Feeding Sodium Hydroxide-Treated Almond Hulls to Assaf Sheep: Effects on Chemical Composition, Nutrient Digestibility, and Zootechnical Performance

Abstract

Feeding accounts for approximately 70% of total costs in livestock production, underscoring the need for cost-effective and high-quality alternative feed sources. Almond hulls (AHs), a byproduct of the almond processing industry, represent a promising option due to their availability and potential nutritional value. Moreover, their inclusion in animal diets contributes to a reduction in environmental waste associated with their disposal. This study examined the effects of incorporating 4% sodium hydroxide (NaOH)-treated AHs into the diets of Assaf sheep (rams, ewes, and growing lambs) on feed utilization and animal performance. The experiment evaluated the chemical composition of AHs, nutrient digestibility, sexual behavior and semen quality in rams, milk composition in ewes, and the performance of growing lambs fed diets with increasing levels of inclusion of AHs. A total of 60 ewes and 21 rams were randomly assigned to one of three treatment groups, receiving diets containing 0%, 20%, or 40% AHs. NaOH treatment reduced the concentrations of organic matter and fiber fractions, while increasing the crude protein concentration of AHs (p < 0.01). Diets containing AHs did not affect nutrient digestibility (p > 0.05). Feeding a diet with 40% Na-OH-treated AHs significantly improved the daily weight gain (p = 0.002) of growing lambs up to 70 days after birth, and enhanced (p < 0.05) the libido, scrotal circumference, and semen quality of mature rams. In addition, ewes fed a diet containing 40% AHs showed (p < 0.05) improved fertility, prolificacy, and milk quality. NaOH-treated AHs are a cost-effective and sustainable feed ingredient that can improve reproductive performance and milk production, thereby increasing overall livestock productivity. The 40% inclusion level yielded the most favorable outcomes across all performance parameters evaluated in rams, ewes, and lambs.

1. Introduction

In traditional sheep production systems, feed expenditures may account for up to 70% of total operational costs [1], highlighting the importance of identifying alternative, cost-effective feed resources [2]. The utilization of agricultural byproducts, such as almond hulls (AHs), presents a viable strategy to address feed shortages and can contribute to reducing the environmental impact of the disposal of this waste. Almond byproducts comprise approximately 54% of the whole almond fruit [3].

The almond (Prunus dulcis, synonym of Prunus amygdalus Batsch) is a highly valued drupe. Originally native to Asia, it is now cultivated globally in hot, arid Mediterranean climates, with the USA being the leading producer [4]. The processing of almonds for edible consumption generates substantial quantities of byproducts, including hulls, shells, and skins.

Almond hulls are derived from the drying of the outer mesocarp layer of the almond fruit, which encloses the hard, woody shell. Hulls are abundant byproducts of the almond industry, constituting about 35% of the total almond drupe fresh weight [5]. The nutritional composition of almond hulls is influenced by several factors such as variety, environmental conditions, and cultivation and cropping practices, which affect their physicochemical and phytochemical properties. The sugar content of almond hulls typically ranges from 18% to 30%. Almond hulls have a relatively low protein content (ranging between 2 and 9%), are rich in fiber (ranging from 10% to 25%) [5,6,7], and contain considerable amounts of non-structural carbohydrates (NSCs). In addition, AHs are rich in polyphenols and pigments, which may have antioxidant activity [8].

Several studies have examined the effects of replacing conventional feeds with AHs, demonstrating that AHs can potentially be a safe and effective feedstuff for sheep, goats, lambs and dairy cows, and pigs, with beneficial effects on animal performance and on the quality of both milk and meat [9,10,11,12]. Swanson et al. [13] found that incorporating up to 20% almond hulls into the diets of lactating dairy cows has been shown to sustain high milk yield and enhance milk fat content, although it may lead to a reduction in milk protein concentration. This aligns with previous results reported by Williams et al. [14], who observed that both AHs and citrus pulp can partially replace costly commercial forage in dairy cow diets; although AHs may be less effective than citrus pulp, because feeding AHs tends to reduce both milk yield and milk protein content. Rad et al. [3] and Scerra et al. [8] concluded that urea-treated AHs can replace alfalfa in the diets of fattening lambs without adversely affecting animal performance, thereby representing a safe and viable alternative feed resource for sheep. Additionally, utilizing AHs may contribute to reducing the environmental impact associated with the disposal of this waste. Therefore, further research into the utilization of almond byproducts for the development of innovative animal feedstuffs is warranted. Such effort could help minimize environmental impact, improve farming sustainability, and increase the competitiveness of the almond industry.

To enhance the feeding value of AH, several treatments have been proposed, with sodium hydroxide (NaOH) and urea identified as the most effective methods for improving their ruminal fermentation and degradability. NaOH treatment has been widely used to improve the quality of lignocellulosic plant materials, such as straw or silage, by disrupting lignocellulosic bonds within plant cell walls [15]. Although NaOH treatment is a well-established method for improving the digestibility of fibrous byproducts, concerns have been raised regarding its environmental footprint. However, when applied in controlled amounts, followed by proper neutralization and drying, the environmental impact can be significantly mitigated [16]. Moreover, transforming agricultural byproducts such as AHs into value-added livestock feed contributes to waste reduction and supports sustainable agricultural practices. Ensiling or air-drying the treated material for an adequate period prior to feeding facilitates the dissipation of residual alkali, ensuring safety for both animal health and the environment. When applied under proper management conditions, NaOH treatment remains a practical and effective approach, particularly in low-income and resource-limited settings aiming to improve feed quality and reduce production costs.

NaOH treatment breaks ester linkages between lignin and compounds such as acetic acid, phenolic acids, cellulose, and hemicellulose through a process known as saponification [5,15,17]. This process not only enhances nutrient availability and reduces anti-nutritional factors such as tannins, which may impair feed efficiency, but also enhances the texture of AH, making this feedstuff more palatable and appealing to livestock [18,19].

Therefore, the aim of this study was to evaluate the effects of feeding diets containing 0%, 20%, or 40% NaOH-treated AHs to Assaf sheep (rams and ewes) on (1) nutrient digestibility, sexual behavior, and semen quality in rams; (2) reproductive efficiency and milk production in ewes; and (3) the growth performance of growing lambs. Our hypothesis is that treating AHs with NaOH can enhance the nutritive value of this byproduct, enabling its inclusion in sheep diets at varying levels without compromising zootechnical performance.

2. Materials and Methods

This study was conducted at the Assaf Sheep Governmental Breeding Farm, located in the village of Beit Qad near the Jenin Governorate in Palestine. The farm is located at approximately 32°27′29″ N, 35°19′17″ E, at an altitude of 100–150 m above sea level. The region receives an average annual rainfall of 500–600 mm, with temperatures ranging from 5–10 °C in winter to 30–35 °C in summer. Assaf sheep, the predominant breed in Palestine, were used in the experiments. The study was approved by the Assaf Sheep Governmental Breeding Farm (ethical approval number 1832-2-25).

