concentrate level as the main factor, while initial age and weight were used as covariates. The inclusion of a covariate in the model was determined only if it yielded statistically significant results. Tukey-Kramer tests were employed to assess the variation among the groups being compared.

4. Results and discussion

4.1 The initial weight and age of the experimental sheep

The initial age and body weight of the ram lambs used in this specific experiment were found to be similar (P > 0.05), with an average age of 7.26 ± 0.19 months and an average body weight of 23.92 ± 1.39 kg. Table 2 provides the specific values for the initial age in months and body weight in kg.

	DM%	OM%	CP%	NDF%	ADF%	ME MJ/Kg DM
Natural pasture hay	89.2	80.8	6.5	75.1	35.4	7.88
Commercial concentrate	93.6	89.4	18.8	46.3	19.1	11.8

Table 2.

Type of feed used and methods of preparation.

4.2 Raw skin weight and size

4.2.1 The weight and dimensions of the raw skin

4.2.1.1 Evaluation and classification of the skin based on its mass and dimensions

The average weight and size of the raw skins were determined to be 3.62 ± 0.19 kg and 7.75 ± 0.30 square feet, respectively. Notably, the skins from the DM crossbreeds exhibited significantly lower weight and size (p < 0.05) compared to those from the AW and AB crossbreeds. This difference can be attributed to the larger size of the lambs born from Awassi rams, as opposed to the smaller size of the Dorper meat breed. As per the Ethiopian Specification for lambskin (code ES B.J6.003), all three crossbreeds’ skins evaluated in this study were classified as extra-heavy (1.50–1.80 kg, standard) and extra-large based on their weight and size. Interestingly, our findings contradict those of Salehi et al. [18], who reported no significant weight differences between Kashmir and Hairy goat types. Given that the market value of fresh skins is determined by their weight and size, our observations indicate that the skins from crossbred sheep hold a high value. Furthermore, the level of concentrate feeding also played a role in determining the weight and size of the raw skins in this experiment. Lambs fed a higher concentrate level (900 g/h/d) demonstrated a 42% increase in skin weight and a 15% increase in size compared to their counterparts receiving 300 g of concentrate supplementation. These findings indicate that implementing enhanced feeding practices can have a favorable impact on the dimensions and mass of crossbreed sheepskin.

4.3 The physical characteristics of leather derived from the skin of crossbreed lambs

4.3.1 The thickness of the skin

In this specific study involving crossbreed lambs, the skin thickness showed a significant improvement, measuring 1.35 mm, which was notably higher than the standard thickness of 0.6 mm.

Specifically, Dorper X Menz (DM) lambs produced a skin thickness of 1.43 mm, while AB and AW crossbreed lambs yielded a thickness of 1.23 mm. These results indicate that sheepskin derived from crossbreed lambs, supplemented with 300–900 g of concentrate in addition to grazing, is highly suitable for producing high-quality upper leather.

It is worth noting that our findings surpass those of Getachew et al. [6, 7] concerning indigenous Washera sheep (0.99 mm) and indigenous Menz sheep (1.18 mm), although they align with the Awassi X Menz 50% sheep (1.23 mm). This suggests that the supplementation of crossbreed lambs has a substantial impact on skin thickness, leading to superior results. In our study, ram lambs supplemented with 900 g/h/d exhibited a skin thickness of 1.49 mm, whereas lambs supplemented with 300 g/h/d yielded a thickness of 1.17 mm. This signifies a thickness advantage of 27% for the higher supplementation level. Getachew et al. [6, 7] conducted a comparable study that likewise showed a 19% increase in thickness due to improved supplementation levels in crossbreed and indigenous sheep breeds such as Washera and Menz sheep.

