Effects of Qaxxee (Hermosa sidoides) and Dheekaa (Grewia tembensis) foliage supplementation on milk yield and milk quality of Somali goats fed a crop-residue-based diet

ABSTRACT

The purpose of this study was to examine at the chemical content of Hermosa sidoides and Grewia tembensis feeds and their impact on milk output and quality in Somali goats. A completely randomized block design, excluding the control treatment, was adopted with three treatment diets. T1 (600 g Hermosa sidoides, 200 g concentrate mixture, maize stover), T2 (600 g Grewia tembensis, 200 g concentrate mixture, maize stover), and T3 (300 g Hermosa sidoides and 300 g Grewia tembensis, maize stover), were the treatments. Hermosa sidoides had a greater crude protein (CP) content (28.7%), 40% neutral detergent fibre (NDF), and 18% acid detergent fibre (ADF), while Grewia tembensis had a lower CP content (27.1%), 47% NDF, and 21.91% ADF. The daily milk production for goats fed treatment food T1 (0.91 kg) was substantially greater (p0.05) than goats fed T2 (0.82 kg) and T3 (0.84 kg) after 90 days of feeding experiments. In general, this study found that supplementing nursing Somali goats’ diets with Hermosa sidoides (Qaxxee) leaves (T1 Diet) considerably increases milk output and cost return. As a result, this study implies that goat feeds, which are often available in the study location, could be used as a suitable diet in the future.

KEYWORDS:

• Hermosa sidoides
• Grewia tembensis
• milk yield
• milk composition
• feed composition

1. Introduction

Capra hircus (indigenous goat husbandry) is becoming more affordable to smallholders in African households (Chokoe et al. 2020). Goats play a vital role in rural smallholder farmers’ food security and economic sustainability. It is known as a poor man’s cow and was the first animal to be domesticated, providing a vital and easily accessible source of animal protein as well as revenue for many low-income families (Lafleur et al. 2018). There are roughly 500 goat breeds documented globally (FAO 2018), of which only half are commonly domesticated for milk purposes. Goats are common in semi-arid and dry locations, and goat milk is widely produced across Africa, as well as the Caribbean, primarily for domestic consumption, but it is occasionally shared within the community (FAO 2020). The average milk production from goats varies greatly between major milk-producing countries. In Sudan, the average goat milk yield is approximately 64 kg/year, while in India, it is more than 179 kg/year (FAO 2023). Despite their considerable tolerance to harsh climatic or geographical conditions and cheap care costs, they have been shown to be viable livestock species for marginal and landless farmers (Waheb et al. 2022).

Dairy goat milk has been an important part of human nutrition for millennia, in part because of the greater similarity of goat milk to human milk, softer curd formation, a higher proportion of small milk fat globules, and different allergenic properties compared with cow milk. (Sumarmono 2022; Hettinga et al. 2023). Goat milk contains an abundance of different macronutrients and micronutrients. When compared to cow milk, goat milk is thought to have reduced allergy potential but better digestion. Furthermore, there is growing interest in the presence of health-promoting chemicals in goat milk (Sumarmono 2022). The global production share of raw goat milk was predicted to be 14826204.19 tons in 2022, with Asia contributing the most (53%), followed by African countries (24%).(FAO 2020). Also, goat’s milk has better digestibility; it contains almost the same amount of lactose as cow’s milk (Waheb et al. 2022), high-quality proteins, and a great content of minerals and vitamins (Massender et al. 2023). Country-wide, goats are managed under an extensive traditional system, and their production is the lowest (daily milk yield ≤0.5L) compared to the other sub-Saharan African countries (Hussein et al. 2023). The purpose of keeping goats varies from area to area due to economic, cultural, and ecological factors (Getaneh et al. 2016). The long-eared and short-eared Somali goats have been so far characterized as a dominant goat breed in the study area, which is highly adapted to heat stress and the harsh conditions of the Borana rangeland. Shortage of feed and the very poor quality of the available feeds during the dry season are the prime limiting factors for increasing the production and productivity of goats (Hagose et al. 2021). The high protein concentration and year-round availability of foliage in browsing plants make it a valuable feed resource for ruminants in tropical and subtropical conditions. During the short dry season, the leaves of Hermosa sidoides and Grewia tembensis remain green next to the acacia species. As long as these densely populated species are in the study area, no distinct literature for Hermosa sidoides has been done so far. Grewia species is browsed by livestock and is considered to be an important and highly palatable browse species in farmer’s surveys in Eastern Africa (Terefe et al. 2022). Most of the time, pastoralists used to feed their animals that stayed at home by cutting and carrying systems like those of calves, sick animals, and sometimes lactating animals. However, the nutritional benefits of feeding Harmosa sidoides and Grewia tembensis to ruminants have not been well studied, and local pastoralists have no idea about the chemical composition of this most abundant feed. Thus, this research was aimed to evaluate the chemical composition as well as its effects to maximize milk production and milk composition in Somali goats.