2.1. Collection of Almond Hulls

Almond hulls, sourced from a private local industry, were collected from various locations across Palestine during August and September 2022, in collaboration with private agricultural companies operating within the Jenin Governorate. The collected almond hulls were sun-dried to reduce moisture content and to ensure adequate preservation. After drying, the hulls were stored in clean plastic bags for later use in various experiments conducted at different times throughout the year.

2.2. Treatments and Chemical Analysis of Almond Hulls

Sun-dried AHs from various varieties were collected and treated with a 4% (w/v) NaOH solution, prepared by dissolving 40 g of technical-grade NaOH beads per liter of tap water, following the procedure described by Lesoing et al. [20]. For the treatment, 1 L of the NaOH solution was added per kg of AH (equivalent to 40 g of NaOH per kg of AH). The materials were thoroughly mixed to ensure complete exposure of the hulls to the alkali, maximizing treatment efficacy. The initial pH of the treated material was approximately 11.5. No rinsing or chemical neutralization procedures were applied. After the alkali treatment, the AHs were air-dried in the shade under adequate ventilation and stored for 40 days, allowing for the gradual evaporation of residual alkali and a progressive decline in pH, thereby minimizing potential risks associated with the inclusion of treated AHs in the diet. Following drying, the treated AHs were stored under appropriate conditions to maintain their quality and ensure their safety as a feed ingredient. All necessary safety precautions were strictly observed throughout the process. This drying and storage phase was crucial to reduce any residual NaOH to a safe level, thereby ensuring the palatability and safety of the feed.

During the feeding trials, animal health was closely monitored. No instances of diarrhea, feed refusal, or abnormal behavior were observed, indicating that the treated AHs were well tolerated by the animals. Samples of both treated and untreated AHs were analyzed to determine their chemical composition. Ash content was measured by incinerating the samples in a muffle furnace at 550 °C for 12 h, following AOAC method ID 942.05 [21]. Crude protein was measured using the Kjeldahl method (ID 954.01), and ether extract (EE) was assessed using diethyl ether in Soxhlet extractors (ID 920.39), following the AOAC protocols [21]. Neutral detergent fiber (NDF) content was determined using α-amylase and sodium sulfite, according to the procedure of Van Soest et al. [22]. Acid detergent fiber (ADF) content was analyzed according to the AOAC [21] method (ID 973.18), with residual ash excluded. Additionally, the concentrations of non-structural carbohydrates (NSCs = 1000 − NDF − CP − EE − ash), cellulose (NDF − ADL), hemicellulose (NDF − ADF), and organic matter (OM = 1000 − ash) were calculated. Acid-insoluble ash (AIA) was determined according to the method described by Liu [23].

2.3. In Vivo Digestibility (Experiment 1)

To evaluate the in vivo digestibility of the experimental diets, 18 Assaf rams, weighing between 100 and 120 kg and averaging two years of age, were randomly allocated into three experimental groups (six rams per group) in a completely randomized design. A sample size of 6 animals per group was determined based on previous studies evaluating digestibility in small ruminant species, ensuring sufficient statistical power (80%) to detect differences at p < 0.05. A power analysis was conducted using standard assumptions for variance in digestibility trials in ruminants. The objective was to evaluate the effects of dietary incorporation of different levels of NaOH-treated AHs on digestibility. In addition to AHs, all animals received wheat straw and a concentrate mixture. AHs were included in the diets at varying levels to partially replace straw, while the amount of concentrate offered remained constant across all diets. The chemical composition of the wheat straw and concentrate feed used in the study (both commercially sourced) is shown in

Table 1. Chemical composition (g/kg DM, unless otherwise stated) of wheat straw and concentrate fed to rams and ewes (as provided by the feed manufacturer).

	Wheat Straw 1	Concentrate 2	Concentrate 3
DM (per kg fresh weight)	901	886	878
OM	927	898	898
CP	34.5	138.8	156.3
EE	8.8	26.3	22.4
NSCs	356	501	493
NDF	527	232	227
ADF	836	378	384
ADL	106	35.1	35.5
TDN (g/kg DM)	414	705	638
Ca	1.7	10.3	10.9
P	0.8	4.8	5.7
Mg	1.3	3.9	3.8

ADF, acid detergent fiber; ADL, acid detergent lignin; Ca, calcium; CP, crude protein; DM, dry matter; EE, ether extract; Mg, magnesium; NDF, neutral detergent fiber; NSCs, non-structural carbohydrates; OM, organic matter; P, phosphorus; TDN: total digestible nutrient. ¹ Wheat straw used for feeding both rams and ewes. ² Concentrate feed mixture fed to rams. ³ Concentrate feed mixture fed to ewes.

. The control group received a diet without AHs, consisting of 1.5 kg wheat straw, and 1.7 kg concentrate feed. The second group (AH20) was fed a diet containing 20% NaOH-treated AHs replacing part of the straw (0.3 kg AH, 1.2 kg straw, and 1.7 kg concentrate). The third group (AH40) received 40% NaOH-treated AH, also replacing part of the straw (0.6 kg AH, 0.9 kg straw, and 1.7 kg concentrate).

Rams were fed twice daily at 07:00 and 16:00 h, with free access to water and salt blocks. Animals were gradually adapted to their respective experimental diets over a 14-day adaptation period. Following this adaptation phase, fecal samples were collected directly from the rectum immediately after the morning meal for 7 consecutive days. The samples were oven-dried at 55 °C for 48 h, and subsequently analyzed for DM, OM, CP, fiber fractions and AIA as previously described.

Apparent digestibility was assessed by an indirect method, using AIA as an internal marker. Apparent DM digestibility (DMD) was calculated following the methods of Sales and Janssens [24] and Dhanoa et al. [25]:

$$\mathrm{DMD} \left(\%\right)=100-\left({\displaystyle \frac{\% \mathrm{AIA} \mathrm{in} \mathrm{feed} \mathrm{DM}}{\% \mathrm{AIA} \mathrm{in} \mathrm{faeces} \mathrm{DM}}}\right)\times 100$$

The apparent digestibility of other feed fractions (OM, CP, NDF, ADF, cellulose) was calculated according to Dhanoa et al. [25]:

$$\mathrm{Apparent} \mathrm{digestibility} \left(\%\right)=100-\left({\displaystyle \frac{\% \mathrm{AIA} \mathrm{in} \mathrm{feed} \mathrm{DM}}{\% \mathrm{AIA} \mathrm{in} \mathrm{faeces} \mathrm{DM}}}\right)\times \left({\displaystyle \frac{\% \mathrm{nutrient} \mathrm{in} \mathrm{faeces} \mathrm{DM}}{\% \mathrm{nutrient} \mathrm{in} \mathrm{feed} \mathrm{DM}}}\right)\times 100$$

2.4. Reproductive Performance of Rams and Ewes

Assaf rams and ewes used to study reproductive performance were subjected to natural autumn mating (September–October 2023). This timing was selected to ensure that lambing occurred in the Spring, when environmental conditions are more favorable for pastures.

