PSIV-27 - Effects of organic complexed or inorganic trace mineral supplementation on cow performance and herd longevity

Abstract: Records for Angus-crossbred cows (n = 219) that were born during a 3-year project to investigate the effects of trace mineral source on beef cow performance were reviewed. For the 3-year cow project, cows were initially assigned to 1 of 4 groups within spring and fall calving herds. Groups within each herd were assigned randomly to 1 of 2 supplemental trace mineral treatments: 1) inorganic sources as Cu, Zn, and Mn in sulfate forms and Co carbonate (ING), or 2) organic sources as Cu, Zn, and Mn amino acid complexed and Co glucoheptonate (ORG). Free choice minerals were provided with appropriate mineral treatments while cattle were maintained on fescue-bermudagrass pastures that were rotated monthly. When forage or hay was limited, treatments were delivered via grain supplements. At weaning, heifer calves remained on their respective dietary treatments through their first breeding season (approximately 15 months of age). The cow project began with pregnant cows, thus all heifers weaned in the first year and some in other years (n = 86) were conceived before their dams received the dietary treatments. Most heifers weaned in Years 2 and 3 were conceived while their dams were on their respective dietary treatments (n = 133). After heifers were confirmed pregnant, they re-entered the cow herd. At the conclusion of this project the Cow-Calf Unit continued to keep performance records. Natural breeding occurred after artificial insemination and open cattle were culled annually. Years of performance data (calving, culling, and death records) were analyzed to determine the long-term effects of trace mineral source. MIXED procedures were used of SAS 9.4 with herd (spring/fall calving) and year weaned as random effects and individual heifer as the subject. Previously reported, heifers supplemented with organic trace mineral sources had a tendency for improved reproductive performance (P = 0.09; ING = 66%, ORG = 76.8%) and a decreased percentage of heifers culled (P = 0.07; ING = 33.7%, ORG = 22.1%) compared to heifers receiving inorganic supplementation. However, in subsequent years previous trace mineral supplementation did not influence (P = 0.65) when cows were culled (ING = 3.01 years, ORG = 3.20 years). The number of calves produced per cow did not differ (P = 0.45) between previous trace mineral source supplementation (ING = 2.45 calves, ORG = 2.78 calves). With heifers that were conceived on the study, there were no differences when they were culled (P = 0.25; ING = 2.83 years, ORG = 3.51 years) or the total calves produced (P = 0.18; ING = 2.24 calves, ORG = 2.95 calves). To conclude, supplementation of heifer calves with different sources of trace mineral did not affect their longevity in the herd, but results suggest further investigation.