Carcass parameters
Generally, animal performance, carcass traits, and meat composition are influenced by breed and diet [36]. In the present trial, carcass characteristics were lower compared to the ones of sheep because goat carcass is leaner and less compact [3, 37] but also compared to other goat breeds because the growth potential of local and indigenous breeds is lower [38]. Final body weight, hot and cold carcass, and carcass composition were similar between treatments as expected from the distributed diets quantities that were similar for energy and nitrogen. Roy et al. [39] reported an initial (11 kg) and final body weight (14.7 kg), and hot carcass weight (6 kg) of Black Bengal goat receiving soybean and sunflower bean, similar to the current results. Abidi et al. [17] found a negative effect of spineless CC on weight performances of sheep and goats that disagrees with the current results.
Carcass yield was lower than norm classically reported for goat (49 – 51%) because the studied animals were younger and this parameter is positively correlated to animal age [40]. However, values were similar to those found by Roy et al. [39] for Black Bengal goat kids (42%).
Gut content represented 72% of full digestive tract weight. This could be explained by its low turnover rate because of its high crude fiber content [13].
Perirenal and mesenteric fats were low, which could be explained by diets with low energy contain or by a low allometric rate of fat development in goats (1.26 – 2.25 for subcutaneous and 1.26 – 1.76 for intramuscular fat) [41] and thus a late fat development that is apparent at maturity [3]. The present results are thus not unexpectable in young animals at slaughter. Kotsampasi et al. [12] reported that partially destoned exhausted OC had no effect on body and carcass weight, yield, and visceral organ that is in agreement with the current results. By contrast, Mioč et al. [13] found that 30% of OC decreases final body weight, hot carcass weight, and carcass yield, and increases digestive tract weight of lamb. The obtained goat muscle index was lower than sheep because goat carcass is smaller, leaner, and less compact [3].
For carcass color, the yellowness of OC carcass agrees with Hamdi et al. [11] who reported an increment of fat yellowness in lamb fed OC because of its richness in carotenoids, which deposited in fat. The inferiority of redness in TCC and TCC+OC groups could be caused by a higher conversion of myoglobin to metmyoglobin due to undesirable microbiology [42] developed in meat with high water retention capacity.
Meat quality
Generally, meat quality is affected by many factors as breed, age, sex, weight, and diet [3]. Color, tenderness and pH are the most important meat properties, and the most representative parameter is pH because it affects shear force, water retention capacity, cooking weight loss, flavor and color [3, 19]. The value of pH0 has to be lower than 6.4 and that of pH24 between 5.4 – 5.7 to be commercialized [11, 43] that is lower than the present results. A high ultimate pH (> 5.8) corresponds to dark and tough meat with a reduced shelf-life [41]. The high ultimate pH of chevon (5.8 – 6.2) is a specificity of goat species related to the excitable nature of temperamental species, highly prone to stress in perimortem [3], which leads to glycogen stores decrease and a high pH of meat [44]. Atti et al. [26] reported an ultimate pH of 6.18 – 6.48 for male goat kids receiving spineless CC that is higher than the present results.
Meat color depends on myoglobin content in muscle and its chemical state. It is an essential parameter because consumer selects meat based on its color [19]. Priolo et al. [45] reported the lack of OC blocks effect on L*, a*, b*, H°, and C* of Barbarine lambs’ meat in agreement with the current results for L. dorsi and Semimembranosus. The lightness was lower in Semimembranosus than L. dorsi in agreement with that was reported for pigs in intensive and extensive systems by Purchas et al. [46] who found a muscle effect on lightness with Semimembranosus inferiority compared to L. dorsi. Semimembranosus muscle was more red and yellow with a higher hue angle and chroma than L. dorsi. Ledward et al. [47] found an effect of electric stimulation of beef on L. dorsi and Semimembranosus muscles color, which means that color differs according to muscle.
Kotsampasi et al. [12] found moisture of 74 – 75% in lambs meat receiving partly destoned exhausted OC and Webb et al. [3] cited a range of 60 – 70% in chevon that is lower than the present results. The effect of muscle type on moisture is in agreement with the found of Badiani et al. [48] for Infraspinatus and Semitendinosus in beef.
