Effect of Rearing Season on Meat and Intramuscular Fat Quality of Beni-Guil Sheep

Twenty Beni-Guil-PGI female lambs were used to study the effects of rearing season on meat quality characteristics, fatty acids profile, and lipid content. The animals were reared according to the pastoral-transhumant system in the eastern region of Morocco. The treatments consisted of 10 female lambs reared in summer-autumn (SA) and slaughtered at winter season and 10 female lambs reared in winter-spring (WS) and slaughtered at spring season. After the slaughter, the longissimus lumborum was collected for each animal for meat quality analysis. Compared to lambs reared in SA, the meat from the WS group showed higher (
 
 p
 <
 0.01
 
 ) pH, chroma, and lightness values (5.79 vs. 5.72, 23.97 vs. 18.46, and 47.03 vs. 41.04, respectively). On the other hand, the meat from WS presented higher (
 
 p
 <
 0.05
 
 ) intramuscular fat content (5.14 % vs. 3.82%, respectively). However, the intramuscular fat of the lambs reared in SA was characterized by greater (
 
 p
 <
 0.01
 
 ) PUFA percentage (16.82% vs. 12.40%, respectively), thrombogenic (
 
 p
 <
 0.001
 
 ) and atherogenic index (
 
 p
 <
 0.001
 
 ), and PUFA/SFA ratio (
 
 p
 <
 0.01
 
 ; 0.42 vs. 0.25, respectively). Nevertheless, those reared in WS season have a higher (
 
 p
 <
 0.001
 
 ) PUFA n − 3 (2.58% vs. 1.14%, respectively) content, and therefore favorable (
 
 p
 <
 0.001
 
 ) n − 6/n − 3 ratio (3.78 vs. 12.98, respectively).


Introduction
In the last decade, with the increasing emphasis on organic food and sustainable agriculture, the use and exploitation of local breeds have received particular attention. In Morocco, a semiextensive breeding system, mainly of native breed or its crosses, is widely practiced to produce a traditional lamb slaughtered around the age of 6-8 months. Local breeds are known to be less productive than the nonnative and/or more selected breeds but are known by their adaptability, even in marginal arid lands, to climatic conditions and their high resistance to local parasites and they produce high meat quality. is is the case of the Beni-Guil IGP breed from the eastern region of Morocco. eir meat characteristics imply its potential use in an ecosustainable or organic selection system to produce a specific meat brand characteristic of the local territory. For ewes, the most frequent systems are semiextensive systems using pastures with the practice of pastoralism. Lambs weaning occurs at the age of 3 months. Generally, breeders implement a finishing stage to lambs (fattening) after weaning to increase their live weight and to improve the commercial quality of carcasses (aesthetic or service quality) according to market demand or to prepare lambs for predetermined times of the year (Aïd of sacrifice).
Red meat is considered a significant source of fat, especially saturated fatty acids (SFA). ese fatty acids (FAs) are involved and associated with diseases such as coronary heart disease [1,2]. However, recent studies have reported the gap between scientific literature and commonly accepted dietary recommendations [3,4]. erefore, special attention is accorded to the profile of fatty acids and their separation into SFA, monounsaturated fatty acids (MUFA), and polyunsaturated fatty acids (PUFA), particularly, PUFA n − 3 in favor of PUFA n − 6 [5]. Consumers tend to prefer grazed lamb meat, considering that this lamb meat is much healthier, tastier, and more natural than meat from intensive production systems. According to the natural reproduction cycle, lambs are generally born in winter and are kept in a sheepfold and breastfed by their mothers only at night until spring, because the climatic conditions are not favorable for newborn lambs to be outdoors. e availability of pasture changes according to the season. ere are two major peaks in sheep feeding change which are winter (December-January) and spring (March-April). erefore, we hypothesized that the season affects the meat quality characteristics. e aim of this study is to evaluate the influence of the rearing season (summer-autumn and winter-spring) on meat quality of Beni-Guil sheep breed.