2.4.1. Reproductive Performance of Rams (Experiment 2)

A total of 21 adult rams (average age 2 years, with body weights ranging from 100 to 120 kg) were randomly assigned to three experimental groups, with seven rams per group. The sample size of 7 rams per group was based on recommendations from prior studies examining reproductive performance in rams, which indicate that this sample size is sufficient to detect significant effects of dietary treatments on reproductive parameters (e.g., libido, semen quality). A statistical power analysis was also performed to ensure the study was adequately powered for detecting such differences. The control group received a diet without AH, composed of 1.5 kg wheat straw and 1.7 kg concentrate feed. In the other experimental groups, wheat straw was partially replaced by NaOH-treated AH, with inclusion levels of either 20% (AH20 diet composed of 0.3 kg AH, 1.2 kg straw, and 1.7 kg concentrate) or 40% (AH40 diet composed of 0.6 kg AH, 0.9 kg straw, and 1.7 kg concentrate feed). Rams were fed twice daily at 07:00 and 16:00 h, with free access to water and salt blocks. The diets were fed to each group of rams for an initial two-week adaptation period, and then for another 5 weeks before assessing reproductive assessment. During the mating period, rams received dietary supplements containing vitamins and amino acids.

Ram libido was assessed by recording the frequency of sexual activity within a specific time frame. Each evaluation lasted at least 30 min, with weekly assessments conducted to ensure reliability and account for time variability. Under natural mating conditions, libido was evaluated by direct observation of mating behavior, using a 1–3 score scale to categorize sexual behavior as low, medium, or high. Observations focused on the frequency of mounting attempts, incomplete mounts, and successful mounts. Reaction time, defined as the time (in seconds) taken for the ram to initiate sexual activity, was recorded within a 5 min window to measure sexual response. To facilitate the evaluations, estrus in female ewes was induced and synchronized [26,27]. Scrotal circumference (SC), an indicator of testicular development and reproductive health, was measured by holding the spermatic cord and recording the scrotal circumference in centimeters. Scrotal circumference was determined each week throughout the study, starting the first week of the experiment, so that 8 measurements were recorded for each ram [28].

Semen was collected from the rams twice weekly over a two-month period, between 07:30 and 08:00 a.m., using a warm water-filled artificial vagina (Minitüb GmbH, Tiefenbach, Germany) maintained at 45–50 °C. The artificial vagina was prepared by assembling a sterile soft rubber outer cylinder, a smooth latex liner, a latex cone, a graduated collection tube, and an insulation bag filled with warm water at 45 °C. Semen from each ram was collected within 2–5 min from one or two successive ejaculates and was immediately placed in a water bath maintained at 37.5 °C. Semen volume was measured using a calibrated semen collection tube, and pH was determined using pH strips [29,30]. The transparency and consistency of semen were assessed visually. Motility, including total and individual motility (progressive, reverse, circular, and local), as well as velocity, were evaluated using Computer-Assisted Semen Analysis (CASA) [31]. Sperm concentration, expressed as the total number of spermatozoa (1 × 10⁹) per mL, was measured using a spectrophotometer [32]. Morphological abnormalities were identified by examining semen smears stained with eosin–nigrosine (1% eosin B, 5% nigrosine, and 3% sodium citrate). A fresh smear was prepared by mixing a drop of raw semen with the stain. To assess the percentage of abnormalities, at least 100 cells were evaluated and categorized based on defects in the head, mid-piece, and tail. The examination was conducted under a light microscope at 100× magnification [33].

2.4.2. Reproductive Performance of Ewes (Experiment 3)

Sixty healthy Assaf ewes, weighing 60–65 kg with a body condition score of 3.5 and a parity of 2, were randomly divided into three groups (twenty ewes per group). The sample size of 20 ewes per group was selected to ensure robust data collection on reproductive outcomes (e.g., fertility, fecundity, and lamb survival). This number was chosen based on prior studies and statistical power considerations, which indicated that 20 ewes per group would allow for the detection of meaningful differences in reproductive performance. The dietary treatments included a control group without AH, a group receiving AHs at 20% (AH20), and a group receiving AHs at 40% (AH40). Diets were formulated according to NRC [34] guidelines and adjusted for each physiological stage of the ewes, including pre-mating, early pregnancy, late pregnancy, and lactation.

Ewes were adapted to each diet over a 15-day period prior to starting the experiment. Following adaptation, flushing (supplemental nutrition prior to breeding) was provided for one month. Subsequently, each ewe was hormonally treated by inserting a vaginal sponge containing 45 mg of fluorogestone acetate (FGA) for 12 days. When the sponge was removed, 600 IU of pregnant mare serum gonadotrophin (PMSG) was administered intramuscularly. Thereafter, the ewes were naturally mated by rams used in Experiment 2. Ewes of each group were mated with rams that had been fed the diet with the same AH inclusion level as the ewes. Four rams were assigned per group (one ram per five ewes), selected based on age (1.8 to 2.2 years) and semen quality.

Pregnancy was confirmed 40 days post-mating by transabdominal ultrasonography using a manual, portable veterinary ultrasound scanner “Kaixin KX5100V” (BIOVET COMPANY LLC, Bila Tserkva, Ukraine), equipped with a 6.4-inch color screen, multiple imaging modes (B, B/M, 4B), USB storage, and a 6.5 MHz rectal probe.

Diets were adjusted monthly to meet the evolving nutritional needs of the ewes throughout pregnancy. Newborn lambs were housed in dedicated barns with straw bedding under strict hygiene conditions. Mothers received assistance during delivery, and newborns were supported to ensure successful suckling. Rates of fertility, fecundity, prolificacy, abortion, lamb mortality, numerical productivity (NP), and weight productivity (WP) were calculated for each group as follows:

$$\% \mathrm{Fertility} (\%)={\displaystyle \frac{\mathrm{Number} \mathrm{of} \mathrm{lambing} \mathrm{ewes}}{\mathrm{Number} \mathrm{of} \mathrm{mated} \mathrm{ewes}}}\times 100$$

$$\% \mathrm{Prolificacy} (\%)={\displaystyle \frac{\mathrm{Number} \mathrm{of} \mathrm{newborn} \mathrm{lambs}}{\mathrm{Number} \mathrm{of} \mathrm{lambing} \mathrm{ewes}}}\times 100$$

$$\% \mathrm{Fecundity} (\%)={\displaystyle \frac{\mathrm{Number} \mathrm{of} \mathrm{newborn} \mathrm{lambs}}{\mathrm{Number} \mathrm{of} \mathrm{mated} \mathrm{ewes}}}\times 100$$

