Use of a novel fodder herb, Commelina species, in Black Head Ogaden lambs: nutrient utilization, weight gain performance, and economic viability

ABSTRACT

This study was carried out to determine the effects of supplementing Commelina forage species on nutrient uptake, weight gain, and economic viability in Black Head Ogaden lambs. Twenty yearling lambs were used in four treatments with five replicates in randomized complete block design. The treatments included Teff straw + 120 g dried Moringa stenopetala leaves (DMSL) for treatment 1 (T1), Teff straw + 120 g DMSL + 300 g C.benghalensis (T2), Teff straw + 120 g DMSL + 300 g C.imberbis (T3) and Teff straw + 120 g DMSL + 300 g concentrate (T4). A 60-day feeding trial was followed by a 10-day digestibility investigation. The study used SAS 9.0 for data analysis; the Duncan multiple range test for mean separation and partial budget analysis for financially feasibility testing. With better responses in T4 followed by T3, T2, and T1, supplementation significantly improved total DM, nutritional intakes, and apparent digestibility (P < 0.001). The two Commelina species and conventional concentrate-supplemented treatments resulted in average daily weight gains of 47.58 and 72.69 g, respectively but the former treatments produced higher marginal returns (2.02) than the later ones (0.22). With promising profit, Commelina species could be used as a supplement to improve the animals’ nutrient uptake and growth efficiency.

KEYWORDS:

• Black Head Ogaden lambs
• Commelina species
• Konso
• nutrient utilization
• Moringa stenopetala

1. Introduction

The sheep industry in Ethiopia is regarded as one of the greatest food-producing engines in the nation since it provides a significant amount of meat, fibre, and monetary income for the people. The keepers also get money by selling the animals, which improves their financial situation and increases their ability to purchase other necessary food inputs (Habtamu 2015). A person’s or a community likes food and the demand for quality food rises as their financial resources do (Getachew et al. 2018). Therefore, domestic demand for food products produced from sheep is anticipated to rise dramatically in the near future in Ethiopia due to the country’s fast-growing population, increasing urbanization, and rising earnings (Shapiro et al. 2017). This presents the sheep industry with a golden opportunity and shows the enormous investment needed to raise output and productivity in the industry (Shapiro et al. 2017; Getachew et al. 2018).

More than 60% of the country’s feed supplies for the animals were made up of natural pasture, crop aftermath grazing, and leftovers. The majority of sheep feed comes from these sources; however, their nutritional content is relatively low. They contain a crude protein level that is much lower than what animals need to maintain themselves (Chalchissa et al. 2014; Mekuanint and Girma 2017). Additionally, they lack sufficient fermentable energy as seen by their relatively poor dry matter and organic matter digestibility as well as their low mineral availability (Mengistu et al. 2017). In order to achieve productivity and satisfy the demand for meals made from sheep in the present and the future, supplementing animals at different growth and production stages with various supplements is necessary to compensate for the nutritional deficiencies of the feed resources (Deribe 2015; Mengistu et al. 2017). It has been demonstrated that conventional supplements aid in the growth and production of animals. However, the incorporation of supplements of unconventional types was required due to the significantly rising costs of the ingredients, the frequently reported unnecessary competition between humans and animals, and limited accessibility to smallholders. When non-conventional feeds were added to the diets of growing animals, the animals’ nutrient uptake, growth, and feed efficiency were significantly improved (Gebeyew et al. 2015; Gelgelo et al. 2017).

There are some research findings about the therapeutic benefits of Commelina forage species. The species were known to be used in traditional medicine systems to cure various diseases like headache, constipation, leprosy, fever, snake bite, mouth thrush, epilepsy, and psychosis (Jayakumar 2016; Sinha 2019). Other scholars (Lanyasunya et al. 2006; Lanyasunya et al. 2008), reported CP, NDF, and ADF values of 17.59–17.71%, 32.60–36.08%, 21.60–22.72% respectively for Commelina difusa and Commelina benghalensis underlining the feed use potential of the species under various ecological conditions. On the other side, considerable number of studies were still reporting Commelina species as invasive weeds aggressively growing in crop fields at different habitat types (Isaac et al. 2013; El-Hamid and El Bous 2019), implying that, further studies reinforcing nutritive potentials and feed use values, utility of the species as a supplement and its impact on livestock performance of the species were still strongly desirable. Therefore, the objectives of this study were to examine the economic viability of the feeding experiment as well as the weight gain performance and nutrient utilization of Black Head Ogaden lambs supplemented with Commelina species.

