The Effects of Jojoba Meal Supplementation on the Performance and Health of Nursing Awassi Ewes and the Pre-Weaning Growth of Their Lambs

Abstract

Utilizing agro-industrial by-products to feed livestock is crucial for environmental protection and, simultaneously, lowering production and feeding costs. In light of these aims, in this study, two trials were conducted to evaluate the impact of jojoba meal (JJM) on Awassi ewes’ milk properties, nutrient intake, digestibility, and the pre-weaning growth of their nursing lambs. In the first trial, 22 Awassi ewes were divided equally between two experimental diets at random (11 ewes per diet): 0% JJM (CON) and 15% JJM (JJM15) of dietary dry matter (DM). In the second trial, 10 ewes were randomly selected (5 ewes/diet) to assess nutritional digestibility and N balance. The results of trial 1 showed that neutral detergent fiber (NDF), acid detergent fiber (ADF), and ether extract (EE) intake values were greater (p ≤ 0.02) in the JJM15 group compared to the CON group. The total gain and average daily gain (ADG) of the lambs in the JJM15 group were significantly higher compared to those of the CON group (p < 0.05). The average milk yield of nursing ewes was similar between the two dietary groups (p ˃ 0.05). The percentage and yield of solids-not-fat (SNF) in the JJM15 group were significantly higher compared to the CON group. The other milk components, including protein, lactose, fat, and total solids yields, were similar between the dietary groups (p ˃ 0.05). The milk production cost was significantly lower for the JJM15 diet than the CON diet (p = 0.004). Triglyceride levels were lower (p = 0.001) in the JJM15 diet group than in the CON diet group. In trial 2, nutrient digestibility and N balance were not affected (p ≥ 0.073) by the consumption of JJM15. In conclusion, JJM at 15% of dietary DM resulted in no negative effects on the health, performance, or milk quality of Awassi ewes. Most significantly, by lowering the cost of production, our results appear to indicate that this dietary supplement improves economic efficiency.

1. Introduction

Small ruminant production is a crucial component of Jordan’s agricultural system. The sheep population of Jordan is estimated at approximately 3 million, with sheep significantly impacting the socioeconomics, poverty alleviation, and food security of rural smallholders [1]. Small ruminant production in arid and semi-arid environments, particularly in Jordan, has been mainly constrained by feed shortages, rangeland shrinkage, and the high cost of conventional feeds [2]. Considering these issues, research into alternative feeds in low-input production systems, such as those in Jordan, must be prioritized to ensure the sustainability of small ruminant production.

Jojoba, Simmondsia chinensis L., is a perennial shrub that belongs to the Simmondsiaceae family [3,4]. It is well suited to growth in arid and semi-arid environments [5]. This shrub is tolerant to various climatic conditions and may be grown in harsh environments [6]. It is cultivated in numerous countries worldwide, including Jordan [6,7,8,9]. In 2023, approximately 307 ha of jojoba seeds were harvested around the globe, with total production reaching 144.36 tons [10]. On a dry matter (DM) basis, jojoba plant seeds contain approximately 40–50% oil [11]. The remaining jojoba meal (JJM) is obtained once the oil has been extracted from the jojoba seeds [12,13]. Different oil extraction methods are employed to produce JJM, including mechanical pressing, solvent extraction, and leaching [14]. Based on the results of Elsanhoty et al. [13], JJM is rich in crude protein (CP) content that varies from 26% to 33% of dry matter (DM) and contains high levels of dietary fiber, making it an advantageous alternative feed for animals. Despite these advantages, JJM is challenging to utilize as animal feed due to anti-nutritional components such as simmondsin, simmondsin-2-ferulate, phenol, and phytic acid [13]. Simmondsin and its derivatives constitute roughly 5–6% of JJM [15], which decreases body weight, suppresses food intake, and alters biochemical parameters [16,17,18,19]. In addition, JJM contains another secondary metabolite, namely, tannins, which are detected in the range of 1.50% to 2.57% [20]. Owing to their anti-nutritional and bioactive properties, tannins have been reported to influence animal performance, nutrient metabolism, and product quality [21]. However, the influence of dietary tannins on ruminant performance can be affected by numerous factors such as animal age, species, breed and level of inclusion, feeding time, and dietary composition [21]. After evaluating JJM in comparison with some other plant protein sources with regards to protein content, digestibility, energy value, and amino acid profile, Motawe [22] concluded that JJM is a beneficial feed once subjected to detoxification. In a previous study by Abdel-Wareth et al. [3], the authors found that including JJM seed oil in the diet of broilers improved broiler growth performance and meat quality under hot climatic conditions. In the study by Abd-Elazem [23], the authors found that feeding JJM-treated meal to growing female Barki lambs improved their daily gain and final body weights. In contrast, El-Kady et al. [24] stated in their study that untreated JJM shows a decreased likelihood of becoming an important feed ingredient for productive livestock owing to the significant negative effects of defatted JJM on the feed intake, gain, and physiological and endocrinological functions of lambs. In the study by Obeidat et al. [25], the authors reported that while the lambs’ performance, carcass quality, and general health seemed to be unaffected by the addition of JJM to their diet, the use of this feed resulted in improved economic efficiency. In another study involving sheep, it was observed that the addition of treated JJM to the diets of sheep led to improved nutrient digestibility, general animal health, and viability, in addition to improvement in metabolic processes [26]. Farghaly et al. [27] found in their study that while feeding growing lambs a diet containing 9% JJM resulted in higher economic efficiency, reducing the levels of JJM in their diets improved digestibility, daily gain, and some carcass traits. The results of a study by Nasser et al. [28] showed that substituting cottonseed meal with 33% JJM for growing lambs resulted in better results compared to the other replacement levels (50% and 100%) regarding feed conversion and economic efficiency.

