Introduction

Livestock production in tropical regions, particularly in sub-Saharan Africa, faces significant challenges due to the increasing cost of conventional feed, seasonal fluctuations in forage availability, and competition between human food supply and animal feed resources. The West African Dwarf (WAD) ram is a crucial breed for smallholder farmers due to its adaptability to harsh environmental conditions, high fertility rate, and ability to thrive on diverse feed sources. However, the reliance on expensive commercial feeds has made sheep production less profitable¹. To address this issue, the use of alternative feed resources that are locally available, cost-effective, and nutritionally beneficial has gained attention.

Several studies have explored the potential of non-conventional feed ingredients in ruminant diets. Mango leaves and neem seed cake are promising due to their rich protein, fiber, and bioactive compounds that can enhance digestion, growth, and overall health². Napier grass is widely used as forage due to its high yield and good palatability. When strategically combined with concentrate diets, these feed resources can optimize nutrient intake, leading to improved growth performance and meat quality³.

Despite the potential benefits of alternative feeds, limited research has been conducted on their specific impact on carcass traits, organ development, and meat quality in WAD rams. Understanding these effects is crucial for formulating balanced diets that ensure efficient livestock production while minimizing feeding costs⁴. Additionally, sustainable feeding strategies that incorporate locally available feed resources could help smallholder farmers mitigate production constraints and improve profitability^5-7.

This study aimed to evaluate the effects of mango leaves, neem seed cake, Napier grass, and concentrate-based diets on the growth performance, carcass characteristics, non-carcass components, and meat quality of WAD rams. By identifying optimal feed combinations, this research contributes to developing sustainable feeding strategies that enhance sheep productivity in tropical regions.

Materials and methods

Housing and study location. The study was conducted at the Teaching and Research Farm of the Department of Animal Production and Health, Faculty of Agriculture, Federal University Oye-Ekiti, Ekiti State, Nigeria. The farm is located at longitude 5.5145° E and latitude 7.7983° N, with an elevation of 570 m above sea level. The climate is tropical, with relative humidity ranging from 57-92% and a mean daily temperature of 68-90°F.

Experimental animals and management

Selection and identification of animals. Forty (40) West African Dwarf (WAD) rams were purchased from the livestock market in Ikole-Ekiti, Nigeria.

Selection criteria included. i) Age range: 8-9 months (determined by dentition and market records). ii) Average initial body weight: 8.00±0.20 kg. iii) Healthy appearance with no visible signs of disease or deformities.

Each ram was marked with numbered ear tags upon arrival for easy identification and to prevent misallocation during feeding and data collection.

Health management. To ensure uniform health status, the animals underwent quarantine and veterinary assessment upon arrival. Preventive measures included. i) Vaccination against prevalent diseases such as Peste des Petits Ruminants (PPR). ii) Deworming (oral anthelmintics to control internal parasites). iii) Administration of an injectable ADE vitamin complex for immune support.

During the study, rams were monitored daily for any signs of illness. No animals were removed from the study due to health complications.

Housing and feeding management. The rams were housed in individual dwarf wall pens (2×2.5 m), constructed with cement blocks, allowing precise monitoring of feed intake and health status. The pens were cleaned and disinfected before the animals' arrival and routinely maintained to ensure hygiene.

Experimental design and diets. The study followed a completely randomized design (CRD) with 4 treatment groups, each consisting of 10 rams. The diets included:

Diets were offered at 5% of body weight per day, ensuring voluntary consumption.

Fresh, clean water and mineral salt licks were provided ad libitum.

Animal weighing and data collection. Body weight measurements were taken weekly at the same time each day (7:00 AM) using a digital livestock weighing scale (precision: ±0.01 kg). The scale was calibrated before each use. Environmental conditions were consistent during weighing to minimize stress-related fluctuations.

Slaughtering and sample collection. At the end of the experiment, all 40 rams were slaughtered following standard ethical guidelines⁸. The slaughter process followed humane handling practices in accordance with guidelines for animal welfare. The following parameters were recorded: Live weight before slaughter.

Carcass weight and dressing percentage. Organ weights (liver, kidney, lungs, heart, spleen, intestines, and stomach).

Organ extraction. Organs were removed immediately after slaughter and weighed using a sensitive digital balance (±0.01 g precision). Data were recorded under standardized conditions to ensure accuracy.

Meat quality evaluation. Meat quality parameters were assessed using standard methodologies^9,10: i) pH Measurement - Determined 45 min and 24 h post-mortem using a pH meter (Hanna Instruments HI 99163, accuracy ±0.01). ii) Water Holding Capacity (WHC) - Evaluated using the Grau and Hamm method (1953). iii) Meat Color Analysis - Assessed with a Minolta CR-400 Chroma Meter, measuring L (lightness), a (redness), and b* (yellowness) values**. iv) Cooking Loss and Tenderness - Cooking loss was measured by percentage weight reduction post-cooking, while tenderness was assessed using a Warner-Bratzler shear force device.

