2022 年 10 巻 p. 155-167
This review presents the analysis of interrelating factors such as pH-parameter, mass content of connective tissue and lipids, proteolytic enzyme activity, as well as animal age, and their influence on the quality of farm-raised and hunted venison produced in New Zealand, Russia, and Spain. It was established that differences in meat shear stress observed between venison from different countries were not associated with stress at the time of slaughter. It was shown the presence of seasonal effects that compensate for the obvious after-stress effects. In general, the country of origin did not affect the total content of polyunsaturated fatty acids in meat, and the levels of monounsaturated fatty acids in venison of New Zealand and Russian production tended to increase. However, n-6/nFactor-3 of venison from all the countries was less than 4 in average values. The ratio of polyunsaturated fatty acids to unsaturated fatty acids, the content of total fatty acids and the n-6/n-3 ratio of animal fats obtained during winter hunting were higher than that of summer grazing deer. There was observed an effect of the country of origin and type of hunting on the amino acid profile of venison. Spanish and Russian venison contained more common essential and non-essential amino acids than New Zealand farm venison. In addition, the composition of venison produced in summer had a higher ratio of essential/non-essential amino acids than venison hunted in winter. Since the mineral composition of venison is closely related to the natural environment in which the deer grazes, the difference in mineral content is not related to the level of stress, but to seasonal changes and forage rations. It has been established that in summer venison contains less than half of the zinc needed as a part of alkaline phosphatase, which is an enzyme necessary for calcium deposition in bone tissue. The reason that may explain the seasonal difference is calcium and magnesium phosphate, which can replace calcium and form horns and bones.
The consumption of red venison meat has increased over the last decade [1, 2]. There are about 12 million of Red Deer (wild and farmed); 440,000 animals of them are slaughtered annually for meat, mostly by hunting [2]. New Zealand is the world leader in the production of venison, where there are about 1 million deer (compared to 4 million of residents) [2]. Spain is the second largest exporter of venison as it produces 11,250 tons of venison, which is almost entirely hunted [2]. The exporting amount of venison from Russia (8.2 tons) took the 9th place [3]. A significant amount of venison is produced on farms in the Kaliningrad region. The largest deer farm in this region is Mushkino Farm. Figure 1 shows a photo of the Red Deer breed grown in Mushkino Farm, in the Kaliningrad region.
Figure 1: Red Deer grown in Russia, in the Kaliningrad region
Most amount of venison is produced by hunting in autumn and winter, but selective summer mortality in different countries (death due to high stress level) leads to culling and reducing the number of vulnerable animals. This is the second source of venison meat. Thus, the most common parameters for comparing venison inevitably show a mixed effect of hunting type and seasonality. In winter and summer, when wild animals have widely different amounts of food available, hunting expands, and it leads to sudden death of animals, even if they are pursued for a long time. According to a literature review of venison quality [4], the studied animals (farmed or wild deer) are slaughtered in certain seasons of the year, most often in autumn or winter [5]. There is little information about the quality of venison obtained in summer. Some studies [4] assessed the impact of various hunting methods on the venison quality. The authors [5] investigated the process of tracking and shooting of farmed deer, belonging to several species of the Red Deer breed. However, they did not obtain information on traditional driven hunting, including the number of animals. Therefore, until now, there is no study assessed the difference in venison quality of red deer slaughtered in driven hunting and hunting for wild deer. In this review, we studied both farm-raised and wild red deer. Figure 1 shows photos of deer raised at the Mushkino Farm in the Kaliningrad region. Figure 2 shows photos of wild Red Deer living in the Kaliningrad region.
Figure 2: Wild Red Deer living in the territory of the Kaliningrad region, Russia
The venison produced on New Zealand farms has been widely studied and analyzed; in Spain, scientists compared the quality of wild venison, obtained not by selective shooting in summer, but in autumn or winter period [6]. To date, no study has compared the most common types of venison on the market (considering the stressful winter hunting and summer tracking in Spain, as well as analyzes of farmed deer in New Zealand and Russia). Therefore, the aim of this study was to assess for the first time the combined effect of country of origin (Spain, New Zealand and Russia) and type/season of slaughter (winter tracking hunting and sudden death in summer free range) [7, 8, 9]. Then, studies have been carried out to reduce the confounding factors associated with the quality and nutritional value of the Red Deer venison [10, 11, 12].
The purpose of this paper was to review the factors affecting the venison quality and compare these indicators for wild and farmed deer in New Zealand, Russia and Spain.