Animal Material.
e experiment consisted of two treatments: ten female lambs born in summer and reared during the summer-autumn season (SA) and slaughtered in winter and ten female lambs born in winter, reared during the winter-spring season (WS), and slaughtered in spring. e choice of female lambs was made randomly from the same breeders in the same region in the two seasons (rural commune of Ain-Beni-Mathar). e female lambs were 6 months old, weaned at the age of 3 months, of the L category specific to sheep under 12 months of age according to the European Commission regulation no. 823/98. e slaughtered animals weighed 35.50 ± 1.94 kg for SA lambs and 35.96 ± 2.13 kg for WS lambs. e average fattening state corresponds to a score of 4 according to the fatness community scale (1: very low-5: very high) for the classification of sheep carcasses EUROP and to the conformation of R class according to the conformation scale EUROP (P: poor-E: excellent) [6,7]. e lambs were reared according to the pastoral farming system used in the eastern region of Morocco. It is a system based on grazing throughout the year (8-12 months/year depending on rainfall availability) with certain supplementation. In this region, animals moved south in winter and north in summer within the same area to graze on the alfa (Stipa tenacissima) and wormwood (Artemisia herbaalba) steppes. In this region, there is a wide variation in food supply depending on the rearing season from winter to spring. In winter, the soils are poor in plants; we find a few woody shrubs such as alfa and wormwood. On the other hand, in the spring there is a great plant diversity with the presence of plant species: wormwood (Artemisia herbaalba), alfa grass (Stipa tenacissima), sparta grass (Lygeum spartum), Atriplex (Atriplex halimus), ray-grass (Lolium perenne L.), laser white (Laserpitium latifolium), and sweet broom (Arthrophytum scoparium), along with the presence of other species, such as Bromus spp., Eruca vesicaria (roquette), Stipa capensis, and Medicago spp. e ewe diet consisted of natural pastures, if necessary, and some supplementation of 150 to 250 g/day based on barley and lucerne hay in drought, hunger season (autumn season), and in some physiological stages, such as at the time of preparation for breeding (flushing) and for lambing (steaming). Four weeks before parturition, the ewes received barley-based supplements to prevent abortions, as well as to improve milk production and quality. Fifteen days after lambing, the lambs were vaccinated against enterotoxemia. During the first two months, the lambs of two season remained in the sheepfold during the day; they were given a supplement based on lucerne hay and barley ad libitum.
en, in the third month, the lambs were pastured in extensive areas of the rural commune of Ain Beni-Mathar (−2.0247 longitude, 34.0081 latitude, and 921 m altitude), with supplementation based on barley (230-250 g/day for SA lambs vs. 100-120 g/day for WS lambs) and lucerne hay. Before slaughter, the lambs underwent a 45-day finishing phase based on barley (1 to 1.5 kg/day) and lucerne hay. e lambs had free access to water and mineral-vitamin supplement, in the form of a lick block. e difference between the two seasons is the share of pasture and concentrate supplementary foods (barely) in the feed ration of lambs and their mothers, where the maximum of pasture and the minimum of barley-based supplement are in the spring conversely in winter. No information was available on the diet chemical composition that they received. e breeders of these lambs are members of the National Association for Sheep and Goat Breeders, and they adopt a rhythm of one lambing per year and practice a pastoral farming system.
In each season, ten female lambs were slaughtered after 12 hours fasting (under water diet) at a local slaughterhouse and the slaughter procedure was carried out according to the Halal procedure. After animals slaughter, the carcasses were kept in the chilling chamber at 4°C for 24 hours. e meat analyses and chemical analyses were carried out on LL muscle obtained 24 h after slaughter.

pH Measurements.
e pH was measured 24 h postmortem in twenty LL muscles (obtained from ten female lambs in each season) using a pH meter with Penetration Probe (pH/Cond 340i WTW, Weilheim, Germany).

Meat
Color. 24 h postmortem, the meat color was successively determined on the LL muscle, according to the CIELAB system proposed by the international center of lighting (CIE) using a Chromameter 400: Konica Minolta CR400 (L * � clarity, a * � red-green color, b * � yellow-blue color). A D65 illuminant was used at an observation angle of 10°and with an aperture of 30 mm. e instrument was calibrated using white standard coordinates. Chromaticity (C * � (a * 2 + b * 2 ) 1/2 ) and hue angle (H * � arctan (b * /a * )) were calculated [8]. Color measurements were made on freshly cut surfaces and represent the mean of 3 measurements performed on the LL muscle.

