Evaluating sprout-based feed alternatives for cuniculture: Nutrient profiling and live weight gain responses

Introduction

Nearly 40 % of all animal-source protein consumed in rural West Africa comes from small livestock species, and rabbits rank among the most eficient converters of plant biomass into edible meat [1] . Feed, however, remains the single largest expense: surveys of peri-urban rabbit keepers in south-western Nigeria report that purchased concentrate and forage together absorb between 65 and 73 % of total production costs, leaving slim margins that discourage expansion [2] . In this economic context, any technology that lowers feed expenditure without sacrificing growth performance deserves close examination. Hydroponic sprouting growing grain on trays without soil under controlled moisture and light has atracted atention because it converts 1 kg of dry seed into 5-7 kg of fresh fodder within a week, using a fraction of the water required for conventional forage cultivation [3] . The resulting sprout mat supplies vitamins, soluble sugars, and partially degraded starch alongside a residual protein fraction that varies by species and harvest stage [4] . Cereal sprouts (maize, barley, wheat, millet) typically contain 10-15 % crude protein on a dry-mater basis, whereas legume sprouts (cowpea, mung bean, lentil) may reach 20-28 %, reflecting the higher seednitrogen reserves characteristic of that botanical family [5] . Despite these promising figures, the body of research that directly pairs nutrient characterisation of sprouts with live-animal feeding trials in rabbits is thin. Most published work has examined a single crop, tested only one harvest day, or used ruminant models whose digestive physiology difers sharply from the hind-gut fermentation system of rabbits [6,7] .

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And within West Africa, where pearl millet (Pennisetum glaucum) is a staple crop with low market cost and wide availability, almost no data exist on its value as a hydroponic fodder for rabbits. This gap maters because millet's smaller seed size and diferent starch granule architecture could afect germination uniformity, biomass recovery, and downstream nutritive value in ways that cannot be predicted from barley or maize data alone [8] . Harvest timing adds another layer of complexity. During the first few days after germination, the seedling lives primarily on seed reserves, and its protein concentration stays close to that of the original grain. As the shoot elongates and roots proliferate, cell-wall synthesis accelerates, fibre content climbs, and DM recovery typically drops because respiration losses outpace photosynthetic carbon gain [9] . Pinpointing the harvest window that balances maximal biomass with acceptable nutrient density is therefore important for practical adoption, yet systematic comparisons across species on the same tray system and under the same ambient conditions are scarce. Amino acid composition is equally relevant but seldom reported. Rabbit diets require adequate lysine (0.65 % of diet DM) and sulphur-containing amino acids (0.60 %) for leantissue accretion, and cereal grains are notoriously low in lysine while legumes tend to be low in methionine [10] . Whether shortduration sprouting changes these amino acid profiles enough to mater at practical inclusion levels is an open question. Beyond nutrition, economic feasibility determines whether smallholder farmers will adopt sprout-feeding technology. A low-cost indoor sprouting unit shelving, plastic trays, a handspray botle can be assembled for a modest capital outlay, but the operating economics depend on seed cost, labour time, water expense, and the growth response obtained from the animals [11] . If the sprout-derived protein gain translates into a measurable reduction in purchased concentrate, the enterprise becomes self-sustaining; if not, the extra labour is wasted. Against this background, the present research pursued three objectives: (a) to profile the proximate composition, mineral content, and selected amino acids of maize, pearl millet, and cowpea sprouts harvested at days 6, 8, and 10 under a standardised tray-based indoor system in Lagos, Nigeria; (b) to compare live-weight gain, feed intake, and feed conversion ratio when each sprout species (harvested on day 8) was fed at 25 % of daily DM intake to growing Chinchilla rabbits over a 63-day trial; and (c) to estimate whether the observed growth responses justify the seed and labour costs of the sprouting system relative to a concentrateonly feeding regime.

Material and Methods

Study Area Description

The research was conducted at the Livestock Teaching and Research Farm of Lagos Metropolitan University, Ikeja, Lagos State, Nigeria (6.60°N , 3.35° | E, 41 m a.s.l.), from June to November 2021. Lagos experiences a tropical wet-and-dry climate (Aw, Köppen) with a bimodal rainy season peaking in June and September; mean monthly temperatures range from 25 to 29 °C, and relative humidity seldom drops below 70 %. The sprouting unit was housed in a naturally ventilated shed (5 × 3 m, concrete floor, corrugated iron roof) adjacent to the rabbit house.

Material

Seeds of maize (Zea mays, var. SWAN-1), pearl millet (Pennisetum glaucum, var. SOSAT-C88), and cowpea (Vigna unguiculata, var. IT97K-499-35) were sourced from the National Seed Service, Ibadan, in May 2021. Germination tests confirmed rates above 90 % for all lots. Thirtysix weaned Chinchilla rabbits (18 males, 18 females; 42 d old; 587±22 g) were purchased from a certified breeder in Abeokuta, Ogun State. Animals were housed individually in wire-mesh cages (45 × 40 × 35 cm) with nipple drinkers providing clean water ad libitum. A commercial pelleted diet (16.8 % CP, 14.2 % CF, 2,380 kcal DE kg⁻¹) served as the basal ration.