The novelty of the study lies in the fact that for the first time a comparative characteristic of venison grown in different countries was carried out, and data from studies of factors affecting its quality were summarized.
According to the literature data, the chemical composition and energy value of venison produced on farms in New Zealand, Spain and Russia are shown in Table 1 [13, 14, 15].
| No. | Indicators | Venison | ||
|---|---|---|---|---|
| New Zealand | Russia | Spain | ||
| 1 | Dry matter | 35.5 | 29.1 | 32.7 |
| 2 | Protein | 19.5 | 18.6 | 17.6 |
| 3 | Fat | 8.5 | 10.0 | 10.3 |
| 4 | Ash | 0.9 | 1.0 | 0.8 |
| 5 | K/calories in 100 g | 145 | 156 | 166 |
Analyzing the tabular data, it is possible to conclude that venison from New Zealand is the richest in protein (19.5%), while the lowest value is observed in venison from Spain (17.6%); the intermediate value is performed by venison from Russia (18.6 %). The same trend is observed for fat content. The most high-calorie venison is meat from Spain (166 Kcal / 100 g); the least caloric is venison from New Zealand (145 Kcal / 100 g).
Concerning the chemical composition of venison produced on Russian farms, the values established are given in Table 2 [13].
| Carcass parts | Moisture | Dry matter | Protein | Fat | Ash | K/calories in 100g |
|---|---|---|---|---|---|---|
| Dorsal part | 62.14 | 37.86 | 17.54 | 19.28 | 1.04 | 181 |
| Hinder part: | ||||||
| Tenderloin | 57.10 | 42.90 | 17.03 | 24.73 | 1.14 | 200 |
| Sirloin | 66.50 | 33.50 | 19.07 | 13.33 | 1.10 | 102 |
| Rump | 66.58 | 33.42 | 18.63 | 13.64 | 1.15 | 133 |
| Thick flank | 73.28 | 26.72 | 20.48 | 5.17 | 1.07 | 117 |
| Brisket part | 65.06 | 34.94 | 19.49 | 14.39 | 1.06 | 179 |
| Blade part | 72.08 | 27.92 | 19.50 | 7.32 | 1.10 | 128 |
| Shoulder part | 72.91 | 27.09 | 20.18 | 5.72 | 1.19 | 126 |
| Flank | 65.84 | 34.16 | 17.51 | 15.64 | 1.01 | 156 |
| Neck | 67.23 | 32.77 | 23.53 | 7.94 | 1.30 | 160 |
| Front shank | 75.01 | 24.99 | 21.03 | 2.92 | 1.04 | 104 |
| Hind shank | 74.41 | 25.59 | 20.74 | 3.76 | 1.09 | 103 |
| General sample | 67.57 | 32.43 | 19.97 | 11.33 | 1.13 | 187 |
When analyzing the tabular data, it was found that the tenderloin of venison from Russia is the most nutritious (200 kcal/100 g), the least nutritious parts are sirloins, front and hind shanks (102, 104 and 103 kcal/100g, respectively).
Venison consumers and processors associate certain characteristics such as safety, tenderness, moisture retention, color and flavor of venison with the quality of the final product being processed and consumed. Basic principles (gender, age, regional influence) and methods (feeding, preliminary processing, transportation, and slaughter method) applying to more traditional lean types of meat, affect the quality and composition of venison in most cases as well [11, 12]. These animals are slaughtered and processed in factories that are designed specifically for venison processing, but using technologies developed for the industrial processing of other meat types [13].
The pH-value from 5.5 to 5.7 (so-called extreme pH), measured approximately 24 hours after slaughter, is within the normal range, but values above 5.8 may lead to a reduction in shelf life, especially for vacuum-packed product [14]. Meat with a very high pH > 6.2, so-called dark, hard or dry meat, is a consistent quality defect found in meat of some mammals [15]. Two comprehensive studies of Red Deer (n = 3500; New Zealand) and Reindeer (n = 3400; Sweden) showed that 11% of the Red Deer carcass meat and 29% of the Reindeer carcass meat had a meat pH value of 5.8, hence there was significant the risk of shortening the shelf life [16].
3.2 Microbiological indicatorsThe shelf life of fresh meat is often determined by microbial growth (the total number and type of microorganisms in the meat). A commonly used critical limit for assessing the microbiological/hygienic quality of meat is 7 log10 CFU/g of aerobic microorganisms. Values above 7 log10 CFU/g indicate that the meat is not suitable for human consumption [17].
