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Article

The Effect of Different Amounts of Glycerol Fed to Lambs on Their Growth, Rumen Fermentation, Carcass Traits, Meat Characteristics, and Shelf Life

by
Uriel Hidalgo-Hernández
1,
María Esther Ortega-Cerrilla
1,*,
Pedro Zetina-Córdoba
2,*,
José G. Herrera-Haro
1 and
José Vian
2
1
Posgrado en Recursos Genéticos y Productividad-Ganadería, Colegio de Postgraduados, Campus Montecillo, Texcoco 56230, Mexico
2
Programa Académico de Ingeniería en Alimentos, Universidad Politécnica de Huatusco, Veracruz 94106, Mexico
*
Authors to whom correspondence should be addressed.
Agriculture 2025, 15(11), 1185; https://doi.org/10.3390/agriculture15111185
Submission received: 19 April 2025 / Revised: 23 May 2025 / Accepted: 26 May 2025 / Published: 30 May 2025
(This article belongs to the Special Issue Effects of New Feeds or Additives on Farm Animal Performance and Carcasses Composition)
Versions Notes

Abstract

Glycerol can effectively replace corn as an energy source in lamb diets without negatively impacting productive performance. This study evaluated the effects of substituting ground corn with different glycerol levels on the productive performance, ruminal fermentation, carcass characteristics, and meat quality at 24 h, 7, 14, and 21 d post-slaughter. A total of 40 male Suffolk × Hampshire crossbred lambs (25 ± 5 kg live weight) were used in a completely randomized design with four treatment groups (n = 10 each): 0% glycerol (GLY0), 5% glycerol (GLY05), 10% glycerol (GLY10), and 15% glycerol (GLY15). Including glycerol in the diet did not affect growth performance (p > 0.05). However, it did lead to an increase (p < 0.05) in the concentrations of NH3-N and the proportions of propionic and butyric acids, while the acetic acid levels decreased (p < 0.05). The backfat thickness, loin eye area (LEA), and carcass yield were not significantly affected (p > 0.05) by the addition of glycerol. Additionally, pH and color were also unaffected (p > 0.05), although the water-holding capacity showed a decrease (p < 0.05) over the shelf life of the meat. The chemical composition of the meat remained similar across all treatments, time points, and interactions (p > 0.05). In contrast, the protein content was significantly affected (p < 0.05) by the glycerol inclusion, time, and interactions between treatment and time. The results indicate that substituting up to 15% of ground corn with glycerol in lamb diets does not negatively impact productive performance, backfat thickness, LEA, carcass traits, or meat quality during shelf life. Throughout the shelf life, the crude protein concentrations and water-holding capacity decreased, while the propionic acid and NH3-N concentrations increased.

1. Introduction

Historically, conventional feed resources have been used to meet the nutritional needs of ruminants, such as the extensive use of grains, legumes, and forages. This raises concerns about future food security, underscoring the need for more sustainable animal production that utilizes agro-industrial by-products [1,2]. Rising feed costs and limited availability have prompted the exploration of agricultural by-products as livestock feed, offering several advantages such as reducing competition for human food resources, decreasing the environmental impact of by-product disposal, and enhancing the quality of animal products [3].
One notable by-product is crude glycerin, derived from biodiesel production, which has strong potential to partially replace starch-rich ingredients like corn, without negatively impacting health or performance; however, optimal formulations for replacement have not yet been established [4,5,6,7]. Glycerol provides energy and can be rapidly incorporated into the gluconeogenesis pathway [8]. Additionally, it has been explored as a feed supplement in ruminant nutrition [9]. It is mainly fermented in the rumen into propionate and butyrate, enhancing glucose availability. Replacing a portion of corn with glycerol has been shown to help maintain productivity [10]. Measurements of fermentation rates and the production of volatile fatty acids have yielded conflicting results, primarily influenced by the dosage and the rate at which substances are eliminated from the rumen. Determining the relative absorption levels of glycerol compared to fermentation is challenging [11], and this factor significantly impacts the productive performance.
Almeida et al. [12] and van Cleef et al. [13] indicated that replacing up to 30% of corn grain with crude glycerin in lamb diets does not compromise health or the development of stomach compartments. However, the level of glycerol inclusion in the diet can influence daily weight gain, with results showing decreases [14], increases [5], or no effects [15] at varying levels of inclusion. This variability may be attributed to the purity of the glycerol used, which affects the dry matter intake.
Several studies using glycerol at different purity levels (68.66% to 83%) and diverse inclusion rates in lamb diets have examined the productive performance, ruminal metabolism, carcass characteristics [4,5,13,14,15,16], and meat quality [17,18,19], with inconsistent results. Carvalho et al. [17] and Syperreck et al. [19] noted increased carcass dressing percentages with glycerol in diets, suggesting that glycerol enhances ruminal fermentation by increasing propionate production and improving feed digestibility [20], contributing to increased daily weight gain and higher carcass dressing percentages.
Thus, it is hypothesized that glycerol (95% purity) can partially replace ground corn in lamb diets without compromising productive parameters or meat quality. This study aimed to determine the effects of including 0%, 5%, 10%, and 15% glycerol in the diets of lambs.