2. Materials and methods

2.1. The study area’s description

This study was conducted in the Dhas districts of Borana in Southern Ethiopia (Figure 1). The Borbor town is the administrative centre of the district, is situated at a distance of around 730 kilometres towards the southeast of Addis Ababa the capital city of Ethiopia and approximately 171 kilometres away from the capital city of the Borena zone (Yabello town).

Figure 1. Map of the study area.

2.2. Animals and experimental design

The study employed fifteen lactating Somali breed goats of the fourth parity. For this study, the animals were rented from local farmers. The average goat’s body weight was 30.4 kg. The goats were housed individually in a 1.5-m x 1.5-m pen for the duration of the experiment and fed separately. For the duration of the experiment, an open-shaded house was prepared and partitioned into pens. The pen included feeding and watering troughs. The goats were immunized against contagious caprine pleuropneumonia (CCPP), Peste des petits ruminants (PPR), and dewormed with Abendazole and ivermectin against internal and external parasites. Prior to the start of the experiment, the animals were given two weeks to adjust to the experimental feeds. The animals were kept in separate housing with enough space and hygienic milk handling was employed.

2.2.1. Feed preparation and administration

Harmosa sidoides and Grewia tembensis are two types of browse species used as treatment feeds. They were chosen for their abundance, goat preference, leaf yield, biomass, and ability to stay green for a long period of time during a short dry season without leaf shattering. The base diet consisted of chopped maize stover. Leaf samples of browsing species were pulverized and evaluated for dry matter (DM, 105°C for 16 hours), organic matter (% OM, 100% crude ash), crude protein (CP, N6.25), and crude ash (CA, 550°C for 8 hours). The dried samples were grinded to pass through a 1-mm sieve of a Wiley mill for chemical analysis. A concentrate mixture of wheat bran and nougat cake was employed. Harmosa sidoides and Grewia tembensis components (branches, twinges, and leaves) were collected from the area, air-dried in the shade, and used as test or treatment feed. Treatment diets were given in two equal portions at 8:00 AM and 4:00 PM, and goats had constant access to water and mineral licks.

2.2.2. Treatments and experimental designs

The experiment was designed with completely random blocks. The experimental animals were placed into three groups based on their baseline body weight (BW), with five animals per group randomly assigned to one of three feeding treatments. The goats were not permitted to graze. To optimize milk production and preserve the goats in good condition for the next lactation, total DM consumption was around 4% of their body weight (McDonald et al. 2002; Patra et al. 2023). The diet was assigned as follows.

T1 (600 g Hermosa sidoides, 200 g concentrate, and chopped maize stover) (600 g Hermosa sidoides, 200 g concentrate, and chopped maize stover), T2 (600 g Grewia tembensis, 200 g concentrate, and chopped maize stove), T3 (300 g Hermosa sidoides plus 300 g Grewia tembensis, 200 g concentrate, and chopped maize stove).

2.3. Sample collection and analyses

2.3.1. Feed intake and body weight change

The goat’s body weight was measured using a spring balance capable of reading up to 50 kg, and weight gain was recorded every 10 days throughout the 90-day trial. The difference between the quantity of feed offered and denied was used to calculate each goat’s daily consumption. The amounts of feed provided in the evening were added to the morning refusal feed, and then the refusal feed was measured once in the evening.

2.3.2. Milk time and milk yield

Milking was done by hand twice daily (6:00 am and 6:00 pm), and daily milk yield data were documented throughout the experiment. The milking activity follows the traditional way of milking, which includes allowing a kind to suckle before milking. Milk yield was measured with a 1000-mL glass measuring cylinder tube, and measurements were taken. The difference in the kids’ body weights before and after suckling was also used to compute total daily milk production taken (Rojo-Rubio et al. 2016; Salama et al. 2020; Firozi et al 2023). The amount of milk consumed was assessed by the kind’s weight change after suckling.

