Complete Replacement of Inorganic Sources of Supplementary Trace Minerals by Organic Sources Alters Systemic Trace Mineral Status, Rumen Fermentation, and Energy Balance in Dairy Cows

Trace minerals (TM) are required for optimal health and performance of dairy cows and the source of supplementation can affect their availability to rumen microbes and absorption in the digestive tract. Our objectives were to evaluate the effects of replacement of supplementary inorganic TM (ITM) by organic TM (OTM) in pre- and postpartum diets on feeding behavior, rumen physiology, energy metabolism, TM status, and performance. Pregnant cows and heifers (n=273) were randomly assigned to ITM or OTM diets at 45 d before expected calving (study d 0). Groups received the same diet, except by the source of TM fed at 100% recommended levels. The ITM group received Co, Cu, Mn and Zn sulfates and Na selenite, and the OTM group received Co, Cu, Mn and Zn proteinates and selenized yeast (Bioplex^® and Sel-Plex^®, Alltech). Automated feed bins were used to assign treatments and to measure ingestive behavior. Rumination was monitored by sensors and ruminal fluid was collected on d -21, 23, and 65. Metabolites and TM were evaluated on d -45, -21, -14, -10, -7, -3, 0, 3, 7, 10, 14, 23, 65 and 105. OTM tended to have longer feeding time (197 vs 188 min/d) and greater dry matter intake (DMI) (13.3 vs 12.9 kg/d), had a more positive energy balance (4.2 vs 3.6 Mcal/d) and shorter rumination time (37.5 vs 40.1 min/kg of DM) than ITM in the prepartum period. In the postpartum period, OTM increased DMI in multiparous (24.7 vs 24.1 kg/d) but not in primiparous cows (18.9 kg/d). Milk yield was not affected in multiparous cows (44 kg/d), however, OTM primiparous cows had lesser yield than ITM primiparous cows (29.8 vs 31.9 kg/d). OTM had a greater milk protein percentage (3.17 vs 3.11%), reduced NEFA in serum (0.40 vs 0.45 mmol/L) and rumination activity (27.8 vs 30.1 min/kg DM). On d 23, OTM had reduced molar proportion of acetate and pH, and tended to have greater concentration of total VFA in ruminal fluid. OTM had greater Se in serum and milk, reduced Se in urine, and greater prepartum Co and reduced postpartum Co in serum. In conclusion, complete replacement of ITM by OTM caused moderate changes in rumen physiology, behavior, energy metabolism, TM status, and performance, and seemed to reduce the energy deficit during the transition period.

Key words: minerals, feed intake, rumen.

Presented at the 2022 Animal Nutrition Conference of Canada. For information on the next edition, click here.