Dietary supplementation of conjugated linoleic acid in adult Creole goats: Effects on weight gain, carcass yield and meat quality

Dietary supplementation of conjugated linoleic acid in adult Creole goats: Effects on weight gain, carcass yield and meat quality Marco A. Sotelo-Turban1, Omar Hernández-Mendo1, Glafiro Torres-Hernández1, Lorenzo D. Granados-Rivera2, Jorge A. Maldonado-Jaquéz3 1 Programa de ganadería, Colegio de Postgraduados, Carretera, México - Texcoco. Km. 63.5 Montecillo, Estado de México, CP. 56230, Mexico 2 Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias, Campo Experimental General Terán, General Terán, Nuevo León, C.P. 67400, Mexico 3 Instituto Nacional de Investigaciones Forestales Agrícolas y Pecuarias, Campo Experimental La Laguna, Matamoros, Coahuila, CP. 27440, Mexico Corresponding author: Omar Hernández-Mendo ([email protected]) Academic editor: Mohammed El Khasmi♦Received 3 June 2025♦Accepted 13 October 2025♦Published 2 December 2025 Abstract The study evaluated the effects of dietary supplementation with rumen-protected conjugated linoleic acid (CLA) on productive performance, carcass characteristics and meat quality in lactating adult Creole goats. The trial included fifteen lactating Creole goats, divided into three dietary treatments: a control group (no CLA), and groups receiving 50 or 90 g/day of CLA supplementation. The experiment lasted seven weeks after a two-week adaptation period. Results showed no significant differences between dietary treatments in terms of dry matter intake, daily weight gain, feed efficiency or back fat thickness. However, goats supplemented with 90 g/day CLA showed a slight but significant reduction in cold carcass yield. Meat quality parameters, such as final pH, shear strength, water holding capacity and chemical composition, were not affected by dietary supplementation with CLA, although all goats produced relatively tough meat, commensurate with their age. In particular, dietary supplementation with CLA significantly increased the content of the cis-9, trans-11 CLA isomer in muscle tissue, especially at the 90 g/day dose, without significantly affecting other major fatty acids. The trans-10, cis-12 CLA isomer did not noticeably accumulate in muscle tissue. Thus, although CLA supplementation effectively enriched goat meat with beneficial CLA isomers, it did not improve growth performance or standard measures of meat quality. In conclusion, this study demonstrates that supplementation with protected CLA can beneficially modify the fatty acid profile of goat meat without negatively affecting meat quality traits, potentially adding nutritional value to meat from lactating adult goats. Keywords Adult goats, Fatty acids, Lipid metabolism, Meat quality, Zoogenetic resources Introduction Goat farming has an advantage over other types of livestock due to the adaptation of goats to adverse conditions, surviving and reproducing even when the available feed does not fully meet nutritional needs. Therefore, the implementation of feed supplementation programs is of great importance not only to improve productive performance, but also to improve the quality of goat products (Gawat et al. 2023). In Mexico, goats represent a primary source of income for many smallholders; production is typically based on extensive grazing, and the output – meat or milk – is used in regional dishes (Tajonar et al. 2022). In this context, conjugated linoleic acid (CLA) has emerged as a potential feed supplement to improve product quality, mainly due to the effects of its bioactive isomers. Two CLA isomers in Copyright Sotelo-Turban, et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Emirates Journal of Food and Agriculture 37: 1–9 doi: 10.3897/ejfa.2025.160938 RESEARCH PAPER Sotelo-Turban, et al.: Meat quality from adult Creole goats2 Emirates Journal of Food and Agriculture particular-cis-9, trans-11 and trans-10, cis-12-have demonstrated anticancer (for cis-9, trans-11) and lipolytic (for trans-10, cis-12) properties (Yang et al. 2015; Ivanović et al. 2016). Several studies have reported that the addition of CLA to ruminant diets can alter the fat metabolism. For example, in cattle, CLA supplementation reduced milk fat content (Granados-Rivera et al. 2017; Candia-López et al. 2025) and in dairy sheep it reduced milk fat without affecting organ fat stores (Sinclair et al. 2010). The two main isomers