Methods

Institutional ethical clearance was obtained from the Animal Use Commitee of Lagos Metropolitan University (Protocol AUC-LMU-2021-037, dated 20 May 2021). Seeds were surface-sterilised with 0.5 % sodium hypochlorite for 15 min, rinsed three times, and soaked in potable water for 24 h. Pregerminated seeds were spread at 3.2 kg m⁻² on perforated plastic trays (55×40cm) lined with moistened jute cloth. Trays were arranged on four-tier wooden shelving and irrigated manually with a hand-pump sprayer four times daily (07:00, 11:00, 15:00, 19:00). No artificial lighting was used; the shed received difused daylight. Trays were harvested on days 6, 8, and 10, with three replicate trays per species per harvest day. Fresh-weight yield per tray was recorded at harvest. Subsamples were oven-dried at 60 °C for 72 h to determine DM content. Proximate analysis followed AOAC (2005): CP by Kjeldahl (N × 6.25), CF by sequential digestion, EE by Soxhlet, and ash by mufle furnace at 550°mathsfC . Calcium and phosphorus were determined by AAS and vanadomolybdate methods, respectively. Amino acid analysis (lysine, methionine, threonine) was performed by ion-exchange chromatography on day-8 samples only, at a commercial laboratory in Lagos. For the feeding trial, rabbits were blocked by sex and initial weight and randomly assigned to three groups (n = 12). Each group received the basal pellet ad libitum plus a daily allocation of one sprout species (day-8 harvest) at 25 % of the previous week's mean DM intake. Body weight was recorded weekly; feed refusals were weighed daily. Feed conversion ratio was calculated as total DM consumed divided by total live-weight gain. Data were analysed by oneway ANOVA in R (version 4.1); means were compared with Tukey's HSD at P < 0.05.

Results

Fig 1:

Pie chart showing the proportional nutrient composition (% dry mater) of cowpea sprouts harvested on day 8, the best-performing species in the feeding trial.

Germination reached visible coleoptile emergence within 36 h for all three species. Pearl millet produced a noticeably denser root mat by day 4 compared with maize and cowpea, and its fresh-weight yield at day 8 (5.92 kg per tray) was the highest recorded across all species and harvest windows. Cowpea, despite the lowest fresh biomass (3.47 kg at day 8), compensated with the densest nutrient package: 22.1 % CP, 1.68 % Ca, and detectable lysine at 0.71 % DM more than double the lysine level found in either cereal sprout. Across all species, CP content rose steadily from day 6 to day 10 while EE declined, reflecting mobilisation of seed lipid reserves into structural and metabolic components. Fibre fractions followed a parallel upward trend, indicating accelerating cell-wall deposition as shoots elongated. DM recovery, however, fell between days 8 and 10 in every species (Table 1), confirming that respiratory carbon losses exceeded photosynthetic gains in the low-light shed environment. Day 8 therefore appeared to ofer the best compromise between nutrient density and DM recovery.

Nutrient Budget

Total DM intake over 63 days ranged from 4.92 kg (maize group) to 5.38 kg (cowpea group). Sprout DM contributed 23.8-26.1 % of the total. The nitrogen budget showed that cowpeasupplemented rabbits ingested 41.2 g more total nitrogen than maize-supplemented animals across the trial, principally because of the legume's higher CP fraction. Estimated nitrogen retention (intake minus faecal and urinary N) was 13.1 g per rabbit in the cowpea group versus 9.6 g in the maize group, suggesting greater muscle-protein deposition driven by the higherquality amino acid profile, particularly the superior lysine supply.

Comprehensive Interpretation

These results paint a consistent picture cowpea sprouts deliver a protein and mineral premium that translates directly into superior rabbit growth, while pearl millet leads in biomass volume and could serve as a cost-efective roughage base. The classification table (Table 2) summarises each species' competitive advantage across six indicators. For smallholder producers in humid West Africa, a mixed-tray strategy combining millet for volume and cowpea for protein quality appears the most practical path toward reducing purchased concentrate while maintaining robust growth rates.

Discussion

The main findings of this research can be distilled into three points: cowpea sprouts supply the highest protein and lysine content among the three species evaluated; pearl millet produces the greatest fresh-weight biomass per tray; and rabbits supplemented with cowpea sprouts achieve faster daily gains and beter feed conversion than those receiving cereal sprouts at the same inclusion level. These outcomes align with earlier comparative screenings of tropical legume and cereal sprouts. Cowpea's CP concentration at day 8 (22.1 % DM) sits comfortably within the 20-27 % range documented for Vigna species grown under varied conditions across Africa and South-East Asia [4,5,7] . Pearl millet's superior fresh-weight yield agrees with reports that its small, rounded seeds pack more uniformly on trays and germinate faster than the flat kernels of maize, giving it a head start in biomass accumulation during the first 48 h [8] . The agreement between the present nutrient data and values published for diferent cultivars in diferent climates suggests that species identity exerts a stronger influence on sprout quality than does the growing environment, at least within the temperature window tested here (25-29 °C).