Oliveira et al. [27] found a linear decrease in goat meat ash content by replacing corn by cactus meal, which is in agreement with the found for L. dorsi. Turner et al. [36] reported 4.3 – 4.4% of ash in the meat of goat kids on pasture that is higher than the current results. However, the present results remained in the range cited by Webb et al. [3] (0.95 – 3.4%) for goat meat.
Meat protein results remained in the range reported by Webb et al. [3] (17 – 29.2%) for goat meat. Mioč et al. [13] found that 30% of OC decreases protein in lamb leg meat that agrees with the results observed in L. dorsi protein content. Atti et al. [26] reported, by contrast, lack of CC effect on protein. Protein content was similar by muscle. However, the interaction muscle/diet effect could be attributed to the dietary effect on meat protein content in L. dorsi.
Goat meat is considered as lean [3]. The intramuscular fat influences meat quality parameters such as juicy, yellowness, and tenderness [49]. Chevon is thus less juicy because of its lower content in intramuscular fat [3]. Fat content was lower than the range cited by Webb et al. [3] (4.4 – 21.2%). Mahouachi et al. [20] found a decrease of fat in L. dorsi by introducing CC in goat kids diet in agreement with the current found for the same muscle. The CC is considered as a forage and Hocquette et al. [50] reported that cattle fed on grass had a high lipidic than glucidic blood profile traduced by a low lipogenesis in adipose tissue. By contrast, Kotsampasi et al. [12] reported a lack of OC effect on moisture, ash, and fat what is in agreement with the current results.
Meat texture is affected by many factors as pre-slaughter temperature, slaughtering management, carcass post-mortem, rigor mortis speed, post-mortem pH, glucose concentration in the muscle, sampled muscle and sample preparation method [3, 51]. Tenderness depends on collagen content, connective tissue reticulation degree, and muscular fibers size [52]. This author reported that females’ meat is tenderer than males’. The parameter also is correlated positively with carcass fatness [53] and depends on sampled muscle, species, and breed [54]. These authors reported that Longissimus thoracic and lumborum muscles are tenderer than Semimembranosus and tenderness differs according to goat species. Meat tenderness beyond 11 kgf is considered as tough for lamb meat. A value beyond 10 kgf is unacceptable and less than 7 kgf, moderately acceptable in beef meat [3]. So, goat Semimembranosus did not reach an acceptable tenderness degree [3]. Tenderness of raw and cooked Semimembranosus was not affected by diet. Costa et al. [19] found that the inclusion of cactus pear has no-effect on ram meat tenderness. The current result of tenderness is near to that found by Swan et al. [54] (9.1 kgf) and lower than reported by Sheridan et al. [55] (11.1 kgf) for Semimembranosus of Boer goat. Chevon is more hardness than sheep meat because it is characterized by a high collagen content with a low solubility, high fibrous residues, and larger and ticker myofibrils [3].
Fatty acid profile
The FA profile of meat influences meat quality (flavor, consumer acceptance, hardness, and palatability), shelf life and human health [3, 12, 23]. Chevon FA profile is healthy because of its high rate of oleic acid (C18:1) and low concentrations of lauric (C12:0) and myristic (C14:0) acids compared to other meats [56]. Generally, the main FA in goat fat are C18:1, palmitic (C16:0), stearic (C18:0) and linoleic (C18:2) acids [23].
The FA concentration results are within the range of C18:0 (6 – 17 g/100g fat) and C18:2 (4 – 15 g/100g fat) and lower than of C18:1 (28 – 50 g/100g fat) and C16:0 (15 – 31 g/100g fat) reported by Banskalieva et al. [23]. The major FA in chevon that was cis form of oleic acid (C18:1n9c) is known by reducing low-density lipoprotein cholesterol (LDL), maintaining high-density lipoprotein cholesterol (HDL) and preventing cardiac diseases [56].
Sampled muscles had a significant effect on FA profile, groups, ratios and indexes what is in agreement with observations reported by Badiani et al. [48], Cho et al. [57] and Raes et al. [58] for beef. Also, Enser et al. [59] reported FA profile differences when comparing a more white and a more red muscles (Longissimus vs Gluteobicepts), which concurs with the observed results.