Water Holding Capacity.
e water holding capacity (WHC) was estimated 24 h postmortem by application of a mechanical force, in accordance with the method described by Grau and Hamm [9]. e samples were sliced into 1 cm thick steaks, with a diameter of 4 cm 2 , wrapped in a layer of gauze, placed between preweighed Whatman papers. e WHC was calculated by the difference of sample weight before and after being subjected to the pressure of 2.250 kg for 5 min.
WHC(%) � (initial weight of the meat − final weight of the meat) initial weight of the meat × 100. (1)

Chemical Analyses.
Before analyses, LL muscle samples were frozen, lyophilized, crushed, and stored at −20°C for subsequent analyses. Dry matter was calculated using the drying method in a stove for 100°C ± 3°C according to the method described by the Association of Official Analytical Chemists [10]. Intramuscular fat (IMF) was extracted and quantified according to Bligh and Dyer [11] by using a mixture of chloroform/methanol/water mixture (2/1/1; v/v/v). Ash was determined by combustion (incineration) in the oven according to AOAC [10]. e Total nitrogen was quantified using the Kjeldahl method according to AOAC [10]. Total proteins were calculated using the conversion index of 6.25.

Statistical Analyses.
Experimental results were presented as means ± standard deviation of triplicate determinations.
e statistical analyses were achieved using the software SPSS version 20 and considering the rearing season (summer-autumn vs. winter-spring) as source of variation. e means were compared using the t-test and the significance was declared at p < 0.05.

Results and Discussion
e effect of the slaughter season on the qualitative characteristics of Beni-Guil sheep meat is presented in Tables 1-3. e results show that the season has a significant effect on the meat qualitative and quantitative characteristics of Beni-Guil breed (p < 0.05).

Meat Physical Characteristics.
e pH of meat is an extremely important commercial quality criterion for the slaughterer, the processor, and the distributor. It affects the quality characteristics of the meat, particularly juiciness and color. In the present study, the pH values obtained for the lambs of the two seasons varied between 5.72 and 5.79 (Table 1), which could be considered within the desired range for meat quality [15]. ese values are similar to the results of other studies [15][16][17]. e results show that lambs slaughtered in winter have a lower pH value than those slaughtered in spring (p < 0.05).
is difference can be explained by the quantity of concentrate ingested by winter lambs compared to spring, which promotes ruminal fermentation and therefore the production of propionic acid, the precursor of muscle glycogen. Our results are in agreement with those reported by Yalcintan et al. [18], where the higher pH values have been observed in winter compared to spring. In contrast, D'Alessandro et al. [19] reported that spring lambs have lower pH values than winter lambs. ey explain this result by a high amount of milk suckled from their mother. e amount of milk, as well as the lactose content, has been positively linked to the production of muscle glycogen [20]. e water holding capacity was determined using analyses of the expressed juiciness. e results show that spring lamb meat has a lower water retention capacity, because it lost more water than winter lamb meat. Likewise, several authors who have studied the effect of the season and the production system have reported that meat raised in spring has a lower water retention capacity [18,21,22]. On one hand, this result can be explained by the difference recorded in pH between the seasons (Table 1). Meats with a pH close to the proteins isoelectric point tend to be drier. We get closer to the isoelectric point of meat proteins. eir charges decrease and they tighten by a reciprocal attraction effect.   Journal of Food Quality ese changes decrease the muscle's water retention capacity, therefore loss of mass during storage. On the other hand, this result can be explained by the water richness of the spring food ration, and consequently, a juicy meat rich in intramuscular juice.