4.3.2 The tensile strength

Table 2 displays the range of tensile strength values obtained in this study, which varied from 9.33 to 12.22 N/mm². Our findings indicate that the tensile strength is lower compared to the results reported by Teklebrhan et al. [19], which ranged from 18.1 to 24.6 N/mm², and by Getachew et al. [6, 7], which ranged from 16.11 to 18.94 N/mm². In our study, breed and diet did not have a significant effect on tensile strength (p > 0.05).

It is important to note that the tensile strength values obtained in this study fall below the standard requirement of 20 N/mm² for skins to be utilized in upper leather production. It is noteworthy to mention that all the lamb breeds examined in our study yielded leather that complied with the quality standards outlined by the leather industry, as stated by BASF [20]. According to BASF [20], lamb garments are required to have a minimum tensile strength of 12 N/mm².

4.3.3 The elongation at break

The average percentage of elongation at break in this study was determined to be 49.73%, with a range of 46–51%. Statistical analysis indicated no significant impact (p > 0.05) of the treatment groups and genotypes on the elongation at break percentage. Specifically, the AB, AW, and DM sheep breeds exhibited elongation at break values of 47, 50, and 51%, respectively. The average elongation at break percentages obtained for these three genotypes (ranging from 47 to 51%) aligns with the findings of Jacinto et al. [21], who reported a value of 53% for crossbreed sheep such as Texel × Native and Santa Inês × Native. A notable trend of improvement can be observed among the different levels of supplementation (46–51%) for the groups receiving 300, 600, and 900 g of concentrate supplementation. This suggests that higher levels of supplementation may enhance the physical properties of the leather compared to lower supplementation levels.

In contrast to our study, Getachew et al. [6, 7] reported higher elongation at break values of 66 and 65%, indicating greater flexibility compared to our findings. Additionally, a study conducted by Teklebrhan et al. [19] on different sheep breeds, including Blackhead Ogaden, Hararghe Highland, Dorper X Blackhead Ogaden, and Dorper X Hararghe Highland, revealed percentage elongation values of 48%, 56%, 52%, and 44%, respectively, which align closely with the results obtained in our study. The elongation at break percentages observed in this particular study falls within the acceptable range of 40–80% and meets the recommended value for sheepskin, signifying that the leather products are well-suited for use by the leather industry in terms of their flexibility and stretchability.

4.3.4 The tear load

The mean tear load parallel to the backbone and perpendicular to the backbone in Newtons (N) did not show a significant effect (p > 0.05) in our study. The average tear load, considering both parallel and perpendicular directions, was 36.72 N. However, a higher average tear load was observed for DM crossbred lambs (37.58 N) compared to AW crossbred lambs (28.73 N), and this difference was statistically significant (p < 0.05). The tear load measured in N/mm did not show any significant difference (p > 0.05) among the tested concentrate feeding levels and genotypes. However, the concentrate feeding level did have a significant effect (p < 0.05) on the average tear load parallel to the backbone, average tear load perpendicular to the backbone, and average tear load when considering both parallel and perpendicular directions.

These findings align with the results reported by Getachew et al. [6, 7], who also observed no influence of genotype and feeding levels on tear resistance. In summary, the tear load parallel and perpendicular to the backbone did not show significant differences overall, but DM crossbred lambs demonstrated higher tear load compared to AW crossbred lambs. The tear resistance was not significantly influenced by genotype and feeding levels, consistent with previous findings.

The tear resistance values obtained in our study were 29.23 N/mm for AB, 23.80 N/mm for AW, and 27.63 N/mm for DM sheep breeds. These values were significantly better (p < 0.05) compared to the range of 15.01 to 15.99 N/mm reported for Awassi X Menz, Menz, and Washera sheep breeds by Getachew et al. [6, 7]. Additionally, our findings were similar to the tear resistance values reported for Brazilian, South African, and German sheep breeds by Snyman and Jackson-Moss [22] and Oliveira et al. [23]. This suggests that the tear resistance of the AB, AW, and DM sheep breeds in our study was superior to that of the Awassi X Menz, Menz, and Washera breeds studied by Getachew et al. [6, 7], and comparable to the tear resistance values observed in sheep breeds from Brazil, South Africa, and Germany as reported by Snyman and Jackson-Moss [22] and Oliveira et al. [23].

