Comparative nutrient utilization efficiency on diets containing combined fruit wastes in view of browser/grazer dichotomy in Ethiopian settings: Woyito-Guji bucks versus Doyo-Gena rams

Abstract

The use of agricultural and food industry waste as animal feed is considered as best option to fill feed shortage gap and efficient utilization of available resources within food-feed production circularity. The aim of this study was to compare the effectiveness of combined fruit waste meal utilization between Woyito-Guji bucks’ vs. Doyo-Gena rams in a 2 × 4 randomized crossover design with two species, four diets and four periods. The treatments were grass hay with 0% fruit waste (FW) + 100% concentrate mix (CM) (T1), 25% FW + 75% CM (T2), 50% FW + 50% CM (T3) and 75% FW + 25% CM (T4). Regardless of species variation, T1, T2 and T3 had comparable (p > 0.05) body weight gain and feed conversion efficiency values higher (p < 0.05) than that of T4. However, daily nutrient intake measurements of all prepared diets in this particular study shown that Doyo-Gena lambs score higher values (p < 0.05) than that of Woyito-Guji goats in all treatment groups. The nutrient digestibility values for organic matter (OM) and dry matter (DM) scored similarly but that of Crude Protein (CP), Neutral Detergent Fiber (NDF), Acid detergent fiber (ADF) and Ash scored higher (p < 0.05) for Woyito-Guji bucks as compared to Doyo-Gena rams. As a result, similar values for daily body weight gain and feed conversion efficiency were recorded in spite of feed intake variation between species. In general, both species had an improvement in nutrient intake, digestion and performance when fruit wastes were added as an alternative feed, although sheep experienced the greatest improvement.

Keywords:

• Doyo-Gena rams
• fruit waste
• nutrient utilization
• Woyito-Guji bucks

REVIEWING EDITOR:

• Pedro González-Redondo, University of Seville, Spain

SUBJECTS:

• Agriculture & Environmental Sciences; Agriculture; Agriculture and Food; Plant & Animal Ecology; Zoology; Entomology

1. Introduction

The key reasons propelling the growth of the global animal feed industry is the rising global food demand as well as the expanding global population. By the end of 2050, worldwide demand for animal source food is anticipated to have increased by more than 50% (FAO, 2006). To attain this, animal production must increase from its current rate by around three times (for dairy and fish) and almost double (for chicken, swine and beef) (Oosting et al. 2022; Monkwe et al., 2023).

Global warming, population growth and slow economic growth have all contributed to decline in the production and availability of animal feed items for subsistence farmers (FAO, 2013). Similarly, food production systems are challenged by biophysical factors like land, soil and water scarcity, competition between food, fuel and feed, increased competition for arable land and non-renewable resources like fossil carbon, water and phosphorus among others considered as influential factors in developing world (Oosting et al., 2014).

The impacts of long-term climate change characterized by misbalance of temperature, wind and rainfall distribution have been extremely manifested on the livestock production and productivity in tropics and sub-tropics (Hidosa & Guyo, 2017). On the other hand, livestock production contributes to food security directly by increasing producers’ food diversity and availability but also that of urban consumers and indirectly through income generation and increased farm resilience. However, the available feed resources are not fed in the right proportion as per the requirements of animals (Belehegn et al., 2021).

Among many factors that could explain this disproportionate role of the sector mainly due to inadequate quantity and quality of feed supply throughout the year to satisfy the annual demand of livestock. Smallholders in the mixed crop–livestock production systems keep some types of livestock in combination with crop production. In mixed farming system, crop residue is the main feed source in addition to natural pasture (Tolera, 2007). As several scholars suggested that, the use of agricultural and food industry waste as animal feed may be con­sidered as best option to fill feed shortage gap and efficient utilization of available resources within food-feed production circularity (Fitiwi & Tadesse, 2018). Similarly, in most of developing countries including Ethiopia, recently livestock keeper have been obliged to use these by-products and crop residues as animal feed due to high feed costs and restricted access to conventional feeds (Mario et al., 2023). Thus, need for alternative animal dietary supplements was driven by the lack of feed for livestock, the increasing competition in the markets for food and animal feed coupled with economic and environmental concerns as reported by (Yang et al., 2021).

Based on the report of Feyiso and Mensa (2021), Gamo zone of southern Ethiopia characterized with widen cultivation of tropical fruits like banana, mango and avocado which resulted in limitation of other crop residues conventionally used as major livestock feed resource in other parts of the country. Researchers have been involved in exploiting feed resources from various processing industries and crop farms. However, fruits and vegetable residues continue to be underutilized because of their perishability and limitation of information, the proportion of inedible parts like peel, seeds and leftover fruits expelled as waste from each small-holder.