Important factors for microbial growth in frozen meat are pH, slaughter hygiene, and conditions/temperature of freezing [18]. Reindeer meat is traditionally sold frozen in the Scandinavian countries and Alaska. However, the demand for fresh chilled venison is slowly growing. Information on handling, packaging and storage of chilled venison is very limited. In contrast, New Zealand has a long history of selling frozen venison to Europe and the US. The New Zealand reindeer-breeding industry practices high quality hygiene, processing, packaging and storage of venison [19]. Microbiological data reported that venison in New Zealand showed values of 2 log10 CFU/g and 4 log10 CFU/g, if venison stored at -1.5 °C for 3 and 9 weeks, respectively [19]. The combination of lower storage temperatures and good hygienic meat quality allows New Zealand producers of venison to guarantee a long shelf life (up to 12–14 weeks) of frozen venison. However, the hygienic quality and shelf life of Swedish venison is much lower. Microbiological data reported of 6.8 log10 CFU/g for venison stored at +4 °C for 3 weeks [20].
3.3 Activity of proteolytic enzymesGrowing demand for fresh, chilled, vacuum-packed venison and its processing is quickly revealing a pH-problem that is currently “invisible” in frozen food [21].
The entire meat industry needs to guarantee the quality and long shelf life of fresh chilled meat. Measuring regularly the pH-level of the whole carcasses used for production of vacuum-packed fresh frozen meat helps to optimize the quality of the reindeer meat and shelf life. Venison does not need to mature for 1–3 days after slaughter [22]. Studies have shown that meat of Red Deer is much tender than beef aged for the same period [23, 24]. The phenomenon of rapid softening of venison is explained by an activity increase of proteolytic enzymes (calpain and cathepsin) [25] and muscle fibers of small diameter [26]. It is not entirely clear why proteolytic enzymes are so active in venison. However, previous studies suggest that this may be due to the strong seasonality of deer growth and to regulation by the photoperiod [27]. This means that sudden changes in body weight and physical condition are a part of the normal annual growth cycle of deer, and proteolytic enzymes perform important functions in living animals [15]. If the carcass cools too quickly, the muscles tend to contract significantly. This fact is known as “cold shrinkage” [16].
Carcasses of farmed animals are often stimulated with electricity. During electrical stimulation, an electric current is applied to the carcass for a short period of time (from 0.5 to 1 minute), causing rapid muscle contraction and depletion of energy reserves (glycogen), thereby it accelerates the natural enzymatic tenderization of meat. Commercial slaughterhouses in many countries use electrical stimulation to process carcasses of cattle, sheep and goats. In New Zealand, electrical stimulation of deer carcasses is a part of the normal slaughter process. However, in the Scandinavian countries, deer-slaughterhouses do not use electrostimulation of deer carcasses.
Meat of deer slaughtered in the wild may be sold locally, unless it is slaughtered on snow when an ambient temperature is below 0 °C, then the carcass is frozen outdoors and thawed until the meat is within the reach of consumers. Since the ambient temperature during slaughter in the wild is usually below -10 °C, temporary chilling and freezing of carcasses inevitably occur, and the risk of temperature decrease in in slaughtered wild deer is obvious. Electrical stimulation immediately after slaughter minimizes this risk. Portable electro-stimulators can be connected to a generator or battery, and they have been shown to work well in harsh winter conditions during hunting on the Seward Peninsula, Alaska [17].
The positive effect of electrical stimulation on meat tenderness was clearly demonstrated by consumers, who considered that the meat of deer slaughtered in the stimulated field was softer than that of unstimulated animals [19].
3.4 Carcass handling conditionsIt is well known that carcass handling conditions during tenderness development play an important role in controlling meat softness. Carcass suspension techniques have been studied in beef and have been shown to affect the tenderness of various muscles [14]. The most common method of suspension carcasses is the Achilles tendon, but pelvic suspension is also used (when the pelvis is engaged). Compared to the Achilles tendon suspension, the pelvic suspension stretches various muscles in the carcass. Normally, with the development of stiffness, the muscles become more stretched and tender. Although this does not apply to the tenderloin (lumbar muscles), the most valuable parts of the carcass (from the back region) are stretched more when the carcass is suspended by the pelvis than when it is suspended by the Achilles tendon. Compared to the Achilles pendant, the pelvic pendant improves the tenderness and softness of some valuable venison cuts [10].