The level of JJM included in the diet is crucial, as it can affect the efficacy of JJM in sheep nutrition. The hypothesis in this regard is that inclusion of up to 15% JJM in Awassi ewes’ diets during the nursing period will impact health, feed intake, and digestibility, resulting in different levels of growth, milk, and economic performance. There is a lack of studies in the literature addressing the response of nursing Awassi ewes to diets containing JJM. In light of this gap, this study was conducted to assess how the inclusion of a specified amount of JJM in place of soybean meal and barley grain during nursing affects the nutrient intake, digestibility, and economic and milk production of Awassi ewes. In addition, the growth performance of their suckling lambs was investigated.

2. Materials and Methods

2.1. Animals and Ethical Approval

Before the commencement of the study, a veterinarian examined the overall health of the ewes and the condition of their udders. The study was performed at Jordan University of Science and Technology (JUST), and study approval was obtained from the Institutional Animal Care and Use Committee (approval code: 16/04/12/502A).

2.2. Diets and Experimental Design

In this study, lasting a total of 70 days (63 days for trial 1 and 7 days for trial 2), two trials were carried out to assess the impact of non-detoxified (untreated) JJM on Awassi ewes’ milk properties, nutrient intake, and digestibility, in addition to the pre-weaning growth of their nursing lambs. During the preliminary period, estrus synchronization involving intravaginal sponges was applied to the 60 ewes to guarantee lambing consistency among the experimental animals.

2.3. Trial 1

From the total number of synchronized ewes, 22 Awassi ewes (weighing on average 58.6 ± 2.01 kg at birth, aged 4.5 to 5.5 years at the start of the study) with similar performance characteristics were purposively selected, considering the criterion that each ewe must be nursing a single lamb, in order to guarantee consistency in maternal load and lessen variability induced by litter size. The 22 Awassi ewes with their single lambs were used as experimental units and were randomly assigned to one of two experimental diets in a completely randomized design (11 ewes per diet): 0% JJM (CON) and 15% JJM (JJM15) of dietary dry matter (DM) to replace barley grain and soybean meal. The chemical composition and components of the diets are illustrated in

Table 1. Ingredients and chemical composition of diets containing jojoba meal (JJM) fed to Awassi ewes.

Item	Experimental Diets 1
	CON	JJM15	JJM
Ingredients (g/kg DM)
Barley grain, whole	500	430
Soybean meal, 440 g/kg CP (solvent)	160	100
Jojoba meal	0	150
Wheat straw	320	300
Salt	10	10
Limestone	9	9
Vitamin-mineral premix 2	1	1
Cost ($US/1000 Kg) 3	457	387
Nutrients
Dry matter (g/kg DM)	915	913	854
Crude protein, (g/kg DM)	152	151	267
Neutral detergent fiber, (g/kg DM)	348	363	334
Acid detergent fiber, (g/kg DM)	156	179	248
Ether extract, (g/kg DM)	9	26	117
Metabolizable energy, Mcal/kg	2.25	2.26	2.67

¹ CON (control diet); JJM15 (150 g/kg of dietary dry matter). ² Composition per kg contained (vitamin A, 600,000 IU; vitamin D3, 200,000 IU; vitamin E, 75 mg, vitamin K3, 200 mg; vitamin B1, 100 mg; vitamin B5, 500 mg; lysine 0.5%; DL-methionine, 0.15%; manganese oxide, 4000 mg; ferrous sulphate, 15,000 mg; zinc oxide, 7000; magnesium oxide, 4000 mg; potassium iodide, 80 mg; sodium selenite, 150 mg; copper sulphate, 100 mg; cobalt phosphate, 50 mg, dicalcium phosphate, 10,000 mg. ³ Calculated based on prices of 2025.