Currently, using of leftover fruits and vegetables wastes as animals feed have got attention of scholars, become prominent and widely accepted mainly due to their role in minimizing the feed costs for livestock producers and to reduce environment pollution burdens (Mario et al., 2023).

Daily use of a little amount of fruit and vegetables might lead to production of tiny amount of fruit and vegetable trashes from each small-holder. Fruit and vegetable wastes like other crop residue, are utmost importance but there are limited study findings related with the value and potential of these organic components, as well as their nutritional roles have typically been examined by scholars were limited.

Likewise, there are no credible study findings in Ethiopia particularly, in the area the use of fruit-based wastes as sources of animal feed due to limitations in the processing sectors and the physical characteristics of fruit and vegetables wastes. On the other hand, reducing feeding costs and raising product quality are currently the key issue in sustainability of ruminant production for subsistence farmers.

Similarly, limited studies have been found using comparable feed types and species, that some theories claimed as goats (typical browsers) are better adapted than sheep (typical grazers) to digest and efficiently convert organic materials from such unconventional feed types. Therefore, this study was carried out with dietary inclusion of avocado and mango seed kernels with peel for grass-based hay as basal diet and concentrate mixture that aimed to evaluate the nutrient intake, digestibility, weight change and feed conversion efficiency of Ethiopian Doyo-Gena rams vs. Woyito-Guji bucks. Moreover, the study also mainly focused to determine whether tropical goats better digest combined fruit waste-based diets than tropical sheep and the application of these diets would have effect on performances in relation to supplementation level or not.

2. Materials and methods

2.1. Study area

The experiment was carried out at Arba Minch University Livestock Research Center, kulfo campus, Arba Minch, Ethiopia. Arba Minch is situated nearer to Lake Abaya and Chamo as well as the NECH SAR National Park. The area is located at 447 km from Addis Ababa and found at an elevation of 1,285 m. a. s. l with an average yearly temperature of 21 °C, a wind speed of 6 km/h and an air humidity of 87%. Moreover, geographically the area found at 6°2′N and 37°33′E. The region provides the majority of the fruits and vegetables that are sold at Ethiopia’s national market. The region is renowned for its high potential of producing tropical fruits including like banana, mango, avocado, lemon papaya and vegetables. Of the projected 135,000 tons of fruit produced annually and estimated share of 10 to 15% of national production. However, it has much more potential and might account for up to 40% of the total production supplied to the capital city.

2.2. Collection and preparation of experimental diets

The basal diet (hay) was harvested from the Arba Minch University College of Agricultural Sciences compound. Commercial concentrate feed mixture consisted of 30% maize, 10% nuge cake, 15% wheat middling, 40% wheat bran, 1% mineral premixes and 1% salt was included in the daily ration. The experimental diet consisted of 47.5% Avocado (Persea americana) kernel, 5% Avocado peel and 47.5% Mango seed kernel collected from the study area and air dried under shade then milled to have about 5 mm sieve size.

2.3. Animals, experimental design and feed management

Twelve yearlings Doyo-gena rams and twelve Woyito-Guji bucks purchased from local markets with the average body weight of 21.26 ± 0.3kg and 18.9 ± 0.4kg for sheep and goats, respectively. All animals were held in quarantine for 15 days and dewormed and vaccinated for ovine and caprine pasteurellosis, sprayed with acaricides, treated with ivermectine for both external and internal parasites. Animals also allowed adapting test feeds and basal diet for 15 consecutive days before starting the experimental works. Randomized crossover design in 2 × 4 combinations served as the base for the investigation. Animals were kept for a total of 2 weeks for adaption of experimental diets and 1 week for data collection before rotating to the next treatment group, lasting with a total of 21 days for each period. The treatments were arranged as T1 = Hay (ad libitum) + 0% FW (fruit waste) + 100% concentrate mix, T2 = Hay (ad libitum) + 25% FW + 75% concentrate mix, T3 = Hay (ad libitum) + 50% FW + 50% concentrate mix, and T4 = Hay (ad libitum) + 75% FW + 25% concentrate mix.