$$\% \mathrm{Abortion} \mathrm{rate} (\%)={\displaystyle \frac{\mathrm{Number} \mathrm{of} \mathrm{aborting} \mathrm{ewes}}{\mathrm{Number} \mathrm{of} \mathrm{pregnant} \mathrm{ewes}}}\times 100$$

$$\% \mathrm{Lamb} \mathrm{mortality} (\%)={\displaystyle \frac{\mathrm{Number} \mathrm{of} \mathrm{died} \mathrm{lambs} \mathrm{before} \mathrm{weaning}}{\mathrm{Number} \mathrm{of} \mathrm{newborn} \mathrm{lambs}}}\times 100$$

$$\% \mathrm{Numerical} \mathrm{productivity} (\mathrm{NP}) (\%)={\displaystyle \frac{\mathrm{Number} \mathrm{of} \mathrm{weaned} \mathrm{lambs}}{\mathrm{Number} \mathrm{of} \mathrm{mated} \mathrm{ewes}}}\times 100$$

$$\mathrm{Weight} \mathrm{productivity} (\mathrm{WP}, \mathrm{kg}/\mathrm{mating} \mathrm{ewes})={\displaystyle \frac{\mathrm{Total} \mathrm{weight} \mathrm{of} \mathrm{weaned} \mathrm{lambs}}{\mathrm{Number} \mathrm{of} \mathrm{mated} \mathrm{ewes}}}$$

Additionally, 50 mL milk samples were collected weekly from each ewe, starting one week postpartum and continuing for 60 days. Samples were collected in sterile containers, stored at 4 °C, and analyzed using a MilkoScope Julie C8 Automatic Milk Analyzer (Scope Electric Instruments, Regensburg, Germany) to assess physicochemical parameters, including density, fat, solids-not-fat, protein, lactose, total solids, and pH.

2.5. Growth Performance of Lambs (Experiment 4)

Lambs born from the ewes involved in Experiment 3 were included in this study, regardless of sex. From birth until one month of age, lambs remained with their mothers and were suckling ad libitum throughout the day to maximize milk intake. Beginning at two weeks of age, creep feed concentrate was offered at 80 g per lamb daily. This amount was gradually increased to 600 g of creep concentrate per lamb per day by the time of weaning. The creep feed concentrate contained (per kg) 881 g DM, 873 g OM, 187 g CP, 26 g EE, 74 g crude fiber, 846 g TDN, 12.9 g Ca, 6.4 g P, 3.3 g Mg, 9150 IU vitamin A, 2776 IU vitamin D, and 111 mg vitamin E. The concentrate was provided twice daily in two equal meals at 09:00 and 17:00 h. At the same age (two weeks), lambs were also offered wheat straw ad libitum to facilitate adaptation to solid feed and the development of a functional rumen. At one month of age, to allocate part of the ewe’s milk production for commercial purposes, lambs were separated from their mothers during the night. Following morning milking at 07:00 h, lambs were reunited with their dams and allowed unrestricted access to milk for the remainder of the day.

Lambs were weighed every 10 days using a precision balance from birth until weaning at 70 days of age. Average daily gain (ADG) was calculated for key growth intervals (0–10 days, 10–30 days, 30–70 days) as follows:

$$\mathrm{ADG}={\displaystyle \frac{\mathrm{Final} \mathrm{Weight} - \mathrm{Initial} \mathrm{Weight}}{\mathrm{Final} \mathrm{age} - \mathrm{Initial} \mathrm{age}}}$$

These age intervals were selected due to their importance in the future performance of weaned lambs. The growth rate during the first 30 days is particularly important for those reared for reproduction and in the interval between 30 and 70 days of age for the lambs for fattening.

2.6. Statistical Analysis

Data were subjected to analysis of variance using the GLM procedure in SAS 9.4, applying a completely randomized design with the model Y_ij = μ + T_i + ε_ij, where Y_ij represents the observation, μ is the overall mean, T_i is the effect of the level of AH inclusion in the diet, and ε_ij is the residual error. The animal (ram, ewe, lamb) was the experimental unit. Polynomial (linear and quadratic) orthogonal contrasts were used to evaluate the responses to increasing levels of AHs in the diets. Additionally, the inclusion of AHs was evaluated by an orthogonal contrast comparing the control diet with those containing AHs.

3. Results

3.1. Chemical Composition of Almond Hulls

The NaOH treatment significantly (p < 0.05) altered the chemical composition of AHs compared to untreated hulls, potentially enhancing their nutritive value (

Table 2. Chemical composition ¹ of almond hulls untreated (Control) or treated with sodium hydroxide (NaOH), (g/kg DM, unless otherwise stated).

	Untreated AH	NaOH-Treated AH	SEM	p Value
DM (g/kg fresh weight)	898	917	8.44	0.187
OM	913	846	0.75	<0.001
EE	26.0	17.6	0.17	<0.001
CP	54.9	44.4	0.85	0.001
NSCs	532	543	3.44	0.090
NDF	300	241	2.38	<0.001
ADF	117	110	1.71	0.041
ADL	84.9	80.0	0.65	0.006

¹ Analyzed values. ADF, acid detergent fiber; ADL, acid detergent lignin; CP, crude protein; DM, dry matter; EE, ether extract; NDF, neutral detergent fiber; NSCs, non-structural carbohydrates; OM, organic matter; SEM, standard error of the mean.

). NaOH treatment reduced (p < 0.001) the concentration of OM of AHs from 917 to 846 g/kg DM. The treatment also increased (p < 0.001) crude fat (26 vs. 18 g EE/kg DM) and protein (55 vs. 44 g CP/kg DM) contents. However, NaOH treatment reduced (p < 0.05) fiber components, including NDF (241 vs. 300 g/kg DM), ADF (110 vs. 117 g/kg DM), and ADL (80 vs. 85 g/kg DM). The NSCs content was marginally affected (543 vs. 532 g/kg DM).

3.2. In Vivo Digestibility in Rams (Experiment 1)

Table 3. In vivo nutrient digestibility (%) in Assaf rams fed diets containing almond hulls at 0%, 20%, or 40% (DM basis).

	Diets 1				p Value
	C	AH20	AH40	SEM	Diet	C vs. A 2	Linear	Quadratic
DM	61.8	62.4	64.5	3.62	0.855	0.713	0.600	0.861
OM	66.9	67.6	68.8	3.44	0.920	0.758	0.692	0.945
CP	57.3	51.0	54.3	4.59	0.633	0.419	0.648	0.406
NDF	56.3	55.1	50.3	5.29	0.700	0.584	0.431	0.783
ADF	58.0	55.8	51.7	4.95	0.661	0.488	0.376	0.879
CEL	64.6	66.3	61.3	4.51	0.732	0.890	0.614	0.550

DM, dry matter; OM, organic matter; CP, crude protein; NDF, neutral detergent fiber; ADF, acid detergent fiber; CEL, cellulose, SEM, standard error of the mean. ¹ Diets: The control (C) diet consisted of a conventional ration including wheat straw as the primary roughage source. In the experimental diets, wheat straw was partially replaced with NaOH-treated almond hulls: 20% replacement in AH20 and 40% replacement in AH40, on a dry matter basis. ² Orthogonal contrast comparing the control diet (C) with those containing almond hulls (A).

shows that no significant (p > 0.05) differences in the in vivo digestibility coefficients were observed among treatments. The inclusion of NaOH-treated AHs in the diet did not affect digestibility.