Meat color is not an important dietary characteristic, but it is a decisive factor in the initial choice of meat by consumers [20]. In the Mediterranean countries, consumers prefer mainly sheep meat with a bright red or pink color, as it is also the case in the Middle East [18,23]. e results show that all the meat has a bright red color with luminance values (L * ) between 41.04 and 47.03. Several studies have shown that meat from grazing lambs is darker than that from underconcentrated lambs due to physical activity, which increase the amount of hemoglobin (pigment) and by the final meat's pH [24,25]. On one hand, the recorded difference in lightness is mainly due to recorded pH values and intramuscular fat content. en we get close to the isoelectric pH of the actin and myosin proteins, allowing the neutralization of the charges and reduction in the spacing of the muscle fibers. is muscular protein network then presents a "closed" structure. ese changes affect how light is reflected and absorbed and reduce light penetration into the muscle, giving the meat a bright red appearance [25]. On the other hand, Hanekom [25] reports that the three muscles from extensively reared lambs contained significantly more myoglobin than those from lambs raised intensively. Numerous researchers concluded that lambs reared extensively produce darker meat due to high levels of activity associated with the production system [26,27]. In agreement to previous studies, spring lambs have a significantly darker color than winter ones (p < 0.05). Since we used lambs of the same age and weight at slaughter, in fact, this result can be explained by the pH value and by the distance covered by spring lambs, since they were reared outdoor with their mothers from the third month of age. On the other hand, those slaughtered in winter, when unfavorable climatic conditions occur, remain indoor because there is practically no pasture persistence to graze outdoor.
Regarding the intramuscular (IMF) fat content, the results show that the season has a significant effect (p < 0.05). Lambs from WS presented higher IMF compared to SA group (5.14% vs. 3.82%, respectively).
is effect can be attributed to the grazing-based farming system, which generally results in better milk production characterized by a high-fat content due to a diet rich in fiber [28]. Lambs slaughtered in the spring have the highest ash content (p < 0.05). is can be attributed to the availability of pasture in spring. Cabrera and Saadoun [29] reported that meats from pasture are richer in minerals than those on a concentrate diet. Tables 2 and 3 present the effect of rearing season on intramuscular fat from LL muscle (percentage of fatty acids by total weight of fatty acids, their sums. and their indices) of Beni-Guil sheep. e results show that the fatty acid profile of SA lambs was significantly different from those of WS season (p < 0.05). e chromatograms obtained from the FAME analysis by GC-FID revealed the presence of 25 and 28 fatty acids in the intramuscular fat of the LL muscle of WS and SA lambs, respectively ( Table 2). In general, the obtained profiles were similar to those reported for Beni-Guil sheep breed [30,31]. e sums, ratios, and indices of FAs are presented in Table 3. e fraction of saturated fatty acids (SFA) is often considered to be detrimental to our health [32]. However, recent studies have pointed to the gap between scientific literature and commonly accepted dietary recommendations [32]. Among the SFA identified in the analyzed meats, those with  short and medium chain (C10 : 0; C12 : 0; C14 : 0; C16 : 0) constitute the majority, with a dominance of C16 : 0 which is often considered as an undesirable cholesterol factor [33]. However, long-chain (C18 : 0) and short-chain SFA are considered as FA with a neutral effect on bad cholesterol and are capable of increasing the content of good cholesterol [34,35]. e results show that the meat of the WS lambs is rich in medium-and long-chain fatty acids (C12 : 0; C14 : 0; C16 : 0; C18 : 0). Similar results were reported by other authors on sheep meat [17,36]. Also, Velasco et al. [36] reported that the fatty acid composition of lamb meat is closely related to the fatty acid composition of their mothers' milk, which is rich in medium-chain and saturated fatty acids. is difference may be due to the difference in milk production performance between the two studied seasons.