2.3.3. Milk sample analysis

Individual milk samples from fifteen goats were collected and delivered to the lab in a thermos box for milk composition analysis each month of the experiment. Milk samples were collected in a sterile bottle to avoid contamination during chemical analysis. The goat milk (45 mL) in plastic tubes was frozen in a static freezer at – 20 ± 1 °C. Every month of the trial, 40 mL of fresh milk was collected at room temperature for analyses of protein, fat, lactose, non-fat solids, density, freezing point, added water, pH, and ash using a lactoscan analyzer (L-18-617, Bulgaria) at the Yaballo Dryland Agriculture Research Centre.

2.4. Feed samples chemical analysis

A sample of the browse species (Hermosa sidoides and Grewia tembensis), basal diet (maize Stover, mixture of wheat bran and nougcake) was taken to the Nutritional Laboratory at Holeta Agricultural Research Center for chemical analysis. The samples were milled to pass through a 1 mm screen and stored in plastic bags until they were analyzed. All feed samples were analyzed for DM, ash, and CP using AOAC procedures (2005). Van Soest et al. (1991) methods were used to determine neutral detergent fibre (NDF). Van Soest and Robertson’s methods were used to determine acid detergent fibre (ADF) and acid detergent lignin (ADL). The total nitrogen (N) of leaf samples was determined using the Kjeldahl technique, which follows AOAC (2005) standard protocols. The content of CP was calculated by multiplying total nitrogen by a conversion factor of 6.25 (CP = N x 6.25).

2.5. Statistical data analysis

Analysis of variance for chemical composition data was done using the GLM procedures of SAS 9.3 (2010) for a factorial treatment arrangement in a Complete Randomized Design (CRD) was used. The Shapiro–Wilk test of normality was employed to ensure that data distributions were normal. The least significant difference (LSD) test was used at P < 0.05 for all parameters to compare mean differences between treatments. The statistical model used for analyzing the data was: Yij = μ + αi + bj+ϵij.

Where: Yij = measurement or observation due to the ith and jth factors; μ = the overall mean; αi = the treatment effect of factor i; bj = block, bodyweight effect of j, ϵij = random error.

3. Results and discussion

3.1. Chemical composition of the experimental feed

The chemical compositions of experimental feeds Hermosa sidoides and Grewia tembensis, as well as their mixtures and basal diets (concentrate feed and chopped maize stover), were presented in Table 1. The dry matter content of the browse species was 90.09% for Hermosa sidoides and 90.84% for Grewia tembensis, but there was a slight increase in DM (90.5%) in the ration containing an equal mixture of the two. According to Zhang et al. (2022), there was no variation in the allocation of dry matter to the shoot and fruit. During the dry season, the DM contents of examined browse forage species in east and southern Ethiopia ranged from 85.6% in Lannea rivae to 93.3% in Balanites rotundifolia (Habte et al. 2021). Similarly, Dalle (2020) and Nsubuga et al. (2020) found that edible browse species have DM concentrations ranging from 88% to 93% in arid and semi-arid regions, which is consistent with the current finding. Furthermore, Melaku et al. (2010) reported a mean DM content of 90.6% for plant species available in semi-arid northern Ethiopia, indicating that the DM constituents of browse forage species did not vary with location. Proteins’ primary functions in the human body are growth and tissue replacement. With CP values of 28.07%, 27.7%, and 26.1% for Hermosa sidoides, Grewia tembensis, and a mixture of these browses, the plant can be considered a high-protein fodder for livestock. The study found similar crude protein content in Moringa oleifera, C. oliterius, and Crassocephalum crepdioides, with slightly higher crude protein content in Moringa oleifera compared to previous studies reported by Daniel, 2014; Soetan and Aiyelaagbe (2016), Noor et al. (2020), and Mode et al. (2023).

Table 1. Chemical composition of treatment feed.