2. Materials and Methods

2.1. Animal Care

All of the experimental procedures involving sheep were approved by the Animal Welfare Committee of the Colegio de Postgraduados, Campus Montecillo, through the regulations established by the Animal Protection Law enacted by the State of Mexico. The experiment was conducted in the sheep module and the Animal Nutrition laboratory at the Colegio de Postgraduados, Campus Montecillo, located in Texcoco, State of Mexico (19°27′33′′ N, 98°54′24′′ W), at an elevation of 2240 m above sea level, from January to June 2017.

2.2. Animal, Diets, Treatments, and Experimental Design

Forty intact male Suffolk × Hampshire cross lambs were used in the study, averaging 60 days of age and weighing 25 ± 5 kg. The animals were housed in individual cages (size 1.20 × 1.20 m), with ad libitum access to diet and water. They were dewormed with Ivermectin (Ivomec F, Boehringer Ingelheim, Ingelheim am Rhein, Germany) at a dosage of 1 mL per 50 kg of body weight. They received a vitamin supplement (Vigantol ADE, Bayer, Mexico City, Mexico) at a dose of 2 mL via intramuscular injection before the start of the experiment.
Four integral diets (Table 1) were used, which replaced ground corn with glycerol (95% purity) in a completely randomized design that included the following treatments (n = 10): GLY0, GLY5, GlY10, and GlY15. These correspond to 0%, 5%, 10%, and 15% glycerol (GLY) inclusion in the diet. The diets were formulated to be isoproteinic and isoenergetic, aligned with the requirements suggested by the National Research Council [21] for growing lambs. The diet was offered ad libitum twice daily (08:00 a.m. and 16:00 p.m.). The animals underwent a 20-day adaptation period for the diet, followed by a 60-day fattening period.

2.3. Growth Performance and Ruminal Fermentation

The body weight of the lambs was recorded at the beginning of the fattening period, before morning feeding, and every 15 days throughout the feeding trial. The average daily weight gain (ADG) was calculated by dividing the difference in body weight by the number of days between weighings. Individual dry matter intake (DMI) was calculated as the difference between the amount of diet supplied and rejected each day. The feed conversion ratio (FCR) was calculated for each lamb based on the total feed intake and weight gain during the experimental period. After 60 days of the experiment, six lambs were selected from each treatment, and ruminal fluid samples were collected via the esophagus to determine pH, the concentration of ammonia nitrogen (NH3-N), and the concentrations of volatile fatty acids (VFAs: acetic, propionic, and butyric). Four milliliters of ruminal fluid were taken, and the pH was measured using a potentiometer (Model HI 99163, Hanna Instruments, Woonsocket, RI, USA) with a glass electrode, which had been previously calibrated at pH 4.0 and 7.0. Subsequently, 1 mL of 25% metaphosphoric acid was added to acidify it in a concentration of 4:1. The NH3-N concentration was measured by absorbance in an ultraviolet−visible light spectrophotometer (Model Cary 1E, Varian®, Santa Clara, CA, USA) at 630 nm; ruminal fluid samples were centrifuged at 1957× g for 15 min and 1 mL of phenol and 1 mL of sodium hypochlorite were added to the supernatant (20 µL). Subsequently, the samples were incubated for 30 min at 37 °C. After the incubation period, the spectrophotometer reading was taken [23]. To determine the VFA concentration, the samples were centrifuged at 1957× g for 15 min. Sample analysis was performed using a gas chromatograph (Model Claurus 500, PerkinElmer, Waltham, MA, USA). Then, 1 µL of sample was injected at an injector temperature of 200 °C, a detector temperature of 250 °C, and an oven temperature of 140 °C. The runtime per sample was approximately 7 min [24].

2.4. Determination of the Backfat Thickness and Loin Eye Area Using Ultrasound

At the beginning (day 0) and end (day 60) of the fattening period, backfat thickness and the eye area of the Longissimus dorsi muscle were evaluated by real-time ultrasound using a signal transducer (Model 5040, Aloka® SSD-500 V, Tokyo, Japan). Image processing of ultrasound images captured using the transecting plane between the 12th and 13th ribs [25] was performed using Centralized Ultrasound Processing software (CUP LAB®, Ames, IA, USA).