of CLA have been identified in muscle tissue; however, their effects on body fat are variable. Wynn et al. (2006) reported that the inclusion of 25, 50 or 100 g/day of a protected CLA supplement in lamb diets increased the proportions of the cis-9, trans-11 and trans-10, cis-12 isomers of CLA in muscle tissue, but did not reduce total intramuscular fat content. Studies in goats are much more limited, especially in local breeds (Ivanović et al. 2014; Youssouf et al. 2019) where only a few productive traits have been evaluated (Granados-Rivera et al. 2022). It has been shown that CLA supplementation in dairy goat diets can improve body condition, weight gain and milk production (Baldin et al. 2014). Research on goat meat quality responses to CLA is scarce (Bautista-Martinez et al. 2025). Despite the economic importance of goat farming and the cultural demand for goat meat in various regional dishes (Tajonar et al. 2022). It is common in Mexico for goat meat to come from adult cull animals (often older females that have completed their productive life), whose meat quality is generally inferior (Oliveira-Marques et al. 2022). The sale of this type of meat is not highly regulated and lacks quality standards (Gökdal 2013). However, consumers continue to demand these traditional goat meat dishes, and high market prices are not a deterrent. In this regard, there is a need for further research on nutritional strategies to improve the quality of cull goat meat. Therefore, the objective of this study was to evaluate the effects of dietary supplementation with protected CLA on productive response, carcass yield and meat quality (physicochemical composition and fatty acid profile) of adult Creole goats. Materials and methods Location The experiment was conducted at the Caprine Experimental Unit of the National Institute of Forestry, Agricultural and Livestock Research (INIFAP), La Laguna Experimental Station, located in Matamoros, Coahuila, Mexico (24°22'N, 103°23'W, 1100 masl). The climate of the region is classified as warm-dry (BWh), with a mean annual temperature of 22.6 °C and an annual precipitation of 215.5 mm. Animals and experimental design 15 non-pregnant adult local (Creole) goats in early lactation (11 ± 7 days in milk) were selected. Their initial mean body weight was 34.8 ± 1.6 kg, with a body condition score of 2.5 (scale 1–5; Walkden-Brown et al. 1994). Goats were balanced into three groups (n = 5 per group) of similar body weight, milk production, and lactation number (all were third parity females). Groups were then randomly assigned to three dietary treatments in a completely randomized design. A two-week adaptation period preceded a seven-week experimental feeding period. The dietary treatments were Control – basal diet without CLA supplementation; CLA-50 – basal diet plus 50 g/day of CLA supplementation; and CLA-90 – basal diet plus 90 g/day of CLA supplementation. The CLA supplement used (Lutrell® Pure, BASF) consisted of a mixture of rumen-protected fatty acids, providing approximately 6 g of cis-9, trans-11 CLA and 6 g of trans-10, cis-12 CLA per 50 g of supplement, and 11 g of each of these isomers per 90 g of supplement. The supplement was added to the feed to ensure complete intake in the CLA-50 and CLA-90 groups. Housing and feeding Goats were housed individually in 2 × 3 m pens equipped with shaded areas, feeders, and free access to clean water. All goats were offered 2.5 kg/day (as is) of basal diet, divided into two equal rations (fed at 08:00 and 14:00 h). The basal diet (Table 1) was formulated as a total mixed ration and consisted of approximately 68% concentrate (grains, bran, soybean meal, urea, molasses, vitamins/minerals) and 32% roughage (alfalfa hay and corn stover). The diet met or exceeded the requirements for lactating meat goats (NRC 2007). CLA supplementation (for CLA-50 and CLA-90 treatments) was administered twice daily by sprinkling the designated amount on the feed at each feeding. Goats were milked by hand once daily (09:00 h) to maintain lactation. Throughout the trial, feed offered and refused by each goat was recorded daily, which allowed calculation of daily dry matter (DM) intake by difference. Feed allocations were adjusted each week according to the live weight of each goat in order to minimize rejections. Measurements and data collection Goats were weighed in the morning once a week to monitor