	Proximate composition of offered feed (%)
Types of feed sample		Feed offers
	DM	ASH	CP	NDF	ADF	ADL
Hermosa sidoides	90.09	4.98	28.07	40.08	18.09	5.59
Grewia tembensis	90.84	3.35	27.7	47.1	21.91	4.57
Hermosa &Grewia	91.99	2.71	26.1	54.7	21.74	6.8
CMZstover	85.64	3.69	6	78.02	40.8	10.1
Concentrate	91.42	4.7	20.9	41.9	6.36	3.07

CMZ stover; concentrate and chopped maize stove; DM-Dry matter, CP – Crude protein, NDF-Neutrent detergent fibre, ADF-Acid detergent fibre, ADL-Acid detergent lignin. T1(600 g Hermosa sidoides, 200 g concentrate and chopped maize stover); T2(600 g Grewia tembensis, 200 g concentrate and chopped maize stove); T3(300 g Hermosa sidoides + 300 g Grewia tembensis, 200gconcentrate and chopped maizestove).

Similarly, Welay et al. (2018) observed a CP content of 18.20.18% for G. tembensis. Muftau et al. (2020) reported on the CP content of Aspilia Africana (17.1%) and Leucina leucocephala (31.2%). In comparison to the current finding, Ogunbosoye and Babayemi (2012) found a lower percentage of CP (15.99%) in Albizia odoratissima. The browsing species gathered in this study had a high CP content due to their favourable environmental conditions. The variance in N concentration between species can be attributable to inherent properties of each species in terms of the ability to extract and accumulate nutrients from soil and others environmental factors (Ogunbosoye et al. 2015).

It is well known that feed with a crude fibre content of less than 45% is as good quality (Welay et al. 2018), therefore the current study supported the claim made by the authors for Hermosa sidoides. Hermosa sidoides had 40% NDF, 18% ADF, and 5.59% ADL. This finding is consistent with the numbers published by Alemu (2016) and Hagose et al. (2021), which are 92.4% and 93.47%, respectively. This finding was comparable to the 91.41% DM value of a concentrate mixture of nougseed cake and wheat bran reported in the study research by Mamo et al. (2021). The CP value of concentrate feed observed in this study was lower than the values of 23.39% and 24.53% reported by Mamo et al. (2021) and Hagose et al. (2021), respectively, and it agreed closely with the crude protein content of concentrate feed (21.01%) reported by Mamo et al. (Alemu, 2016). However, the basal diet/maize stover had the lowest CP (6%) and the highest fibre content (78% NDF, 40% ADF, and 10.1% ADL). This finding agreed with Gebeyehu (2017), who found 6% CP, 70% NDF, 40% ADF, and 10.9% ADL in maize stover.

Roughage feeds with NDF less than 45% are classified as high-quality roughage, those with 45% to 65% as medium-quality roughage, and those with more than 65% as low-quality roughage. McDonald et al. (2002) explained that a higher ADF content in crop residues may be associated with lower digestibility because feed digestibility and ADF are negatively correlated. As a result, crop residues in this study were classified as low-quality roughages that may limit animal performance.

3.1.1. Daily dry matter and nutrient intake

The nutrients and dry matter for the feed chemical composition of an experimental diet on a dry matter basis were presented (Table 2). According to the current findings, the T1 diet had a higher browse dry matter intake (BDMI) than T3. Total dry matter in nutrient intake differed for daily rations of Hermosa sidoides, Grewia tembensis, and their mixture’s leaves and foliage weighing in grams. For feed treatments containing Hermosa sidoides, total crude protein intake was high. Due to its hard and coarse texture and high fibre content, the maize stover/basal diet in this experimental feed reduced feed intake. As a result, the difference in dry intake may be attributed to the fibre concentration of browse in the T1 diet, which has a smaller particle size and is more palatable to goats than the other treatment diet. The crude protein nutrient intake for the experimental feed treatment was found to be high in treatment diet T1. The nutrient and dry matter intake of crude fibre in this feed treatment was higher for NDF, ADF, and ADL in the T1 and T3 diets. As a result, nutrient intake was higher in this case for the treatment diet (T1), indicating that the feed browse in this treatment has a lower and smoother particle size and is highly palatable. Reduced DM intake of feed may have an effect on the animals’ milk production and, as a result, their nutrient intake (Silva et al. 2022). The maximum and minimum fibre contents in the diet to maximize intake and production efficiency were not well defined in a previous study by De Carvalho et al. (2021) for dairy goats. As a result, he discovered that a low value (27%) of NDF from high-quality forage optimized dry matter intake and milk yield. As a result, feed in various particle sizes can affect the animal’s feed intake and production requirements.