.

Together with their single lambs, the ewes were kept in 22 separate shaded pens measuring 0.75 × 1.5 m and given isonitrogenous diets. The experimental units were given unlimited access to food and water through plastic troughs in the enclosures, and daily nutrient consumption was recorded. The trial lasted 63 days, during which the animals were given time for adaptation over the first 7 days and data were collected over the subsequent 56 days. The ewes were fed their experimental diets once daily at 8:00 a.m. during the trial, and they were given unlimited access to water. The diets were formulated to provide the ewes with 15.1% crude protein (CP), which is appropriate for nursing ewes [29]. Feeders were developed to provide 110% of daily needs to minimize feed waste. Feed refusals and daily feed samples offered were recorded to measure the amount of feed consumed.

2.3.1. Ewe and Lamb Performances

After the adaptation period, the animals’ body weight (BW) and milk yield were assessed at 8:00 am on days 0, 14, 28, and 56 of the experimental period. To assess milk production, the lambs were kept away from their mothers for 4 h. Thereafter, milk secretion was triggered by the intravenous administration of 0.75 mL oxytocin at the beginning and end of the 4 h, with the ewes milked by hand thereafter. The total daily milk yield was calculated over a 24 h period, following the method described by Obeidat [30]. A 125 mL milk sample was procured from each ewe and assessed for total solids (TS) (using a forced-air oven set at 55 °C), CP (using the Kjeldahl technique; N × 6.38) and fat using the Gerber technique (Gerber Instruments, K. Schnider and Co. AG; 8307 Langhag, Effretikon, Switzerland). Milk lactose content was measured using Milk Scan (MASTER ECO, Milkotester Ltd., 9 Todor Kableshkov Str., 4470 Belvo, Bulgaria). Feed efficiency (kg of DM intake–kg of milk yield) was calculated by dividing DM intake by milk yield. Following the method of Baldi et al. [31], the formula used to determine the energy value of the milk (MEV; kilocalories per kilogram) was as follows: 203.8 + (8.36 × fat%) + (6.29 × protein%). The energy-corrected milk calculation formula (ECM; kg/d) was as follows: 0.3246 × milk yield + (12.86 × fat yield) + (7.04 × protein yield). Diet samples and feed refusals were subjected to chemical analysis. The samples were dried in a forced-air oven set to 105 °C overnight to estimate the DM content [32]. The Kjeldahl technique was used to calculate the crude protein (CP) concentration (N × 6.25), and the Soxtec method was used to determine ether extract (EE) based on AOAC [32] methods. Neutral detergent fiber (NDF) and acid detergent fiber (ADF) were analyzed using an ANKOM2000 fiber analyzer (ANKOM Technology Corp., Fairport, NY, USA) based on the procedures of Van Soest et al. [33]. Nutrient consumption was calculated by subtracting cases of feed refusal from the amount of supplied feed.

2.3.2. Blood Analysis

Before feeding, blood samples were drawn from the ewes’ jugular vein at 8:00 a.m. at the beginning and end of the trial using plain vacutainers. The blood samples were then centrifuged at 1008× g for 15 min at room temperature to obtain blood plasma. Thereafter, serum samples were kept at −20 °C to measure the biochemical parameters.