3.5 Moisture retention capacityApproximately 75% of meat is water, and the retention of this water throughout the entire consumption chain is an indication of the meat quality during its consumption and processing. The water retention capacity of chilled meat is often referred to moisture retention capacity. Tenderness is an important quality characteristic of venison, but the increased rate of proteolysis associated with rapid softening makes it more susceptible to reduced water retention capacity, which is a major problem in meat processing and consumption [3]. In such countries as New Zealand, Australia and Mexico [19], food industry export large quantities of vacuum-packed frozen venison cubes. Since venison is one of the leanest meats, its ability to retain water during cooking, such as deep-frying, grilling, and other methods, is important to maintain the palatability of the product. Failure to retain this moisture can destroy the soft parts of the venison and make it not succulent enough.
3.6 Indicators of venison colorConsumers judge the acceptability of the venison color by the bright red color of the surface layer. The darkening of the meat, which determines the duration of color development, is due to the reaction of the transition of red oxymyoglobin to brown methemoglobin. Compared to beef, venison contains higher concentrations of myoglobin [26] and antioxidants such as iron and copper [27]. These facts may explain the reason of venison being dark in color and quick spoilage (i.e. less resistant to discoloration than beef) [26]. The difference in quality between beef and venison strongly suggests that meat processors need to make certain adjustments to processing parameters in order to optimize meat preservation and color [13].
3.7 Growing conditions of deerNatural or controlled pastures (grasses, shrubs) are rich in polyunsaturated fatty acids (PUFA) in total fatty acids and are rich in various antioxidants. Grain-based fodder is rich in saturated fatty acids (SFA), and commercial feed formulas often contain antioxidants such as vitamin E. When an animal is grazing or eating grains, the composition of fatty acids in its muscles depends on the food composition [16].
The distribution of fatty acids in venison depending on the type of feed has been studied carefully and is associated with the taste of venison. Pasture venison is rich in PUFA and has a “grassy” and “wild” taste, while meat from grain-fed animals contains significantly less PUFA and is “soft”, has the taste and aroma of beef [9]. Differences in these tastes have been demonstrated through special sensory programs and consumer tests. It has been established that feeding deer with grain-based feed mixtures with an increased content of PUFA is comparable to feeding deer in a healthy, natural environment, when grass-based feeds are found to have a high content of oleic acid [28]. As the industry expands and implements feeding strategies that are more intensive, deer-breeding farms need to be careful in their use so as not to tarnish the image of premium meat producers in expensive markets around the world [29]. Venison is synonymous with naturalness, natural origin, subtlety and tenderness of taste. All these qualities appeal to the most demanding meat consumers. To continue to succeed, venison processing plants and local meat processing practices should adapt to the rapid softening and color stabilization of venison to optimize the palatability and aesthetic qualities of venison [29].
Physiological state of any animal organism depends entirely on feed availability, and presence of minerals, including vitamins. Vitamin deficiency leads to metabolic disorders and causes diseases associated with avitaminosis [3]. Vitamins enter an animal body mainly with plant foods. In the diet of wild Red Deer in Russia, herbaceous green plants predominate - 83.8% and shrubs make up 21.3% [5]. On average, venison of wild Red Deer contains 30–35 μM/g. However, deer fawns are not able to synthesize taurine themselves, and receive it from their mother's milk. Taurine is a growth factor, it is of great importance in vision functioning, plays the role of a neurotransmitter, and performs a regenerative function in the eye retina [17, 18, 28].
Natural antioxidant coenzyme Q10 neutralizes the harmful effects of free radicals, slowing down the body’s natural aging process. Red Deer venison is rich in coenzyme Q10 [17]. Most of all, the coenzyme is found in deer heart and liver, its concentration does not depend on the meat fat content [17].
Red Deer venison contains L-carnosine, which is synthesized by human body up to a certain age, and then its synthesis is greatly reduced, which leads to rapid body aging [10]. Table 3 shows the comparative content of L-carnosine in meat of various animals and poultry [18].
| No. | Type of meat | Content of L-carnosine, mg/100 g |
|---|---|---|
| 1 | Rare part of a horse | 616 |
| 2 | Turkey fillet | 538 |
| 3 | Pork | 466 |
| 4 | Chuck of a horse | 420 |
| 5 | Beaf | 379 |
| 6 | Marbled beef | 330–379 |
| 7 | Venison | 290–330 |
| 8 | Gammon of bacon | 276 |
| 9 | Chicken | 271 |
| 10 | Lamb (rare part) | 190 |
| 11 | Chicken thigh | 140–176 |
An analysis of the tabular data allows concluding that venison ranks the seventh place in terms of the content of L-carnosine, and practically does not differ from marbled beef, which is popular all over the world.