2. Materials and methods

2.1. About the study area

The study was conducted in Konso Zone of southern Ethiopia. The study site is located about 595 Km south of Addis Ababa, the capital city of Ethiopia, and 360 Km south of Hawassa, the capital of the southern nation nationalities and people’s regional state (SNNPRS). The total land area of the Zone is 2016.24 Km². The altitude of the area is between 501 and 2000 metres above sea level. The main agroecological divisions of Konso are 70% lowland and 30% midland. The mean annual temperature of the zone ranges between 17.6 and 27.50°C. The mean annual rainfall ranges between 601 and 1200 mm (Cheung et al. 2008). Geographically, it is located at 5⁰10'0'’ to 5⁰40'0''N latitude and 37⁰0'0'’ to 37⁰45'0'’ E longitude.

2.2. Experimental animals and their management

Twenty healthy male yearling Black Head Ogaden lambs were obtained from a local market for an average body weight of 19.79 ± 1.57 kg. Dentition and owner information were used to estimate the age of the animals. To acclimate to the habitat and for a health check, the animals were isolated for 21 days at the experimental site. Informed consent was obtained from animal owners. The animals were dewormed to prevent internal parasites and sprayed to prevent exterior parasites throughout this time. They were also given vaccinations against pasteurellosis and anthrax. Individual pens with separate feed and watering troughs were employed to house the animals. Neck collars were used to identify the lambs.

2.3. Feed preparation and feeding

The Teff straw was purchased from farmers that grow Teff in the study area, then bought and stored in the shade to preserve its quality and guard against rain or sun damage. The concentrate mixture was purchased from an animal feed processing business in Arba Minch Town. To offset the low protein content of the basic diet and create a ration satisfying, at least, the experimental sheep’s maintenance requirements, M. stenopetala leaves were acquired from the farmers, dried under shade, and fed to all animals. Commelina imberbis and Commelina benghalensis were collected from several locations in the study area, dried, and stored in the shade. In the morning, the basic feed, water, and mineral licks were all freely available. Throughout the course of the trial, the rejection % was modified every four days based on the refusal of the previous day. The concentrate mix and Commelina supplements were given to the animals in two equal parts each day at 8:00 and 16:00, while dried M. stenopetala leaves were given to each animal individually once a day in the morning in the feeding bucket. All of the experimental feeds (the teff straw, the two Commelina species, M.stenopetala, and concentrate mix) were provided individually in separate feeding troughs. The rejected straw was gathered and weighed every morning prior to offering the morning meal. Over the course of the 60 feeding days, samples of offers from all the diets and refusals from straw were gathered, weighed, bulked, and sub-sampled for laboratory analysis.

2.4. Experimental design and treatment

A randomized complete block design was used to perform the experiment, which included four treatments—one control and three supplemental—each reproduced five times. The lambs were fasted for the night at the end of the quarantine period and initial body weight (IBW) was recorded. Two successive weighings were used to calculate the animal’s body weight. Based on their IBW, the animals were then divided into four groups of five animals to have five animals per each treatment (Table 1). Diet compositions of the experimental animals were prepared assuming 2.5% of live body weight intake per day and a minimum of 7% CP requirement for maintenance (NRC 2007). All treatment groups received a supplement of 120 g of dried M. stenopetala leaves (DMSL) to complement the low protein content of baseline diet. The treatment diet composition was as indicated below.

Table 1. Diet composition of the feeding experiment.

Treatment	Teff straw	DMSL (g DM)	C. benghalensis (g DM)	C. imberbis (g DM)	Concentrate mix (g DM)
1	Ad libitum	120	-	-	-
2	Ad libitum	120	300	-	-
3	Ad libitum	120	-	300	-
4	Ad libitum	120	-	-	300

DMSL, Dried M. stenopetala leaves; Concentrate = wheat bran + maize + Noug Seed cake (2:1:1).