live weight changes. Daily weight gain (DWG) was calculated for each goat as the difference between final and initial weight divided by the trial duration of 49 days. Feed efficiency (FE) was calculated by dividing DWG by daily DM intake and feed conversion index (FI) by DM intake divided by DWG. At the end of the experiment, all goats were humanely slaughtered in a federal inspection-type slaughterhouse according to the guidelines of NOM-033ZOO-1995. Hot carcass weight was measured immediately after evisceration. Hot carcass yield was calculated as (hot carcass weight/final live weight) × 100. Carcasses were then cooled to 4 °C for 24 h, after which cold carcass weight was recorded and cold carcass yield was calculated analogously. Back fat thickness was measured on the Emir. J. Food Agric ⋅ Volume 37 ⋅ 2025 3 Emirates Journal of Food and Agriculture cold carcass over the Longissimus dorsi muscle, between the 12th and 13th ribs, using a digital vernier (Somet Inox, 150 mm). Muscle pH was measured in the Longissimus muscle at 45 minutes post-mortem (initial pH) and at 24 hours post-mortem (final pH) using a portable potentiometer (Maki-Petays et al. 1991). After chilling for 24 hours, a section of the Longissimus dorsi (loin) was removed from each carcass to analyze meat quality. Meat color (L*, a*, b* for lightness, redness and yellowness) was measured on fresh loin cuts using a colorimeter (taking the average of three readings per sample) (Robertson 1977). Shear strength was measured as an indicator of tenderness: tenderloin sub-samples were cooked at 70 °C internal, cooled and cores were removed to determine shear strength (kg/cm²) using a Warner-Bratzler type knife (Honikel 1998). Water holding capacity was determined by the pressed juice method (expressed in mL of water released per 100 g of meat) (Plá 2000). The water activity (Aw) of the meat was also measured using a calibrated water activity meter (Plá 2000). For chemical composition, minced meat samples were analyzed for moisture, crude protein, intramuscular fat, collagen and ash by near infrared spectroscopy (FoodScan™ apparatus, FOSS Analytics), following the manufacturer’s procedures (three readings per sample, averaged) (Anderson 2007). Proximal composition results are expressed as percentages of fresh meat. Fatty acid analysis For fatty acid profile determination, aliquots of Longissimus dorsi muscle were processed to extract lipids and then methylated to fatty acid methyl esters (FAME) using the one-step acid-catalyzed methylation method of Palmquist and Jenkins (2003). The extraction of FA was performed according to the methodology modified by Granados–Rivera et al. (2017). A Hewlett Packard 6890 chromatograph with an automatic injector and a silica capillary column (100 m × 0.25 mm × 0.20 μm thick, Sp–2560, Supelco) was used to quantify FA methyl esters. The identification of FA was done comparing the retention times of each peak obtained from the chromatogram, with a standard of 37 FA methyl ester components (Supelco 37 Component FAME) and a specific standard for isomers C18:1 t11 (Sigma–Aldrich) and cis–9, trans–11 and trans–10, cis–12 (Nu–Check–Prep.). Statistical analysis Performance data (growth) and carcass traits were analyzed as a completely randomized design with repeated measures (for weekly weight data), using the MIXED procedure of SAS (SAS Institute 2008). Meat quality and fatty acid composition variables were analyzed by one-way ANOVA using the GLM procedure of SAS, with dietary treatment as a fixed effect. For variables measured over time (e.g., weekly weights), the model included the fixed effect of week and the treatment × week interaction. Initial live weight was included as a covariate for the performance and intake variables. Tukey’s post-hoc test was used to compare treatment means where appropriate. Significance was declared at P ≤ 0.05, and trends were noted for 0.05 < P < 0.10. Results Daily dry matter (DM) intake was not significantly different among the three groups (overall mean ≈1.7 kg/day; P > 0.05). Average daily weight gain (ADG) was also unaffected by CLA supplementation (P > 0.05). Goats in all treatments gained approximately 0.12 kg/day (Table 2). Feed efficiency and feed conversion ratio did not differ between treatments (P > 0.5), neither was hot carcass Table 1. Ingredients, chemical composition and fatty acid composition (g/100 g FA) of