This study aimed to explore the effects of dietary fiber level and breed on the growth performance, nutrient utilization, intestinal morphology, slaughter performance, and meat quality of finishing pigs using fermented corn straw (FCS) as the fiber source. The experiment employed a 2 × 4 factorial design, selecting 96 Songliao Black (SLB) and Duroc × Landrace × Yorkshire (DLY) crossbred finishing pigs (a total of 192 pigs, with an initial body weight of 60.52 ± 4.59 kg) randomly assigned by breed to four dietary treatment groups (A: 2.92% crude fiber; B: 4.82% crude fiber; C: 6.86% crude fiber; D: 9.01% crude fiber). The results showed that DLY finishing pigs had higher final weight (FW), average daily gain (ADG), and average daily feed intake (ADFI) in both finishing stages 1 and 2 compared to SLB pigs (p < 0.05), while the ratio of feed to weight gain (F/G) showed no significant differences (p > 0.05). Compared to the basal diet, increasing the dietary fiber level to 4.82% improved FW and ADG in both SLB and DLY finishing pigs (p < 0.05) and reduced F/G (p < 0.05). Additionally, SLB finishing pigs had lower ether extract (EE) digestibility but higher crude fiber (CF) and acid detergent fiber (ADF) digestibility than DLY (p < 0.05). Dietary fiber level and breed exhibited an interaction effect on dry matter (DM) and crude protein (CP) digestibility in finishing pigs (p < 0.05). At a dietary fiber level of 4.82%, villus height, crypt depth in the jejunum, and cecal volatile fatty acid (VFA) concentrations were increased in both SLB and DLY finishing pigs (p < 0.05). Dietary fiber level and breed showed an interaction effect on cecal VFA production in finishing pigs (finishing stage 1; p < 0.05). The dietary fiber level of 4.82% increased loin eye area (LA) (p < 0.05) and decreased backfat thickness (BT) (p < 0.05) in both SLB and DLY finishing pigs. Dietary fiber level and breed had an interaction effect on LA in finishing pigs (p < 0.05). SLB pigs had higher muscle redness (a*), shear force, and contents of crude protein (CP), EE, saturated fatty acid (SFA), and polyunsaturated fatty acids (PUFA) than DLY (p < 0.05). Increasing the dietary fiber level improved pH_24h and reduced drip loss and shear force in both SLB and DLY finishing pigs (p < 0.05). Dietary fiber level and breed showed an interaction effect on pig meat color and drip loss (p < 0.05). In conclusion, FCS is a beneficial source of dietary fiber for SLB and DLY pigs. Its proper addition can enhance the growth performance, carcass traits, and meat quality in fattening pigs.

In order to further reveal the special characteristics of energy metabolism and the characteristics of energy requirements of fattening pigs grown in low-temperature environments, this study used a 2 × 2 × 2 factorial array of treatments, which harnessed two temperatures (low-temperature, LT group: 10 °C; normal-temperature, NT group: 20 °C), two feed energy levels (normal-energy, NE group: 14.02 MJ/kg metabolic energy; high-energy, HE group: 15.14 MJ/kg metabolic energy), and two feed energy sources (LF group: low fat, HF group: high fat). Thirty-two Songliao black fattening pigs with an initial body weight of 85.48 ± 2.31 kg were completely randomized into eight treatment groups, with four replicates in each treatment group and one pig in each replicate. The pigs were placed in a respiratory metabolic chamber for a 6-day trial. There was one pig per respiratory metabolic chamber in a single cage. The results showed that the average daily weight gain in the normal-temperature, high-energy, and high-fat groups was higher than that of the low-temperature, normal-energy, and low-fat groups (p < 0.05). The fat deposition rate, protein oxidation, and fat oxidation of the high-fat group were higher than those of the low-fat group (p < 0.05). The energy digestibility, protein digestibility, and fat digestibility in the high-fat group were higher than those in the normal-energy group (p < 0.05). The fat digestibility and energy deposition rate in the high-fat group were higher than those in the low-fat group (p < 0.05). The respiratory quotient in the high-energy group was lower than that in the normal-energy group (p < 0.05), and the respiratory quotient in the high-fat group was lower than that in the low-fat group (p < 0.05). There was an interaction between temperature and energy sources in terms of the respiratory quotient, fat oxidation, blood urea nitrogen content, and glucose content (p < 0.05). Appropriately increasing the energy level of the diet and improving the energy structure of the feed (increasing the level of fats and oils) will benefit Songliao black fattening pigs by increasing their energy use efficiency and at the same time reducing greenhouse gas CO₂ emissions, and these changes are more pronounced in cold environments.