4.4 The chemical properties of leather derived from crossbreed lambs

4.4.1 The moisture content of the raw skin, expressed as a percentage

Table 3 presents the moisture content, expressed as a percentage, for both raw and wet blue skin in this study. The average moisture content of raw skin was determined to be 34%, while for wet blue skin, it was 62%. The breed of the sheep had a significant impact (p < 0.05) on the moisture content of the raw skin, with DM lambs exhibiting lower moisture content compared to AB and AW lambs. However, the levels of concentrate supplementation did not show a significant effect (p > 0.05) on the moisture content at both the raw and wet blue stages. Additionally, there were no significant differences observed in the moisture content at the wet blue stage among the lamb breeds AB, AW, and DM.

Variable	Average thickness; (mm)	Tensile strength; (N/mm^2)	Elongation at break; (%)	Mean; tear load; Parallel to the backbone (N)	Mean; tear load; Perpendicular to the back; Bone (N)	Average tear load; (N)	Tear-Load (N/mm)
Overall (44)	1.35 ± 0.08	10.26 + 0.81	49.73 + 1.73	32.73 + 0.01	36.72 + 0.45	34.43 + 1.88	27.03 ± 1.32
Breed	*	ns	ns	ns	ns	*	ns
Awassi x Bonga (10)	1.23 ± 0.09^a	12.11 ± 1.05	47.22 ± 2.13	35.14 ± 4.42	35.14 ± 4.42	32.57 ± 3.87^ab	29.23 ± 2.96
Awassi x Washera (13)	1.23 ± 0.08^a	10.27 ± 0.86	49.51 ± 1.73	31.91 ± 3.60	31.31 ± 3.60	28.73 ± 3.15^a	23.80 ± 2.42
Dorper x Menz (21)	1.43 ± 0.06^b	9.33 ± 0.68	50.56 ± 1.37	39.84 ± 2.84	39.84 ± 2.84	37.58 ± 2.49^b	27.63 ± 1.90
Treatment	*	ns	ns	*	*	*	ns
Grazing +300 g concentrate (12)	1.17 ± 0.09^a	10.31 ± 0.69	46.44 ± 1.99	23.28 ± 3.72^a	30.31 ± 4.15^a	26.32 ± 3.63^a	25.03 ± 2.78
Grazing +600 g concentrate (16)	1.28 ± 0.07^ab	10.22 ± 0.78	50.00 ± 1.57	33.22 ± 2.93^ab	32.98 ± 3.26^b	33.16 ± 2.86^b	26.19 ± 1.19
Grazing +900 g concentrate (16)	1.49 ± 0.07^b	11.18 ± 0.78	50.85 ± 1.58	37.66 ± 2.94^b	43.01 ± 3.28^b	39.41 ± 2.87^b	29.43 ± 2.20

Table 3.

Least squares means (±SE) of skin thickness (mm), tensile strength (N/mm²), Elongation (%), tear load parallel (N), tear load perpendicular (N), mean tear load (N), tear-load (N/mm) of skins produced from crossbred sheep under different feeding levels.

Means with different superscripts for a class within a column differ significantly, *** - P<0.001; ** - P<0.01; * - P<0.05, ns - non-significant.

“a” was denoted for lower values and “b” is for the next higher values etc.

Regarding the moisture content at the wet blue stage, it ranged from 61 to 62% for different levels of concentrate supplementation. These values were slightly lower than the findings reported by Negussie et al. [24], who obtained moisture content ranging from 69 to 74% for Blackhead Ogaden sheep subjected to various feeding regimes. This suggests that the moisture content of the wet blue skin in our study was relatively lower, potentially indicating more efficient processing and reduced water content in the leather.