the diet. Ingredients (% DM) Grain sorghum 17.1 Grain corn 17.1 Wheat bran 9.0 Soy flour 9.0 Urea 1.2 Molasses 4.8 Vitamins and minerals †1.8 Corn stubble 8.0 Alfalfa hay 32.0 Chemical composition (% DM) Dry matter 90.2 Crude protein 11.4 NDF 35.4 ADF 20.5 ME(‡) (Mcal/kg DM) 2.6 Fatty acids Dietary basis Supplement § <C16:0 2.55 3.56 C16:0 24.54 11.60 C16:1 1.50 Nd C18:0 2.94 46.42 C18:1 n-9 16.68 12.08 C18:2 n-6 18.74 1.01 C18:3 n-3 32.28 Nd Cis-9, Trans-11 CLA ¶nd 12.03 Trans-10, Cis-12 CLA nd 12.26 C20:0 0.77 0.56 C22:0 nd 0.48 † Premix of minerals and vitamins (Ca 24%, P 3%, Mg 2%, Na 8%, Cl 12%, K 0.50%, S 0.50% and antioxidant 0.50% Cl; lasalocid 2000 ppm, Cr 5 ppm, Mn 4000 ppm, Fe 2000 pp, Zn 5000 ppm, I 100 ppm, Se 30 ppm, and Co 60 ppm; vitamin A 500 000 IU, vitamin D 150 000 IU, vitamin E 1000 IU. ‡ Calculated according to NRC (2007). nd = Not detected. § Supplement = Lutrell Pure ®, BASF. (¶) CLA = Conjugated linoleic acid. Sotelo-Turban, et al.: Meat quality from adult Creole goats4 Emirates Journal of Food and Agriculture yield, which averaged 42.6% in all groups (Table 2). However, cold carcass yield did show treatment effect (P < 0.05), where the 90 g CLA group had a lower cold carcass yield (by approximately 1.5 percentage points) compared to the control and CLA-50 groups. Regarding back fat thickness, the treatments evaluated also had no significant effect (P > 0.05). Hot and cold carcass pH, physicochemical characteristics and chemical composition of meat from adult goats were not different between treatments (P > 0.05), except luminosity (L value), which was lower (P < 0.05), which means darker meat, in the CLA-90 group compared to the control (Tables 3, 4). Dietary supplementation with CLA had a clear effect on the fatty acid profile of meat in one important aspect, the level of cis-9, trans-11 CLA in goat meat increased significantly with CLA treatments (P = 0.0001). In longissimus muscle, the concentration of cis-9, trans-11 CLA was highest in the CLA-90 group, intermediate in CLA-50 and lowest in the control (Table 5). In contrast, the isomer -trans-10, cis-12 CLAwas not significantly different in meat between treatments. Discussion Animal performance Although the average daily weight gain was not different between treatments, there was some variation in weight gain over time, with all goats showing a marked increase in the first two weeks, due basically to compensatory growth Table 2. Animal performance of adult goats supplemented with different levels of protected conjugated linoleic acid in the diet. Treatment, Protected Conjugated Linoleic Acid, g d-1 Variable Control 50 90 SEM P Daily dry matter (kg/d) 1.82 1.75 1.62 0.042 0.146 Daily live-weight gain (kg/d) 0.12 0.14 0.11 0.010 0.517 Food efficiency 0.06 0.08 0.07 0.005 0.532 Feed conversion 16.21 12.08 14.69 1.131 0.345 Hot carcass yield (%) 42.89 42.23 42.92 0.608 0.889 Cold carcass yield (%) 42.61a 42.58ab 38.28b 0.707 0.028 Back fat (mm) 3.0 3.18 3.10 0.058 0.473 Values with different literals in the same row are significantly different (P ≤ 0.05). SEM = Standard error of the mean. Table 3. Hot and cold carcass pH and physicochemical characteristics of meat from adult goats supplemented with different levels of protected conjugated linoleic acid in the diet. Treatment, Protected Conjugated Linoleic Acid, g d-1 Variable Control 50 90 SEM P Hot carcass pH 7.31 7.17 7.22 0.086 0.787 Cold carcass pH 6.24 6.09 6.17 0.029 0.153 Color L*51.20a 38.27b 38.76b 1.151 0.001 a16.63 19.43 22.04 1.380 0.317 b6.53 6.66 7.40 0.230 0.283 Shear force (kg cm-2)5.52 6.09 5.24 0.412 0.696 Water activity 0.99 0.99 0.99 0.004 0.173 Water holding capacity (ml 100 g-1of meat) 15.9 12.3 13.5 1.074 0.407 Values followed by a different letter in the same row are significantly different (P ≤ 0.05). SEM = standard error of the mean. Table 4. Chemical composition of meat from adult goats supplemented with different levels of protected conjugated linoleic acid in the diet. Treatment, Protected Conjugated Linoleic Acid, g d-1 Variable 050 90 SEM P Protein (%) 21.32 21.07 21.81a 0.296 0.593 Fat (%) 7.48 8.91 6.98 0.936 0.689 Collagen (%) 2.37 2.12 2.01 0.067 0.130 OM (%) 97.40 97.72 98.11 0.156 0.219 Humidity (%) 71.24 70.50 71.48 0.615 0.797 Ash (%) 2.60 2.28 1.89 0.156 0.219 Values with different literals in a row are different (P ≤ 0.05). OM, organic matter; *SEM = Standard error of the