Ruminant Nutrition: Dairy: Feed Additives

Multiparous Holstein cows (n = 60) were used to determine effects of trace mineral source on oxidative metabolism, subclinical endometritis, and performance of transition cows. After a 1-wk preliminary period, cows were assigned randomly to one of 3 topdress treatments from 21 d before expected calving through 84 d post calving: 1) Inorganic sources based upon sulfates of Zn, Cu, and Mn (ITM); 2) a blend (75:25) of sulfates and chelated sources of Zn, Cu, and Mn (ITM/OTM); and 3) Hydroxy Trace Minerals (HTM) of Zn, Cu, and Mn (IntelliBond; Micronutrients, Inc., Indianapolis, IN). Final concentrations of Zn, Cu, and Mn were similar among treatments and averaged 40, 10, and 27 ppm before calving and 59, 15, and 40 ppm after calving. An interaction of treatment and week existed (P = 0.02) for milk yield such that cows fed HTM increased milk yield faster than cows fed the other 2 treatments; a similar interaction was also present for yields of fat-corrected milk (P = 0.03) and lactose (P = 0.05). Cows fed HTM during the prepartum period tended (P = 0.08) to have higher body weight and had higher body weight during the postpartum period (P = 0.04) than those fed the other 2 treatments. Plasma antioxidant capacity was lower in cows fed HTM than ITM during both prepartum (1.84 vs. 2.09 mM; P = 0.03) and postpartum (1.95 vs. 2.16 mM; P = 0.04) periods; cows fed ITM/ OTM had intermediate values. Cows fed HTM tended to have lower concentrations of plasma thiobarbituric acid reactive substances than those fed ITM during whole study period (1.95 vs. 2.11 μM; P = 0.07). Endometrial cytology as characterized by low volume uterine lavage at 7 d postcalving and on one day between 40 and 60 d post calving was not affected by treatment. In conclusion, supplementation with HTM sources of Zn, Cu, and Mn resulted in evidence of improved productive performance during early lactation along with modulation of plasma variables related to oxidative metabolism.