2.5. Slaughter and Carcass Characteristics

At the end of the fattening period, and after a 12 h fast, six animals per treatment were weighed and slaughtered according to the Official Mexican Standard NOM-033-SAG/ZOO-2014 [26]. Immediately after, the weights of the rumen and intestines with and without digestive contents and mesenteric fat, red viscera, blood, head, and limbs were recorded. The hot carcass weight (HCW) was recorded, and the empty body weight (EBW) was obtained from the difference between the slaughter weight and the digestive content of the green viscera. The hot carcass yield (HCY) was calculated by dividing the HCW by the slaughter weight ×100 [27]. The pH reading was quantified at the intercostal space of the 12th–13th rib, specifically in the Longissimus dorsi muscle, using a portable potentiometer (Model HI 99163, Meat HANNA®, Waterproof Tester, Woonsocket, RI, USA) equipped with a digital penetration electrode, directly on the hot carcass [28].

2.6. Physicochemical Characteristics of Meat During Shelf Life

The evaluation was performed on Longissimus dorsi muscle samples extracted from the carcass at the time of slaughter. These samples were divided into four portions, individually packaged, identified, and stored at 4 °C to determine the meat’s pH, color, water-holding capacity, and chemical composition at 24 h, 7, 14, and 21 days postmortem. The pH readings were taken in triplicate on the muscle surface using a potentiometer (Model HI 99161, Meat HANNA®, Waterproof Tester, Woonsocket, RI, USA). For color analysis, a portable colorimeter (Model CR-400/410, Konica Minolta®, Ramsey, NJ, USA) was used to measure the L* (Lightness), a* (red-green intensity), and b* (yellow-blue intensity) values, according to the CIE-L* a* b* guide for meat color measurement [29]. The Longissimus dorsi samples were exposed to oxygenation for 20 min to stabilize the color; the final values were reported as the average of three measurements taken on the muscle surface. To determine the WHC, 10 g of finely chopped, fat-free meat was homogenized with a 16 mL solution of 0.6 M NaCl, stirred with a glass rod in centrifuge tubes for 1 min, and refrigerated for 30 min. The samples were subsequently centrifuged (Model 420101, Clay Adams, Sparks, NV, USA) at 1957× g for 15 min; the supernatant was decanted into a graduated cylinder, and the final volume was measured, with the initial volume subtracted [30]. The chemical composition of the meat samples stored at 4 °C was determined. Dry matter (DM: method 930.15), crude protein (CP: method 990.03), ether extract (EE: method 920.39), and ash (method 942.05) were determined according to the AOAC [31] at 24 h, 7, 14, and 21 days.

2.7. Chemical Analysis of the Diet

The experimental diets were formulated to meet the requirements for dry matter (method 930.15), crude protein (method 990.03), ether extract (method 920.39), and ash (method 942.05) [31]; additionally, neutral detergent fiber (NDF) and acid detergent fiber (ADF) were quantified in the diets using the method proposed by Van Soest et al. [32].

2.8. Statistical Analysis

The SAS [33] statistical software (version 9.4, Statistical Analysis System, Cary, NC, USA) was used to perform the analyses of variance. The collected data on ADG, DMI, FCR, ruminal fermentation, and carcass traits were analyzed using PROC GLM using the following statistical model:
Yij = µ + τi + Єij
where Yij is the jth observation in the ith treatment, µ is the general mean, τi is the effect of the ith treatment, and Єij is the random error.
Data on backfat and loin eye area, as well as the physical and chemical characteristics of the meat during its shelf life, were analyzed with PROC MIXED for repeated measurements over time, according to the following statistical model:
Yijk = µ + τi + δj(i) + Pk+ (tP)ik + Єijk
in which Yijk is the response variable, µ is the general mean, τi is the effect of the ith treatment, δj(i) is the effect of the jth replicate within the ith treatment, Pk is the effect of the kth period, (τP)ik is the treatment × period interaction, and Єijk is the random error.
The least squares means were separated using the Tukey-adjusted test (p < 0.05).

3. Results

3.1. Animal Performance and Ruminal Variables (pH, Ammonia Nitrogen, Volatile Fatty Acids)

The addition of glycerol to the diet did not significantly impact (p > 0.05) the initial and final weights, daily weight gain, dry matter intake, or feed conversion ratio in lambs (Table 2). Similarly, there were no significant effects (p > 0.05) on ruminal pH. However, the concentration of NH3-N was affected (p < 0.05) by the inclusion of GLY in the diet, with the highest concentration observed at 15% GLY. Acetic, propionic, and butyric acid concentrations were also affected (p < 0.05). Notably, there was a tendency for propionate to increase with higher levels of GLY, while acetate concentrations decreased with increasing GLY levels in the diet.

3.2. Backfat Thickness and Loin Eye Area

No significant differences (p > 0.05) were observed in backfat thickness and the loin eye area of the Longissimus dorsi due to the addition of GLY to the diet (Table 3). However, both variables increased (p < 0.05) at the measurement times of 0 and 60 days, as the backfat and Longissimus dorsi area both grew in lambs. The interaction between dietary GLY levels and measurement time was not significant (p > 0.05).

3.3. Carcass Characteristics

The inclusion of various levels of GLY in the diet did not significantly affect the empty live weight, hot carcass weight, carcass biological performance, or carcass pH (p > 0.05) (Table 4).