mean. Table 5. Fatty acid profile (g 100 g-1 of total FA) of meat from adult goats supplemented with different levels of protected conjugated linoleic acid in the diet. Treatment, Protected Conjugated Linoleic Acid, g d-1 Fatty acids 050 90 SEM P Saturated Capricor 0.118 0.152 0.124 0.123 0.519 Lauri 0.064 0.061 0.153 0.026 0.301 Myristi 2.043 2.213 2.420 0.131 0.518 Palmitic 23.667 23.546 23.723 0.412 0.984 Stearic 19.553 22.295 20.442 0.964 0.515 Arachidi 0.051 0.045 0.042 0.005 0.784 Heneicosanoic acid 0.124 0.175 0.205 0.020 0.314 Heptadecanoi 1.150 1.103 1.451 0.079 0.193 Monounsaturated Myristoleic 0.554 0.325 1.110 0.176 0.218 Palmitoleic acid 2.158 1.921 2.288 0.196 0.748 C 10, Heptadecanoic 0.877 0.694 1.132 0.117 0.343 Oleic 43.102 41.747 38.693 1.254 0.370 Polyunsaturates Linolelaid 0.202 0.159 0.178 0.014 0.505 Linoleic 2.784 2.360 3.358 0.427 0.643 Elaídic 2.153 1.574 2.474 0.327 0.541 Linolenic 0.257 0.340 0.253 0.029 0.421 C 9, T 11, CLA 0.277b 0.590a 0.673a 0.024 0.0001 C 12, T 10, CLA 0.163 0.180 0.268 0.039 0.531 Arachidonic 0.718 0.513 0.862 0.140 0.607 Total, fatty acids Saturated 46.750a 49.590b 48.560b 0.220 0.516 Monounsaturated 46.689a 44.687b 43.223b 0.436 0.419 Polyunsaturates 6.549b 5.716b 8.066a 0.142 0.464 Total 99.988 99.993 99.849 0.266 0.466 Values with different letters in a row are different (P ≤ 0.05). CLA, conjugated linoleic acid; SEM = standard error of the mean. Emir. J. Food Agric ⋅ Volume 37 ⋅ 2025 5 Emirates Journal of Food and Agriculture in the transition from a grazing diet to a nutrient-rich stall diet, as stated by Gusha et al. (2015), who reported that goats transitioning from pasture to a high-concentrate diet showed an initial weight gain. Notably, the goats in our study were lactating, therefore, a significant portion of nutrients was toward milk production and may inherently limit growth rates compared to non-lactating goats (Candia-Lopez et al. 2025). The dry matter intake level found in this study is higher than some values reported in the literature for similar goats (Rodriguez-Zamora and Elizondo-Salazar 2012), which have attributed the lower intakes to fiber-rich diets that slow the rate of passage and favor rumen filling. In our study, the palatability of the diet could have contributed to the relatively high intake, even though the palatability of the diets was not evaluated, which agrees with that stated by Quiroz-Cardoso et al. (2015), who reported that local goats increased feed intake when a forage-based diet was supplemented with sweet-tasting legume pods. The fact that feed efficiency and feed conversion ratio were not different between treatments indicates that the addition of 50–90 g/day of protected CLA to the diet had neither detrimental nor beneficial effects on feed utilization for growth under these conditions. The known effect of CLA in lactating animals is milk fat depression (Granados-Rivera et al. 2017; Candia-López et al. 2025), which may improve energy balance by reducing energy production in milk fat. This theoretically could save energy for body weight gain as observed by improved energy status in dairy goats supplemented with CLA (Granados-Rivera et al. 2017). However, in the present study, no increase in weight gain was observed in the CLA groups, perhaps because the lactating goats were already in a positive energy balance or the duration of supplementation (seven weeks) was insufficient to manifest changes in body weight. Hot carcass yield did not differ significantly between treatments, but cold carcass yield did show a treatment effect, where the 90 g CLA group had a lower cold carcass yield. This is basically due to a high inclusion of unsaturated fatty acids in the diet, CLA for instance, may have affected tissue characteristics related to water loss during chilling (Webb et al. 2005). Sometimes diets rich in unsaturated fats can reduce the water holding capacity of meat, resulting in higher drip loss and lower chilled carcass yield. In our study, treatment with 90 g/day CLA might have slightly decreased carcass water retention, which is consistent with the trend of lower chilled yield in that group. However, further research would be necessary to confirm this mechanism. No differences in backfat thickness were observed between treatments, which contrasts with the expectation that CLA-especially the trans-10, cis-12 isomer-can reduce adiposity. In