Table 2. Descriptive data of daily and total nutrient intake per dry matter basis.

Treatments	BDMI	CDMI	TDMI	TCPI	TNDFI	TADFI	TADLI	TashI
T1	530g	210g	838g	203g	519g	262g	140g	40g
T2	510g	220g	833g	193g	456g	191g	30g	30g
T3	480g	240g	828g	181g	491g	212g	130g	30g

TDMI-Total dry matter intake, TCPI-total crude protein intake, TASHI-total ash intake, TNDFI-total nitrogen detergent fibre intake TADFI-, total acid detergent fibre intake, TADL-total acid detergent lignin intake, SDMI stover dry matter intake, BDMI-browses dry matter intake; T1(600 g Hermosa sidoides, 200 g concentrate and chopped maize stover); T2(600 g Grewia tembensis, 200 g concentrate and chopped maize stove); T3(300 g Hermosa sidoides + 300 g Grewia tembensis, 200gconcentrate and chopped maizestove)

3.2. Milk yield and quality

3.2.1. Milk yield

The average daily milk yield of Somali goats differed significantly (P < 0.05) across three experimental treatments. However, goats fed a ration containing Hermosa sidoides foliage (T1 diet) in 4% DMI of body weight could maintain a milk production of 1 kg at the 40th, 60th, and 70th days in milk, whereas the peak yield recorded during the same study period for goats fed T2 and T3 diets was 1 kg of milk on the 60th and 70th days in milk, respectively (Table 5). Goats fed the T1 diet produced milk 10 days earlier than their counterparts. This could be due to the high nutrient content of crude protein and low fibre content observed in the T1 diet. The peak is usually between the fifth and eighth weeks of lactation (El-Tarabany et al. 2018). The average daily milk yield is shown in Table 5. According to the findings, there was a significant difference in milk yield at p < 0.05. The goat fed the T1 diet had a higher mean SD of 0.91 ± 0.05 milk yield, while the goat fed the T2 diet had a lower mean and SD of 0.82 ± 0.03 kg, and the goat fed the T3 diet had a lower mean and SD of 0.84 ± 0.02. (Table 5). Damascus goat milk yield peaked at 616 ml per day in week 6 (42 days), but it was lower than Jamnapari goat milk yield of 785 ml per day in the same weeks (Zailan and Yaakub 2018; Ibrahim and Tajuddin 2021). During the entire lactation period, the daily milk yield of a Saanen goat ranged from 700 ml to 900 ml (Gokdai et al 2020). In Ethiopia, indigenous Somali goats reported daily milk yields ranging from 0.3–0.45 kg (Mengistu et al. 2007). The daily milk yield of Somali goats ranged from 0.38 kg to 1 kg under concentrate supplementation, which was consistent with the current finding but lower when compared to Mestawet et al. (2012), who reported a daily milk yield of Arsi-bale goats of 1.13 kg under improved management conditions. Mestawet et al. (2012) also reported a daily milk yield of 0.85 kg for Somali goats. As a result, this result was comparable to our results from goats fed T2 and T3 diets during the first 90 days of lactation (experimental trial). However, the milk yield trended downward from the middle of the experimental period until the end (Table 3). During early lactation, the doe bodies began to increase their feed intake to increase milk production and achieve maximum production during mid-lactation (Makun et al. 2013). Late lactation milk production was the lowest and fell because they used up their nutrient intake to build body condition rather than produce milk, and all of them had almost reached the dry period.

Table 3. The mean average of ten days interval daily milk yield (kg) of Somali goats at (p < 0.05).

Treatments (±SD)
Days in milk	T1	T2	T3	CV	P-Value
10^th	0.79 ± 0.09^a	0.66 ± 0.08^b	0.65 ± 0.05^c	11.6	0.03
20^th	0.66 ± 0.07	0.58 ± 0.08	0.58 ± 0.06	12.3	0.19
30^th	0.85 ± 0.12	0.73 ± 0.10	0.79 ± 0.04	8.67	0.17
40th	1.01 ± 0.10	0.88 ± 0.07	0.96 ± 0.04	4.96	0.08
50th	1.03 ± 0.07^a	0.93 ± 0.01^b	0.96 ± 0.03^c	4.53	0.01
60^th	1.06 ± 0.04^a	1.02 ± 0.05^b	0.95 ± 0.04^c	4.2	0.008
70th	1.05 ± 0.03^a	0.92 ± 0.04c	1.01 ± 0.04^b	4.2	0.001
80th	0.99 ± 0.05^a	0.92 ± 0.03^c	0.97 ± 0.04^b	4.2	0.03
90^th	0.65 ± 0.05	0.59 ± 0.05	0.60 ± 0.05	8.7	0.17
ADMY	0.91 ± 0.05^a	0.82 ± 0.03^c	0.84 ± 0.02^b	4.41	0.004