3.4. Physicochemical Characteristics of the Meat

There were no significant differences (p > 0.05) in pH when GLY was added to the diet. However, pH values decreased over time (p < 0.05), and the interaction between time and treatment was not significant (p > 0.05). In terms of meat color, the lightness (L*), redness (a*), and yellowness (b*) indices were not significantly affected (p > 0.05) by the treatments. However, there was a tendency for these values to decrease over time (p < 0.05) (Table 5). The treatment−time interaction did not influence color (p > 0.05). The water holding capacity showed significant effects (p < 0.05) from treatments, shelf life, and the interaction between treatments and time.

3.5. Chemical Composition of Meat During Shelf Life

Adding GLY to the diets did not result in significant changes (p > 0.05) to the chemical composition of the meat. However, in the treatment without GLY, the crude protein content decreased over time (p > 0.05), with a significant treatment−period interaction (p < 0.05) (Table 6).

4. Discussion

4.1. Growth Performance and Rumen Fermentation

Including 0%, 5%, 10%, and 15% GLY in the lamb diets did not affect the DM, ADG, FCR, or final weight. These results are consistent with the findings of Gunn et al. [34], de Rezende et al. [35], Silva et al. [15], Bölükbas et al. [1], and Syperreck et al. [19]. In contrast, Lage et al. [36], Orrico-Junior et al. [14], Saleem y Singer [37], and Ribeiro et al. [38] observed a decrease in DMI with GLY inclusion levels of 0%, 2.5%, 3%, 5%, 6%, 7%, 7.5%, 9%, 10%, 12%, 14%, 15%, and 21% when replacing corn. These findings suggest that higher levels of glycerol in diets may be rejected due to the specific characteristics of the glycerol itself, such as quantity, purity, and methanol content, as well as factors like salts and residues present in recycled oils and reagents used during the transesterification process [39,40]. Additionally, factors such as the administration method, diet composition [37], and interactions with other feed ingredients [10] can adversely affect the productive performance of sheep. GLY is ultimately converted into acetyl-CoA and oxidized in the Krebs cycle, increasing ATP production and enhancing the energy status of hepatocytes, which generates signals to the satiety center in the hypothalamus [41]. In the present study, as noted by Syperreck et al. [19], since feed efficiency is linked to DMI and ADG, and both parameters showed similarities, the hypothesis that the equality in ADG between treatments is due to DMI is supported. Furthermore, GLY can be applied at levels up to 18% without compromising feed intake efficiency, digestibility, or yield, as it does not promote metabolic disorders in fattening lambs [5].
Rumen pH is critical for maintaining rumen homeostasis, typically ranging from 5.0 to 7.5, depending on ruminal metabolism, fermentation patterns, diet type, and feeding frequency in various ruminants [42,43]. In this study, the pH ranged from 6.28 to 6.39, aligning with the results reported by various authors when including up to 30% GLY in sheep diets [10,16]. This pH range (6.0 to 7.2) is conducive to the presence of ruminal microorganisms and supports the normal functioning of ruminants [44,45]. The observed pH levels may be attributed to the decreased starch intake with GLY, as diets high in fermentable carbohydrates can lead to a more acidic rumen pH than in animals with a low energy intake [39]. The findings are similar to those of Van Cleef et al. [16], but differ from Almeida et al. [4], who reported pH values lower than 6 but higher than 5.6 when GLY was included at 10%, 20%, and 30%. According to Filho et al. [10], the discrepancy in ruminal pH is challenging to explain and may be related to the animals’ feeding behavior or the sampling protocol used.
GLY is absorbed through the ruminal epithelium or can escape from the rumen via the omasal orifice; however, the absorption rate is low. It is mainly fermented in the rumen by bacteria of the Selenomonas genus, leading to an increased proportion of propionate and butyrate at the expense of acetate. Propionate is metabolized to methylmalonyl-CoA and then to succinyl-CoA, entering the Krebs cycle to convert into oxaloacetate and serve as a precursor for gluconeogenesis, primarily in the liver. This process is utilized by animals in the first 4 to 6 h post-ingestion, contributing to regulatory effects on satiety regarding energy [4,46,47,48,49,50]. In the current study, GLY intake ranged from 75.9 to 78.65 g/d, significantly altering the ruminal propionate-to-acetate ratio, especially at GLY inclusion levels of 10% and 15%, which aligns with the findings of Filho et al. [10].
The optimal concentration range for NH3-N is between 2.37 and 27.3 mg/dL. Fluctuations in rumen NH3-N concentration reflect dietary nitrogen degradation and its utilization by rumen microorganisms [51,52]. Nitrogen can reach the rumen through various routes, including non-protein nitrogen, true protein from the diet, urea recycling via saliva, and microbial degradation [53]. Microbial protein is ruminants’ most crucial nitrogen source, supplying 40% to 80% of their protein needs [54]. In this study, NH3-N concentrations ranged from 15.33 to 17.33 mg/dL with the inclusion of up to 15% GLY in the diet, exceeding the minimum ruminal NH3-N level of 5 mg/dL [55], which is adequate for effective ruminal fermentation and optimal bacterial growth [53]. The effects of glycerol on rumen NH3-N concentrations can vary. Van Cleef et al. [16] found no significant differences in NH3-N levels in diets with 10%, 20%, and 30% GLY. In contrast, Menezes et al. [53] reported an effect when glycerol was included at levels of up to 7.5% of the diet.

