Table 2. Effects of subcutaneous injection of melatonin on blood biochemical index of Holstein cows.

Group	Index	Before injection	1 d after injection	3 d after injection
MT (SCC:3 × 105–1 × 106 cells/mL)	IgG (g/L)	10.26 ± 1.31Aa	12.18 ± 1.26Ba	8.92 ± 0.63Ca
NON-MT (SCC:3 × 105–1 × 106 cells/mL)		10.86 ± 1.82Aa	10.53 ± 1.35Ab	10.29 ± 1.27Ab
Healthy control (SCC < 1 × 105 cells/mL)		5.87 ± 1.01c	—	—
MT (SCC:3 × 105–1 × 106 cells/mL)	IgM (g/L)	2.63 ± 0.21Aa	3.39 ± 0.23Ba	2.14 ± 0.20Aa
NON-MT (SCC:3 × 105–1 × 106 cells/mL)		2.74 ± 0.63Aa	2.75 ± 0.44Ab	2.65 ± 0.44Ab
Healthy control (SCC < 1 × 105 cells/mL)		2.12 ± 0.20b	—	—
MT (SCC:3 × 105–1 × 106 cells/mL)	ALB (g/L)	29.92 ± 1.44Aa	33.58 ± 1.31Ba	33.92 ± 1.44Ba
NON-MT (SCC:3 × 105–1 × 106 cells/mL)		30.08 ± 1.78Aa	31.75 ± 1.60Ab	28.25 ± 1.22Bb
Healthy control (SCC < 1 × 105 cells/mL)		38.5 ± 2.72c	—	—
MT (SCC:3 × 105–1 × 106 cells/mL)	ALT (U/L)	25.42 ± 4.03Aa	34.17 ± 4.04Ba	35.50 ± 4.38Ba
NON-MT (SCC:3 × 105–1 × 106 cells/mL)		24.83 ± 3.93Aa	30.00 ± 4.81Bb	31.42 ± 5.95Bb
Healthy control (SCC < 1 × 105 cells/mL)		35.5 ± 6.42b	—	—
MT (SCC:3 × 105–1 × 106 cells/mL)	LDH (U/L)	801.33 ± 66.48Aa	940.67 ± 103.13Ba	904.67 ± 96.38Ba
NON-MT (SCC:3 × 105–1 × 106 cells/mL)		847.92 ± 85.03Aa	844.83 ± 86.80Ab	842.83 ± 93.57Ab
Healthy control (SCC < 1 × 105 cells/mL)		945.7 ± 87.28b	—	—
MT (SCC:3 × 105–1 × 106 cells/mL)	GLU (mmol/L)	4.06 ± 0.23Aa	4.32 ± 0.24Aa	4.21 ± 0.19Aa
NON-MT (SCC:3 × 105–1 × 106 cells/mL)		3.96 ± 0.23Aa	4.16 ± 0.31Aa	4.14 ± 0.23Aa
Healthy control (SCC < 1 × 105 cells/mL)		4.16 ± 0.22a	—	—

MT (melatonin-treated cows); NON-MT (non-melatonin-treated cows). Data expressed as the means ± SEM (n = 10). Values with different superscript letters, such as ^abrepresent a significant difference within the same group, (P < 0.05); Values with different superscript letters ^ABrepresent a significant difference between different groups (P < 0.05); The same letters represent no significant difference (P > 0.05).