The purpose of this study was to investigate the effects of the optimization of dietary energy supply on the growth performance, nutrient digestibility, energy metabolism, nutrient oxidation, slaughter performance, and meat quality of growing and fattening pigs under a low-temperature environment. In this study, forty-eight 60-day-old growing barrows (Duroc × Landrace × Large White) with an initial body weight of 31.24 ± 3.56 kg were completely randomized into two treatment groups, with four replicates in each treatment group and six pigs in each replicate. The two groups were fed diets with equal protein levels and different energy levels (a conventional diet and an energy-optimized diet); the dietary energy level was increased by 8% by adding 6% fat, and the two groups were kept at the same ambient temperature (10 ± 1 °C) all day. After 5 d of prefeeding, the final weight reached approximately 110.00 kg prior to slaughter (99 days of age), and four pigs with a body weight of about 80.00 kg were selected in the two groups for digestion, metabolism, and respiratory calorimetry. The results showed that the average daily feed intake of the TES group (energy-optimized diet group, high fat and energy) was lower than that of the CON group (conventional diet group, normal fat and energy) (p < 0.05). Compared with the CON group, the feed-to-gain ratio was lower in the TES group during the fattening period (60–110 kg) (p < 0.05). Compared to the CON group, fat and energy digestibility in the TES group were higher (p < 0.05), fecal nitrogen and urine nitrogen were lower (p < 0.05), the nitrogen deposition rate increased (p < 0.05), and fat oxidation and the sedimentation energy rate also increased (p < 0.05). The serum triglyceride concentration in the TES group was higher than that in the CON group (p < 0.05). Compared to the CON group, the carcass weight, body fat content, backfat thickness, and eye muscle area in the TES group increased (p < 0.05); the L* value of flesh color also increased (p < 0.05); and the shear force was lower (p < 0.05). The dietary energy should be optimized under a low-temperature environment, and the feed conversion efficiency of fattening pigs could be improved by improving dietary energy levels by adding fat, increasing the fat oxidation proportion, promoting nitrogen deposition and sedimentation energy, and improving slaughter performance and meat quality.

The aim of this experiment is to investigate the effects of optimizing the dietary energy supply of Songliao Black growing and fattening pigs on their growth performance, nutrient digestibility, nitrogen balance, energy metabolism and oxidation energy supply, slaughter performance, and meat quality at a low ambient temperature. Forty-eight 75-day-old Songliao Black growing barrows with an initial weight of 33.38 ± 1.29 kg were randomized into two groups, with four replicates in each group and six pigs in each replicate. Two groups (CON group: low fat, normal energy; TES group: high fat, high energy) were fed isonitrogenous diets with different energy levels and fat contents. The experimental animals were raised at the same ambient temperature (10 ± 1 °C) all day. After 5 days of pre-feeding, the formal experiment began. Four Songliao Black barrows weighing approximately 80 kg were selected from each group for a five-day experimental period for digestibility and metabolism and respiratory calorimetry tests. All pigs (185 days of age) were slaughtered simultaneously at the end of the 110-day experimental period when their average body weight reached approximately 110 kg. The results showed that the average daily feed intake of the TES group was lower than that of the CON group (p < 0.05). Compared with the CON group, the feed-to-gain ratio was lower in the TES group during the fattening period (p < 0.05). Compared with the CON group, the crude fat digestibility, deposition energy, energy deposition rate, deposition energy of fat, and fat oxidation were higher (p < 0.05), and the intake and urinary nitrogen, carbohydrate oxidation, urinary energy, and protein oxidation were lower in the TES group (p < 0.05). Compared with the CON group, the serum high-density lipoprotein concentration, low-density lipoprotein concentration, and triglyceride concentration were higher in the TES group (p < 0.05), while alanine aminotransferase and aspartate aminotransferase concentrations were lower in the TES group (p < 0.05). Compared with the CON group, the backfat thickness was higher in the TES group (p < 0.05). Compared with the CON group, the weight gain/digestible protein and live lean meat mass/digestible protein were higher in the TES group (p < 0.05). Compared with the CON group, the yellowness (b*_45min) value of the longissimus thoracis was higher in the TES group (p < 0.05), and the shear force was lower (p < 0.05). Therefore, at a low ambient temperature, appropriately increasing the levels of dietary fat and energy was beneficial for improving the production performance and energy utilization efficiency and reducing CO₂ emissions and protein oxidation, saving protein resources of Songliao Black pigs.