4.2. Backfat Thickness and Loin Eye Area, Carcass, and Physicochemical Characteristics of Meat

No differences were observed in the loin eye area, backfat thickness, carcass yield, or pH when 5%, 10%, and 15% glycerol were included in the diets of Suffolk × Hampshire cross lambs. The consistency in the loin eye area can be attributed to the similar final weights across diets containing 0%, 5%, 10%, and 15% glycerol, which aligns with the findings by Costa et al. [50]. These results contrast with those reported by Bezerra et al. [56] who noted that including up to 15% glycerol in the diets of Boer goats led to decreased final weights. The increase in fat observed with more than 5% glycerol may be due to the higher energy availability in glucose, which promotes lipogenesis and increased fat deposition [19]. This observation correlates with the thickness of backfat in this study, as the diets were isoenergetic. Although increased propionate levels due to glycerol were noted, it was insufficient to cause significant backfat deposition. Generally, fat deposition in carcasses is influenced by factors such as the breed, age, sex, and rearing system. The increase in the loin eye area is attributed to higher slaughter weights and age [56].
Carcass size variation can affect chilling rates and pH, potentially leading to meat quality issues [56]. Moreover, subcutaneous fat acts as a thermal insulator during the cooling process, slowing the carcass cooling rate and impacting the regular drop in pH [36,57]. The results obtained in this research align with those reported by Gunn et al. [34], Brant et al. [58], and Syperreck et al. [19], who included varying percentages of glycerol (5%, 10%, 15%, and 20% for Suffolk sheep and 14%, 25%, and 5%, 10%, 15%, and 20% for Dorper × Santa Inés cross sheep) in their diets. An increase in dietary energy typically improves the production performance and is closely related to carcass characteristics [59]. For instance, levels of 1% and 7% glycerol in the diets for Kazakh sheep, as reported by Hangdong et al. [60], positively influenced carcass yield, contrasting with the present study’s findings, which may be linked to the sex of the animals. The uniformity in slaughter weight may explain the lack of effects of glycerol on carcass characteristics, indicating that the inclusion of glycerol did not impact the studied parameters [19]. Additionally, carcass yield can vary due to age, live weight at slaughter, sex, physiological status, and feeding regime [61].
The decrease in muscle pH after slaughter is caused by anaerobic glycolysis, which is one of the most critical factors affecting meat quality, as it can influence tenderness, color, and WHC [4]. Furthermore, it enhances shelf life and improves organoleptic characteristics [62]. Meat shelf life is diminished when pH exceeds 5.8, resulting in darker meat, impacting consumer purchasing decisions [63]. In this study, the pH of the meat did not vary with the substitution of corn by glycerol. Thus, physical parameters like color and WHC also remained unaffected. These findings are consistent with those reported by Borghi et al. [64], Silva et al. [15], da Costa et al. [18], and Gomes et al. [65], who investigated varying levels of glycerol (0%, 6%, 10%, 12%, 18%, and 20%) in diets.
During the initial hours post-slaughter, muscle transforms into meat, involving the depletion of muscle glycogen reserves and the production of lactic acid [16]. Typically, the pH of lamb muscle decreases to its final value 24 h postmortem, coinciding with muscle fibers entering rigor mortis and achieving complete firmness [66]. Xiao et al. [67] indicated that before 12 h postmortem, lamb muscle is in the pre-rigor phase; it enters the rigor mortis phase from 12 to 24 h, and is in the post-rigor phase from 3 to 7 days, according to reported pH and shear stress values. The current research highlighted a decrease in pH during the meat’s storage time (24 h, 0, 7, 14, and 21 days), which affected its color and water retention capacity. However, pH values remained within the normal range (5.5–5.9), as reported by Teixeira et al. [68], and color was acceptable, with L*, a*, and b* values at or above 34 [69], 9.5 [70], and close to 3.38 [71], respectively. The color characteristics of lamb meat may be influenced by diet, production system, slaughter weight, breed, gender, and muscle type [72].
Furthermore, proteins are crucial for WHC, and the decrease in WHC in frozen meat over time is likely due to damage to structural cells and protein denaturation. This damage impairs the meat’s retention capacity and increases fluid loss [73,74]. Replacing up to 15% of corn with glycerol does not affect meat pH, color, or WHC.
The inclusion of GLY at 24 h, 7 days, 14 days, and 21 days of storage did not impact the chemical composition of the meat. During slaughter, the energy deficit caused by increased plasma insulin concentrations is mitigated, which helps reduce muscle protein degradation and preserves protein content in the carcass post-slaughter [75]. Lage et al. [36] reported that gradually increasing GLY in sheep diets led to a reduction in meat CP, which was attributed to a decrease in DMI due to the high impurity content in GLY that affected the yield and, consequently, fat deposition. However, in the present study, DMI was not affected, likely due to the 95% purity of the GLY used, which did not directly modify the DMI of the sheep. As a result, there was no effect on CP content at 24 h, 7 days, 14 days, and 21 days postmortem.
Regarding propionate production in the rumen, GLY is a precursor for glucose [8] that suggests an expected increase in fat deposition and intramuscular fat content [60], as indicated by Schoonmaker et al. [76], who noted that glucose is the primary carbon source for fatty tissue deposition. As GLY levels increased in the diets, there was an observed rise in propionate production; however, the concentration was insufficient to affect the ether extract content in the meat. Ultimately, there was no change in the percentage of ether extract in the meat, which may be due to the similar energy content across treatments. This finding is consistent with the results reported by Carvalho et al. [17].