2.4. Trial 2

Nutrient Digestibility

At the end of the first trial (after the 63 days of trial 1), 10 ewes from trial 1 (weighing on average 55.6 ± 1.96 kg at the end of trial 1) were randomly allocated, at 5 ewes/diet, to one of the two diets used in trial 1 and housed in separate metabolic crates (1.0 m × 0.8 m) to assess nutritional digestibility and N balance. The remaining ewes and lambs were returned to the flock at Animal Farm. While housed in the metabolic cages, each ewe was milked daily to maintain production levels. This milk was not included in the study data. Over the 4-day data collection period, preceded by 3 days for adaptation, feed intake, orts, and fecal output were assessed. Daily, 10% of each ewe’s feces was gathered and combined for a subsequent chemical analysis. To evaluate DM content, dietary and fecal samples were dried for a few days at 55 °C in a forced-air oven until they reached a consistent weight. Thereafter, the samples were pulverized in a Wiley mill (Brabender OHG, Kulturstrase 51–55, type 880845, Nr 958084, Duisburg, Germany), run through a 1 mm screen, and then placed in plastic bags at room temperature for further analysis. Using the methods described by the Association of Official Analytical Chemists (AOAC), an approximation analysis of the ground samples’ DM, CP, NDF, ADF, and EE contents was carried out. In this study, the procedures used for assessing feed intake, leftovers, fecal output, and nutritional digestibility were performed according to those employed by Obeidat et al. [34]. Urine samples were collected from each ewe using a urine collection container with 50 mL of 6 N hydrochloric acid to prevent ammonia losses. The samples were then weighed and recorded, and 5% of the urine was used as subsample to determine the N content. Urine subsamples were then mixed, and the N content was calculated using the Kjeldahl method. Nitrogen intake was calculated as DM intake multiplied by the N content of each diet. The nitrogen loss in the urine and feces was obtained by multiplying the respective nitrogen content by the output of the urine and feces. Nitrogen excreted in milk was calculated on day 56 of trial 1 and included in the data for calculating the nitrogen retention. Then, retained N (g/day) was estimated by subtracting fecal, urinary output, and nitrogen excreted in milk from the N intake. Nitrogen retention (g/100 g) was estimated by dividing retained nitrogen by nitrogen intake recorded.

2.5. Data Analysis

All data were analyzed using SAS’ MIXED procedure in a completely randomized design in SAS software (Version 8.1, 2000, SAS Institute Inc., Cary, NC, USA) [35], with diet treatment as the fixed effect and ewes receiving treatment as the random effect. The assumptions of residual homogeneity and normality were tested before model application. The variance analysis for repeated measures was applied to examine milk production and ewe and lamb body weights. The diet, week, and treatment–week interaction were all considered in the model (i.e., animals’ body weights and milk production on days 0, 14, 28, or 56). The only specified effect of treatment was on ewe and lamb body weights, nutritional intake, milk composition and yield, and diets. For the serum blood analysis, day 0 was used as a covariate. A significant difference was determined with a p-value of ≤0.05.

3. Results

JJM and the experimental diets were chemically analyzed, with the results presented in Table 1. Data from the JJM analysis showed that it contains a greater amount of CP (26.7%), ADF (24.8%), EE (11.7%), and ME (2.670 kcal/kg) than the experimental diets. Both experimental rations (CON and JJM15) were formulated to be iso-nitrogenous with 16% CP of dietary DM. The diets contained similar amounts of DM, NDF, and ME, with greater ADF and EE content in the JJM15 diet. The ration cost was 15.3% cheaper for JJM15 than for the CON diet.

The results of the experimental diets on the nutrient intake of Awassi ewes are presented in

Table 2. Effects of feeding jojoba meal (JJM) on nutrient intakes of Awassi ewes.

Item	Experimental Diets 1
	CON (n = 11)	JJM15 (n = 11)	SED 2	p-Value
Nutrient intake
Dry matter, g/d	1782	1884	61.4	0.127
Crude protein, g/d	269	287	9.3	0.092
Neutral detergent fiber, g/d	621	683	21.8	0.017
Acid detergent fiber, g/d	278	338	10.3	0.000
Ether extract, g/d	17	48	1.2	<0.0001
Metabolizable energy, Mcal/day	4.0	4.3	0.14	0.104

¹ CON (control diet); JJM15 (150 g/kg of dietary dry matter). ² SED (standard error of the difference).

. No differences were observed for DM and CP nutrient intake (p > 0.05) between the two dietary groups. However, NDF, ADF, and EE intake values were found to be greater (p ≤ 0.02) in the JJM15 group compared to the CON group.

The animals’ body weight responses to the JJM diet are shown in

Table 3. Effects of feeding Jojoba meal (JJM) on ewes’ body weight change and pre-weaning growth of their suckling lambs.

Item	Experimental Diets 1
	CON (n = 11)	JJM15 (n = 11)	SED 2	p-Value
Ewes
Initial weight, kg	58.3	58.8	2.01	0.792
Final weight, kg	55.1	56.1	1.96	0.621
Body weight change, kg	−3.2	−2.7	0.73	0.545
Lambs
Initial weight, kg	5.3	5.3	0.47	0.970
Weaning weight, kg	16.9	17.8	0.60	0.175
Total gain, kg	11.7	12.6	0.40	0.046
Average daily gain, g	208.1	224.1	7.08	0.048

¹ CON (control diet); JJM15 (150 g/kg of dietary dry matter). ² SED (standard error of the difference).

