Methionine is the first or second limiting amino acid for ruminants, such as sika deer, and has a variety of biological functions such as antioxidant activity, immune response, and protein synthesis. This study aimed to investigate the effects of methionine supplementation on antler growth, serum biochemistry, rumen fermentation, and the bacterial community of sika deer during the antler-growing period. Twelve 4-year-old male sika deer were randomly assigned to three dietary groups supplemented with 0 g/day (n = 4, CON), 4.0 g/day (n = 4, LMet), and 6.0 g/day (n = 4, HMet) methionine. No significant difference (p > 0.05) was found in the production performance between the three groups, but antler weight was higher in both the LMet and HMet groups than in the CON group. Methionine supplementation significantly increased the serum glutathione peroxidase activity (p < 0.05). The serum immunoglobulin G level was significantly higher in the HMet group than in the other two groups (p < 0.05). No significant effect was found on the apparent amino acid digestibility of the three groups, but cysteine and methionine digestibility were higher in the LMet group. The serum hydroxylysine level was significantly lower in the LMet and HMet groups, whereas the serum lysine level was significantly lower in the HMet group compared with the CON group (p < 0.05). The LMet group had the highest but a nonsignificant total volatile fatty acid content and significantly higher microbial protein content in the rumen than the CON group (p < 0.05). The phyla Bacteroidetes, Firmicutes, and Proteobacteria were dominant in the rumen of the sika deer. The principal coordinate analysis (PCoA) and analysis of similarities (ANOSIM) results showed a significant change in the bacterial composition of the three groups (p < 0.05). The relative abundance of Prevotella and Rikenellaceae-RC9 was significantly higher in the LMet group compared with the CON group and CON and HMet groups, respectively. These results revealed that methionine supplementation improved the antioxidant activity and immune status, affecting amino acid metabolism and rumen microbial composition of the sika deer.

This study assessed the meat quality of Sika deer (Cervus nippon) from various age and sex groups using the longissimus dorsi (LD) muscle. Samples from different age groups (2, 3, and 4 years old) were analyzed for various parameters. The results show that, with increasing age, there is a decrease in moisture and drip loss (p < 0.05), alongside increases in ash, protein, fat, and cooking loss (p < 0.05). Female deer showed an increase in tenderness (p < 0.05), whereas males generally had a higher amino acid content (p < 0.05). Interestingly, 2-year-old female Sika deer had more saturated fatty acids (p < 0.05), while 3- and 4-year-old females had more unsaturated fatty acids compared to age-matched males (p < 0.05). Notably, 3-year-olds had higher levels of monounsaturated and polyunsaturated fatty acids in both the male and female groups (p < 0.05). Overall, this study provides the first comprehensive evidence that Sika deer meat is a nutritious source of lean protein. Notably, meat from 3-year-old Sika deer, regardless of sex, contains higher nutrient levels and is more tender compared to meat from deer of other ages. Additionally, meat from females tends to be more tender than that from males.

This study evaluated the nutrition composition, the nutrient digestibility, and the energy value of six protein ingredients used in pet food by the difference method in six beagles within a 7 × 6 incomplete Latin square design. The results showed that the apparent total tract digestibility of gross energy (GE) and organic matter (OM) in beagles fed the fish meal (FM) and corn gluten meal (CGM) diets was higher than for those fed the meat and bone meal (MBM), soybean meal (SBM), mealworm meal (MM), and yeast extract (YE) diets (p < 0.05). The digestible energy (DE), metabolizable energy (ME), and net energy (NE) of the MM diet were greater than the other diets, and MBM was the lowest (p < 0.05). The ME of protein ingredients was positively correlated with organic matter and negatively correlated with the ash content. The NE of protein ingredients was positively correlated with the crude protein content and negatively correlated with the ash content. The study resulted in predictive energy equations for protein ingredients that were more accurate than the NRC’s predictive equation of ME when the ash content of the ingredient was more than 30% DM. In conclusion, the nutrient digestibility and energy value of corn gluten meal were similar to those of fish meal and those of soybean meal were similar to yeast extract. All predictive energy equations for six protein feedstuffs had slight differences with measured energy values.

This study examined the effects of dietary crude protein (CP: 18%, 15%) and crude fat (EE: 8%, 4%) levels, and their interactions, on growth performance, nutrient digestibility, serum indices, and rectal fecal microbiota in sika deer fawns during early wintering. A two-month 2 × 2 factorial experiment was conducted using 32 healthy five-month-old male fawns randomly assigned to four groups: P18E8 (18% CP, 8% EE), P18E4 (18% CP, 4% EE), P15E8 (15% CP, 8% EE), and P15E4 (15% CP, 4% EE). The P18E4 group showed the highest total weight gain and average daily gain (p < 0.05), along with greater apparent digestibility of dry matter, crude protein, calcium, and fiber fractions (p < 0.05). Serum urea content was significantly lower in this group, indicating improved nitrogen utilization (p < 0.05). Dominant fecal microbiota at the phylum level across all groups included Firmicutes_A and Bacteroidota, with the P18E4 group showing a unique genus composition within Bacteroidota, known for enhancing fiber digestion. In summary, a diet with 18% CP and 4% EE optimized growth performance, nutrient digestibility, and gut microbiota composition, providing a strategy for improving the health and productivity of sika deer fawns during overwintering.

This study investigated the effects of replacing soybean meal with fermented rapeseed meal (FRSM) in the diets of sika deer (Cervus nippon) during the pre-antler growth period. A single-factor experimental design was employed. A total of 24 male sika deer aged 2–3 years were randomly divided into four groups with six deer per group, including a control group (0% substitution) and three treatment groups fed diets containing 2.8%, 5.6%, and 8.4% fermented rapeseed meal (FRSM), defined as the low (L-FRSM), medium (M-FRSM), and high (H-FRSM) substitution groups, respectively. The feeding trial lasted 63 days, with measurements collected on days 30 and 63. Growth performance, nutrient digestibility, serum biochemical indices, and rectal fecal microbiota were determined. The results showed that the final body weight, total weight gain, and average daily gain L-FRSM were higher in the L-FRSM group than in the control group and other substitution groups (p < 0.05), accompanied by a reduced feed conversion ratio (p < 0.05). In addition, body height and chest circumference were improved in the L-FRSM group. Regarding nutrient digestibility, the apparent digestibility of neutral detergent fiber and dry matter at day 30, as well as calcium digestibility at day 63 were higher in the L-FRSM group compared to the control and higher-substitution groups (p < 0.05). In contrast, crude fat and dry matter digestibility were significantly lower in the H-FRSM group (p < 0.05). No statistical differences were observed among treatments in serum biochemical indices related to energy metabolism, protein metabolism, liver function, lipid metabolism, antioxidant capacity, or humoral immunity (p > 0.05). Similarly, no significant differences were detected in core microbial composition or α-diversity of rectal fecal microbiota among groups (p > 0.05). In conclusion, substituting soybean meal with 2.8% fermented rapeseed meal effectively improves growth performance and nutrient utilization without compromising health status or intestinal microbial stability in sika deer during the pre-antler growth period. The findings provide a scientific basis for optimizing dietary strategies and support the rational application of fermented rapeseed meal in sika deer production.