The vitamin content in the meat of wild Red Deer in Russia is presented in Table 3 by the animal age groups [13, 18].
| No. | Vitamins | Fawns | Sires | Heifers | Average value |
|---|---|---|---|---|---|
| 1 | А (retinol), mg | 5.68± 0.32 | 4.69± 0.28* | 5.74±0.24 | 5.37±0.34 |
| 2 | D (calciferol), µg | 3.11± 0.06 | 2.91± 0.05* | 3.12±0.04 | 3.04±0.06 |
| 3 | Е (tocopherol), mg | 5.23± 0.13 | 4.92± 0.11* | 5.25±0.09 | 5.13±0.10 |
| 4 | В1 (thiamine), mg | 5.80 ±0.31 | 4.82 ±0.27* | 5.86±0.23 | 5.49±0.33 |
| 5 | В2 (riboflavin), mg | 2.15 ±0.06 | 1.96 ±0.05* | 2.16±0.04 | 2.09±0.006 |
| 6 | В3 (pantothenic acid), mg | 6.30 ±0.26 | 5.48 ±0.23* | 6.37±0.19 | 6.05±0.28 |
| 7 | В6 (pyridoxine), mg | 4.18 ±0.05 | 4.24 ±0.03* | 4.22±0.10 | 4.21±0.01 |
| 8 | В12 (cyanocobalamin), µg | 6.46 ±0.26 | 5.65 ±0.23* | 6.51±0.19 | 6.20±0.27 |
| 9 | Вс (folic acid), µg | 6.95 ±0.23 | 6.23 ±0.20* | 7.00±0.17 | 6.72±0.24 |
| 10 | Biotin (vitamin Н), mg | 5.36± 0.16 | 4.69 ±0.19* | 5.32±0.12 | 5.12±0.21 |
| 11 | РР (niacin), mg | 5.75 ±0.15 | 5.13 ±0.17* | 5.67±0.11 | 5.51±0.19 |
*р≥0.05
According to the data from Table 4, venison is rich in all vitamins, especially A, B1, and B12, which stimulate appetite and contribute to the energy accumulation [3]. The most valuable dietary product is the meat of fawns born in the current year as it is characterized by fine fiber and a minimum amount of fat. Our studies show that the content of vitamins in the meat of Red Deer (fawns of the current year of birth) and heifers is approximately the same, but it exceeds the content in sire venison. The high content of vitamins in venison of Red Deer characterizes its dietary value. Averaged data on the content of vitamins by sex and age groups show that this type of meat is the richest in vitamins A, E, B1, B6, B12, Bc, and H [13, 18].
Many studies have evaluated wild deer (e.g. Poland, South Africa) or farmed deer (e.g. Czech Republic, Poland, Italy) in different countries [29, 30, 31]. These studies also examined the meat of wild deer in South African [32] and farmed deer in New Zealand [28]. Deer slaughter (whether in the wild or on a farm, whether because of stress or sudden death) was carried out by different research groups using different scientific tools and methodologies. All of these studies used the same scientific instruments, reagents, and personnel to evaluate meat samples from different countries. Thus, some of the anomalies found by comparing existing literature may actually observed due to methodologies rather than regional differences themselves.
The quality of hunting venison depends on the method of hunting and the hunting season [30]. Slaughtered wild deer do not bleed out immediately after death, and it usually takes several hours from death to butchering the carcass. Therefore, carcasses are usually processed after they have become tough, as it affects the product properties. Generally, the slaughter of farmed deer should result in higher quality of meat. In fact, according to owners of wild animals and personal interviews, meat-processing companies pay higher prices for the meat of animals obtained by hunting than for the meat of forcedly slaughtered animals [31]. The results obtained show for the first time that the effect of mixed hunting types and seasons has some effect on meat quality (pH, cooking losses) but, surprisingly, not on its tenderness (shear force).
Recently, the authors of a study [32] proved that there were no differences in the body weight of female deer depending on the hunting season. However, the authors argue that venison obtained in winter is technologically of better quality than venison produced in summer. In fact, lower vacuum blasting losses, free water, free water to total water, and water losses during warm-up procession were observed. In addition, venison meat obtained in winter is brighter and less red than venison meat obtained in summer [33]. Color characteristics and moisture retention determine the shelf life of the meat and its suitability, especially for vacuum-packed storage.
