Fe28 standard

Soil pH was measured at a water/soil ratio of 2.5:1 using a pH meter (Mettler Toledo FE28-Standard, Switzerland). The total SOC content was determined by the H₂SO₄–K₂Cr₂O₇ external heating method. Available N was determined by the alkali diffusion method. Soil available P was determined by spectrophotometry (Shimadzu UV-1780, Japan) (Shao et al., 2019 (link)). Available K was determined by flame photometry (Chen et al., 2021 (link)). Soil moisture content was measured by the drying method. Soil total C and total N was determined by an elemental analyzer (Euro EA3000, Italy).

The blood acid metabolism variables of the collected 0.5–1 ml arterial blood were measured using an automatic blood gas analyzer (ABL90 OSM, RADIOMETER, Denmark), and the pH_e, BE (mM), HCO₃⁻ (mM) and LAC values (mM) were recorded.
For the determination of pH_i in skeletal muscle, 80 mg of muscle tissue was homogenized in 800 μl of non-buffered solution (145 mM NaCl, 10 mM KCl, and 5 mM NaF). The pH_i of the homogenate was measured using a pH meter (FE28-Standard, METTLER TOLEDO, Switzerland).

After the soil was suspended with water at a ratio of 1:2.5 (weight:volume), the pH was measured with a pH meter (FE28-Standard, METTLER-TOLEDO, Switzerland). Soil organic carbon (SOC) was determined by dichromate oxidation and titration with ferrous sulfate. Soil total nitrogen (TN) was determined using the Kjeldahl digestion distillation method. Soil available nitrogen (AN) and phosphorus (AP) were determined using alkali hydrolyzation and the Bray method, respectively [33 (link)]. Soil enzyme activities of invertase (INV), urease (UE), acid phosphatase (ACP), catalase (CAT), polyphenol oxidase (PPO), and peroxidase (POD) were determined using kits from Beijing Solarbio Technology Co. Ltd according to the manufacturer’s instructions [34 (link), 35 ].

Soil pH was measured at a water/soil ratio of 2.5:1 using a pH meter (Mettler Toledo FE28-Standard, Switzerland). Soil electric conductivity (mS cm^-1) measured by electric conductivity meter (Keruiyongxing DDS-11A, China). Soil organic carbon content (g kg^-1) was determined by the H₂SO₄–K₂Cr₂O₇ external heating method (Bao, 2000 ). Available N (mg kg^-1) was determined by the alkali diffusion method. Soil available phosphorus (mg kg^-1) was extracted by NaHCO₃ and then determined by spectrophotometry (Shimadzu UV-1780, Japan) (Bao, 2000 ). Available potassium (mg kg^-1) was extracted by CH₃COONH₄ and then determined by flame photometer (Shanghaiyuefeng FP6400, China) (Bao, 2000 ).

The outline of the LT cross-section was delineated with sulfuric acid paper, and the eye muscle area was calculated with ADOBE PDF (version 1.2, San Jose Co., Ltd., CA, United States) after scanning. At 45 min, 24 h, and 48 h after slaughter, the pH was determined using a pH meter (FE28-Standard, METTLER-TOLEDO Co., Ltd., Shanghai, China) in the cut surface of the LT. A colorimeter (NR10QC, 3nh Co., Ltd., Shenzhen, China) was used to measure meat color on the surface of the LT about 45 min after slaughter. The meat samples were cut into 1 cm thick pieces, wrapped in plastic bags, heated to 70°C, and taken out to cool. The meat was cut into strips with a cross-section of 1 cm × 1 cm along the fiber direction, and then the shear force was measured using a tenderness meter (TA. XTPlus, SANHAO Co., Ltd., Suzhou, China). The meat was cut into long strips (5 cm × 2 cm × 2 cm) and weighted as N1. After being packed into plastic bags and hanging suspended for 24 h in a 4°C freezer, the weight was scored as N2. Drip loss% = (N2/N1) × 100%. Then, after centrifugation (1,500 × g, 30 min at 4°C), the centrifugal water loss rate was calculated. Analyzing DM, CP, EE, and ash of meat according to the AOAC method and amino acids using a full-automatic amino acid analyzer (LA8080, Hitachi Co., Ltd., Tokyo, Japan).

The pH of breast muscle was measured at 45 min and 24 h postmortem using a handheld pH meter (FE28-Standard, Mettler-Toledo, Zurich, Switzerland) by inserting the electrode into the muscle. The lightness (L*) and yellowness (b*) were measured using a Chroma Meter (TS7700, Group 3NH, Shenzhen, China) according to the manufacturer’s instructions. About 5 g of breast muscle sample was placed in a polyethylene container and reweighed after being hung at 4 °C for 24 h. The drip loss was calculated as a percentage of the initial weight. Another part of the breast muscle was cut into 2 cm (length) × 1 cm (width) × 0.5 cm (height) parallel to the muscle fibers, and the shear force was measured using a meat shear machine (C-LM36, Northeast Agricultural University, Harbin, China).