5. Conclusions

This research showed that replacing up to 15% of ground corn with glycerol in lamb diets does not adversely affect the productive performance, backfat, or lean eye area. However, it does increase propionic acid and ammonia nitrogen concentrations while maintaining carcass characteristics and meat quality throughout shelf life.

Author Contributions

Conceptualization, U.H.-H., P.Z.-C., and M.E.O.-C.; methodology, U.H.-H., M.E.O.-C., and J.V.; software, J.G.H.-H. and P.Z.-C.; validation, U.H.-H. and M.E.O.-C.; formal analysis, J.G.H.-H. and P.Z.-C.; investigation, U.H.-H., M.E.O.-C., and P.Z.-C.; resources, M.E.O.-C. and J.V.; data curation, J.G.H.-H. and P.Z.-C.; writing—original draft preparation, U.H.-H., P.Z.-C., J.G.H.-H., and M.E.O.-C.; writing—review and editing, U.H.-H., P.Z.-C., M.E.O.-C., and J.V.; visualization, U.H.-H. and M.E.O.-C.; supervision, M.E.O.-C., P.Z.-C., and J.V.; project administration, M.E.O.-C. and J.G.H.-H.; funding acquisition, M.E.O.-C. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Animal care and handling procedures were conducted according to the technical specifications for the production, care, and use of laboratory animals established in the Official Mexican Standard (NOM-062-ZOO-1999). The study was conducted according to the guidelines of the Declaration of Helsinki and approved by the Institutional Review Board of the Colegio de Postgraduados (COBIAN/001/17), approved on 11 January 2017.

Data Availability Statement

The datasets used and analyzed during the current study are available from the corresponding author upon reasonable request.

Acknowledgments

The authors thank the Colegio de Postgraduados, Campus Montecillo, for providing the necessary facilities to conduct this study. They also acknowledge the research line “Knowledge Generation: Efficient Livestock with Biotechnology and Animal Welfare Considering Climate Change”.

Conflicts of Interest

The authors declare no conflicts of interest.

