Effects of Zinc (Zn) from Different Sources on Production Performance, Health Status, Antioxidant Properties and Immune Regulation of Dairy Cows in Early Lactation.

This study aimed to investigate the effects of various Zn sources on the performance, health, antioxidant activity, and immune response in early lactation dairy cows. Thirty Holstein cows with similar physiological conditions were randomly assigned to one of three treatment groups, each receiving a distinct supplement: Zn sulfate (CON), Zn amino acid complex (Zn-AA), or Zn methionine complex (Zn-Met), at a dosage of 60 mg/kg on a dry matter basis. The experiment lasted for 67 days, including a 7-day pre-feeding period. The results indicated that supplementation with Zn-AA and Zn-Met significantly reduced the milk somatic cell count compared to the control group ( = 0.001). Interestingly, glutathione peroxidase (GSH-PX) levels were markedly increased in both the Zn-AA and Zn-Met groups relative to the control group ( = 0.003), with Zn-AA also demonstrating a significant increase in catalase (CAT) content ( = 0.001). Both Zn-AA and Zn-Met led to significant elevations in IgA and IgM content ( < 0.05). Furthermore, milk Zn content in the Zn-Met groups was significantly elevated than that compared with the control group ( < 0.001). In conclusion, organic Zn supplementation resulted in a reduction in the somatic cell count, alongside notable increases the immunoglobulins, milk Zn content, and GSH-PX levels. This study suggests that organic Zn sources, particularly the Zn-AA, are more effective for enhancing the health of dairy cows.