2.5. Measurements

2.5.1. Feed intake, body weight changes and feed conversion efficiency

Following the 15 days of adaption, each animal received a treatment diet for 60 days (Marten et al. 1989). Every day, samples of the feed that was presented and rejected were taken and stored in plastic pails after being weighed, recorded, and stored for each animal individually. Each animal’s refuse samples, which were taken every 10 days for each treatment, were bulked up and pooled according to the treatments. The difference between the feed that was offered and rejected was utilized to compute daily DM or nutrient intake. After 21 days of adaption, the animals were fasted overnight before the start of the feeding trial, and their initial weight was determined by averaging the results of two separate measurements. At intervals of 10 days during the trial period, body weight measurements were taken (Kinder 2016). Average daily gain (ADG) was measured as the difference between final and initial body weights divided by the number of feeding days, whilst weight gain was calculated as the difference between final and initial body weights (Akbulut et al. 2013). The ratio of a unit of body weight growth to the number of units of feed consumed was used to calculate feed conversion efficiency (FCE) (Brown et al. 2001). $\mathrm{FCE}={\displaystyle \frac{\mathrm{Body}\mathrm{weight}\mathrm{gain}\mathrm{in}\mathrm{g}/\mathrm{day}}{\mathrm{DM}\mathrm{intake}\mathrm{in}\mathrm{g}/\mathrm{day}}}$

2.5.2. Apparent nutrient digestibility

Following the feeding trial, a digestibility test was conducted with all of the animals in each treatment. To prepare the lambs for carrying faecal collection bags throughout the digestibility study, they were harnessed for three days. Each animal then underwent seven days of faeces collection. Prior to providing water and feed, each lambs’ complete daily faecal production was collected, weighed, well mixed, and allowed to thaw at room temperature. To create a single weekly composite faecal sample for each animal, a sub-sample of 10% of the daily faecal excretion was obtained and pooled across the collection period (Galyean 2010). In airtight polyethylene bags, dried samples of meals, refusals, and faeces were stored for chemical analysis after being pulverized to pass a 1 mm filter. Non-dried faeces samples were used for N analysis. Using the following equation, digestibility was obtained (Galyean 2010). $\mathrm{Digestibility}\mathrm{of}\mathrm{DM}\mathrm{or}\mathrm{Nutrient}(\text{\%})={\displaystyle \frac{\mathrm{DM}\mathrm{or}\mathrm{nutrient}\mathrm{intake}\text{–}\mathrm{DM}\mathrm{or}\mathrm{nutrient}\mathrm{in}\mathrm{feces}}{\mathrm{DM}\mathrm{or}\mathrm{nutrient}\mathrm{intake}}\times 100}$

2.6. Chemical analysis

Determination of DM, OM, Ash, and CP were done according to methods of AOAC (2000). NDF, ADF, and ADL were determined using their standard procedures (Van Soest and Robertson 1985).

2.7. Statistical analysis

Analysis of variance (ANOVA) in SAS 9.0 was used to examine the data. By using the Duncan Multiplied Range Test, treatment means were isolated. The significant differences among means were considered at P < 0.05. The following statistical model was used for data analysis: $Y_{ij}=\mu +{\alpha }_i+{\text{ß}}_j+\sum ij$Where Yij = is the response variable; μ, is the overall mean; αi = is treatment effect, βj, is the block effect, ∑ij = is the random error

2.8. Partial budget analysis

Economic feasibility of the feeding experiment was tested by partial budgeting. A due attention was given to major costs disregarding labour, housing, and veterinary costs which were common for all treatments under consideration (Soha 2014.). Purchasing and selling prices of all animals were recorded so that total return (TR) was calculated as a difference of the two prices. Experienced sheep market dealers assisted estimation of selling prices. Net income (NI) generated by Commelina supplementation was the amount of money left when total variable costs (TVC) were subtracted from the total returns (TR). Variable costs included purchase of lambs, cost of Teff straw, and supplements. The change in net income (ΔNI) was computed as the difference between the change in total return (ΔTR) and the change in total variable cost (ΔTVC); Where the change in total return (ΔTR) is a total return of the given supplemented treatment minus total return of the control treatment (T1) and change in total variable cost (ΔTVC) is total variable cost of supplemented treatment minus total variable cost of the control. The marginal rate of return (MRR), which is the measure of the net return on additional capital invested in the feeding Commelina to the animals, expressed as a percentage, was calculated as a ratio of change in net income (ΔNI) to change in total variable cost (ΔTVC) multiplied by 100.

3. Results

3.1. Chemical composition of experimental feeds

Table 2 provides the chemical composition of the diets employed in the current investigation. The DM content of all of the experimental feeds does not vary as such amongst the diets. The teff straw had lower ash and CP but higher fibre fractions (NDF, ADF, and ADL) as compared to the other feeds. Next to it, lower CP values and higher fibre content were observed in the Commelina species while comparable values were recorded for both of the species. The lowest fibre fractions and highest protein values were observed in Moringa stenopetala and then the concentrate mix.

Table 2. The chemical composition of treatment feeds.