cows, trans-10, cis-12 CLA is known to inhibit fat synthesis in adipose tissue (Baumgard et al. 2002; Zhang et al. 2015). However, evidence in goats and sheep suggests that typical CLA supplementation levels do not generally reduce subcutaneous fat (Sinclair et al. 2010; Granados-Rivera et al. 2017). Our results agree with those findings, even the highest dose of CLA did not appreciably affect backfat deposition. According to Wynn et al. (2006), older animals, such as the adult goats from own study, tend to accumulate fat with age regardless of diet, mostly in internal depots, and any anti-adipogenic effect of CLA was too small to detect in subcutaneous fat. Furthermore, the amounts of CLA used may not have been sufficient to cause significant changes in body fat, as noted by Wynn et al. (2006), who found no effect on backfat when feeding protected CLA to sheep at similar doses. Carcass and meat quality Other than the small change in cold carcass yield, other carcass characteristics were largely unaffected by CLA. Final meat pH (measured in the loin after 24 h of chilling) was 6.1–6.2 on average and did not differ between treatments (P > 0.05). The initial pH of muscle after slaughter (~7.2 at 45 min) was also similar between groups. These pH values are higher than the normal range reported for goat meat at 24 h post-mortem (typically pH 5.6–5.8). High meat pH in goats is common and is generally attributed to pre-slaughter stress causing low muscle glycogen stores (Lokman et al. 2017; Gawat et al. 2023). Goats are known to be very susceptible to stress, which may limit the pH drop after slaughter. In our study, although management was standard, the goats experienced stress during transport and lairage prior to slaughter. An elevated final pH may negatively affect meat quality (resulting in darker and drier meat). Alende et al. (2014) observed that when goats experience even moderate stress prior to slaughter, muscle glycogen depletion leads to a slower decline in pH. The consistently high pH here suggests that all groups, regardless of diet, likely had some degree of pre-slaughter stress. Meat color was slightly influenced by CLA treatments. The control and CLA-supplemented groups showed no difference in redness (a-value) or yellowness (b-value) of meat. However, there were indications that meat from CLA-supplemented goats was darker, since luminosity (L value) was lower in the CLA-90 group compared to the control. This is consistent with observations that higher final pH, as observed in our goats, often results in darker meat color. It has been reported that animals fed certain supplements had meat with lower L* values (darker color), possibly associated with changes in muscle chemistry. Martinez (2020) suggested that dietary factors that improve muscle antioxidant status or myoglobin content may also affect color, but in our case the key factor is probably pH and age of the animals. All goats were old (retired breeders), which inherently contributes to darker muscle pigmentation and lower L*. Therefore, any effect of CLA on color would be secondary to these dominant factors. Meat tenderness, as indicated by shear strength, was not significantly different among treatments. Mean shear strength values were about 5.0–6.0 kg/cm² for all groups, Sotelo-Turban, et al.: Meat quality from adult Creole goats6 Emirates Journal of Food and Agriculture which exceeds the typical threshold for “tender” meat. In fact, these values classify the meat as relatively tough. This result is not surprising given the age of the animals (5–6 years). Older goats develop more cross-linked collagen in the muscle, which increases toughness. Our shear strength results were higher than the maximum for “soft” meat according to Webb et al. (2005). The advanced age and continued use of these females for breeding probably contributed to tougher meat, regardless of diet. In practical terms, this meat in Mexico is often used for slow-cooked dishes (e.g., birria) where prolonged cooking at high temperatures mitigates toughness. Yakan et al. (2016) reported high shear strength values in meat from cull Damascus goats, emphasizing that cooking methods can compensate for inherent toughness. Furthermore, diet did not appear to influence tenderness in our study. Contrary to popular belief, diet type (within typical diets) usually has minimal direct effect on goat meat tenderness, unless