The pH meat values obtained in the studies were similar to those previously observed in farm-raised deer from New Zealand, and deer from Spain and Russia, subjected to hunting on farms [2, 9, 10]. However, no data were found to compare the average pH values of wild deer obtained in Spain. The results showed that the pH of wild deer meat in Spain (total) was the same as that of deer farmed in New Zealand and Russia, but the pH of wild venison was the lowest. This is not surprising, as transporting deer to the slaughterhouse is also stressful. Recently, the authors of a study [34] showed cortisol levels in 20 deer hunted as a result of tracking by people were significantly lower than in deer hunted with dogs (21.8 and 66.1 nmol/l, respectively). As for the effect of time, meat harvested in winter has a higher pH than meat harvested in summer. However, it was found that the pH of the longissimus muscle, measured 24 hours after slaughter, was 0.22 units higher in summer-produced venison than in winter-produced one. This is consistent with current results of venison color and literature reports that preslaughter stress affects bleeding rate and increases oxymyoglobin levels, supporting an effect of temperature type on skin color [35]. According to the results obtained in the study [36], venison slaughtered in summer is redder and darker than venison obtained in winter. In the studies, the values of color characteristics were obtained similar to those obtained when hunting took place in New Zealand and Spain [10, 25].
The fat content is similar to previously recorded values for venison from the New Zealand deer, as well as deer of autumn and winter slaughter in Spain and Russia [7, 8, 17]. However, the most interesting information concerned the differences in body fat of small wild Spanish deer in different seasons and types of hunting applied. The average fat content of summer wild venison was 0.90%, which was significantly higher than the average fat content of winter wild venison (0.11%). This may be a seasonal difference (less likely due to death stress) as deer begin to graze frequently in spring and summer. Therefore, it is known that the improvement in the physical condition of deer occurs mainly due to the increase in fat and weight in the spring-summer period. In contrast, conditions associated with reduced body fat were higher in autumn and winter [37]. In addition, deer lose weight in autumn due to a significant reduction in feed intake during estrus [32]. In support of this hypothesis, studies [2] found that thighs of deer slaughtered in autumn had higher levels of fat and cholesterol than those obtained in winter. Meat loss during cooking was similar to previously reported values for farm-raised New Zealand deer and stressed deer in Spain and Russia [30], but due to stress/seasonal effects, they were higher for summer hunting animals.
Seasonal effects on cooking losses were explained previously. The reasons for the differences observed in this study, as scientists have shown, may be related to the level of stress during slaughter [38, 39].
Differences between the data of the authors studied venison may be due to several interrelated factors, such as pH, connective tissue content, fat content, proteolytic enzyme activity, and age of the animals. Variety in shear strength observed in venison of different origin (in Spanish venison it is higher by 58.7% than in New Zealand meat and by 62.4% than in Russian venison) were not related to slaughter stress. Differences in shear strength of venison from Spain were not observed depending on the type/season of hunting. In fact, studies [40] confirm a larger seasonal effect on occlusal measurements (100% shear deformation, force of 5g at 24 hours and on the 14th day after slaughter). However, the current study does not include occlusal measurements. There are seasonal effects that offset the apparent effects of stress, and further research may be needed to conclude if they produce significant effects.
In general, country of origin does not affect total PUFA content, and MUFA levels tend to increase in venison of New Zealand and Russian origin. However, venison from New Zealand farms contained more n-3FA and long-chained n-3PUFA and less n-6 FA, than venison from wild animals in Spain. The obtained n-6/n-3 ratios (in the range from 1.22 to 3.71) correspond to the values obtained by other studies of venison [41]. In any case, as recommended by WHO/FAO [42], the average value of n-6/nFactor-3 in venison from all the studied countries was less than 4 points.
It may have been that one of the most notable effects of seasonal differences found in the current study is not the mineral content of the diet, but another very interesting and unique physiological characteristic of deer. This effect is caused by rapid growth of horns in males (1 cm per day or more), which leads to the depletion of certain minerals in bones and the inability to transfer them to the horns [28]. Since minerals are carried in the blood, it is obvious that this fact also affects the mineral composition of muscles. This phenomenon may explain why venison in summer contains less than half of the zinc needed for alkaline phosphatase, an enzyme necessary for calcium deposition in bone tissue [43]. Thus, the reason that may explain this difference is calcium phosphate (although calcium is more stable in the blood) as well as magnesium (which can replace calcium and form horns and bones).