2.4. Body weight change and feed conversion efficiency measurement

Live body weight of animals was measured at 21-day interval for each period. Sheep and goats were weighed early morning before feeding and watering. The average daily weight gain (ADG) was calculated on a period basis as the difference between final live weight and initial live weight divided by the number of days. Feed conversion efficiency (FCE) was measured through proportion of average daily weight gain (ADG) to daily feed intake (McDonald et al., 2010).

2.5. Digestibility trail

Digestibility trial was conducted before the commencement of the feeding trial and lasted for 10 days with a three days adaptation period to accustom the sheep and goat to carrying the fecal bags, which was followed by a total collection of feces for seven consecutive days. The total fecal output was collected by emptying the bag per day per animal each morning prior to offering feeds and water. The feces were weighed fresh, thoroughly mixed and 20% of the feces were subsampled for each sheep and goat then stored in a deep freezer at –20 °C. The samples were pooled per animal and 20% of which subsampled, weighed and partially dried at 60 °C for 72 hours. The partially dried feces were ground to pass through a 1 mm sieve, stored in airtight plastic container until laboratory evaluation. Apparent digestibility percentage of DM and other nutrients were determined by using the following formula; $$\begin{array}{l}\mathit{\text{Nutrient\hspace{0.33em}digestibility}}\hspace{0.17em}\left(\text{\%}\right)\\ =\frac{\left(\mathit{\text{nutrient\hspace{0.33em}intake}}-\mathit{\text{nutrient\hspace{0.33em}excreted\hspace{0.33em}in feces}}\right)}{\mathit{\text{nutrient\hspace{0.33em}intake}}\hspace{0.17em}}\text{*}100\end{array}$$

2.6. Chemical analysis of feed and fecal sample

The samples of all feed types offered and refused were collected, weighed and separately stored for each animal in all study periods and kept in a room with suitable natural ventilation until the end of the experimental periods. The dry matter (DM), organic matter (OM) and ash contents of the feed and fecal samples were determined according to AOAC (2005). The crude protein (CP) was calculated as N × 6.25. Neutral detergent fiber (NDF) was determined according to Van Soest et al. (1991), whereas Acid detergent fiber (ADF) and Acid detergent lignin (ADL) were determined following Van Soest and Robertson (1985) procedures.

2.7. Statistical analysis

All recorded data in each period were subjected to R software packages for analysis of variance (ANOVA) by using two-way repeated measure procedures to evaluate the effect of different treatments and species variation on body weight change of both sheep and goats. The Bonferroni test adjustment was applied leading to statistical significance being accepted at the P < 0.05 level. The model applied for all variables indicated below; $${\mathrm{Y}}_{\text{ijk}}=\mu +{\alpha }_{\mathrm{i}}+{\beta }_{\mathrm{j}}+{\gamma }_{\mathrm{k}}+\alpha {\gamma }_{\text{ik}}+{\Sigma }_{\text{i jk}}$$ where Y_ijk, = the response due to the animal i, in period j, treatment k, and interaction effects; μ = the overall mean effect; αi = the fixed effect of species (sheep or goat); β_j = the random effect of the j^th period (j = 1, 2, 3); γ_k = the fixed effect of the k^th treatment (k = 1, 2, 3); αβik = the interaction effect between species i and treatment k; and Σ_ijk = the random error.

3. Results

3.1. Chemical composition of experimental diets

The proximate composition of differently processed mango seed, avocado seed and avocado peel meal are presented in Table 1. The ash content of the feedstuffs ranged from 4.96 to 8.80%, the highest value obtained from concentrate mix and lowest was recorded from avocado seed kernel. The lowest value of crude protein (6.42%) obtained from basal diet (hay) and the higher CP content (16.91%) was recorded from concentrate mix. The NDF values of feed materials used in this experiment ranged as 58.58% (for hay) to 22.49% (avocado peel); higher values obtained from grass hay and the lower value was from avocado peel. There was wide variation of ADF values among test diets as indicated ranged from 17.51 to 27.34%, the highest was from grass hay and the lowest was obtained from mango seed.

Table 1. Chemical composition (%DM) of the dried test diets

Sample	DM	Ash	CP	NDF	ADF	ADL
Avocado seed	90.53	4.96	12.2	30.24	18.22	3.88
Avocado peel	85.64	6.21	14.54	22.49	24.37	3.49
Mango seed	90.79	7.51	10.66	27.95	17.51	4.21
Hay	91.78	5.44	6.24	58.58	27.34	5.63
Concentrate mix	90.22	8.80	16.91	25.76	16.53	1.83

DM: dry matter; CP: crude protein; NDF: neutral detergent fiber; ADL: acid detergent fiber; ADL: acid detergent lignin.