it involves extreme diets or beta-adrenergic agonists (Karami and Bagheri 2019). The level of physical activity may also affect toughness; our goats had been on pasture prior to the trial, and exercise may increase muscle firmness (Revilla et al. 2021). In summary, any potential softening effect of CLA (e.g., through altered fat deposition) was not evident, probably overshadowed by the age of the animals and pre-experimental handling. Other physicochemical attributes of meat showed no adverse effects of CLA. Water activity (aw) of meat was uniform (~0.99) in all treatments and water holding capacity did not differ significantly. Water holding capacity values (around 12–16 mL/100 g) are within normal ranges for 24-h post-mortem goat meat. This trait is closely related to pH; higher pH may correspond to higher water retention. In our study, despite elevated pH in all groups, measured water holding capacity did not vary significantly among diets. Lokman et al. (2017) reported slightly lower water retention values in goat meat than those observed by us, but those goats had a more normal pH decline. The lack of differences here suggests that CLA supplementation, at these levels, did not negatively impact the ability of muscle to retain moisture during initial chilling and storage. The chemical composition of goat meat was not significantly altered by CLA treatments. Meat from all groups had similar percentages of protein (~21.1–21.8%), intramuscular fat (~7–9%), collagen (~2.0–2.4%), ash (~2%) and moisture (~70–71%) (P > 0.10). These values are within the expected ranges for adult goat meat 24 hours post-mortem and showed no trend attributable to the diets. This indicates that feeding protected CLA, even up to 90 g/day, did not dilute or concentrate the major nutritional components of the meat. Previous studies in lambs and goats also found no change in proximal meat composition with CLA supplementation (Wynn et al. 2006; Pormalekshahi et al. 2019). Our findings concur: although CLA could redistribute fat between depots, it did not change the overall fat or protein content in muscle. Meat fatty acid profile Dietary supplementation with CLA had a clear effect on the fatty acid profile of meat in one important aspect: the level of cis-9, trans-11 CLA in goat meat increased significantly with CLA treatments (P = 0.0001). In longissimus muscle, the concentration of cis-9, trans-11 CLA was highest in the CLA-90 group, intermediate in CLA-50 and lowest in the control (Table 5). This result is expected because the supplemented CLA was an approximately equal mixture of the two major isomers, and part of the dietary CLA bypassed ruminal biohydrogenation to be incorporated into the tissues. In addition, cis-9, trans-11 CLA can be formed endogenously in ruminant tissues via Δ^9-desaturase from vaccenic acid (trans-11 C18:1), a rumen fermentation intermediate (Pariza et al. 2001; Gómez-Pastén et al. 2010). By supplying more CLA (especially in the CLA-90 treatment), we provide more substrate (both CLA itself and the precursor of vaccenic acid) for its deposition in muscle. The significant increase in cis-9, trans-11 CLA content in meat at the 90 g dose demonstrates a nutrigenomic effect of CLA supplementation, as also noted by Abdelatty et al. (2019) in a study on CLA and gene expression in muscle. This result is nutritionally positive, as cis-9, trans-11 CLA is the isomer associated with anti-cancer properties and is considered a value-added component in meat. In contrast, the isomer -trans-10, cis-12 CLAwas not significantly different in meat between treatments (Table 5). The variability was large and the differences were not statistically clear (P > 0.05). Pormalekshahi et al. (2019) found that both CLA isomers in goat meat increased with supplementation of 15 g/kg CLA, although cis-9, trans-11 normally predominates. In our study, the trans-10, cis-12 isomer may have been metabolized more extensively or deposited less efficiently. It is also possible that goat tissues preferentially incorporate or synthesize the cis-9, trans-11 isomer (Adeyemi et al. 2016). Notably, trans-10, cis-12 CLA is usually more active in inhibiting fat synthesis in mammary gland and adipose tissue. Its lack of accumulation in muscle is consistent with findings that its effects are most pronounced in reducing milk fat (not muscle fat) and that it can be partially converted or