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Table 1. Ingredients and chemical composition of diets with increasing levels of glycerol used in feeding Suffolk × Hampshire lambs.
Table 1. Ingredients and chemical composition of diets with increasing levels of glycerol used in feeding Suffolk × Hampshire lambs.
Treatments
ÍtemGLY0GLY05GLY10GLY15
Ingredients (%)
Ground corn30282420
Ground sorghum30282523
Alfalfa hay12141314
Soybean meal10111314
Corn stover9787
Glycerol051015
Molasses4444
Minerals supplement *2222
Urea1111
Chemical composition
Dry matter (DM) (g/kg)92.1892.2492.8192.23
On DM basis (g/kg)
Crude protein17.9317.7117.0717.12
Neutral detergent fiber43.6643.7343.6143.40
Acid detergent fiber18.2818.8218.4518.87
Ether extract3.163.533.323.70
Ash6.056.636.276.55
Gross energy (kcal/100 g) **360.32360.09362.76361.22
GLY0: control diet; GLY05: control diet plus 5% of glycerol; GLY10: control diet plus 10% of glycerol, GLY15: control diet plus 15% of glycerol. * CoSO4 0.068%, CuSo4 1.04%, FeSO4, 3.57%, ZnO 1.24%, MnSO4 1.07%; IK 0.052%; y NaCl 92.96%. ** Data calculated according to FAO [22].
Table 2. Growth performance and ruminal fermentation of Suffolk × Hampshire lambs fed diets supplemented with glycerol.
Table 2. Growth performance and ruminal fermentation of Suffolk × Hampshire lambs fed diets supplemented with glycerol.
Treatments
ÍtemGLYy0GLY05GLY10GLY15SEMp-Value
Performance
Initial weight (kg)24.0623.7824.5923.930.40630.9102
Final weight (kg)46.5547.0646.6145.180.52070.6478
Dry matter intake (kg)1.5961.5731.5181.5220.0660.7933
Daily weight gain (kg/d)0.3740.3880.3660.3540.0080.2304
Feed conversion ratio4.204.084.134.320.1540.6094
Ruminal variables
pH6.03 6.286.386.390.2040.6554
Ammoniacal nitrogen (mg/dL)14.85 c15.33 cb16.70 ab17.33 b0.3560.0003
Volatile fatty acids (mmol/L)
Acetate (A)74.29 a72.35 ab69.46 b67.59 b1.4730.0040
Propionate (P)16.23 b17.60 b20.11 ab22.08 a1.4300.0060
Butyrate9.47 b10.04 ab10.41 a10.32 ab0.1300.0289
Ratio A:P4.58 a4.11 a3.45 ab3.06 c0.4280.047
GLY0: control diet; GLY05: control diet plus 5% of glycerol; GLY10: control diet plus 10% of glycerol; GLY15: control diet plus 15% of glycerol; SEM: standard error of the mean. a,b,c Mean in the same row with different superscripts differ significantly (p < 0.05).
Table 3. Backfat thickness and loin eye area of Suffolk × Hampshire lambs fed glycerol-supplemented diets.
Table 3. Backfat thickness and loin eye area of Suffolk × Hampshire lambs fed glycerol-supplemented diets.
Variables
TimeTratBackfat Thickness (cm)Loin Eye Area (mm2)
0 daysGLY02.0 b816 b
GLY052.0 b831 b
GLY102.1 b831 b
GLY152.3 b810 b
SEM0.0628.46
60 daysGLY03.8 a1217 a
GLY054.5 a1208 a
GLY104.2 a1159 a
GLY154.1 a1228 a
SEM0.1528.46
p-valueTreat0.2480.629
Time<0.0001<0.0001
Treat × time0.0960.516
GLY0: control diet; GLY05: control diet plus 5% of glycerol; GLY10: control diet plus 10% of glycerol; GLY15: control diet plus 15% of glycerol. BT: backfat thickness; LEA: loin eye area; SEM: standard error of the mean. a,b Mean in the same row with different superscripts differ significantly (p < 0.05).
Table 4. Carcass characteristics of Suffolk × Hampshire lambs fed diets supplemented with glycerol.
Table 4. Carcass characteristics of Suffolk × Hampshire lambs fed diets supplemented with glycerol.
Treatments
ÍtemGLY0GLY05GLY10GLY15SEMp-Value
Weights (kg)
Slaughter weight 51.1850.8051.5551.430.6390.847
Empty body weight42.1542.1942.7342.720.5640.808
Hot carcass weight25.4025.5625.9126.010.4020.673
Hot carcass yield (%)49.6050.3550.2650.600.5900.670
pH (slaughter)7.17.27.27.00.1390.845
GLY0: control diet; GLY05: control diet plus 5% of glycerol; GLY10: control diet plus 10% of glycerol; GLY15: control diet plus 15% of glycerol; SEM: standard error of the mean.
Table 5. pH, color, and water holding capacity (WHC) during shelf life of meat from Suffolk × Hampshire lambs fed diets supplemented with glycerol.
Table 5. pH, color, and water holding capacity (WHC) during shelf life of meat from Suffolk × Hampshire lambs fed diets supplemented with glycerol.
Time p-Value
ÍtemTreatments24 h7 d14 d21 dSEMTreatTimeTreat × Time
pHGLY0 6.10 a 5.96 b5.85 c5.70 d1.080.7510.0010.421
GLY56.10 a5.95 b5.82 c5.71 d
GLY106.17 a5.96 b5.81 c5.71 d
GLY156.12 a5.94 b5.84 c5.76 d
L* (Lightness)GLY036.63 a36.22 ab35.55 ab34.82 b0.770.9320.0010.972
GLY536.48 a36.33 a35.70 ab34.16 b
GLY1036.82 a36.65 a35.28 ab33.60 b
GLY1535.95 a35.16 a34.74 ab32.99 b
a* (Redness)GLY018.20 a 17.54 ab17.47 ab 16.83 b0.950.7860.0010.986
GLY517.34 a17.34 a16.56 a16.49 a
GLY1017.76 a17.35 a17.24 a16.82 a
GLY1517.80 a17.31 ab17.30 ab16.59 a
b* (Yellowness)GLY04.3 a3.9 ab3.9 ab3.4 b0.730.8380.0010.998
GLY54.0 a3.6 a3.5 ab2.9 b
GLY104.2 a4.0 a3.8 ab3.1 b
GLY154.1 a3.9 a3.5 b3.0 b
WHC (mL/100 g)GLY024.41 bx17.83 cy17.33 aby13.66 bz2.250.0010.0010.001
GLY528.16 ax24.66 ax18.71 aby16.31 by
GLY1028.33 ax21.86 by15.50 bz15.16 abz
GLY1528.16 ax23.48 aby 16.65 abz13.66 bz
GLY0: control diet; GLY05: control diet plus 5% of glycerol; GLY10: control diet plus 10% of glycerol; GLY15: control diet plus 15% of glycerol; SEM: standard error of the mean. a,b,c,d Mean in the same column with different superscripts differ significantly (p < 0.05). x,y,z Mean in the same row with different superscripts differ significantly (p < 0.05).
Table 6. Chemical characteristics during shelf life of meat from Suffolk × Hampshire lambs fed diets supplemented with glycerol.
Table 6. Chemical characteristics during shelf life of meat from Suffolk × Hampshire lambs fed diets supplemented with glycerol.
Time
ÍtemTreatments24 h7 d14 d21 dSEMTreatTimeTreat × time
MoistureGLY0 73.35 a73.68 b73.92 b74.00 b2.70.9410.3810.416
GLY573.73 a73.93 a74.15 a73.37 a
GLY1074.35 a 73.03 b74.26 ab73.37 ab
GLY1573.95 a73.96 a73.46 a72.78 a
Dry matterGLY0 26.6526.3426.0525.990.950.9350.3800.434
GLY526.2526.0625.8426.60
GLY1025.64 b26.93 a25.74 ab26.60 ab
GLY1526.0326.0326.5427.22
Crude proteinGLY0 17.23 ax14.64 by13.59 by11.62 bz0.480.0010.0010.030
GLY518.22 ax16.68 ay15.26 ay14.72 ay
GLY1018.00 ax 16.78 ay14.91 ay14.06 az
GLY1517.63 ax15.76 ay15.54 ay12.40 az
Ether extractGLY0 4.20 a4.38 a4.26 a4.30 a1.050.7340.9160.992
GLY54.16 a4.41 a4.59 a4.25 a
GLY104.70 a4.56 a4.44 a4.50 a
GLY154.31 a4.43 a4.61 a4.41 a
AshGLY0 4.02 a 3.89 a4.03 a3.80 a 1.950.4040.5090.806
GLY53.73 a4.17 a4.00 a3.95 a
GLY104.08 a4.33 a4.33 a3.90 a
GLY153.98 a4.08 a3.89 a4.11 a
* Gross energy
(Mcal/100 g)		GLY0 112.98 ax98.03 bcdy 82.28 dz85.26 cdy2.150.0070.00010.016
GLY5110.35 ax106.50 aby102.30 bcdy97.38 bcdy
GLY10114.36 ax108.18 aby99.67 bcdy97.37 bcdy
GLY15109.40 abx102.91 abcy103.91 bcdy90.39 bcdy
GLY0: control diet; GLY05: control diet plus 5% of glycerol; GLY10: control diet plus 10% of glycerol, GLY15: control diet plus 15% of glycerol; SEM: standard error of the mean. a,b,c,d Mean in the same column with different superscripts differ significantly (p < 0.05). x,y,z Mean in the same row with different superscripts differ significantly (p < 0.05). * Data calculated according to FAO [22].
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MDPI and ACS Style