Ethical Considerations.

All procedures adhered to the ethical guidelines of the Federal University Oye-Ekiti Animal Ethics Committee (approval number: FUOYE/APH/2024/ 003). The study followed international standards for humane animal handling, feeding, and slaughtering practices⁸.

Results

Table 2 provides the proximate composition of feedstuffs used in the experimental diets. It shows that ML have high CP content but also high crude fiber, while NSC has the highest crude protein content and relatively low CF. NG has a moderate protein content but high fiber, and the CD has the highest protein content and lowest fiber among the feedstuffs.

In Table 3, the intake, weights, and carcass traits of rams fed different diets are summarized. Notably, Diet B had the highest slaughter weight, empty body weight, hot carcass weight, and hot carcass yield, while Diet C generally showed the lowest values across these parameters. These differences suggest that Diet B might be more efficient in promoting growth and carcass traits compared to the other diets.

Table 4 presents the percentages of non-carcass components for the four different diets. It indicates significant differences in organ percentages among the diets. Diet D generally had higher percentages in several organs, while Diet B displayed notable effects on liver, kidneys, lungs, and rumen/reticulum. Diet C, on the other hand, generally had lower percentages across various organs compared to the other diets.

This figure combines bar and line charts to show the values of various parameters for each diet. Bars represent specific parameter values per diet, while lines illustrate trends and comparisons, enabling quick identification of diet-related differences.

Figure 1 Parameter values for each diet 

The meat quality parameters assessed in this study provide valuable insights into the effects of different diets on the sensory and textural properties of West African Dwarf ram meat. pH level is an important indicator of meat freshness and stability, with lower pH values associated with increased tenderness and shelf life. The slight variations in pH levels among the diets suggest potential differences in meat maturation and post-slaughter processes.

Color measurements (L*, a*, b*) reflect aspects of meat appearance such as brightness, redness, and yellowness. These parameters influence consumer perception and acceptability of meat products. The observed differences in color values among the diets may be attributed to variations in feed composition and pigments present in the alternative feed resources.

Water holding capacity (WHC) is a critical factor affecting juiciness and succulence in cooked meat. Diets with higher WHC values generally result in moister and more flavorful meat.

The histogram displays the distribution of parameter values across diets, showing how frequently certain values occur within each diet category. This helps identify diet patterns, concentration ranges, and potential outliers in the diet parameter data.

Figure 2 Diet distribution histogram 

A radar chart compares normalized parameters across multiple diets, with each axis representing a distinct parameter. This star-shaped chart visually captures diet profiles, making it easy to see strengths and weaknesses of each diet

Figure 3 Radar chart for all diets 

This line plot connects parameter values for each diet, forming a performance curve. The connecting lines highlight trends and shifts in parameter levels across diets, making it useful for assessing relative diet performance.

Figure 4 Performance curve 

Discussion

By analyzing proximate compositions of the feedstuffs, intake, carcass yield, non-carcass components, and meat quality parameters, the research provides significant insights into optimizing feeding strategies to enhance livestock productivity.

Proximate composition of feedstuffs. Table 3 and Figure 1 illustrate the proximate composition of the experimental feedstuffs. NSC had the highest CP (23.88 %), while ML provided a good protein source (18.4 %) but were high in CF (27.06 %), potentially limiting digestibility. NG), with its lower protein content (7.95 %) and high fiber (31 %), serves as a basal feed. The CD offered the highest NFE (57.16 %), a crucial energy source, making it essential for enhancing energy balance in the rations.

The higher crude fiber in ML and NG might influence rumen development, as De Souza et al.¹¹ demonstrated fiber’s role in enhancing rumen fermentation. Meanwhile, NSC aligns with Detmann et al.¹², who reported that protein-rich feeds significantly improve growth and internal organ development. Chia et al.¹³ further confirmed that NG provides valuable forage for livestock, particularly in combination with protein-dense supplements, for balanced growth.

Feed intake, body weight, and carcass traits. Table 2 and Figure 4 highlight trends in feed intake, body weights, and carcass traits. Diet B (ML + NG + CD) showed the highest slaughter weight (11.33 kg) and hot carcass yield (53.05 %), consistent with findings by Paulino et al.¹⁴ that balanced energy-protein diets promote better muscle deposition. Conversely, Diet A (ML alone) had the lowest values in performance metrics, likely due to its high fiber limiting energy utilization.

Diets combining forages like NG and concentrates appear particularly effective in enhancing feed efficiency. Kariuki et al.¹⁵ observed similar results when supplementing NG with legumes or concentrates, leading to improved nutrient intake and growth. Additionally, Rahman et al.¹⁶ confirmed that concentrates improve digestibility and live weight gain in ruminants when paired with NG.

Chilling losses were lowest in Diet B (7.82 %), as seen in Figure 3, suggesting better meat quality preservation. Similar patterns were noted in studies by Edwards et al.¹⁷, where optimal feed combinations reduced post-slaughter losses. This underscores the role of protein-energy synergy in reducing carcass fat losses while supporting higher yields.