Feed	DM	Ash	OM	CP	NDF	ADF	ADL
Teff straw	93.74	6.27	87.47	5.97	66.41	32.73	4.76
DMSL	93.03	10.27	82.76	27.26	18.73	10.31	2.98
C. benghalensis	93.27	17.07	76.19	12.11	43.69	28.47	7.46
C. imberbis	91.56	16.91	74.65	14.88	42.34	24.68	6.07
Concentrate	92.40	13.16	79.24	19.34	36.30	19.11	4.08
Teff straw Refusals
T1	92.91	6.36	86.55	3.98	66.67	33.11	4.81
T2	92.62	6.55	86.07	4.17	66.97	35.39	5.17
T3	93.70	6.79	86.91	4.32	64.79	33.38	4.65
T4	92.30	6.10	86.20	4.32	64.79	33.38	4.65

DM, dry matter; OM, organic matter; CP, crude protein; NDF, neutral detergent fibre; ADF, acid detergent fibre; ADL, acid detergent lignin; T1, Teff straw ad libitum +120g Dried M. stenopetala leaves (DMSL); T2, Teff straw ad libitum + 120g DMSL + 300g C. benghalensis; T3, Teff straw ad libitum + 120g DMSL + 300g C. imberbis; T4, Teff straw ad libitum +120g DMSL + 300g concentrate.

3.2. Nutrient intake

In the current investigation, supplementation had a significant (P < 0.001) impact on the daily nutritional consumption of the experimental animals (Table 3). T4 had a higher consumption of total hay and nutrients compared to the other treatments. While T1 scored the lowest response in terms of hay and nutrient intake, T2 and T3 showed intermediate values comparable with each other. Intake of OM also showed a similar pattern of variability stated among all treatments. All of the treatment meals in the current investigation had significantly different CP intake records (P < 0.001) from one another. It exhibited the pattern that, the CP intake of T4 > T3 > T2 > T1. A substantial improvement was also observed in NDF and ADF intake of the experimental animals in the current investigation (P < 0.001).

Table 3. Daily nutrient intake of intact yearling Black Head Ogaden lambs supplemented with Commelina species.

Intake (g/d)	Treatments, mean					P- value
	T1	T2	T3	T4	SEM
Teff straw DM	322.44^c	366.07^b	377.38^b	487.64^a	15.78	<0.0001
Total DM	442.44^c	786.07^b	797.38^b	907.64^a	42.45	<0.0001
OM	386.94^c	649.4^b	653.85^b	764.69^a	33.91	<0.0001
CP	54.23^d	92.63^c	101.35^b	121.41^a	5.89	<0.0001
NDF	240.98^c	394.27^b	401.55^b	454.78^a	19.63	<0.0001
ADF	119.83^d	209.35^c	215.04^b	228.35^a	10.52	<0.0001

^a,b,c,d means within a row not bearing a common superscript are significantly different; ADF, acid detergent fibre; ADL, acid detergent lignin; CP, crude protein; DM, dry matter; OM, organic matter; NDF, neutral detergent fibre; T1, Teff straw ad libitum + 120 g Dried M. stenopetala leaves (DMSL); T2, Teff straw ad libitum + 120 g DMSL + 300 g C. benghalensis; T3, Teff straw ad libitum + 120 g DMSL + 300 g C.imberbis; T4, Teff straw ad libitum + 120 g DMSL + 300 g concentrate; P, probability; SEM, standard error of mean.

3.3. Nutrient digestibility

Table 4 below shows how readily DM and nutrients were assimilated by Black Head Ogaden lambs fed teff straw supplemented with Commelina species. In the current investigation, supplementation had a significant impact (P < 0.05) on digestibility of DM and all of the nutrients. Digestibility of DM was highest for T4, medium for T2, T3 having a comparable response with T4 and T2. Of all treatments, T1 had the lowest digestibility of DM. The trend for OM digestibility in treatment diets was comparable to that for DM digestibility. Animals in T3 showed DM and OM values equivalent to those of T4 while sharing values with T2. Due to the different levels of protein quality in the treatment diets, the CP digestibility exhibited significant variance. T4 had significantly higher CP digestibility (P < 0.01) than all followed by T3 and T2. Remarkably, T1’s CP digestibility was comparable to that of T2.

Table 4. Apparent nutrient digestibility (%) of intact yearling Black Head Ogaden lambs supplemented with Commelina species.