Table 2 lists the chemical make-up of treatment feedstuffs. The feeds that are a part of each treatment are designed to meet maintenance and extra nutrient needs. The composition of fruit wastes varies across treatment but the chemical composition of all feed ingredient proportional in all treatment groups with slight variation observed in the combination. For example, the CP contents of treatment feedstuff ranged from 16.75 (T4) to 18.56 (T1), with NDF contents ranging from 34.75% (T1) to 36.54% (T4).

Table 2. Chemical composition of experimental diets (%DM) basis in all treatments

Parameters	T1	T2	T3	T4
OM	93.46	93.68	94.12	94.22
DM	90.42	90.28	91.23	91.07
Ash	6.54	6.32	5.88	5.78
CP	18.56	17.55	17.04	16.76
NDF	34.75	35.64	35.84	36.54
ADF	20.35	19.85	21.56	22.84
ADL	3.94	4.25	4.07	5.04
EE	4.66	4.85	5.42	5.87

OM: organic matter; DM: dry matter; CP: crude protein; NDF: neutral detergent fiber: ADF: acid detergent fiber; ADL: acid detergent lignin; EE: ether extract; T1: basal + 0%FW + 100 + CM; T2: basal + 25%FW + 75%CM: T3: basal + 50%FW + 50%CM; T4: basal + 75FW + 25%CM.

3.2. Nutrient intake

Table 3 shows the consumption of nutrients by experimental animals, as well as differences in intake by goats and sheep assigned to different treatment groups. Both sheep and goats fed T1, T2, and T3 had increased DM, OM, CP and ADF intake when compared to T4 (p < 0.05). There was a wide variance in consumption for all feed ingredients between species, with sheep having the highest values and goats having the lowest among treatment groups fed similar diets. According to the findings of this study, animals fed T4 (grass hay + 75% fruit waste meal) had reduced nutritional intake regardless of species variation, although the remaining T1 (control group), T2 and T3 had statistically equivalent values (p > 0.05). Similarly, the intake of CP at T4 was considerably lower in both sheep and goats across treatment groups. Other feed constituents, such as NDF, ADL, and Ash, were eaten similarly, although ADF consumption varied considerably (p < 0.05) for sheep under T3 and T4. Furthermore, identical feed ingredient intake (NDF, ADF, ADL, and Ash) was detected with modest numerical variation, but there is no statistical variation among the goats in all treatment groups. The result indicated that the effect of supplementing with concentrate alone did not show significant differences (p > 0.05) on average daily body weight gain, final body weight and feed conversion efficiency of among all treatment groups for both species.

Table 3. Least square means for daily nutrient intake for sheep and goats (in gm/kg DM)

Nutrients	Species	Treatments mean				SEM	p-Value
		T1	T2	T3	T4		S	T	S × T
OM	Sheep	852.35^a	829.85^a	832.46^a	819.45^a	12.04	<0.001	0.002	0.338
	Goat	633.34^b	614.22^b	603.87^b	590.62^b
DM	Sheep	934.01^a	909.85^a	915.75^a	897.23^a	12.29	<0.001	0.002	0.298
	Goat	684.23^b	663.57^b	650.75^b	638.03^b
CP	Sheep	114.37^a	113.72^a	112.57^a	110.95^a	1.49	<0.001	<0.001	0.562
	Goat	87.85^b	85.18^b	83.13^b	81.34^b
NDF	sheep	449.46^a	446.83^a	443.98^a	445.64^a	8.14	<0.001	<0.001	0.922
	Goat	304.27^b	296.14^b	298.68^b	297.54^b
ADF	Sheep	278.05^a	273.85^a	268.70^a	267.60^a	5.96	<0.001	<0.001	0.420
	Goat	167.96^b	158.46^b	155.33^b	153.43^b
ADL	Sheep	17.34^a	18.18^a	18.98^a	19.56^a	0.26	<0.001	<0.001	0.072
	Goat	13.39^b	13.36^b	16.24^b	16.08^b
Ash	Sheep	81.65^a	79.87^a	78.99^a	77.81^a	1.61	<0.001	0.002	0.983
	Goat	50.88^b	49.37^b	47.88^b	47.42^b

^a,bMeans with different superscripts down the column indicate significant variation at (p < 0.05) within each treatments for sheep & goats; OM: organic matter; DM: dry matter; CP: crude protein; NDF: neutral detergent fiber; ADF: acid detergent fiber; ADL: acid detergent lignin; SEM: standard error for means; S: species; T: treatment; S × T: interaction effect of species & treatment; T1: basal + 0%FW + 100 + CM; T2: basal + 25%FW + 75%CM; T3: basal + 50%FW + 50%CM; T4: basal + 75FW + 25%CM.