a,b,c,-different superscript in the same column indicate different mean, T₁-Hermosa sidoides + concentrate mix basal feed,T_{2 –} Grewia tembensis + concentrate mix + basalfeed, T_3-mixture of two browse concentrate mix + basalfeed feed, CV-coefficient of variancevariance, ADMY – average daily milk yield,

3.2.2. Milk fat

In the current study, there were no significant (P > 0.05) differences in milk fat content between treatments (Table 4). In the current study, milk fat increased as the day of milking progressed; as the day of milking progressed, the milk fat content increased. Milk fat and dry matter levels rise with lactation stage, as expected from lactation physiology, while lactose levels fall (Yakan et al. 2019). Zakaria et al. (2020) found that goats fed Napier grass combined with concentrates of 18% crude protein and 20% crude fibre had a milk fat content of 2.54%. Lallo et al. (2019) found 1.34% to 2.75% milk fat in the Toggenburgen breed of goat, which was lower than the current study. According to Ketto et al. (2014) and Kralickova et al. (2013), the milk fat content in early lactation is 3.4%, and the milk fat content in late lactation is 4.55%. Similarly, Ibrahim and Tajudin (2021) found that Saanen goats fed on 3–4 kg of concentrate in the morning and 89% of DM Bachiaria humidica grass yielded 2.79% in early lactation and 3.5% in late lactation. For Moroccan goats on extensive grazing, Ibnelbachyr et al. (2015) reported milk fat content ranging from 3.35% in early lactation to 5.30% in late lactation.

Table 4. Mean Milk chemical composition of Somali goats (%±SD).

Trt			Variable%
	Period	Fat	Lactose	SNF	Protein	pH	Ash	FP
T1	3	3.08 ± 0.45	4.48 ± 0.03	8.86 ± 0.10	3.47 ± 0.18	6.97	0.8	−0.66
T2	3	3.64 ± 0.33	4.44 ± 0.11	8.80 ± 0.11	3.55 ± 0.14	6.93	0.8	−0.66
T3	3	3.59 ± 0.32	4.51 ± 0.07	8.84 ± 0.03	3.45 ± 0.10	6.84	0.8	−0.64
CV		10.92	1.79	1.07	4.2	1.42	2.8	−1.74
P-value		0.21	0.59	0.76	0.69	0.32	0.9	0.12

Trt, treatment; SNF; solid nonfat, period, month of the study; T1,ration contain Hermosa sidoides + concentrate mixture & basal feed; T₂, ration contain Grewia tembensis, concentrate mixture + basalfeed; T₃, ration contain mixture of (Harmisa and Grewia), concentrate mixture, basal feed.

Arsi-bale goat milk fat content was reported to be 5.3% and 5.15%, respectively (Nurfeta et al. 2012; Getaneh et al. 2022). Mastewat et al. (2012) reported 4.9% milk fat content in Somali goats, following the same trend. However, different results could be due to differences in breeds, location, management, and environmental factors that may affect milk fat composition. Similarly, the richness of goat milk fat is influenced by the quality and quantity of feeds, genetics, and seasons (Makun et al. 2013). According to the majority of studies, milk fat and total solid content increased toward the end of the lactation period, coinciding with a decrease in milk yield (Kralickova et al. 2013; Ketto et al. 2014). The fat content varies due to breed, nutrition, and seasonal factors (Lai et al. 2016).