catabolized. Overall, our fatty acid results are consistent with the idea that supplementation with protected CLA can enrich ruminant products with CLA without negative effects on other fatty acids. Adeyemi et al. (2016) similarly reported increases in total PUFA and specifically cis-9, trans-11 CLA in goat meat with dietary CLA, while observing a simultaneous increase in total SFA. We also observed a trend toward higher SFA content in the CLA groups (CLA-fed goats had ~1–2 percentage points more SFA than the control in our data, although it was not statistically significant). This increase in SFA could be related to incomplete ruminal biohydrogenation of the additional unsaturated fatty acids, resulting in more saturated end products. However, in this case the changes were of small magnitude. Importantly, the increased CLA content in meat from CLA-supplemented goats could be considered Emir. J. Food Agric ⋅ Volume 37 ⋅ 2025 7 Emirates Journal of Food and Agriculture a functional improvement in the nutritional profile of the meat, as CLA is often touted for its health benefits in human diets. Conclusion Inclusion of rumen-protected conjugated linoleic acid supplementation at 50 or 90 g/day in the diet of lactating adult Creole goats did not significantly improve growth performance or alter most carcass and meat quality parameters. Dry matter intake, weight gain, feed efficiency and carcass yields (hot carcass yield and backfat thickness) were similar between CLA-supplemented goats and non-supplemented controls. At the highest CLA dose, a reduction in cold carcass yield was observed. Meat physicochemical properties – including pH, color, tenderness, water holding capacity and proximal composition – showed no detrimental effects of CLA supplementation. All goats, being older lactating animals, produced meat with a high final pH and firm texture, regardless of diet. The most notable impact of CLA supplementation was on the fatty acid profile of goat meat. Feeding protected CLA, especially at 90 g/day, markedly increased the content of the beneficial cis-9, trans-11 CLA isomer in muscle tissue. This increase in CLA content in meat was achieved without adversely affecting other major fatty acid classes. The trans-10, cis-12 CLA isomer did not accumulate significantly in meat. In summary, dietary supplementation with CLA in cull dairy goats under these conditions enriched the meat with conjugated linoleic acid, but did not result in improvements in growth rate or conventional meat quality traits. These results suggest that although protected CLA can be used to modify the fatty acid profile of goat meat (which could add value for health-conscious consumers), it does not necessarily translate into improved animal performance or tenderer or cleaner meat in older goats. Future research could explore CLA supplementation in younger meat goats or for longer periods, as well as combinations with management strategies to mitigate pre-slaughter stress, to fully evaluate any potential benefits of CLA in goat meat production. Author contributions All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by MAST, LDGR, JAMJ and OHM. The first draft of the manuscript was written by MAST and OHM and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript. Funding This research was supported by the Research Department of the Colegio de Postgraduados-Mexico, and INIFAP – La Laguna Experimental Campus, at Matamoros, Coahuila, México. Ethical statement The care and use of the animals was carried out in accordance with the guidelines of the Federal Animal Health Law (Federal Official Gazette, 25-07-2007) and the study protocol was approved by the Institutional Animal Care Committee (COBIAN/013/23). At the end of the trial, the goats were slaughtered following the humane slaughter guidelines outlined in the Mexican Official Standard NOM-033-ZOO-1995. Disclosure statement Authors declare no competing financial interests or personal relationships that could potentially affect outcomes reported in this manuscript. Data availability statement The data that support the findings of this study are available from the corresponding author [OHM], upon reasonable request. Acknowledgements We greatly thank the National Council of Humanities, Science and Technology (CONAHCyT-Mexico) for the scholarship granted to the first author. 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