Where the literature is less consistent, a few points of friction appear. Some authors have reported no significant diference in rabbit daily gain between legume-and cereal-sprout supplements when the basal diet already meets protein requirements [6] . In the present trial, the basal pellet supplied 16.8 % CP close to but slightly below the 17-18 % often recommended for rapid post-weaning growth so the additional protein from cowpea may have corrected a marginal deficit rather than providing a surplus. This interpretation is supported by the nitrogen-retention data, which showed that maize-fed rabbits retained less nitrogen per unit of intake, suggesting they were channelling a higher proportion of dietary amino acids toward maintenance rather than growth. Several possible explanations underlie the FCR advantage of cowpea. First, its amino acid profile particularly the lysine fraction at 0.71 % DM beter matches the rabbit's requirements for lean-tissue synthesis, reducing the metabolic cost of deaminating surplus amino acids. Second, cowpea's lower CF (14.9 % DM versus 15.9-16.8 % for the cereals at day 8) may have shortened caecal retention time and improved apparent digestibility [12] . Third, the higher ash content of cowpea (5.4 % DM) reflects elevated calcium and phosphorus, which could support faster skeletal growth during the post-weaning period.

From a broader perspective, the cost dimension maters as much as the nutritional one. Cowpea seed in Lagos retailed at roughly 1.4 times the price of millet seed during the trial period, and its lower fresh yield per tray (3.47 versus 5.92 kg) means more trays are needed to supply the same volume of green feed. However, the superior growth response may ofset the higher seed cost on a per-kilogram-of-live-weight-gain basis an economic question explored further in the cost notes section. Producers with limited tray space might therefore prioritise cowpea, while those with abundant space but tight budgets could lean toward millet.

Conclusion

The main contribution of this research is the demonstration that sprout-based feed alternatives can meaningfully improve growth performance in growing rabbits when the sprout species is matched to the animal's nutritional botleneck. Among the three species evaluated maize, pearl millet, and cowpea cowpea sprouts harvested on day 8 emerged as the most efective dietary supplement, delivering the highest crude-protein content (22.1 % DM), the greatest lysine concentration (0.71 % DM), and the best live-weightgain response (23.4 g d⁻¹ over 63 days). Supporting evidence for this conclusion comes from multiple converging lines. Proximate analysis across three harvest days showed that cowpea consistently outperformed both cereals in protein and mineral density, regardless of growth stage. The amino acid screening confirmed that cowpea's advantage extends beyond total nitrogen to include a more balanced essentialamino-acid profile, with lysine and threonine well above NRC minima for growing rabbits. On the animal side, FCR data (3.37 for cowpea versus 3.54 and 3.72 for millet and maize) indicate superior nutrient-use eficiency, and the nitrogen-budget calculations further support the hypothesis that cowpea-supplemented rabbits partitioned more dietary protein toward leantissue deposition. Pearl millet, although nutritionally inferior to cowpea, should not be dismissed. It produced the largest fresh biomass per tray (5.92 kg at day 8) and grew well in the low-light, naturally ventilated shed without supplemental illumination an important practical point for farmers without access to electricity. Its intermediate growth response (21.3 g d⁻¹, FCR 3.54) positions it as a reasonable roughage base when combined with a higherprotein ingredient, whether that is cowpea sprouts, a commercial concentrate, or locally available legume grain.

For the broader field of small-scale cuniculture in sub-Saharan Africa, these findings carry several implications. First, they confirm that sprouted feed can partially replace expensive commercial concentrate without depressing growth, provided the sprout species is chosen wisely. Second, they highlight the importance of harvest timing: day 8 ofered the best balance of CP concentration and DM recovery across all species, whereas day 10 sprouts had higher fibre and lower DM recovery, which would dilute nutrient intake in practical rations. Third, the data draw atention to calcium-to-phosphorus ratios, which in cowpea sprouts (4.31: 1) considerably exceed the recommended 1.5-2: 1 band, calling for atention when formulating complete diets.

Several questions remain open. The trial did not include a carcass analysis, so whether the weight-gain diferences observed translate into proportional diferences in dressing percentage and meat quality is unknown. Extending the feeding period beyond 63 days and carrying animals to market weight would provide more commercially relevant data. Testing additional legume species soybean sprouts, for example, or pigeon pea would broaden the menu of options available to farmers in diferent agro-ecological zones. Mixed-species trays, where cereal and legume seeds germinate side by side, have been proposed as a way to combine biomass volume with protein density in a single harvest; controlled trials comparing mixed versus single-species trays are needed. Seasonal replication of the research, particularly during the dry season when ambient humidity drops and mould risk may increase, would test the robustness of the sprouting protocol. Finally, a formal economic analysis that accounts for seed cost, labour, water, and the opportunity cost of space would help producers decide whether sprouting technology fits their enterprise budget.

Acknowledgement

Acknowledgements Funding SourcesFinancial support was provided by the Faculty of Agriculture research fund at Lagos Metropolitan University. No external commercial sponsorship was received.

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