4.4.2 The fat content of the leather samples, expressed as a percentage

Sheepskin typically contains a natural fat content ranging from 30–40%, which plays a crucial role in the leather’s acceptance of fat liquor substances during the tanning process [25]. To remove excess fat, a degreasing operation is performed. If the natural fat is not adequately eliminated, it can hinder the hydrophilic properties of chemicals, specifically liquoring agents. This can result in undesirable quality problems, including decreased physical strength, hardness, imperfect dyeing, and unpleasant odors in the final product [26].

In this study, the fat content of all treatment groups was observed to fall within the recommended standard range of 4 to 10% for the production of upper shoe leather. The average fat content of the skin in this study was determined to be 6%. The lamb genotype and feeding regime did not exhibit a significant impact (p > 0.05) on the fat content of the skins. Nonetheless, a minor reduction in fat content was observed across the different feeding regimes, with percentages of 6.29, 6.11, and 5.39% recorded for 300, 600, and 900 g concentrate supplementation, respectively. These results suggest that higher levels of concentrate supplementation contribute to improved leather quality by reducing the fat content.

These findings are consistent with the research by Haroun et al. [27], who reported fat content values of 6 to 7% for Sudan Desert sheep. However, the fat content in our study was lower than that reported by Negussie et al. [24] for Blackhead Ogaden sheep under different concentrate supplementation regimes. In contrast, our study yielded higher values compared to the results reported by Teklebrhan et al. [19] for Hararghe Highland, Black Head Ogaden, Dorper X Hararghe Highland, and Dorper X Blackhead Ogaden sheep.

The fat content in sheepskins can vary widely, ranging from 4 to 50%, whereas in cattle hides, it typically falls between 2 and 12%. These variations depend on factors such as the breed, age, and sex of the animal [28]. During the tanning process, the lower fat content observed in the AB, AW, and DM lamb breeds after degreasing indicates the production of higher-quality leather. This finding aligns with the conclusions mentioned by Sarkar [29], suggesting that lower fat content contributes to the production of superior leather.

In summary, the present study demonstrated that the fat content of the skins fell within the standard range for upper shoe leather production. Lamb genotype and feeding regime did not significantly affect the fat content. However, higher concentrate supplementation levels were associated with lower fat content, indicating improved leather quality. These findings are consistent with prior research, demonstrating that the AB, AW, and DM lamb breeds achieved a low fat content after degreasing, which is indicative of higher-quality leather. These results further support the conclusions mentioned by Sarkar [29].

4.4.3 The hide substance content, expressed as a percentage

The study found that, on average, the hide substance percentage obtained was 33 (Table 4). The results indicated that lamb genotype and feeding regime did not have a significant effect on the hide substance of the lambs’ skin, as the p-value was greater than 0.05. As a result, the differences in lamb genotype and feeding regime did not lead to significant variations in the percentage of hide substance.

Variable	Moisture content for raw skin (%)	Moisture content wet blue (%)	Fat content (%)	Hide substance (%)
Overall (44)	34.06 ± 1.93	61.48 ± 0.68	6.08 ± 0.46	32.46 ± 1.33
Breed	**	ns	ns	ns
Awassi x Bonga (10)	44.16 ± 3.83^b	62.12 ± 1.53	5.06 ± 1.06	31.51 ± 3.11
Awassi x Washera (13)	38.64 ± 03.12^b	63.09 ± 1.25	6.03 ± 0.87	32.16 ± 2.54
Dorper x Menz (21)	27.42 ± 02.46^a	60.20 ± 0.99	6.67 ± 0.68	33.16 ± 2.00
Treatment	ns	ns	ns	ns
Grazing +300 g concentrate (12)	42.03 ± 3.59	61.93 ± 1.44	6.26 ± 0.99	32.64 ± 2.92
Grazing +600 g concentrate (16)	33.33 ± 2.83	61.16 ± 1.13	6.11 ± 0.78	30.53 ± 2.30
Grazing +900 g concentrate (16)	34.85 ± 2.84	62.32 ± 1.14	5.39 ± 0.79	33.67 ± 2.31

Table 4.