3.3. Reproductive Performance of Rams (Experiment 2)

Table 4. Sexual behavior and semen quality of Assaf rams fed diets containing almond hulls at 0%, 20%, or 40% (DM basis).

	Diets 1				p Value
	C	AH20	AH40	SEM	Diet	C vs. A 2	Linear	Quadratic
Libido score	1.71 b	2.28 a	2.57 a	0.026	0.027	0.038	0.032	0.660
Testicular circumference (cm)	34.4 b	35.6 b	38.5 a	0.71	0.002	0.007	0.008	0.371
Semen concentration × 109	2.09 b	2.16 ab	2.19 a	0.024	0.012	0.005	0.004	0.555
Semen volume (ml)	1.83 c	2.02 b	2.24 a	0.020	<0.001	<0.001	<0.001	0.599
Semen pH	6.84 c	7.01 b	7.09 a	0.018	<0.001	<0.001	<0.001	0.045
Sperm total motility (%)	76.7 c	80.3 b	82.4 a	0.13	<0.001	<0.001	<0.001	<0.001
Sperm progressive motility (%)	56.6 c	60.5 b	65.2 a	0.16	<0.001	<0.001	<0.001	0.100
Sperm fast motility (%)	41.6 c	45.8 b	48.5 a	0.22	<0.001	<0.001	<0.001	0.007
Sperm slow motility (%)	14.2 b	13.8 b	16.2 a	0.17	<0.001	<0.001	<0.001	<0.001
Sperm circular motility (%)	0.89 a	0.86 a	0.56 b	0.029	<0.001	<0.001	<0.001	0.002
Sperm local motility (%)	20.1 a	19.9 b	17.1 b	0.11	<0.001	<0.001	<0.001	<0.001
Immotile motility (%)	23.3 a	19.7 b	17.6 c	0.13	<0.001	<0.001	<0.001	<0.001
Straight-line velocity (µm/s)	38.5 b	38.8 a	38.8 a	0.07	0.004	0.001	0.003	0.137
Curvilinear velocity (µm/s)	101.7 b	104.2 a	103.0 ab	0.46	0.007	0.007	0.040	0.001
Separated head (%)	4.84 a	4.61 b	3.52 c	0.037	0.024	<0.001	0.001	0.001
Mid-piece defects (%)	5.65 a	5.41 b	4.97 c	0.395	0.003	0.004	<0.001	0.900
Separated tail (%)	3.54 a	3.48 b	2.78 c	0.014	<0.001	<0.001	<0.001	0.052
Spiraled tail (%)	5.69 a	5.62 b	5.59 b	0.013	<0.001	<0.001	<0.001	0.172
Curved tail (%)	3.48 b	4.59 a	3.32 b	0.029	<0.001	<0.001	<0.001	<0.001

Means in the same row with different letters differ (p < 0.05). The p value represents the observed significance level of the F-test for the diet effect; SEM stands for the standard error of the mean. ¹ Diets: The control (C) diet consisted of a conventional ration including wheat straw as the primary roughage source. In the experimental diets, wheat straw was partially replaced with NaOH-treated almond hulls: 20% replacement in AH20 and 40% replacement in AH40, on a dry matter basis. ² Orthogonal contrast comparing the control diet (C) with those containing almond hulls (A).

summarizes the effects of AH inclusion on ram reproductive performance. Libido scores increased linearly (p = 0.038) from 1.71 in the control treatment to 2.28 in the AH20 treatment, and to 2.57 in the AH40 treatment. Rams fed the AH40 diet showed greater (p = 0.008) testicular circumference (38.5 cm) compared to the control diet (34.4 cm). Semen concentration increased linearly (p = 0.005) from 2.09 × 10⁹ in the control group to 2.19 × 10⁹ in the AH40 group. The inclusion of AHs at both levels in diets (AH20 and AH40) also increased (p < 0.001) semen volume (2.02 and 2.24 vs. 1.83 mL) and pH (7.01 and 7.09 vs. 6.84) compared to the control group. Total motility, progressive motility, and fast motility were increased (p < 0.001) with the AH20 and AH40 diets compared to the control. Conversely, circular, local, and immotile motility were significantly decreased (p < 0.001) with the inclusion of NaOH-treated AHs in the diet. The straight-line velocity was increased (p < 0.01) with both AH diets compared with the control, whereas the curvilinear velocity was increased (p < 0.01) only with the AH20 diet. The presence of defective spermatozoids such as separated head, mid-piece defects, or flawed tails (curved, spiraled or separated) was decreased (p < 0.05) with the AH40 diet compared to the control.

3.4. Reproductive Performance of Ewes (Experiment 3)

The effects of feeding AHs on ewe reproductive efficiency and productivity are summarized in

Table 5. Reproductive efficiency and productivity of Assaf ewes fed diets containing almond hulls at 0%, 20%, or 40% (DM basis).

	Diets 1				p Value
	C	AH20	AH40	SEM	Diet	C vs. A 2	Linear	Quadratic
Reproductive parameters for the flock
Fertility (%)	75	80	90
Prolificacy (%)	160	163	178
Fecundity (%)	120	130	160
Abortion rate (%)	25	20	10
Lamb mortality (%)	25	19	12
Number of lambs born alive
per mated ewe	0.90	0.95	1.35	0.187	0.171	0.273	0.087	0.438
per lambing ewe	1.20	1.50	1.69	0.164	0.067	0.037	0.021	0.772
Litter weight at lambing	6.27	7.84	7.82	0.742	0.201	0.075	0.116	0.375
Litter weight at weaning	25.0 a	28.8 ab	36.0 b	3.21	0.037	0.053	0.012	0.656

Means in the same row with different letters differ (p < 0.05). The p-value represents the observed significance level of the F-test for the diet effect; SEM stands for the standard error of the mean. ¹ Diets: The control (C) diet consisted of a conventional ration including wheat straw as the primary roughage source. In the experimental diets, wheat straw was partially replaced with NaOH-treated almond hulls: 20% replacement in AH20 and 40% replacement in AH40, on a dry matter basis. ² Orthogonal contrast comparing the control diet (C) with those containing almond hulls (A).

