Abstract

The aim of this study was to investigate the effects of two different concentrate feed allotments on the feed intake, weight gain, and venison quality (mineral and amino acid content, and chemical and fatty acid composition) of sika deer. Sixteen deer were allocated into two groups: T1 (feed allotment of 1.5% of the body weight) and T2 (ad libitum consumption). The results showed no significant differences in the average daily weight gain and feed conversion ratio between the two treatment groups. Analysis of the proximate composition of sika deer meat showed that the muscle tissue of T1 had a significantly lower (P < 0.05) fat content compared with that of T2. There were no significant differences in moisture, crude protein, ash, mineral, and amino acid content between the treatments. In contrast, the composition of fatty acids and total amount of saturated, monounsaturated, and polyunsaturated fatty acids showed significant differences. Compared with T1, deer meat from T2 had significantly higher (P < 0.05) levels of palmitoleic and linoleic acids and significantly lower (P < 0.05) levels of myristic and stearic acids.

1. Introduction

Unconventional animals are a valuable food source for humans globally ^{1, 2}. Meat consumers evaluate various meat qualities such as flavor, tenderness, and nutrients ³, which are fulfilled by meat of a superior quality with excellent nutritional and sensory values ^{4, 5}. Venison meets most of the consumer standards due to its low fat content, desirable fat composition, and high mineral content ⁶. Further, the special taste of game meat is attractive to consumers, and therefore, there is a growing interest in rearing meat production animals under conditions similar to those in the wild ⁶. Given that the meat quality of ruminants is affected by breed, age, sex, diet, and climate ⁷, pasture-based production systems are important to the world’s venison industry. However, as pastures are a scarce resource, especially in winter, deer are often fed supplements or substitutes ⁸.

The feed requirements of deer depend on various types of information, such as seasonal voluntary feed intake, growth, and seasonal production potential, which determines metabolizable energy requirements, diet selection, animal behavior, environmental constraints, pasture and other feed availability, management choices, and marketing opportunities ⁹. Although farm-raised deer are often fed supplements during periods of pastoral feed deficiency ¹⁰, there is little research investigating the relationship between concentrate supplementation and meat production in farmed deer. Moreover, research into efficient feed management techniques in Korea is lacking ¹¹. Therefore, the aim of this study was to investigate feed intake and weight gain of sika deer fed two different rations of concentrate feed and to compare the physical and chemical properties of their meat.

2. Materials and Methods

The experiment was conducted between March and October on a farm in Buan County, North Jeolla Province, South Korea. Sixteen sika deer (average body weight = 27.4 ± 1.6 kg) were randomly assigned to two groups: T1 (n = 8) was fed a supplementary concentrate feed at 1.5% of the average body weight, and T2 (n = 8) was fed the concentrate feed ad libitum. Both groups had unlimited access to water, mixed hay rations as roughage, and were provided with the supplementary feed twice daily at 09:00 and 16:00. The chemical composition of the feed (Table 1) was analyzed using AOAC ¹² methods.

The intake of concentrate and mixed hay by sika deer was determined by measuring the difference between the amount of feed supplied and the amount remaining after intake. Unconsumed feed was collected and weighed before being resupplied the next morning. The animals’ weight was measured every 30 days (over the eight-month period) before supplying the morning feed. Weight gain was calculated as the initial weight subtracted from the final weight.

The deer were slaughtered at the National Institute of Animal Science (NIAS), following the NIAS standard procedure. The carcasses were stored at 4 °C for at least 24 h before dissection. Loin muscle tissue was dissected from the venison saddle and all extraneous fat was removed. Samples were vacuum-packed and stored at 1 °C for seven days post-mortem, then frozen at -20 °C until analysis. Measurements were made within three months post-mortem, and samples were thawed at 1 °C overnight before analysis. The analyses of homogenized samples were performed in triplicate, and proximate composition was determined using AOAC ¹² methods.

To analyze the mineral content of venison samples, sirloin samples from each test group were added to a flask containing 10 mL of concentrated sulfuric acid. On a hotplate, concentrated nitric acid was added to the flask until the sample color was clear, and then, its volume was adjusted to 100 mL by adding distilled water. Samples were filtered through a filter membrane (Whatman No. 6) and analyzed for inorganic components using an inductively coupled plasma (Atom Scan 25; Thermo Jarrell Ash Co., France). The analysis was conducted at an approximate radio frequency power of 1,150 W, pump rate of 100 rpm, nebulizer pressure of 30 psi, and 15 mm observation height.