Fatty Acids Profile Analysis.
In particular, WS lambs practically receive more milk than those born in the dry season (SA season). Moreover, in a previous study, Beriain et al. [37] reported that the milk diet produces high levels of C14 : 0 and C16 : 0, while pastures produce high levels of C18 : 0 fatty acids. Concerning monounsaturated fatty acids, the highest percentage is found in the meat of SA lambs (42.44 % vs. 38.48 %;p < 0.05). is difference is mainly due to the difference in oleic acid (C18 : 1), which dominates this fraction with a percentage of more than 90 % and which is considered as fatty acid with hypocholesterolemic property [34,38].
is result can be attributed to the breeding system adopted in the autumn-winter season, which is mainly based on a ration rich in concentrate because of the scarcity of grazing in this season. Scerra et al. [39] found that meat from a stalling system has a higher oleic acid content than that produced on pasture. In addition, the meat of SA lambs has the highest content of polyunsaturated fatty acid (16.82% vs. 12.4%; p < 0.05). is finding can be explained by the diet in the autumn-winter season which is rich in concentrate (rich in carbohydrates), influencing the time of feed congestion in rumen, decreasing the biohydrogenation of unsaturated fatty acids [40]. us, Sauvant and Bas [40] have reported that the food intake rich in carbohydrates affects the residence time of lipids in the rumen and, consequently, decreases their biohydrogenation. In addition, the higher C18 : 2n6 content in the meat of SA lambs may arise, likely, from a high content of this FA in the concentrate [41,42]. e PUFA n − 6/PUFA n − 3 ratio is an important parameter to evaluate the nutritional quality of meat fat in regard to the prevention of coronary heart diseases and anticarcinogenic activity, in the context of human health, which is recommended to be below 4 [29,43]. Meanwhile, PUFA/SFA is recommended to be above 0.4. e results show that the rearing season influenced the ratios, nutritional indices, and nutritional value of the intramuscular fat (n − 6/n − 3, AI, h/ H). In particular, the proportion of linoleic (C18 : 2) and arachidonic (C20 : 4n6) acids was significantly higher (p < 0.05) in the muscle of the SA lambs. is higher content in C18 : 2n6 and its metabolites in the meat of lambs reared in autumn-winter may arise, likely, from a high content of this FA in the concentrate [22,26]. is is associated, from one side, with more favorable ratios of PUFA/AGS (0.42 vs. 0.25) above the recommended value (0.4) [44], hypocholesterolemic/hypercholesterolemic (2.5 vs. 1.67), and an interesting nutritional value (2.61 vs. 2.13), while from another side, it is associated with an unfavorable n − 6/ n − 3 ratio (12.98). e SA lambs have a higher n − 6/n − 3 ratio (12.98) compared to the nutritional recommendations.
is richness could be explained by the use of barley (Hordeum vulgare) as a main concentrate supplement food in the dry season which is rich in PUFA n − 6 [45]. Yousefi et al. [46] report lower PUFA/SFA ratios for lambs of two Iranian breeds (0.19 and 0.16) to ours. Similar to findings from this study for SA lambs, Sinanoglou et al. [47] reported PUFA/SFA ratios between 0.37 and 0.49 for Greek lambs. However, WS lambs have a high content of linolenic acid (0.5% vs. 2.54%) and a favorable n − 6/n − 3 (3.78) ratio. e SA lambs have a higher n − 6/n − 3 ratio (12.98) compared to the nutritional recommendations, considering the fact that this ratio intake by humans should not exceed the value of 4 [43].
is result is due to the pasture availability in WS season, which is associated with the increase in the proportion of linolenic acid (ALA). Pasture is linked to a higher PUFA n − 3 content since the grasses chloroplasts may provide a natural protection of PUFA in the rumen compared to concentrate-based diet [48]. Valvo et al. [49] and Atti et al. [50] reported that sheep raised on pasture produce ALA-rich milk compared to those fed in a stable. Indeed, Velasco et al. [51] reported that pasture-fed suckling lambs produce meats richer in PUFA and lower in n − 6/n − 3 ratios compared to the profile of suckling lambs raised on a highconcentrate ration. Interestingly, Scerra et al. [39] found that the proportion of PUFA was higher in muscular fat of lambs whose mothers had access to pasture than lambs from ewes of a stall-fed group. e obtained n − 6/n − 3 ratio for WS lambs is lower than those reported by Berrighi et al. [52] for Reimbi sheep breed, by Vasta et al. [53] for Barbarine sheep breed and Blasco et al. [54] for Segureña lambs (15.32-15.47). However, the recorded values are higher than those reported by Margetín et al. [55] for Ile de France breed (1.86-2.23). e nutritional indices (AI and TI) represent key parameters to assess the effect of proatherogenics on the potential risk of blood platelets aggregation [47,56]. According to Sinanoglou et al. [47], AI and TI should not exceed 1.0. In this context, our results show that the lambs presented favorable AI and TI values which do not exceed the norm, with the superiority of the SA lambs (AI: 0,47 vs. 0,83 < 1; TI: 0.70 vs. 0.91 < 1). is recorded value is similar to the results reported by Sinanoglou et al. [47] for Lacaune (0.83) and Chios (0.91) lambs and is lower than those found by Margetín et al. [55] in sheep meat of the Ile de France breed raised on pasture and by Vacca et al. [56] in the meat of the Sarda breed and its crosses.

Conclusion
e effect of the season on the quality of intramuscular lipids has been studied. e results show that the rearing or slaughtering season has a significant effect on the physicochemical characteristics of Beni-Guil sheep meat. In particular, the meat of female lambs raised in the winterspring season had a higher content of intramuscular fat and polyunsaturated fatty acid with favorable n − 6/n − 3 ratio. On the other hand, those reared in autumn-winter season have high content of PUFA and more favorable PUFA/SFA ratio.

Data Availability
e data used to support the findings of this study are available from the corresponding author upon request.

Conflicts of Interest
e authors declare that they have no conflicts of interest.

Authors' Contributions
KB was responsible for designing the research methodology, carried out all experimental tasks, and wrote the first draft of the manuscript; FM was responsible for statistical analysis and data interpretation; MS and MB carried out data analysis and interpretation; MLF contributed to designing the research methodology and data analysis; SCH and AE conceived the study, contributed to the design and coordination, supervised all analyses, and finished the final version of the manuscript.