Nutrients	Treatments, % average					P value
	T1	T2	T3	T4	SEM
DM	59.8^c	65.8^b	69.6^ab	72.6^a	0.0169	0.0002
OM	63.4^c	68.3^b	71.9^ab	75.7^a	0.0156	0.0001
CP	67.2^c	71.1^bc	73.7^b	81.0^a	0.0165	0.0016
NDF	61.0^c	64.7^bc	69.6^ab	72.2^a	0.0169	0.0196
ADF	53.9^b	60.1^ab	62.5^a	64.0^a	0.0166	0.039

^a,b,c means within a row not bearing a common superscript are significantly different; ADF, acid detergent fibre; ADL, acid detergent lignin; CP = crude protein; DM = dry matter; OM,organic matter; NDF, neutral detergent fibre; T1, Teff straw ad libitum + 120 g Dried Moringa stenopetala leaves (DMSL); T2, Teff straw ad libitum + 120 g DMSL + 300 g C.benghalensis; T3, Teff straw ad libitum + 120 g DMSL + 300 g C.imberbis; T4, Teff straw ad libitum + 120 g DMSL + 300 g concentrat; P, probality; SEM, standard error of mean.

3.4. Body weight change

With the exception of beginning weight, the animals’ body weight parameters (P < 0.01) and feed conversion efficiency (P < 0.05) in this experiment demonstrated a considerable difference from one another (Table 5).

Table 5. Body weight parameters and feed conversion efficiency of intact yearling Black Head Ogaden lambs supplemented with Commelina species.

Parameters	Treatments
	T1	T2	T3	T4	SEM	P
Initial body weight (kg)	19.62	19.84	19.98	19.46	0.36	0.293
Final body weight (kg)	21.05^c	22.51^b	23.01^ab	23.82^a	0.47	0.0023
Body weight gain (kg)	1.43^c	2.67^b	3.04^b	4.36^a	0.27	<0.0001
Average daily gain (g/d)	23.83^c	44.53^b	50.63^b	72.69^a	4.53	<0.0001
FCE (g ADG/g DMI)	0.0538^b	0.0565^b	0.0637^ab	0.0802^a	0.0034	P < 0.05

^a,b,c means within a row not bearing a common superscript are significantly different; CP = crude protein; DM = dry matter; OM = organic matter; NDF = neutral detergent fibre; T1 =  Teff straw ad libitum + 120 g Dried M. stenopetala leaves (DMSL); T2 =  Teff straw ad libitum + 120 g DMSL + 300 g C.benghalensis; T3 =  Teff straw ad libitum + 120 g DMSL + 300 g C.imberbis; T4 =  Teff straw ad libitum + 120 g DMSL + 300 g concentrate; SL = significance level; SEM = standard error of mean.

Concentrate supplanted groups of animals had higher (P < 0.01) final body weight than those in the control and C.benghalensis supplemented groups. C.imberbis supplemented animals had final body weight values comparable with concentrate supplemented ones. Both body weight gain and average daily gain showed similar pattern of variability among the treatment groups of this study with the highest and lowest values (P < 0.001) observed in T4 and T1 respectively whereas the Commelina species supplemented groups (T2 and T3) had intermediate records comparable with each other. The highest feed conversion efficiency was noted equally for T3 and T4 while the rest two treatments had values comparable with each other and with T3 also.

The body weight changing pattern over the feeding period is depicted in Figure 1 below. T1 showed a trivial changing trend as compared to other treatments. From the onset till mid of the feeding regime, all three supplemented treatments seem comparable in their body weight changing pattern, the graphs overlapping appearing very close to each other. It was from the mid of the experimental period onwards that T4 steeply raised over the others followed by T3.

Figure 1. Body weight changing trend of intact yearling Black Head Ogaden lambs supplemented with Commelina species.

3.5. Partial budget analysis

The partial budget analysis of the experiment is indicated in Table 6. The net return of treatments in this study differed from each other as returns of T3 > T2 > T4 > T1.

Table 6. Partial budget analysis of Commelina supplementation to intact yearling Black Head Ogaden lambs.