. The inclusion of JJM did not have any significant effects on the live weight of lactating ewes, with a decrease of 5.8% and 4.8% in the average final BW of the ewes in the CON and JJM15 treatment groups, respectively (p ≥ 0.50). The weaning BW of the lambs was found to be similar between the two diets. However, the total gain and ADG of the lambs in the JJM15 group were greater than those of the CON group (p < 0.05).

Information on the impact of JJM on the milk production and composition of nursing Awassi ewes is presented in

Table 4. Effects of feeding Jojoba meal (JJM) on milk yield and composition and efficiency of Awassi ewes.

Item	Experimental Diets 1		SED 2	p-Value
	CON (n = 11)	JJM15 (n = 11)		Diet	Week	Interaction
Milk production, g/d	1909	2103	108.9	0.091	0.001	0.171
Milk composition (%)
Fat	7.80	7.60	0.250	0.418	0.018	0.953
Protein	6.18	6.23	0.059	0.473	0.021	0.079
Lactose	4.61	4.69	0.053	0.140	0.304	0.202
Solid-not-fat	11.31	11.49	0.079	0.034	0.127	0.073
Total solids	19.11	19.09	0.258	0.917	0.037	0.779
Milk composition (g/d)
Fat	149.01	159.63	10.400	0.320	0.143	0.387
Protein	118.22	131.16	7.109	0.084	0.001	0.097
Lactose	88.32	98.68	5.586	0.079	0.001	0.197
Solid-not-fat	215.87	241.47	11.837	0.043	0.005	0.516
Total solids	364.88	401.09	21.500	0.108	0.020	0.427
MEV 3, kcal/kg of milk	307.93	306.47	2.210	0.517	0.006	0.897
ECM 4, kg/d	3.37	3.66	0.213	0.186	0.023	0.238
Efficiency parametrs
Feed efficiency (kg DM intake: kg milk)	0.95	0.91	0.051	0.380	-	-
Cost, $US/kg milk	0.44	0.35	0.023	0.004	-	-

¹ CON (control diet); JJM15 (150 g/kg of dietary dry matter). ² SED (standard error of the difference). ³ MEV (milk energy value). ⁴ ECM (energy correct milk).

. The average milk yield of nursing ewes was similar between the two dietary groups (p ˃ 0.05). There was no treatment–week interaction effect on milk yield and composition (p ≥ 0.073). As demonstrated by the results of the chemical analysis, the percentages of fat, protein, lactose, and TS in the milk samples were comparable between the two treatment groups. However, the solids-not-fat (SNF) percentage in the JJM15 group was significantly higher compared to that in the CON group (p = 0.03). With respect to the daily yield of milk components, only the percentage of SNF (g/d) was significantly higher in the JJM15 group compared to the CON group (p = 0.04). The other milk yield components, including the protein, lactose, fat, and TS yields, were similar between the dietary groups (p ˃ 0.05).

The efficiency of nursing ewes in converting the consumed feed into milk was similar between the two dietary groups. However, the milk production cost was significantly lower for the JJM15 diet than for the CON diet (p = 0.004). Regarding the milk energy content of lactating ewes, no differences were observed in the ECM and MEV values between the two diets.

As illustrated in

Table 5. Effects of feeding Jojoba meal (JJM) on nutrient digestibility and N balance of Awassi ewes.

Item	Experimental Diets 1
	CON (n = 5)	JJM15 (n = 5)	SED 2	p-Value
Nutrient intake
DM, g/d	1873	1822	110.7	0.668
CP, g/d	285	275	17.0	0.601
Digestibility, %
DM	79.4	81.8	2.12	0.315
CP	81.9	82.6	2.38	0.773
NDF	64.9	66.8	2.35	0.479
ADF	58.8	60.2	2.51	0.594
EE	85.2	88.3	1.27	0.073
N balance
N intake, g/d	45.5	44.0	2.79	0.616
N excreted in milk, g/d	13.4	15.1	0.72	0.073
N lost in feces, g/d	8.2	7.6	1.01	0.550
N lost in urine, g/d	9.5	8.9	0.99	0.566
Retained N, g/d	14.4	12.5	2.18	0.417
N retention, %	31.6	27.9	3.58	0.361

¹ CON (control diet); JJM15 (150 g/kg of dietary dry matter). ² SED (standard error of the difference).