No effect of C14:0 and C18:0 because these FA are related to weight increase [40] and the body weight was similar for all groups in this study. The low content of C16:1 in TOC and TCC groups compared to control might be explained by its low content in CC and OC compared to control diet. Mele et al. [7] found that 35% of OC decreases C16:1 in lamb meat, which is in agreement with the current work. The C20:3n3 that is a metabolic product of the oleic acids (C18:1n9) [35], is a ω-3 acid that is increased by fresh forage [60], which could explain its high rate in TCC group with the incorporation of CC that is considered as a green forage.
The high concentration of C15:1 in Semimembranosus for the control group could be explained by the dietary carbohydrates that produce high quantities of propionate that are used to synthesize odd-chain FA in fat [61]. The high content of C6 and C8 acids in Semimembranosus for TOC group could be caused by the high content of oil in OC that could alter ruminal bacteria and inhibit long-chain FA synthesis [39].
The diet effect on C18:3n3 level in Semimembranosus is in agreement with Kotsampasi et al. [12] that found an increment of C18:3n3 by OC diet and with Vasta et al. [42] feeding OC and CC silage in lamb meat. This increase could be explained by its escape from ruminal biohydrogenation because of the presence of tannins that depressed the biohydrogenation process in the rumen, which results in a high concentration of α-linolenic acid in intramuscular fat [12]. Also, Δ5 and Δ6 desaturase enzymes in association with elongase permit the formation of long-chain PUFA (C20-C22) from C18:3n3 and C18:3n6 [60], which explains the high content of C20:2 and C22:2 in intramuscular fat of OC chevon.
Luciano et al. [6], Abidi et al. [17], Mahouachi et al. [20] and Atti et al. [26] reported a lack of CC effect on SFA, MUFA, and PUFA in lambs and goat kids meat that is in agreement with the current results. Generally, SFA are positively correlated to meat palatability and hardness [23]. The fiber in the diet stimulates the ruminal activity and the biohydrogenation that provokes an increment in SFA [51]. However, a diet containing rapidly degradable carbohydrates has a short stay in rumen, which perturbs the biohydrogenation process and conducts implicitly to a high content of unsaturated FA [51]. The DFA in goat meat is higher than in cattle and sheep. In the present work, the DFA is in the range of chevon DFA (61–80%) [23].
Generally, long-chain FA (PUFA and ω3) are more susceptible to escape the biohydrogenation, and comparatively to be absorbed and deposited as ω3 and ω6 in animal tissues [51]. Berthelot [52] reported that in a lean muscle, PUFA n-6 are high because these acids are from membrane cell origin. The high content of ω-6 is undesirable because it generates eicosanoids with more thrombotic tendency compared to ω-3 that could cause coronary diseases to human [3].
The ω-6/ω-3 ratio that associated with the risk of cancers and heart diseases [62], is lower than 4, which is considered as benefic in human nutrition [56].
The lack of diet effect on PUFA : SFA and MUFA : PUFA ratios, atherogenicity (AI) and thrombogenic index (TI), and (C18:0 + C18:1) / C16:0 in L. dorsi and Semimembranosus, agrees with Kotsampasi et al. [12] who found a lack of OC effect on SFA, MUFA, PUFA, PUFA / SFA, the AI and the (C18:0 + C18:1) / C16:0 ratio of lamb meat. The PUFA : SFA ratio that presents the risk of a diet to provoke coronary heart disease [35], should have a high value to be beneficial in human nutrition, and a value of 0.45 is recommended [59]. The current result PUFA : SFA ratio was below 0.4 and 0.3 in L. dorsi and Semimembranosus respectively and lower than the recommendation that is normal in ruminants’ meat because of unsaturated FA biohydrogenation in rumen [23]. Mahouachi et al. [20] reported the absence of CC effect on PUFA : SFA ratio in chevon as observed presently in this experiment. This parameter is lower for ruminant than monogastric because of the hydrogenation by microflora in rumen. Ulbricht and Southgate [35] consider that AI and TI are indicators of cardiovascular disease risks because they take into consideration other factors and permit a comparison between diets. The AI and TI obtained in L. dorsi and Semimembranosus are close to stewed ox liver that is considered as an antithrombogenic food (AI = 0.41 and TI = 0.82) [35]. The (C16:0 + C18:1) / C18:0 ratio, which describes the health effects of different lipid types [23], is mainly influenced by diet and breed. It ranged from 3.2 to 4 that is in the range and slightly higher than values reported by Banskalieva et al. [23] (1.37–3.64).