3.3. Body weight gain and feed conversion efficiency

Table 4 shows the mean initial and final body weights, average daily gain (ADG) and feed conversion efficiency (FCE) of the experimental animals based on different treatment diets and species. In all treatment groups, the initial body weight of all animals showed no significant difference (p > 0.05). However, the total mean of sheep initial body weight was larger (p < 0.05) than the average initial body weight of goats in all treatment groups. Similarly, final body weight measurements of all sheep showed with significant variation (p < 0.05), which is lower for goats in separate treatment groups but average daily body weight gain (ADWG) showed without statistical variation (p > 0.05) and slight numerical variations were recorded for both species in each treatment group.

Table 4. Body weight change and feed conversion efficiency

Parameters	Species	Treatments mean				SEM	p-Value
		T1	T2	T3	T4		S	T	S × T
IBW(kg)	Sheep	21.86^a	21.95^a	22.10^a	22.32^a	0.23	<0.001	0.888	0.997
	Goat	18.93^b	19.13^b	19.20^b	19.12^b
FBW(kg)	Sheep	23.59^a	23.38^a	23.66^a	23.20^a	0.24	<0.001	0.711	0.898
	Goat	20.37^b	21.04^b	20.78^b	20.14^b
BWG(kg)	Sheep	1.81	1.23	1.11	0.98	0.04	<0.055	<0.001	0.262
	Goat	1.46	1.08	1.24	0.89
ADWG(g)	Sheep	86.05	61.11	46.42	34.52	2.36	0.005	<0.001	0.273
	Goat	79.44	56.82	43.65	33.74
FCE	Sheep	0.09	0.08	0.09	0.05^b	0.03	0.002	0.542	0.052
	Goat	0.10	0.14	0.12	0.08^a

^a,bMeans with different superscripts down the column indicate significant variation at (p < 0.05) within each treatments for sheep & goats; IBW: initial body weight; FBW: final body weight; BWG: body weight gain; ADWG: average daily weight gain; FCE: feed conversion efficiency; SEM: standard error for means; S: species; T: treatment; S × T: interaction effect of species & treatment; T1: basal + 0%FW + 100 + CM; T2: basal + 25%FW + 75%CM: T3: basal + 50%FW + 50%CM; T4: basal + 75FW + 25%CM.

Although there was some numerical variance between species in (FCE), there is no statistical variation among treatments with all animals regardless of species differences. The feed conversion efficiency (FCE) of sheep and goats was seen similarly without variation, with the exception of T4, which is lower for sheep (p < 0.05) than goats when compared to other treatment groups.

3.4. Trends of body weight change for lambs and bucks in each period

The body weight changes and feed conversion efficiency values were presented in Table 3 meanwhile the trend of weight gain performance (average body weight gain achieved in each study period) for all groups of goats and sheep was performed in box plot (Figure 1) to evaluate the performances of animals on a given diets over time (1period = 21 days). It was considered as random effect in this particular study for both species. The trends of growth rate (total average weight achieved in each study period) as indicated in figure, sheep body weight values were 20.2, 21.8, 23.3 and 24.4 (in kg) at period 1, 2, 3, and 4, respectively. Similarly goats’ body weight record was 17.8, 18.7, 19.4 and 20.8 (in kg) at period 1, 2, 3 and 4, respectively. The progressive increment of body weight change for sheep rated as 1.3, 1.6, 1.5 and 1.1 in respective periods and for goats 0.9, 1.3, 1.2 and 1.4, respectively. This implies that, all feed ingredients prepared for experimental works potentially served as required nutrients without affecting their normal growth pattern although animals supplemented with different level of commercial concentrate in all respective study periods.

Figure 1. Average body weight change of goats & sheep in each period.

3.5. Apparent digestibility of nutrients

Table 5 shows the apparent digestibility coefficients of nutrients in each treatment. Despite differences in feed ingredients among treatment combinations, the digestibility values of formulated diets showed with similar values for both species on OM and DM, but statistically significant variation (p < 0.05) was observed in CP, NDF, ADF and Ash digestion, indicating that goats digest more fibrous parts than sheep on each respective treatment groups. As a result, both sheep and goats’ body weight change and feed conversion efficiency assessments showed without statistical variation (p < 0.05), even with the fact that sheep’s daily nutrient consumption was statistically larger (p < 0.05) than goats.