, Awassi ewes fed the experimental diets were found to have similar (p ≥ 0.073) DM and CP nutrient intake, nutrient digestibility and N balance throughout the experimental period.

The concentration of triglycerides was lower (p = 0.001) in the JJM15 diet group than in the CON diet group, as shown in

Table 6. Effects of feeding Jojoba meal (JJM) on blood metabolites of Awassi ewes.

	Experimental Diets 1
Item 3	CON (n = 11)	JJM15 (n = 11)	SED 2	p-Value
Urea N (mg/dL)	28.0	26.5	1.70	0.380
Glucose (mg/dL)	59.9	71.5	9.65	0.259
Cholesterol (mg/dL)	42.0	40.8	3.21	0.720
Triglycerides (mg/dL)	8.4	5.2	0.66	0.001
HDL (mg/dL)	17.6	19.6	1.74	0.257
LDL (mg/dL)	22.8	20.2	2.98	0.398
AST (IU/L)	50.3	44.6	12.95	0.668
ALT (IU/L)	5.2	4.5	1.65	0.668
ALP (IU/L)	63.6	60.6	16.71	0.898
Creatinine (mg/dL)	0.9	0.7	0.11	0.214

¹ CON (control diet); JJM15 (150 g/kg of dietary dry matter). ² SED (standard error of the difference). ³ HDL (High-density lipoprotein); LDL (Low-density lipoprotein); AST (Aspartate aminotransferase); ALT (Alanine aminotransferase); ALP (Alkaline phosphatase).

. The addition of JJM had no effect (p ≥ 0.214) on other serum constituents, such as blood urea nitrogen, cholesterol, glucose, HDL, LDL, creatinine, AST, ALT, and ALP.

4. Discussion

In this study, the CP content of the JJM noted in the present study was fairly comparable to the results of other studies [22,27,36]. Based on the findings of Pérez-Gil et al. [37] and Motawe [22], extracting the oil from jojoba seeds results in a meal that contains higher CP and crude fiber (CF) content and lower EE and ME content. However, in this study, adding JJM to the experimental diet increased its EE content. This effect was most likely induced by the fact that jojoba is a high-oil plant that retains its oil content even after oil extraction, which increases its EE content. The extraction method, seed pretreatment technique, and extraction conditions can affect the efficiency of oil extraction, resulting in variations in JJM nutrient content [14]. In addition, the diet containing JJM was more cost-effective than the control diet as feed costs were reduced by roughly 15.3%. This cost reduction was the result of a decrease in the proportion of expensive ingredients, namely, barley grain and soybean, to 14% and 38%, respectively (Table 1). This finding is in accordance with those of previous studies by Obeidat et al. [25], Abdou and El-Essawy [38], and Farghaly et al. [27], who also reported reduced feed costs when JJM was added to formulated diets. From an economic perspective, using JJM as an alternative feed component could drive broader adoption among farmers and reduce reliance on conventional feeds, improving farm profitability, sustainability, and resilience to feed price fluctuations and consequently having a positive effect on the environment.

Excluding NDF, ADF, and EE, the feed intake of the ewes remained unaffected in the current study. The increased intake of NDF, ADF, and EE may be explained by their higher levels in the JJM (JJM15) diet compared to the CON diet. In accordance with our results, Obeidat et al. [25] found that only the ADF and EE intake of Awassi lambs increased when their diet was supplemented with 10% JJM. However, the authors of other studies found that the addition of untreated JJM to their experimental diets decreased feed intake [17,27,38,39]. The authors of the aforementioned studies found that exposure to the JJM diet or increasing the level of JJM in the diets reduced the amount of feed consumed by the animals. This alteration is linked to anti-nutritional factors such as traces of simmondsin and other secondary metabolites that adversely affect the palatability of the diets and decrease feed intake. However, based on the findings of Manos et al. [36], ruminants are more tolerant to anti-nutritional factors due to the detoxifying ability of microorganisms in the rumen. Moreover, El-Kady et al. [24] found in their study that the feed intake of growing Ossimi lambs was negatively affected by the addition of untreated JJM in the diet at levels of 10, 20, and 30%. In comparison with the results of El-Kady et al. [24], in our investigation, we found no negative effects on feed intake or nutrient digestibility. This variation between the studies could be ascribed to several possible confounding factors such as species difference, the ages and weights of the animals, the jojoba meal processing method, the inclusion level, the diet formulation, and the sufficiency of the ruminal adaptation period.