. The traits evaluated were calculated for each group (most of them could not be calculated individually for each sheep). Therefore, no statistical analysis was possible for the parameters calculated for the whole flock, but numerical trends seem to be noticeable. Fertility, prolificacy, and fecundity were lower, whereas abortion rate and lamb mortality were higher, in the flock receiving the control diet compared with those fed a diet containing NaOH-treated AH. All the parameters were numerically increased as the level of AH inclusion was greater. The average annual productivity of ewes (either as number of weaned lambs or as kg of weaned lamb per lambing ewe) increased when diets containing NaOH-treated AHs were fed compared with the control. However, feeding the AH40 diet decreased (p = 0.037) the litter weight at weaning compared to the control.

The inclusion of increasing levels of treated AHs has significant effects (p < 0.001) on the milk composition of ewes (

Table 6. Milk composition of Assaf ewes fed diets containing almond hulls at 0%, 20%, or 40% (DM basis).

	Diets 1				p Value
	C	AH20	AH40	SEM	Diet	C vs. A 2	Linear	Quadratic
Density (g/cm3)	1.03	1.03	1.03	0.001	0.836	0.604	0.550	0.977
Fat (%)	6.43 c	7.03 b	7.89 a	0.029	<0.001	<0.001	<0.001	0.002
Protein (%)	5.47 b	5.53 b	5.79 a	0.019	<0.001	<0.001	<0.001	<0.001
Lactose (%)	5.17 b	5.07 c	5.53 a	0.027	<0.001	<0.001	<0.001	<0.001
Total solid (%)	19.4 c	20.4 b	21.7 a	0.05	<0.001	<0.001	<0.001	0.014
Solids-not-fat (%)	12.1 c	13.2 b	13.7 a	0.04	<0.001	<0.001	<0.001	<0.001
pH	6.59	6.60	6.59	0.003	0.472	0.269	0.481	0.299

Means in the same row with different letters differ (p < 0.05). The p value represents the observed significance level of the F-test for the diet effect; SEM stands for the standard error of the mean. ¹ Diets: The control (C) diet consisted of a conventional ration including wheat straw as the primary roughage source. In the experimental diets, wheat straw was partially replaced with NaOH-treated almond hulls: 20% replacement in AH20 and 40% replacement in AH40, on a dry matter basis. ² Orthogonal contrast comparing the control diet (C) with those containing almond hulls (A).

). Fat, lactose, solid-not-fat, and total solids were greater in the milk of sheep fed the AH20 or AH40 diets than in milk from control ewes. Milk protein was increased only with the AH40 diet. Significant linear and quadratic effects of the levels of dietary inclusion of AHs were observed for most milk components, indicating that AHs positively influenced milk composition. No changes were observed in milk density or pH.

3.5. Growth Performance of Lambs (Experiment 4)

Initial weights at day 0 (W0) were comparable across all treatments (5.23, 4.43, and 4.69 kg for control, AH20, and AH40, respectively). From day 10 (W10) to 70 (W70), no significant differences in lamb body weight were observed (

Table 7. The inclusion of AHs was evaluated by an orthogonal contrast comparing the control diet with those containing AHs.

	Diets 1				p Value
	C	AH20	AH40	SEM	Diet	C vs. A 2	Linear	Quadratic
W 0	5.23	4.43	4.69	0.260	0.083	0.033	0.111	0.078
W 10	6.92	6.05	6.47	0.278	0.082	0.048	0.210	0.046
W 20	8.88	8.09	8.54	0.314	0.184	0.130	0.403	0.084
W 30	11.0	10.2	10.9	0.32	0137	0.253	0.825	0.047
W 40	13.4	12.5	13.3	0.33	0.102	0.259	0.907	0.034
W 50	15.7	14.9	15.8	0.35	0.077	0.402	0.779	0.029
W 60	18.3	17.6	18.4	0.35	0.124	0.509	0.724	0.051
W 70	20.8	20.5	21.4	0.37	0.123	0.823	0.241	0.125
ADG 0–10	169	162	178	5.9	0.132	0.911	0.288	0.115
ADG 0–30	192 b	193 b	207 a	3.6	0.012	0.144	0.011	0.172
ADG 10–30	203 b	208 ab	221 a	5.5	0.029	0.094	0.015	0.456
ADG 30–70	247 b	257 ab	263 a	3.2	0.010	0.006	0.002	0.619

W0: lamb weight at birth; W10, W20, W30, W40, W50, W60, and W70: lamb weight at 10, 20, 30, 40, 50, 60, and 70 days of age, respectively; ADG i–f: average daily gain between i (initial) and f (final) days of age. Means in the same row with different letters differ (p < 0.05). The p value represents the observed significance level of the F-test for the diet effect; SEM stands for the standard error of the mean. ¹ Diets: The control (C) diet consisted of a conventional ration including wheat straw as the primary roughage source. In the experimental diets, wheat straw was partially replaced with NaOH-treated almond hulls: 20% replacement in AH20 and 40% replacement in AH40, on a dry matter basis. ² Orthogonal contrast comparing the control diet (C) with those containing almond hulls (A).

and Figure 1). Average daily gain (ADG) from day 0 to 10 was similar across treatments. However, from day 0 to 30 days, lambs on the AH40 lambs showed a significantly greater ADG (p = 0.029) than those on the control and AH20 diets. From day 30 to 70 days, ADG remained higher in the AH40 than in the control group (p = 0.01).

4. Discussion

4.1. Chemical Composition of Almond Hulls

Optimizing both the quantity and quality of feed resources is crucial for identifying cost-effective alternatives and enhancing the economic efficiency of livestock operations. Among various possible alternatives, the inclusion of NaOH-treated AHs in sheep diets has been investigated in this study. Treatment of AHs with 4% NaOH altered the chemical composition of the parent material, potentially affecting their suitability as a feed resource. The NaOH treatment reduced OM, likely due to the addition of mineral matter with the NaOH, in agreement with the results reported by Bachmann et al. [35] for wheat straw.

The NaOH treatment increased crude fat and protein and reduced fiber components, particularly NDF, ADF, and ADL. Uzatici et al. [15] observed that treating common reed grass (Phragmites australis) straw with NaOH increased the ash content and reduced OM, NDF, and ADF contents, without affecting CP content. This suggests that the effect of NaOH on CP may vary depending on the type of feed material. The reduction in NDF, ADF, and ADL observed in the present study may be attributed to the potential of NaOH to break ester bonds between cell wall components such as acetic acid, phenolic acids, cellulose, hemicellulose, and lignin. This process enhances nutrient availability for microorganisms, thereby improving digestibility [5,15]. Recently, Zoabi et al. [36] reported that treating AHs with 4% NaOH for 40 days resulted in a reduction in CP, as well as structural and non-structural carbohydrate contents. Ibrahim et al. [37] applied NaOH treatments at concentrations of 2%, 4%, 6%, and 8% to Hedychium gardnerianum, Pittosporum undulatum, Arundo donax, and Acacia melanoxylon. Ash content and dry matter digestibility were highest under the 8% NaOH treatment compared to the other concentrations.