Least squares means (±SE) of moisture content for raw skin (%), moisture content of skin at wet blue stage (%), fat content of skin (%), and hide substance (%) of skins produced from crossbred sheep under different feeding levels.

Means with different superscripts for a class within a column differ significantly, *** - P<0.001; ** - P<0.01; * - P<0.05, ns - non-significant.

“a” was denoted for lower values and “b” is for the next higher values etc.

5. Conclusion

Based on the study presented in this chapter, several significant conclusions can be drawn:

• Concentrate supplementation levels significantly impacted lambs’ raw skin weight and size.

• Higher concentrate supplementation (900 g/h/d) resulted in 42% more skin weight and 15% larger size compared to 300 g supplementation.

• Crossbred lambs had better skin thickness (1.35 mm) compared to the standard thickness of 0.60 mm.

• Lambs supplemented with 900 g/h/d had 27% thicker skin (1.49 mm) compared to those supplemented with 300 g/h/d (1.17 mm).

• DM lambs had thicker skin (1.43 mm) compared to AB and AW crossbreeds (1.23 mm).

• Breed and diet did not significantly affect skin tensile strength (ranging from 9.33 to 12.22 N/mm²).

• Average tear load was higher in DM crossbred lambs (37.58 N) compared to AW crossbred lambs (28.73 N).

• Skins’ fat content was within the standard range (6%) for upper shoe leather production and slightly decreased with higher concentrate supplementation.

• Lamb genotype and feeding regime did not significantly affect hide substance percentage.

• In summary, crossbred sheep like DM, AB, and AW demonstrated favorable skin quality that meets industry standards. They have the potential for both meat and skin production, benefiting farmers and sheep raisers in Ethiopia.

5.1 Recommendations and future directions

Based on the results of this study, the following recommendations are suggested:

• Conduct further studies on optimizing concentrate supplementation levels and their effects on skin quality attributes to provide comprehensive guidelines for farmers and sheep raisers.

• Evaluate the economic viability of crossbred sheep production for both meat and skin compared to other livestock production systems.

• Investigate market demand and value chain opportunities for crossbred sheepskin products, both domestically and internationally based on the benefits of feeding systems.

• Assess the potential of crossbred sheep for meat and skin production in different geographical regions based on different levels of feeding systems.

• Conduct economic assessments considering production costs, market demand, value chain opportunities, and profitability for farmers and sheep raisers.

• Facilitate scaling and knowledge transfer through collaboration, capacity building, and adoption of best practices.

• Promote the development of a sustainable and competitive sheepskin industry in Ethiopia through the integration of crossbred sheepskin production into the livestock sector.

Acknowledgments

The authors would like to express their gratitude to the Debre-Birhan Agricultural Research Center and the Ethiopian Agricultural Research Institute (EIAR) for providing financial support for the project, The authors are also grateful to Accelerating the Impact of CGIAR Climate Research in Africa (AICCRA) project and CGIAR initiative on “Sustainable Animal Productivity for Livelihoods, Nutrition and Gender inclusion (SAPLING)” for partially funding this research”. They would also like to thank the Leather Industry Development Institute (LIDI) of Ethiopia for their assistance in analyzing the chemical and physical characteristics of the skins. Additionally, the authors appreciate the support received from Mr. Alemayehu H/M and Mr. Deribew Bekele. Their assistance was invaluable to the success of the study. This work is part of a Ph.D. work of Mr. Ayele Abebe derived from the large data set on Dorper crossbreeding evaluation work in Ethiopia.

A. Appendix

See Figure A1.

Figure A1.

Pictures of experimental sheep and final products from these breeds at LIDI.