In the present study, JJM inclusion did not improve the growth performance of the lactating ewes; the performance of the growing lambs fed the JJM15 diet was enhanced, however. The improved daily gain (224 g/d vs. 208 g/d) of the lambs could be ascribed in part to the improved milk yield and milk composition, particularly the solids-not-fat of the nursing ewes fed the JJM15 diet compared to the CON diet (Table 4). The increased milk SNF content may have improved nutrient availability, particularly protein and lactose yields necessary for tissue development and energy supply, which would have improved early lamb growth. It is important to note that the lambs in this study depended only on their mother’s milk for growth. In a previous study by Khalel et al. [17], the authors reported that the inclusion of untreated JJM decreased the final, daily, and total gain of lambs compared to the control diet and diets containing treated JJM. The authors of another study found that the addition of untreated JJM to lambs’ diets did not affect their growth performance in terms of final body weight and daily and total gain [38]. Moreover, based on the findings of El-Kady et al. [24], the average daily gain of growing lambs was lower for those fed diets containing different levels of untreated JJM compared to the control diet. Furthermore, the results of a previous study showed that the weight gains of ewes were significantly reduced with increasing levels of JJM in their diets from 0 to 5 and 10% [36]. As a further illustration, in a study by Abdou [26], the authors found no significant difference in the total average daily gain of lambs among all diets containing different levels of treated JJM with fungi (0, 7, and 14%). Conversely, in a study by Abd-Elazem [23], the authors observed improvement in the average daily gain and total gain of lambs with increasing levels of treated JJM with fungi in their diets (0, 7, and 14%).

The inclusion of JJM at a level of 15% in the ewes’ diet did not adversely affect the average milk yields, percentages, and yields of milk components (Table 4). However, it was found to increase the yield and percentage of SNF. The increase in the SNF value could be related to the numerical increase in protein (131 g/d) and lactose (99 g/d) yields in milk or nutrients and mineral contents of JJM [12,36,40], which improved nutrient availability, impacting SNF in milk. Numerically, the JJM15 diet resulted in greater milk yield (almost 194 g/d) compared to the control diet (Table 4), with a slight difference (about 102 g/d) in terms of daily DMI (Table 2) between the two groups. The primary cause of the lack of change in milk yield and nutrients may be the similarity in the nutrient digestibility of nursing sheep between the two diets (Table 5). Despite the fact that the JJM15 diet contained substantially higher fat content, there was no indication of milk fat decline or decreased nutritional digestibility in the current study. This finding suggests that the elevated fat level, as determined based on EE (48 g/d), was well tolerated and did not affect ruminal fermentation and fiber breakdown. Similarly, by conducting a meta-analysis, Boukrouh et al. [41] demonstrated that the addition of lipid-rich microalgae to the diet of goats enhanced the fatty acid profile and milk composition without negatively impacting digestibility parameters or inducing milk fat decline. Amer et al. [42] reported an increase in milk production in doe rabbits when biologically treated JJM was included in their diets compared with the control group. In the current study, no differences were observed across the dietary groups for the energy efficiency of milk production (MEV and ECM values), which indicated that the JJM15 diet provides ME (Table 2) and digestibility (Table 5) similar to the CON diet. Including 15% JJM in the ewes’ diet had no effect on feed efficiency, as measured by the ratio of milk output to DM consumption. Nonetheless, compared to the CON diet, the JJM diets resulted in significantly lower milk production expenses. The improvement in the diet formulation through the addition of inexpensive substitute feed sources, particularly JJM, to the diet may be the factor responsible for the decrease in milk production costs. Similar results were noted when JJM was added to the diet; the cost of gain decreased and the economic efficacy improved [15,17,25,26,38,42].

Nutrient digestibility is a crucial factor influencing animals’ performance. In the current study, we found no significant differences in nutrient digestibility between the dietary groups. This finding may be derived from the diets’ comparable chemical compositions. Similar findings were reported in the study by Obeidat et al. [25], who found that JJM did not improve nutrient digestibility when added to lamb diets at a level of 10%. Moreover, El-Kady et al. [24] reported similar digestion coefficients among dietary groups when defatted, untreated JJM was included in the diet of lambs at levels of 0, 10, 20, and 30%. However, the results of previous studies [17,38] have shown that lambs and sheep fed untreated JJM recorded the lowest digestibility values compared to those in the control and JJM-treated groups. In trial 2, although it is common to use such a small sample size in ruminant research due to various constraints such as logistical, ethical, and financial considerations, one limitation of conducting a nutrient digestibility trial is the relatively small sample size (five ewes per diet), which may limit the statistical power of the study, particularly in detecting subtle differences. In light of this limitation, a larger sample size should be considered in future studies.