Table 5. Digestibility of experimental diets for both bucks and rams.

Nutrients	Species	Treatments mean				SEM	p-Value
		T1	T2	T3	T4		S	T	S × T
OM	Sheep	73.07	72.59	72.71	71.74	0.001	0.061	0.446	0.593
	Goat	74.50	73.32	74.14	73.16
DM	Sheep	69.42	69.28	69.79	68.55	0.003	0.740	0.998	0.753
	Goat	70.32	70.21	69.26	69.75
CP	Sheep	82.53^b	81.42^b	82.70^b	80.86^b	0.002	<0.001	<0.001	0.008
	Goat	86.41^a	86.88^a	85.45^a	83.49^a
NDF	Sheep	62.31^b	61.70^b	62.41^b	61.40^b	0.002	<0.001	<0.078	0.021
	Goat	66.44^a	65.07^a	64.87^a	64.26^a
ADF	Sheep	55.76^b	56.40^b	54.11^b	55.30^b	0.003	0.004	0.476	0.269
	Goat	60.51^a	58.60^a	58.25^a	57.85^a
Ash	Sheep	70.39^b	69.53^b	68.34^b	68.40^b	0.004	<0.001	<0.001	0.131
	Goat	77.25^a	78.58^a	75.74^a	74.86^a

^a,bMeans with different superscripts down the column indicate significant variation at (P < 0.05) within each treatments for sheep & goats; OM: organic matter; DM: dry matter; CP: crude protein; NDF: neutral detergent fiber; ADF: acid detergent fiber; ADL: acid detergent lignin; S: species; Treatment; S × T: interaction effect of species & treatment; T1: basal + 0%FW + 100 + CM; T2: basal + 25%FW + 75%CM: T3: basal + 50%FW + 50%CM; T4: basal + 75FW + 25%CM.

Overall mean of digestibility coefficients of nutrients in sheep compared to goats for all groups were observed as; 72.53 vs. 73.78%, 69.26 vs. 70.49%, 83.87 vs. 85.56%, 61.95 vs. 65.06%, 55.39 vs. 58.55%, and 69.16 vs. 76.61% for OM, DM, CP, NDF, ADF, and Ash, respectively. The results of this investigation showed minimal variation among treatments for both species, which could be due to homogeneity in feed ingredient and equal access of different meal proportions during all the study periods. The wide range of documented values could be related to species differences and the capacity to digest various meal ingredients.

4. Discussion

4.1. Chemical composition of test and basal diets

The study discovered that the chemical makeup of the available meals varies significantly. The variation could be attributable to plant species (differences in genetic traits of plants), soil type (environmental factors), plant components (example kernel, peel), and other factors. The CP content of the diets utilized as supplements in this trial was higher than the minimal protein requirements of feeds (average 7%) to ensure appropriate microbial activity and small ruminant maintenance requirements (McDonald et al., 2010). The CP values of avocado seed, used in this feeding trail work slightly lower than that of Ejiofor et al. (2018), Arukwe et al. (2012) and Talabi et al. (2016), 15.55 ± 0.36%, 17.94 ± 1.40% and 15.58 ± 0.18%, respectively. The CP content of mango seed is consistent with the (10.06 ± 0.12) reported by Fowomola (2010) and higher than the raw sun dried mango seed values of 5.90 and 3.24% values reported by Okoruwa and Omoragbon (2017) and Orayaga (2016), respectively. Plant variety, soil type, plant fraction, climate and most importantly the stage of maturity and time of harvest, collection and storage, processing methods and other factors could all contribute to the differences. As a result, the content of CP in the current study’s fruit waste mixed meals might be functioning as useful ingredient to achieve fast growth rates and used to support for animals that are solely depended on natural pasture crop residues alone. Based on recommendation of NRC (1985), for maintenance, sheep should be given fodder with a crude protein concentration of 7–9% and a total digestible nutrient (TDN) value of 50%.

Sheep and cattle require a particular amount of fiber to keep the rumen working properly. The moderate NDF contents of the treatment diets, which were less than 37%, were found to be beneficial to the experimental animals. The NDF (McDonald et al., 2010; NRC, 1985; Salah et al., 2014) or total insoluble fiber, which comprises cellulose, lignin and hemicellulose were better indicator of total fiber and are the most commonly used assessment of fiber requirements. The NRC (1985) recommends that 30% NDF in the diet, with at least 21% coming from forage sources considered as better in content. According to these principles, the higher the quantity of NDF in fodder, the less it is consumed by sheep and goats. Sheep, for example, ingest 1.8–2.0% of their body weight in dry feedstuff on average every day. NDF levels below 30% may cause rumen health concerns such as acidosis. NDF levels exceeding 50% reduce feed intake. Therefore, the fiber contents of current experimental diets could be suitable and laid at reasonable level for normal rumen activities.