3.2.3. Milk protein

Protein content results for three different treatment diets revealed no significant difference (P > 0.05). These results were slightly higher than the previous results, which took 2.50% of the protein content (Lallo et al. 2019), 2.5% – 2.60% of the protein content (Mourad et al. 2022), and 2.58% – 2.99% of the protein content (Nor et al. 2020). However, it was consistent with the results reported by Kučevićet al. (2016), who noted the milk protein content of goat milk to be 2.79% to 3.76%; Ibnelbachyr et al. (2015) reported milk protein (3.45% to 4.37%); and Tessema and Alemayehu (2019) reported milk protein 3.5–4.8% for Ethiopian indigenous breeds of goats. Mestawet et al. (2012), on the other hand, reported the highest milk protein content of 4.9% in the Somali goat breed under good management conditions. According to Markhan et al. (2014), when milk yield peaked in the early and mid-stages of lactation, protein and fat content were low; however, when milk yield was low in late lactation, protein and fat content were higher.

3.2.4. Lactose content of milk

Table 4 shows the lactose content of goat milk. The results show that there is no significant difference (P > 0.05) in the lactose content of goat milk across treatment groups. Idamokoro et al. (2017) found that the lactose content of three goat breeds ranged from 5.0–6.7% for Nguni goats, 4.6–5.4% for Boer goats, and 4.7–5.4% for non-descriptive goats. Previous studies found that the lactose content of goat milk was 4.4% – 4.7%, 4.65%, 5.22% – 5.41%, and 4.07% – 4.71%, respectively, as reported by Mourad et al. (2022), Zakaria et al. (2020), Zailan and Yaakub (2018), and Nor et al. (2020). As a result, the lactose content in the current study was within the range of lactose content that meets the minimum requirement of lactose content in goats’ milk.

3.2.5. Ash, solid non-fat, density and PH

The total minerals in milk are represented by ash, which is the remaining residue after incineration (Lai et al. 2016). The current result’s ash content was not significantly different (P > 0.05) (Table 4). The ash content of the goat in this experimentally fed treatment (T1, T2, and T3) was 0.8%, 0.8%, and 0.8%, respectively. These findings were higher than those of Zakaria et al. (2020) and Hassan et al. (2010), who discovered that the ash content of goat milk ranged from 0.69–0.74% and 0.7%, respectively. These could occur as a result of management and breed factors that cause variation. In the current study, there was no significant difference (p < 0.05) for solid nonfat (SNF) in all milk samples from treatment diets T1, T2, and T3 (Table 5). SNF in the current study was uniform, ranging from 8.86% to 8.80% to 8.84% for all treatment diets over the course of the study. The SNF of a Saanen goat was 7.26% in late lactation and 7.84% in mid and early lactation (Ibrahim and Tajudin 2021). Nutrition, genetics, disease, stage of lactation, and season of the year have all been reported to have an impact on nonfat solids in milk production Ibrahim et al. (2021). Accordingly, the solid nonfat content of goat milk ranged from 9.10–10.30, 9.20–10.00, and 8.80–9.90 for nguni, boer, and non-descriptive goats (Idamokoro et al. 2017). As compared to the current study, these differences could be due to agro-ecological and nutritional differences.

Table 5. Period effect on Milk chemical composition of Somali goats (%±SD).

Trt	Period	Fat	Density	Lactose	SNF	Protein	pH	Ash	FP
T1	1	3.20 ± 0.22	33.75 ± 5.78	4.51 ± 0.14	8.83 ± 0.22	3.37 ± 0.15	6.8	0.78	−0.65
T2	1	3.67 ± 0.64	34.09 ± 1.33	4.51 ± 0.18	8.91 ± 0.25	3.49 ± 0.07	6.67	0.81	−0.67
T3	1	3.28 ± 0.36	35.0 ± 2.34	4.48 ± 0.17	8.74 ± 0.17	3.42 ± 0.16	6.7	0.8	−0.66
P-value		0.74	0.8	0.7	0.88	0.14	0.43	0.33	0.42
T1	2	3.37 ± 0.20	34.05 ± 1.5	4.55 ± 0.14	9.01 ± 0.18	3.57 ± 0.2	6.76	0.84	−0.67
T2	2	3.66 ± 0.4	35.82 ± 1.3	4.58 ± 0.12	8.98 ± 0.37	3.74 ± 0.11	6.9	0.83	−0.66
T3	2	3.83 ± 0.28	35.8 ± 1.5	4.51 ± 0.16	8.90 ± 0.26	3.52 ± 0.26	6.87	0.82	−0.66
P-value		0.24	0.85	0.99	0.49	0.12	0.79	0.31	0.49
T1	3	3.96 ± 0.52	31.11 ± 5.33	4.48 ± 0.24	8.87 ± 0.41	3.34 ± 0.16	6.67	0.77	−0.65
T2	3	4.12 ± 0.70	32.58 ± 3.08	4.44 ± 0.20	8.77 ± 0.24	3.71 ± 0.15	6.8	0.8	−0.69
T3	3	3.85 ± 0.49	32.8 ± 2.06	4.36 ± 0.27	8.77 ± 0.43	3.39 ± 0.30	6.69	0.79	−0.65
P-value		0.11	0.36	0.78	0.81	0.26	0.33	0.65	o.28