The N balance parameters in this study remained unaffected by the addition of JJM. This finding may partially reflect how comparable the two diets are in terms of CP consumption and digestion. Likewise, Obeidat et al. [23] highlighted in their study that the N balance of lambs remained unaffected by the consumption of a diet containing JJM at a rate of 10%. However, Khalel et al. [17] noted in their study the lower nitrogen intake, nitrogen balance, and biological value of dietary N in sheep fed a diet containing untreated JJM compared to the control diet and a diet containing treated JJM. Furthermore, Abdou [15] noted in their study that while the percentage of treated JJM increased in lamb diets, the percentage of nitrogen balance also increased.

The determination of blood metabolite levels is essential in assessing overall animal health and nutrient metabolism. The levels of AST, ALT, and ALP enzymes in the blood are key indicators of liver function. The levels of waste products in serum (urea N and creatinine) are used to assess kidney function. Other serum metabolites, including glucose and lipid types (cholesterol, triglycerides, LDL, and HDL), are used to determine energy and lipid metabolism. In this study, excluding triglycerides, the addition of JJM did not affect the other blood metabolites (Table 5). The significant decrease in triglyceride levels in ewes fed JJM15 could be ascribed to the saponin compounds in JJM that may particularly affect intestinal triglyceride absorption by inhibiting pancreatic lipase activity [43]. Pancreatic lipase can hydrolyze dietary fats into glycerol and fatty acids for subsequent absorption [44]. Saponins can also alter the rumen environment by modifying ruminal metabolites and the microbial community [45]. Although we did not assess the jojoba meal’s saponin content in the present study, it is widely documented in previous studies that jojoba meal contains saponins [26,38]. However, ruminants’ response to saponins is influenced by different factors, including dietary composition, their levels, and their sources [46]. To confirm this link, saponins should be quantified in future studies. The decrease in blood triglycerides could also be explained by lactogenesis, milking, and the mammary metabolism during suckling (e.g., reduction of triglyceride-rich lipoproteins of β mobility) [47]. However, serum biochemical analysis results by Obeidat et al. [25] showed that only HDL levels increased in lambs fed a diet containing 10% JJM compared to the control. In a study by Abd-Elazem [23], the authors also found no change in urea nitrogen, triglyceride, and liver enzyme concentrations; however, they found a significant decrease in the levels of creatinine and total lipids, in addition to a significant increase in glucose levels when the treated JJM was added at varying levels (0, 7, and 14%). Moreover, in another study, Abdou and El-Essawy [38] reported no significant variations in urea nitrogen, creatinine, liver enzyme, total lipid, and triglyceride levels in lambs when untreated JJM was added to their diet. Furthermore, in their study, El-Kady et al. [24] detected no observable changes in glucose, urea and creatinine concentrations in lambs when untreated JJM was added to their diet at varying levels (0, 10, 20, and 30%); in comparison, the levels of total cholesterol, triglycerides, HDL-cholesterol, AST, and ALT were significantly higher in lambs fed a 30% JJM diet. In one study by Abdou [15], the results showed that urea nitrogen and creatinine levels were similar among the different dietary groups containing treated JJM at different levels (0, 10, 20, and 30%); in comparison, liver enzyme levels (ALT and AST) were significantly lower in the 10% JJM diet group. In another study by the same author [26], the results showed a significant increase in urea nitrogen and total lipid levels and a stable level of creatinine and liver enzymes (ALT and AST) when the treated JJM was added at varying levels (0, 7, and 14%). In a previous study by Cokelaere et al. [48], the authors found that important biochemical parameters for kidney (urea nitrogen and creatinine) and liver function (ALT and AST) were all within normal limits in rats when treated with 3% JJM feed supplementation.

5. Conclusions

In this study, we assessed the effect of including non-detoxified (untreated) JJM meal in Awassi ewes’ diet. Our study findings show that the addition of 15% JJM resulted in no negative effects on the nutrient digestibility, health, or milk characteristics of ewes or the growth rate of their lambs. However, this inclusion improved the profitability of sheep farming by lowering production costs. Further investigations are warranted in the future to investigate the effects of treated (detoxified) JJM in different proportions on sheep milk performance.