Free amino acid composition was analyzed according to methodologies described by Hughes et al. ¹³ and Kim et al. ¹¹. Data were collected using a Waters high performance liquid chromatography system (1525 HPLC with binary gradient delivery, 717 autosampler and injector, 1500 column heater, and 2487 dual-wavelength UV detector), and analyzed using Breeze software (Waters, Milford, MA, USA). A control with a known amino acid composition was included to ensure the accuracy and repeatability of the experiment.

Total fat was extracted from the samples according to methodology described by Folch et al. ¹⁴, with modifications described by Kim et al. ¹¹. Each fatty acid class was expressed as a proportion of the total fatty acids. Saturated (SFA), monounsaturated (MUFA), and polyunsaturated (PUFA) fatty acids were also expressed as a percentage of the total amount of fatty acids.

Data analysis was performed using the statistical software SPSS 12.0 for Windows (SPSS Inc., Chicago, IL, USA). Continuous variables are presented as mean ± standard error, and significant differences were verified using Duncan's multiple range test.

3. Results

The voluntary intake of mixed hay decreased when the amount of concentrate increased in the sika deer diet (Table 2).

Meat from T1 had a significantly lower (P < 0.05) crude fat content than that of T2 (Table 3). There were no significant differences in moisture, crude protein, and ash content between T1 and T2 groups.

The element with the highest content in the deer meat was potassium (K), followed by phosphorus (P), sodium (Na), magnesium (Mg), calcium (Ca), iron (Fe), zinc (Zn), and copper (Cu) (Table 4). No significant differences were found between the two groups (P > 0.05).

The content of essential, semi-essential, and non-essential amino acids was not significantly different among T1 and T2 groups (Table 5). Meat samples from both T1 and T2 contained high levels of non-essential amino acids (0.79–3.62%) and the essential amino acid lysine (2.11–2.15%). Glutamic acid accounted for the highest proportion of all amino acids analyzed (Table 5).

Meat from the T2 group contained more palmitoleic than that from the T1 group (P < 0.05), whereas myristic and stearic acid content were lower (P < 0.05) in T2 than T1 (Table 6). Palmitic and oleic acid content were the highest and linolenic acid content was the lowest among all fatty acid classes in both test groups.

4. Discussion

In the present study, the quality and composition of sika deer meat differed depending on the feed rations. Additionally, deer fed the concentrate for ad libitum consumption showed increased feed intake and weight gain. The supply of roughage limits feed intake in deer due to physical satiety, whereas the supply of concentrated feeds improves intake and weight gain ^{15, 16}. Previous studies further showed that, compared to game meat, meat from livestock has a lower protein content but higher fat content, indicating higher energy levels ¹⁷. Venison is low in fat and high in protein content, thus satisfying the expectations and dietary needs of modern meat consumers ⁶. Accordingly, in the present study, sika meat was rich in protein (24.22–24.50%), but low in fat (0.78–1.26%). Kim et al. ¹⁸ previously reported similar results for elk meat; moisture, protein, and fat content of Musculus longissimus dorsi were 73.1, 22.4, and 2.11%, respectively. Other studies on roe deer meat accordingly reported average ranges of 19.2–24% and 0.3–3.7% for protein and fat content, respectively ^{19, 20}. Moreover, our results aligned with Mushi et al. ²¹, which revealed an increase in fat content in Longissimus dorsalis associated with an increase in concentrate feed. Stearic acid is a major fatty acid crucial for fat hardness; its conversion to oleic acid increases fat softness ²². A higher proportion of oleic acid compared with palmitic and stearic acids was reported in well-fattened cattle ²³. In our findings, stearic acid was significantly lower in T2 compared with T1; thus, the meat quality of sika deer may be improved by providing a diet richer in concentrate feed. Therefore, we suggest that the amount of concentrate feed provided to the deer, which is an effective management to improve the overall production efficiency of sika deer.

5. Conclusions

This study compared the venison quality (e.g., protein, fat, and mineral content, as well as fatty acid and amino acid composition) of sika deer subjected to two different supplementary feeding treatments. In conclusion, concentrate feeds directly influence the chemical composition of venison, and the effective supervision of concentrate feeding rations is advised for improving venison quality.

Acknowledgments

This work was supported by the Cooperative Research Program for Agriculture Science & Technology Development (Project No. PJ01431501) and the Fellowship Program of the National Institute of Animal Science, Rural Development Administration, Republic of Korea.

Competing Interests

The authors have no competing interests.

Abbreviations

MUFA, monounsaturated fatty acids; NIAS, National Institute of Animal Science; PUFA, polyunsaturated fatty acids; SFA, saturated fatty acids; USFA unsaturated fatty acids.

References