NaOH treatment, if applied at high concentrations or without proper management, may pose environmental risks due to the formation of potentially toxic or polluting residues. To mitigate these risks, a low NaOH concentration (4%) was employed in our study to effectively disrupt the lignocellulosic matrix while preserving animal health and feed safety. By optimizing both the concentration of NaOH and the dietary inclusion rate, the use of treated AHs offers a sustainable strategy for enhancing ruminant productivity without exerting adverse effects on the environment.

4.2. In Vivo Digestibility in Rams

In our study, the inclusion of NaOH-treated AHs at either 20% or 40% in the diet of rams did not affect nutrient digestibility. This aligns with previous research suggesting that although NaOH can break down fibrous components such as cellulose and hemicellulose, its overall impact on digestibility may be limited. It was expected that NaOH would affect the digestibility of AH. Berger et al. [38] observed that NaOH treatment of corn cobs at levels of 2.0%, 4.0%, 6.0%, and 8.0% linearly increased the rate of passage and decreased ruminal retention time with increasing levels of NaOH. Moreover, Jami et al. [39] reported that including 5% NaOH-treated corn straw as a substitute for 15% wheat hay in the diets of lactating cows decreased voluntary feed intake without affecting in vivo DM and OM digestibility. However, it reduced CP digestibility and increased the digestibility of NDF, cellulose, and hemicellulose. Additionally, a reduction in rumination time was observed. Among the eight bacterial species quantified by real-time PCR, the NaOH-treated group showed a notable decrease in cellulolytic bacteria and an increase in lactic acid-utilizing bacteria.

It is well established that feeding NaOH-treated forages, particularly cereal straws, can lead to an increase in water intake by ruminants. This is largely attributed to the elevated sodium content and the osmolality of the treated feed, which stimulates water consumption to maintain the osmotic balance [38]. Although water consumption was not recorded in the present study, no signs of excessive drinking behavior or dehydration were observed in Assaf sheep fed diets containing 20% or 40% NaOH-treated AH. This outcome may be due to the low NaOH concentration (4%) and the distinct structural and compositional characteristics of almond hulls compared to conventional cereal straws. Animals had free access to clean water throughout the duration of the experiment, and no metabolic disturbances related to fluid balance were noted. Although water intake was not quantitatively measured, our observations suggest that incorporating NaOH-treated AHs at the tested levels did not negatively impact animal hydration. Nonetheless, future studies could benefit from including precise measurements of water intake to confirm this assumption and fully assess the impact of alkali-treated AHs on water balance.

Uzatici et al. [15] observed only marginal improvements in the digestibility of common reed straw following NaOH treatment. Similarly, Reed and Brown [11] reported that increasing the inclusion level of untreated AHs in the diet to 25% and 35% reduced the digestibility of DM, OM, and fiber. However, Zoabi et al. [36] stated that treating AHs with 4% NaOH for 40 days increased in vitro DM digestibility without affecting the digestibility of fibers. Ibrahim et al. [37] reported that NaOH treatment of different plant byproducts did not affect the invitro OM digestibility; however, a 2% NaOH concentration positively influenced the digestibility of both ADF and NDF. Untreated AHs have a high fiber content and, when fed in excess, can limit the digestive utilization of other dietary components and reduce overall feed intake [40]. Our results suggest that NaOH treatment can improve the digestibility of AH. However, several factors may influence the effectiveness of this treatment, including animal physiology, the specific AH variety, processing methods, digestive capacity, and the adaptations of rumen microbes in sheep consuming AH. Yalchi [10] found that AHs are richer in sugars and more digestible than alfalfa hay. Swanson et al. [41] observed that pure AHs are more digestible than raw AHs containing debris. Additionally, natural compounds in AHs, such as tannins, can reduce protein digestibility [5,42]. According to Kahlaoui et al. [7], tannin content in AHs ranges from 70 to 120 mg/g, which has been associated with reduced protein digestibility. Despite the limited benefits of NaOH treatment, AHs can still be effectively incorporated into livestock diets without adversely affecting total tract digestibility.

4.3. Reproductive Performance

There is a lack of specific studies directly examining the effects of AH inclusion in the diets of rams or ewes on their reproductive performance. However, studies on other species have shown positive or neutral outcomes. For instance, almond-supplemented diets have been reported to improve reproductive function in male rats [43]. The inclusion of up to 15% AHs in a laying hen diet had no adverse effect on egg production or egg quality [44].

The significant effects observed in rams fed AH-supplemented diets, particularly the AH40 diet, suggest enhanced reproductive performance and improved semen quality. Rams fed the AH40 diet showed the best outcomes in terms of libido score, testicular circumference, and semen volume. Improvements in sperm concentration, total motility, progressive motility, and fast motility indicate enhanced sperm vigor and functionality. Additionally, spermatozoa from AH40 rams showed increased curvilinear and straight-line velocities, supporting enhanced sperm movement and fertilization potential. Reductions in abnormal motility patterns, such as circular, local, and immotile sperm, as well as fewer morphological defects, including mid-piece abnormalities, spiraled tail, separated tail, and curved tail, further indicate improved sperm integrity and quality, particularly with the AH40 diet [45]. These enhancements in both sperm motility and morphology seem to demonstrate the response to dietary interventions.

Almond hulls are rich in fiber, fatty acids, and antioxidants [7,46,47,48,49], which may affect rumen fermentation and nutrient utilization, subsequently supporting overall reproductive function [50]. The antioxidant properties of AHs may contribute to reducing sperm defects [51], while maintaining a balanced pH contributes to a healthier semen environment. These findings underscore the pivotal role of nutrition in optimizing overall reproductive health and highlight the potential of dietary interventions to improve both physiological and reproductive performance in livestock [52,53].

Incorporating AHs into ewe diets had a sizeable impact on reproductive performance, as evidenced by increased key traits such as fertility, prolificacy, fecundity, numeric productivity (NP), and weight productivity (WP), along with decreased abortion rate and lamb mortality. Notably, AH40 treatment resulted in the highest fertility, prolificacy, and fecundity, indicating optimal reproductive performance. The AH20 treatment showed intermediate values for these indicators, while the control treatment had the lowest. This analysis highlights the beneficial effects of AHs on reproductive outcomes in ewes [13]. Higher fertility rates for ewes supplemented with AH20 and AH40, as compared with those of the control group, suggest that AHs improved conception rates in ewes, while increased prolificacy and fecundity indicate a greater number of lambs born and fewer losses. It can be suggested that improving the body conditions of ewes through flushing before and during mating, combined with increasing the inclusion rates of AH, was an effective strategy to enhance fertility, which is known to have low heritability [54]. Acock et al. [55] reported that feeding gestating beef cows wheat straw treated with NaOH did not affect calf birth weight, incidence of calving difficulty, or the subsequent reproductive performance of the cows.