4.2. Nutrient intake

Throughout the feeding trial, the feed offered and denied for each treatment and animal were recorded on daily basis and daily feed intake (DFI) was computed as the difference between offer and refusal. The overall intake of dry matter (DM), organic matter (OM), crude protein (CP) and other components was found to be greater in sheep and lower in goats. In contrast, with Bangulzai et al. (2020) who concluded that goats had higher intake than sheep in all offered feed type. The goats adapt wide range of feed types and chemical characteristics as reported by many scholars, Babikera et al. (2017), Bangulzai et al. (2020) and Kechero et al. (2015), comparative study on feeding value of Moringa leaves for both species and responses to tannin rich diets for both species respectively.

The present study revealed that, there was no apparent difference (p > 0.05) observed in organic matter and other nutrient intake among the treatments except T4 (75%: 25%) ratio of fruit waste to concentrate mix. Likely, intake of supplement was slightly higher (p < 0.05) at T1, T2 and T3. However, the finding of this study revealed that sheep consume more than goats of all feed type prepared for this experimental works. The current study is in accordance with Hassen et al. (2020), who stated that supplementation of different proportions of concentrate contained forage mix instead of sole concentrates mixture had no significant effect (p > 0.05) on organic matter, total DM and basal DM intake for Afar goats. The feed intake values of goats recorded from current study was slightly higher than that of Fitiwi & Tadesse (2018) tested with different level of sesame seed cake supplementation. Moreover, variation on feed intake of animals in current study could be due to attribution of initial body weight variation, preference variation, selective feeding behavior of goats and their instantaneous adaptation to browsing fodder species as compared to sheep mainly depend on grazing species in the area.

4.3. Body weight gain performances and feed conversion efficiency

The highest body weight gain of T1, T2 and T3 may be attributed to increased nutrient intakes, better digestibility and nitrogen utilization of the animals with irrespective of species variation. The result also found that substituting varying amounts of concentrate by fruit waste mix up to 40-50% instead of providing single concentrate feed had no significant influence on body weight gain and feed conversion efficiency of small ruminants. As a result, mono concentrate feed supplementation is not better than fruit waste-based diets with a 50% inclusion rate in small ruminant rations. The current study’s results of average daily weight gain/growth and feed conversion efficiency of sheep was comparable to Wagi et al. (2018) who investigate the varying proportions of faba bean straw with concentrate shows similar values in weight gain and feed conversion efficiency.

The body weight gain of goats in the current study is lower than that of Jiwuba et al. (2021) of West African dwarf goats fed on four phytogenic browse plant leaf meal, but feed conversion efficiency is practically identical. Kechero et al. (2015) found that average daily body weight gain (ADWG) and feed conversion efficiency were higher in both species when fed tannin-free, tannin-rich feed with and without polyethylene glycol 6000 (PEG) in their diets. The variance could be attributed to animal breed type, feed type and animals’ protracted adaption to diets. The body weight gain and feed conversion efficiency (FCE) of goats in this study (gm/day) were significantly higher than Gumuz and Abergelle goats tested with different proportions of pigeon pea (Cajanus cajan) and Neem (Azadirachta indica) leaves and different industrial by-products (wheat bran, nuge seed cake, cotton seed cake, molasses and maize grain in different proportions) reported by Mulisa et al. (2019). The body weight change and overall performances of this study was consistent with Bangulzai et al. (2020), who observed that the average body weight gain and feed conversion efficiency for both ewe and goats were similar in all experimental groups fed different summer fodders. The same author discovered that goats and sheep fed on the same fodders performed similarly.

In this study, all animals (sheep and goats) fed varied fractions of the experimental diets improved in weight gain, nutrient intake and feed conversion efficiency. This could imply that fruit waste meal can be employed as a supplemental source in dietary formulations to maintain and improve feed conversion ratio and growth of small ruminants in general. The consistent weight change observed throughout all study periods was indicative of good nutritional properties of the experimental diets as compared to supplemented with concentrate mix alone. Hassen et al. (2020) stated that pure concentrate feed supplementation was not superior to varying proportions of forage mix and concentrate included supplementation.