Non-carcass components. Non-carcass organ weights (Table 5) reveal the influence of diet on organ development. Diet D (ML + NSC + NG + CD) demonstrated the highest liver (2.50 %) and kidney (1.42 %) weights, attributed to bioactive compounds in NSC. Kariuki et al.¹⁵ highlighted neem’s beneficial effects on animal health, which might explain these observations. Diet B also enhanced lung weights (1.35 %) and rumen/reticulum (1.98 %), which align with findings by Shem et al.¹⁸, where protein-energy-rich supplements enhanced organ development.

Fiber-rich diets like Diet A contributed to higher rumen weights, as seen in De Souza et al.¹¹ and Tarigan et al.¹⁹, who linked high-fiber feeds to improved rumen development and fermentation. However, lower organ weights in Diet C suggest an imbalance in nutrient composition, underscoring the need for diet optimization. Figure 2 visualizes the distribution of these traits, indicating consistent organ development in Diets B and D.

The variations observed in the organ percentages could be attributed to differences in the nutritional composition of the diets. Studies by^14,20 have shown that diets rich in protein and energy tend to promote higher organ weights and growth rates in ruminants. Pulina et al.²⁰ found that diets with higher protein content led to increased organ weights in lambs, which supports the higher protein diets' influence on organs observed in this study.

Moreover, the fiber content in the diets could affect rumen development and subsequently impact the weights of organs like the rumen/reticulum. Research by De Souza et al.¹ demonstrated that diets with higher fiber content promoted rumen development in sheep, which could explain the differences observed in the rumen/reticulum weights among the diets in this study.

The significant effects of Diet D on various organs could also be related to specific nutrients or bioactive compounds present in the diet. For instance, Neem Seed Cake, a component of Diet D, has been reported to contain bioactive compounds with potential health benefits for ruminants^21,22. These compounds could influence organ development and function in rams.

In summary, the diets seem to have varying impacts on different organs, with Diet D showing higher percentages in several organs, Diet B having notable effects on liver, kidneys, lungs, and rumen/reticulum, while Diet C generally has lower percentages across various organs compared to the other diets. These differences could reflect the varying nutritional compositions of the diets and their influence on organ development or metabolism.

Meat quality. Meat quality parameters (Table 5) showed minimal variation across diets. Diet B recorded the highest water-holding capacity (WHC, 76.2 %), indicating juicier, more flavorful meat. Oluwadele et al.¹ observed similar benefits with balanced protein-energy diets enhancing meat succulence. WHC is crucial, as it impacts consumer acceptability and economic returns.

Color parameters (L*, a*, b*) varied slightly across diets due to differences in feed pigmentation. Tarigan et al.¹⁹ highlighted the role of forages like NG in influencing meat color through carotenoid levels. Lower shear force across diets suggests comparable tenderness, aligning with findings by Tawose et al.² and Tamir & Asefa²³.

The line plot in Figure 4 indicates that Diet B consistently improved WHC and color stability, highlighting its potential to enhance meat quality. Ebrahimi et al.²⁴ reported similar results in goats fed jackfruit foliage supplements, where energy-rich feeds improved textural and sensory properties.

Broader implications. The study highlights the interplay between nutrient composition and livestock performance. Diets B and D, combining protein-dense feedstuffs with energy-rich concentrates, outperformed others, as observed in studies^25,26. Excessive fiber in Diet A limits energy utilization, as also noted by Nsahlai et al.²⁷.

Balanced diets like Diet B not only enhance carcass yields but also boost economic value, supporting findings by Tarigan²⁸, where Indigofera supplements increased growth and market returns. Furthermore, organ health benefits from neem compounds in Diet D underscore their role in promoting metabolic efficiency.

Napier grass, a staple forage, proves versatile when supplemented with concentrates, as also confirmed^29,30 who noted its positive effects on rumen function and growth. However, challenges such as feed resource availability and cost³¹.

The differences in WHC among the diets indicate potential effects on meat texture and palatability.it agrees with the findings of Oluwadele et al.¹. Shear force measurements reflect meat tenderness, with lower shear force values indicating greater tenderness. The minimal differences in shear force values among the diets suggest similar levels of tenderness across the treatments.

Overall, the variations in meat quality parameters among the diets highlight the importance of feed composition in influencing the sensory and textural properties of West African Dwarf ram meat. Further research is needed to elucidate the underlying mechanisms driving these differences and optimize feeding strategies for improved meat quality in sheep farming.

This study highlights the importance of balanced protein-energy diets in optimizing growth performance, carcass traits, organ development, and meat quality in West African Dwarf rams. Diets B and D, which combined Napier grass, mango leaves, neem seed cake, and concentrates, produced superior results. Future research should explore cost-effectiveness and long-term effects to enhance sustainable small ruminant production.