The increase in the number of weaned lambs produced per ewe could be attributed to increased colostrum intake, leading to better health and reduced lamb mortality in the offspring of ewes fed the AH40 diet [56]. The higher litter weight at weaning in the AH40 group would also reflect improved lamb survival and greater growth rate in milk-fed lambs, resulting in heavier lambs at weaning. Based on these findings, the addition of AHs up to 40% to sheep diets (both ewes and rams) before and during mating seems to be a worthwhile feeding practice to improve animal performance, and a cost-effective strategy to improve sheep breeder income.

Incorporating AHs into ewe diets led to significant improvements in milk composition, with higher levels of fat, protein, lactose, total solids, and solids-not-fat. These effects became more pronounced as the amount of AHs in the diet increased, following a linear trend that suggests a consistent increase in these nutritional components in milk with greater AH inclusion. The increase in fat content is attributed to the addition of a high-fiber feedstuff in the ration, a relationship that has been extensively studied [57,58]. Jami et al. [39] reported that including 5% NaOH-treated corn straw in the diet of lactating cows increased both milk fat and milk protein contents. Although we did not measure the profile of ruminal volatile fatty acids, Zoabi et al. [36] reported that treating AHs with 4% NaOH increased the production of ruminal acetate, which is highly correlated with milk fat concentration [59]. Swanson et al. [13] support our findings that dietary AHs can be associated with increased milk fat content, although a potential decrease in milk protein was observed in this study, in contrast with our results showing an increase in protein content. Similarly, Williams et al. [14] reported reductions in both milk production and protein yield when AHs were included in the diet. This discrepancy suggests that the effect of AHs on milk protein may vary depending on breed differences and genetic factors influencing milk production and lactation [60,61,62], and on the composition of the diet in which AHs is incorporated. Despite the increase in protein levels observed in our study, the levels remained within the typical range for the Assaf breed, known for its relatively high protein content [63]. The elevated protein levels in Assaf sheep milk are particularly important for high-quality cheese production, as proteins are critical for curd formation during cheese-making. Higher protein concentrations contribute to increased cheese yield, improved texture, and a more concentrated flavor [64]. Even moderate increases in protein and total solids in milk can enhance cheese production [65,66], further underscoring Assaf sheep’s potential to produce protein-rich milk for premium dairy production. The increase in the milk lactose concentration with the AH40 diet highlights the effectiveness of NaOH treatment in enhancing fiber breakdown [67,68], which may increase the availability of carbohydrates necessary for lactose synthesis. Earlier studies by Can et al. [69] reported that goats fed a diet containing 400 g of untreated AHs and shells per kg of diet DM had greater DM intake (3% of BW) compared to those fed 400 g of wheat straw per kg of diet DM (2.37% of BW). The AHs and shells used in this study were soft, easily breakable by hand, and more palatable than straw, leading to greater consumption rates among the goats. Although not recorded in our study, any increase in feed intake in ewes receiving AHs diets would raise energy supply through the entire reproduction cycle from flushing to steaming and the post-lambing period.

4.4. Growth Performance of Lambs

Feeding AHs to Sarda lambs did not adversely affect growth performance, feed conversion ratio, or carcass weight, and improved the oxidative stability of meat when refrigerated [8,40,70,71]. Our study involved suckling lambs (not fattening lambs), and AHs were included in the diets of the nursing ewes. Incorporating AHs into the diet of ewes improved the growth performance of their lambs, particularly those born from ewes fed the AH40 diet. A meta-analysis by Roca Fraga et al. [72] highlighted the critical importance of managing ewe nutrition during late pregnancy to meet the basic nutritional requirements for optimal weight, vitality, and survival of newborn lambs. In our study, lamb weight at birth was slightly reduced by the inclusion of AHs in the ewe diet. In comparison, lower lamb birth weights were reported by Bekkouche et al. [73]. These variations could be attributed to differences in breed, ewe nutrition during pre- and post-partum periods, litter size, and lamb sex. It is noteworthy that ewes fed the AH20 and AH40 diets showed greater litter sizes (prolificacy) than the control group, which likely contributed to the smaller individual lamb size at birth. A reduction of 500 g in birth weight is considered more detrimental to the potential performance of a twin lamb compared to a typically heavier singleton [72]. This emphasizes the need to identify singleton- and multiple-bearing ewes during pregnancy and to adjust their feeding accordingly to meet pregnancy-specific nutritional requirements. As the trial progressed, lambs nursed by dams fed the AH40 diet exhibited a faster growth rate, particularly between 30 and 70 days of age. This resulted in greater weaning weights and higher average daily gains across the intervals of 0–30, 10–30, and 30–70 days. This enhanced growth rate can be attributed to a higher consumption of milk from their mothers, which also had superior nutritional content, as milk from ewes fed the AH40 diet contained more fat, lactose, protein, and total solids than milk from control ewes. Consequently, milk-fed lambs from AH40 ewes received more nutrients during suckling. This suggests that higher levels of AHs may enhance lamb growth, likely due to improved milk yield. Significant linear and quadratic trends also indicate a relationship between AH inclusion and lamb growth, with optimal effects becoming more apparent as the lambs were heavier. It can be suggested that during times of high feed prices, AHs are a potential cost-controlling feed source in growing lamb diets.

Although this study primarily focused on the biological responses to dietary inclusion of NaOH-treated AHs, it is worth noting that AHs are an abundant, low-cost agro-industrial byproduct. The use of treated AHs in sheep diets could significantly reduce feed costs. Preliminary economic observations indicate a potential reduction in feed expenses due to partial replacement of conventional ingredients with AHs, particularly at the 40% inclusion level, which showed enhanced productive and reproductive performance. However, a comprehensive cost–benefit analysis considering treatment costs, labor, and market prices is necessary to fully validate its economic viability. This will be the focus of future work to better support the adoption of AHs as a cost-effective feed resource under commercial farming conditions.

5. Conclusions

Treatment of almond hulls with 4% NaOH alters the chemical composition of the raw material, notably by reducing the fiber fractions, thereby enhancing the suitability of treated hulls as a feed ingredient for ruminants. The inclusion of NaOH-treated almond hulls in the diets (at 40%) of rams and ewes improved their reproductive performance. In lactating ewes, this dietary supplementation was also associated with enhanced milk composition, including increased concentrations of fat, protein, lactose, and total solids, which may contribute to improved milk quality for cheese production. The growth performance of suckling lambs was also improved when their lactating dams received diets supplemented with NaOH-treated almond hulls (at 40%). The findings of this study suggest that the incorporation of treated almond hulls at 40% into sheep diets represents an effective strategy for enhancing animal performance and potentially improving the economic efficiency of sheep production systems. Further research is recommended to explore the long-term effects of treated almond hull inclusion, particularly regarding optimal inclusion rates and potential impacts on the meat quality of weaned lambs for fattening and the economic impact of the use of this ingredient in sheep diets under field conditions.