Parameters	Treatments
	T1	T2	T3	T4
Purchase price per lambs (ETB)	1,004	1,006	1,006	1,004
Hay consumed (kg/lamb)	19.34	21.96	22.64	29.25
DMSL consumed (kg/ lamb)	7.2	7.2	7.2	7.2
C. benghalensis consumed (Kg/ lamb)	-	18	-	-
C. imberbis consumed (Kg/ lamb)	-	-	18	-
Concentrate consumed (kg/ lamb)	-	-	-	18
Feed costs
Cost of Teff straw (ETB/ lamb)	96.7	109.8	113.2	146.25
Cost of DMSL (ETB/ lamb)	16.2	16.2	16.2	16.2
Cost of C. benghalensis (ETB/lamb)	-	36	-	-
Cost of C. imberbis (ETB/ lamb)		-	36
Cost of concentrate (ETB/lamb)	-	-	-	324
TVC (ETB/ lamb)	1116.90	1,168	1,171.40	1490.45
Gross return (ETB/ lamb)	2045.00	2190.00	2224.00	2500.00
Total return (TR) (ETB/ lamb)	1,041	1,184	1,218	1,496
Net return (NR) (ETB/ lamb)	−75.90	16.00	46.60	5.55
Change in total return (ETB/ lamb)	-	143.00	177.00	455.00
Change of total variable cost (ΔTVC)	-	51.10	54.50	373.55
Change in net income (ΔNI) (ETB/ lamb)	-	91.90	122.50	81.45
Marginal Rate of Return (MRR) (ΔNI/ΔTVC)	-	1.798	2.248	0.218

4. Discussion

4.1. Chemical composition of experimental feeds

The discrepancies observed in the nutritional content of the experimental diets allow varying effects of the feed materials on animal performance to be expected. The CP content of teff straw in the current study was close to the 5.56% reported by Geremew et al. (2017) but was substantially higher than the 3.78% reported by Mekuanint and Girma (2017) for the highlands of the bale zone in southern Ethiopia. The findings of this study and those of prior studies may differ due to environmental factors such as altitudinal variances and concomitant differences in soil fertility as well as post-harvest management strategies. However, there was a small difference between the given Teff straw’s CP content and treatment refusals in the current trial. This is a sign that the experimental animals preferentially eat the feed offering that is the most nutrient-dense. For optimum microbial activity to ensure satisfactory feed intake in tropical animals, a minimum of 7.5 per cent CP is needed (Van Soest 1994). Therefore, the lower CP content of the teff straw used in this study would lead to lower voluntary feed intake, less digestibility, and an inability to meet the animals’ maintenance needs when given exclusively.

According to Singh and Oosting's (1992), roughage feeds with an NDF content of less than 45% are classified as good quality, those with an NDF content of 45–65%as medium quality, and those with an NDF content of more than 65% as low-quality roughages. As a result, it was determined that the teff straw employed as a base diet in the current investigation was low-grade roughage whereas all the rest experimental diets fall under the feed category of good quality. NDF was largely used to assess how much of the feed was difficult for animals to digest and as a gauge of how bulky the feed was, which could reduce consumption (Mauro and Cristina 2010). In addition, Van Soest (1994) attested that the amount of DM consumed by animals when the NDF concentration of a diet exceeds 55% drops significantly. As a result, the greater NDF concentration of teff straw found in this study indicates that it has the potential to have a detrimental impact on feed intake when offered exclusively. A considerable drop in the feed’s digestibility was seen as ADF concentration in the diet increased (McDonald et al. 2010). The ADF content combined with the lower CP composition of the teff straw in the current study indicates that it could not support potential feed DM and nutrient degradability when fed as a solitary diet, even though the ADL content of the teff straw does not deviate significantly from the optimal 5% level recommended for normal rumen stability (Garnsworthy and Haresign 2014).

Low protein source feeds are defined as having a crude protein content of less than 12%, whereas medium and high protein source feeds are defined as having a crude protein content of 12–20% and above 20%, respectively (Lonsdale 1989). As a result, among the treatment meals used in this experiment, teff straw was in the category of low protein source feeds, whereas both the Commelina species and concentrate mixture were considered to be medium protein source feeds and the dried Moringa stenopetala leaves (DMSL) fell in the high protein source feed category. The NDF of both Commelina species ranged from 42.34 to 43.69%, which is significantly less than the cut-off point intended to restrict feed intake and degradability (Van Soest 1994). Additionally, the CP content of both Commelina species (12.11–14.88% DM) exceeded the minimal levels necessary to promote lactation (12%) and development (11.3%) in ruminants (ARC 1984), implying their potential supplement capacity to enhance growth performance in young animals and, milk production in lactating animals.

4.2. Nutrient intake

The substantially varying feed consumption responses of the animals seen in this study were a result of the treatment meals’ different nutritional compositions, particularly the CP. The statistically higher intake responses of the supplemented groups compared to the control ones were an indication of the potency of the Commelina species to serve as a supplement to upsurge feed intake and, consequently, performance of animals consuming low-quality diets therefore. This confirms the beneficial influence of supplementation on DM and nutrient intake.