Trt, feed treatment; FP, freezing points, P – probability (P > 0.05) value; Period, month of each experiment.

The current result did not show a significant difference in pH value (p > 0.05). Because it converts milk to cheese via protein coagulation, pH is a critical parameter for determining milk quality. The pH values in this study were nearly consistent with the findings. According to Zakaria et al. (2020), the pH of goat milk ranged from 6.50–6.53, which was the normal value of goat milk. Similarly, the current result’s mean pH value was 6.7 for all treatment diets. This normal pH value may be due to the high buffer capacity of goat milk, which may resist change. As stated by Ma et al. (2023), the normal pH value indicates that there is no sign of mastitis infection in a given specific sample. In general, management systems are one of the most important factors influencing milk yield and chemical properties, particularly feeds with high intake, palatability, and crude protein content (Islamiyati et al. 2015). It is critical to provide dairy goats with a multi-nutrient feed supplement made from locally available feedstuffs to correct the nutrient problem. An important factor in optimizing rumen fermentation systems is the synchronization of energy and protein availability in the rumen.

The period’s effect on milk’s chemical composition for fat, density, SNF, lactose, and protein was presented in the study (Table 5). According to the current study, there was no statistically significant difference in chemical milk composition across all parameters. This result indicates that the period of milking has an effect on milk chemical composition, particularly milk fat and milk protein, and that goat feed containing Grewia tembensis in experimental feed T2 shows high milk fat and protein content during the decline of milk yield at the later stage of this experiment. This supports the findings of Makun et al. (2013), who found that during the decline of milk production at the late stage of lactation, there was a high milk fat and protein content, whereas during the early to mid-lactation, where milk production was high, the protein content and fat were low.

4. Conclusion

The study demonstrates that supplementing Hermosa sidoides and Grewia tembensis foliage in Somali lactating goat diets improves milk yield and composition, assisting small flock herders in correcting low-quality feeds. Milk yields were highest for Hermosa sidoides, while Grewia tembensis had higher levels of fat, protein, and SNF. Grewia tembensis’ fibre fraction has minimal effect on milk production due to its low intake. Supplementing goats with Hermosa sidoides and Grewia tembensis can improve milk yield, chemical composition, and profitability. The study shows that goats supplemented with Hermosa sidoides, Grewia tembensis foliage, and maize stover improve milk yields and chemical compositions under arid and semi-arid conditions. Small flock holder producers should learn about the importance of Hermosa sidoides foliage for improving daily milk yield and chemical composition of goat milk, especially during dry seasons. This study concluded that capacity building and raising awareness are critical for feed conservation and crop residue utilization, during dry periods, and replacing concentrate or browse plants with more sustainable alternatives.

Author contributions

Jarso T: methodology, validation, formal analysis, investigation, data curation, and writing the original draft. Roba J: conceptualization, methodology, resources, investigation. Yilkal: investigation. Seifu B reviews, edits, and supervises.

Public interest statement

The availability of feed and current utilization are areas that need to be better understood to better focus on what options exist to provide sufficient feed resources and alternative nutritional aspects of feeds throughout the dry and rainy seasons by raising pastoralist awareness and informing policymakers about what is available on the ground. Furthermore, goat owners must acknowledge that the evolution of non-conventional feeding practices has had an impact on goat production. These findings will contribute to an enhanced feeding system, which is crucial for goat farmers to maximize production because it makes the feed situation in the study area available.

Statement on animal welfare

The authors confirm that they followed the journal’s ethical policies, as stated on the author guidelines page, and that they followed EU standards for the protection of animals used for scientific purposes and feed legislation.

Disclosure statement

No potential conflict of interest was reported by the author(s).