The body weight gain performance of all farm animals is economically important trait that can be interpreted in different ways. It is a change in organ weight or size, tissue/organ composition or living weight that occurs throughout time. It has also been reported that growth rate is related to maturation rate and adult body weight in animals and that these qualities are associated to lifelong productivity measures. Low growth results in low market prices and is regarded as a limiting issue impacting the profitability of any livestock enterprise, particularly small-scale ruminant production as reported by Mohammadi et al. (2019). In this regard, the progressive weight change values recorded across all the study periods of the current investigation shown as the prepared feed materials have great nutritional roles to meet the additional demands of animals at their early stage of life times.

4.4. Apparent digestibility of nutrients

Table 4 shows the dry matter and other nutrient digestibility of experimental diets supplied to both sheep and goats fed varied proportions of fruit waste and other feed ingredients. In all treatment groups, goats had greater (p < 0.05) digestibility values for CP, NDF, ADF and Ash than sheep. The current findings was in accordance with Kechero et al. (2015), who reported that goats are better than sheep in digesting and using fibrous diet (ADF and NDF). With fruit waste supplementation levels of 0, 25, 50, and 75% for both species, the current findings of digestibility values did not demonstrate significant variation among OM and DM. This shows that the feed material used to replace commercial concentrate was profitable and an excellent source of nutrients. It can be utilized as a substitute feed resource for livestock, which may help small-holder farmers who are experiencing feed scarcity.

The digestibility values of nutrients in the current study for sheep were higher than that of Fekadie et al. (2022) who reported that, lower measurements of organic matter and other nutrients digestibility recorded for Washara sheep fed wheat straw and different level of effective microorganisms. Similar to this, the current study’s OM, DM and CP digestibility coefficients were greater than those of Sileshi et al. (2021), finding which looked at the impact of feed intake and digestibility on both Ethiopia’s Hararghe highland and Afar sheep breeds. According to Evitayani et al. (2021), who stated that the use of Indigofeira zollingeriana at 30% level to substitute concentrate feed in the diet of Etawa goats observed with the best digestibility values of fiber fractions. The measurements of the digestibility coefficient of fibers for goats in the current study are consistent with his findings. In general, balanced NDF and adequate energy contents in the test diets may be connected to improvements in digestibility coefficient values for both sheep and goats. These factors support rumen microbial growth and the fastest rate of substrate absorption in the rumen.

5. Conclusion

Both sheep and goats fed T1, T2, and T3 had increased DM, OM, CP and ADF intake when compared to T4 (p < 0.05). There was a wide variance in feed intake for all feed ingredients between species, with sheep having the highest values and goats having the lowest among treatment groups fed similar diets. The digestibility values of formulated diets showed a similar trend for both species of OM and DM despite variations in the feed ingredients across all treatment combinations. Moreover, statistically significant variation (p < 0.05) was observed in NDF, ADF and Ash digestion indicating that goats on each individual treatment groups can digest more fibrous components than sheep. The result also indicated the potential utilization of fruit waste meal as a replacement of concentrate feed without influencing the growth performances of small ruminants. Therefore, the use of these fruit wastes as an alternative feed resource for small ruminants may help to mitigate the feed shortage gap and used to reduce the feed costs of small-scale ruminant fattening practitioners and subsistence farmers in the area.

Acknowledgements

We would like thank AMU-IUC-VILROUS project and AMU research coordination office for their live animal and financial support to accomplish this work.

Disclosure statement

We declare that we have no personal relationships with other people or organizations that can inappropriately influence our work; there is no professional or other personal interest of company that could be construed as influencing the content of this paper. No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

Mitiku Yohannes

Mitiku Yohannes is MSc holder in Animal production and management. He has done a research on small ruminant production systems and interested to maintain ruminant production under fruit based crop-livestock mixed productions. Currently he is senior researcher and lecturer at Arba Minch University College of Agricultural Sciences.

Yisehak Kechero

Yisehak Kechero is PhD holder and professor of animal nutrition and feed science. He has articulate many research works, editor in chief of Omo journal, local coordinator of AMU-IUC project in the country. Currently he is a senior researcher and academic instructor at Arba Minch University.

Yilkal Tadele

Yilkal Tadele is PhD holder in animal nutrition. He has done more than four researches on different types of feed for ruminants and their impacts with practical feeding trail activities. Currently he is coordinator of post-graduate offices at Arba Minch University College of Agricultural Sciences.