The total DM intake of lambs in the current study (averaged 730.01 g/day) was similar to the 730.48 g/d reported for Bonga sheep fed noug seed cake, dried mulberry (Morus indica), and mixed Vernonia amygdalina leaves meal (Gezahegn 2019), but slightly higher than the 700 g/d reported by Abreha et al. (2019) for local sheep fed hay supplemented with conventional supplement, local brewery by-product (Atella) and leguminous browse leaf meal. The variations in daily DM intake reported by various authors could be caused by variations in the kind and quality of the base diet, the supplements utilized, and breed variances.

The CP intake influencing pattern observed in the current study directly correlates with the CP content of the corresponding treatment diets. According to the results of the present study and Prakash et al. (2006) and Mekuriaw and Asmare (2018), experimental animals’ consumption of CP and DCP increased as a result of a diet’s higher protein content. According to Goodchild and McMeniman (1994) and McDonald et al.(2010), good protein source feeds, when given as a supplement to low-quality forage, increase the availability of nitrogen to ruminal microorganisms, speeding up the rate of feed decomposition and utilization. Supplementation had a substantial impact on the experimental animals’ intake of NDF in the current investigation (P < 0.001). While the other two treatments exhibited non-significantly different NDF intakes, T4 and T1 fed animals had the highest and lowest NDF intakes, respectively. The observed variation in NDF consumption among treatment groups was strikingly a clear reflection of the NDF composition of the diets composing the respective treatments.

In the current study’s findings, T4 showed a leading effect on ADF consumption (P < 0.001) and T1 the least This may be explained by the greater ADF concentrations, which are thought to interfere with digestion, increase ruminal fullness, and restrict voluntary feed intake. Low-protein, high-fibre feed ingredients restrict an animal’s voluntary feed consumption. Total DM intake was equal for the two Commelina species-based treatments, whereas T2 (P < 0.001) had a greater ADF intake than T3. And this discrepancy should be expected given that C. benghalensis has a substantially greater ADF content (28.48%) than C. imberbis (24.68%). In concurrency to the present investigation, Abreha et al. (2019) attested that supplementing commercial and unconventional supplemental feeds had a substantial impact on the NDF and ADF intake of local sheep breeds. The level of intake increased as the amount of the indicated nutrients in the supplemental meals they used increased.

4.3. Nutrient digestibility

The statistically variable nutrient digestibility enhancing effect of the treatment diets reported in the present investigation directly mirrors the protein content and nutrient utilization efficiency of the respective treatments. According to Okunade et al. (2014), consumption and digestibility of feeds by herbivores were positively correlated with the CP contents. So, the higher CP digestibility observed in T4 than all other treatments could be associated with the higher CP% of the concentrate mix supplemented to animals in this particular group. The findings of this study clearly and boldly showed that C. imberbis is just as potent as the standard supplement to sustain reasonable nutrient digestibility for the animals consuming it. The digestibility and bioavailability of nutrients in a given feed were known to be negatively impacted by the ADL content of that meal (McDonald et al. 2010). Therefore, the lack of CP digestibility difference seen among treatments T1 and T2 may be attributed to the Teff straw’s relatively lower ADL as compared to that of C. benghalensis. This may present a better opportunity for the rumen microbes to increase protein digestibility in the diets of control treatments. The observed equivalence in NDF and ADF digestibility of T3 and T4 in the present study could indicate that C. imberbis supplementation significantly improved the fibre digestibility in the experimental animals comparable to that which could be achieved by the conventional concentrate.

In accordance with the findings of the current study, growing Bonga lambs supplemented with commercial and unconventional feeds (Gezahegn 2019) and Hararghe Highland Sheep supplemented with dried tomato pomace and Concentrate (Gebeyew et al. 2015) both showed a significant improvement in NDF digestibility. The results of the present investigation were in conflict with those of Abreha et al. (2019), who found that the addition of concentrate and unconventional protein sources had no discernible impact on the digestion of NDF. And the quantity and quality of the supplements utilized, particularly their fibre content, could be the reason why the results of this study and those of earlier ones differ. No discernible difference between T1 and T2’s ADF digestibility was found. The greater CP value of the DMSL and the lower ADL value of the Teff straw could provide a favourable environment for the microbial population and be assumed as a potential cause for the similar ADF digestibility response of T1 with T2. Because the composition of other feeds included in a ration and taken alongside it also affects a feed’s ability to be digested (McDowell 1988). Growing animals frequently saw an increase in ADF digestibility of low-quality meals as a result of supplementing (Mekuriaw and Asmare 2018).

