Supplementing Zn, Mn, and Cu from amino acid complexes and Co from cobalt glucoheptonate during the peripartal period benefits postpartal cow performance and blood neutrophil function.

The physiologic and metabolic stresses that dairy cows experience during the transition into early lactation can promote oxidative stress, inflammation, and immune dysfunction. Optimal supply of micronutrients such as trace minerals (e.g., Zn, Mn, Cu, and Co) via more bioavailable forms (e.g., AA complexes) might minimize these negative effects. Multiparous Holstein cows were enrolled at 60 d before dry-off (~110 d before calving) and remained on experiment until 30 d in milk (DIM). Cows were offered a common diet supplemented entirely with inorganic trace minerals (INO) from -110 to -30 d before calving. From -30 to calving cows received a common prepartal [1.5 Mcal/kg of dry matter (DM), 15% crude protein] diet, and from calving to 30 DIM a common postpartal (1.76 Mcal/kg of DM, 18% crude protein) diet. Both diets were partially supplemented with an INO mix of Zn, Mn, and Cu to supply 35, 45, and 6 mg/kg, respectively, of the total diet DM. Cows were assigned to treatments in a randomized complete block design to receive an oral bolus with a mix of INO (n=21) or organic AA complexes (AAC; n=16) of Zn, Mn, Cu, and Co to achieve supplemental levels of 75, 65, 11, and 1mg/kg, respectively, in the total diet DM. Inorganic trace minerals were provided in sulfate form and AAC were supplied via Availa Zn, Availa Mn, Availa Cu, and COPRO (Zinpro Corp., Eden Prairie, MN). Liver tissue was harvested on -30, -15, 10, and 30 d, and blood samples for biomarker analyses were obtained more frequently from -30 to 30 DIM. Short-term changes in blood ketones were measured via Precision Xtra (Abbott Diabetes Care, Alameda, CA) every other day from 1 to 15 d postpartum. Prepartal DM intake was lower in AAC cows. In contrast, a tendency for a diet by time (D × T) interaction resulted in greater postpartal DM intake of approximately 2 kg/d in cows fed AAC. Milk and milk protein yield had a D × T interaction because AAC cows produced approximately 3.3 kg/d more milk and 0.14 kg/d more protein during the first 30 DIM. Although blood glucose, fatty acids, and liver triacylglycerol were not affected by diet, the Precision Xtra ketones (1.44 vs. 2.18 mmol/L) and γ-glutamyltransferase (liver function biomarker) were lower in AAC than INO. Furthermore, feeding AAC increased (D × T) polymorphonuclear neutrophilic lymphocyte phagocytosis, antioxidant capacity postpartum, and overall concentration of liver tissue Co and Cu. Overall, the positive response in milk yield and milk protein in AAC cows might be partly explained by the beneficial effects of AAC on postpartal DM intake driven at least in part by better liver and immune function as a result of improved antioxidant status.