Hidalgo-Hernández, U.; Ortega-Cerrilla, M.E.; Zetina-Córdoba, P.; Herrera-Haro, J.G.; Vian, J. The Effect of Different Amounts of Glycerol Fed to Lambs on Their Growth, Rumen Fermentation, Carcass Traits, Meat Characteristics, and Shelf Life. Agriculture 2025, 15, 1185. https://doi.org/10.3390/agriculture15111185

AMA Style

Hidalgo-Hernández U, Ortega-Cerrilla ME, Zetina-Córdoba P, Herrera-Haro JG, Vian J. The Effect of Different Amounts of Glycerol Fed to Lambs on Their Growth, Rumen Fermentation, Carcass Traits, Meat Characteristics, and Shelf Life. Agriculture. 2025; 15(11):1185. https://doi.org/10.3390/agriculture15111185

Chicago/Turabian Style

Hidalgo-Hernández, Uriel, María Esther Ortega-Cerrilla, Pedro Zetina-Córdoba, José G. Herrera-Haro, and José Vian. 2025. "The Effect of Different Amounts of Glycerol Fed to Lambs on Their Growth, Rumen Fermentation, Carcass Traits, Meat Characteristics, and Shelf Life" Agriculture 15, no. 11: 1185. https://doi.org/10.3390/agriculture15111185

APA Style

Hidalgo-Hernández, U., Ortega-Cerrilla, M. E., Zetina-Córdoba, P., Herrera-Haro, J. G., & Vian, J. (2025). The Effect of Different Amounts of Glycerol Fed to Lambs on Their Growth, Rumen Fermentation, Carcass Traits, Meat Characteristics, and Shelf Life. Agriculture, 15(11), 1185. https://doi.org/10.3390/agriculture15111185

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