4.4. Body weight change

The visible discrepancy in final weight achieved by the treatments in this investigation is exactly in line with the DM digestibility of the corresponding treatments. T3 attained a final body weight comparable to that of T4, demonstrating that C. imberbis has a growth enhancing potential comparable to that of the standard supplement. The disparity observed in body weight gain and average daily gain of the animals in the present study was a direct reflection of the total DM and OM intake and digestibility seen in the treatment groups. None of the treatments in the current study resulted in any weight loss in the experimental animals. Even though the rate was much lower than it was for the supplemented groups, the control groups were seen to be making gradual gains all the way through the experimental period. This shows that the DMSL employed in the treatment mixture to make up for the Teff straw’s protein shortage and satisfy the control group’s maintenance requirement was successfully achieving its intended goal. Additionally, records of successful weight growth could be qualified by nutrient consumption and digestibility. And positive weight gain records could be qualified by nutrient intake and digestibility. Because the DM digestibility coefficient in the present study surpassed the threshold value of 42–45% digestibility suggested as a minimum value on a dry weight basis to assure body maintenance needs (McDowell 1988).

Improvement in daily weight gain of growing animals, consuming fibrous diets, as a result of supplementation was a very common observation but different authors reported varying records. The observation of the present study (47.78 g/day) was higher than ADG (45.g/d) of local sheep in northern Ethiopia supplemented with 330 g/d DM local brewery by-product (Atella) (Abreha et al. 2019) but lower than 52.52 g/d reported for Hararghe Highland Sheep supplemented with dried tomato pomace and Concentrate (Gebeyew et al. 2015). The FCE values recorded by the treatment rations of the present study showed that T4 and T3 were comparably efficient with each other but more effectual over the other two treatments. This finding supports the report of Mekuriaw and Asmare (2018) who testified a significant progression in FCE of Washera lambs supplemented with graded levels of Chibha (Ficus thonningii) leaves but stands in contrary to the statement of Gezahegn (2019) who observed insignificant difference between FCE of control and supplemented Bonga lambs.

The body weight change trend clearly shows how the daily growth of the experimental animals was being driven by the respective treatment diets. Except T1, the remaining treatments did not appear as such far from each other till the mid of the feeding season. The changing trend observed in the body weight of the animals was in line with the nutrient composition of the treatment diets and uptake by the experimental animals.

4.5. Partial budget analysis

In the present investigation, T3 returned better profit for all treatments. While the growth data shows a slight positive change in T1, the net return indicates a loss of 75.9 ETB per head. This could be associated with the trivial weight change irrespective of the feed cost invested for the treatment category. All supplemented treatments of the present study generated a positive MRR value and the records suggest that an additional one unit of ETB cost increment per animal resulted in one ETB and an additional 1.79, 2.25, and 0.22 ETB benefit for T2, T3, and T4, respectively. Unfortunately, both of the Commelina species constituting treatments generated better marginal profit over the commercial concentrate. This indicates that for low-income farmers having plenty of Commelina species in their locality, it is economically feasible to use the Commelina species as a supplement rather than using the expensive commercial supplements to get improved performance in animals and obtain better production returns. And with comparable costs, supplementation of C. imberbis is more profitable than C. benghalensis.

5. Conclusion

The Commelina species that were employed in this investigation were distinguished to be medium-protein source feeds with promising potential to enhance nutrient utilization and growth performance in growing animals. Supplementation considerably increased the experimental animals’ total DM and nutritional consumption. Commelina species comprised treatments demonstrated considerably higher intake response than the control group but lower feed intake improvement than the commercial concentrate. Similar findings were made for the experimental animals’ body weight measurements and feed digestibility. C.imberbis supplemented treatments had comparable DM, OM, NDF, and ADF digestibility with that of commercial concentrates. The present investigation underlined a meaningful variation between daily gains acquired by control treatments (23.83 g/d), that of the meals containing C. benghalensis (44.53 g/d), C. imberbis (50.63 g/d), and standard concentrate (72.69 g/d). In conclusion, Commelina species have a promising potential to be used as a supplement to improve feed intake, digestibility, and consequently performance of animals consuming subpar diets. As compared to both non-supplemented and commercial concentrate-fed animals, the group of animals given Commelina species produced much more profit. As a result, using Commelina species as a supplement for animals consuming low-quality meals is both practical and economically advantageous wherever they are present in abundance.

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability statement

The data that support this study will be shared upon reasonable request to the corresponding author.