Submitted to: Western Section of Animal Science Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: June 1, 2012
Publication Date: July 16, 2012
Citation: Whitehurst, W.A., Paterson, J.A., Harbac, M.M., Petersen, M.K., Duff, G.C., Geary, T.W. 2012. Comparison of organic versus inorganic trace minerals on rate and efficiency of gain and pregnancy rates in beef heifers. Western Section of Animal Science Proceedings. 90(Suppl. 3):242. Abstract No. 275. Technical Abstract: Objectives of this experiment were to compare rate and efficiency of gain, and conception rates of yearling heifers supplemented with Cu, Zn and Mn in either a methionine chelated form (ORG) or the same trace minerals in a SO4 form. The experimental design utilized 3 ranches, each having 2 replications per treatment with pen as the experimental unit for ADG, DMI and G:F. Individual heifer was the experimental unit for pregnancy rates. Ranch A contained 498 Angus cross heifers, ranch B, 236 Red Angus cross heifers, and ranch C, 1,742 Angus cross heifers. All ranches fed silage based diets that contained approximately 13.5% CP, 64% TDN (DM basis) and had no significant levels of SO4, Mo, or Fe in feed or H2O. Total diets contained an average of 24 ppm Cu, 70 ppm Zn and 64 ppm Mn. Supplements were fed for 181d (Ranch A), 149d (Ranch B) and 151d (Ranch C) prior to breeding. Heifers were weighed once at trial initiation (initial BW 270kg ± 2.8), end of drylot feeding, at breeding and at pregnancy diagnosis. Ranch A heifers were bred by AI followed by natural service (45d breeding), Ranch B heifers were bred by natural service (50d breeding) and Ranch C heifers were bred by AI once. Pregnancy was determined via ultrasound using trained technicians. Ranch effects were significant (P < 0.001) for gain, ADG, G:F and overall pregnancy rate, but not for conception in the first 21d. No ranch x treatment interactions were detected for any measurements (P = 0.47) and no differences (P = 0.46) were detected between treatments for total gain, ADG, G:F or the number of heifers that conceived during the first 21d on Ranches A or B. Conception rate increased (P = 0.03) for ORG heifers from ranch C with one AI breeding. Across the 3 ranches, conception rates during the first 21d of breeding did not differ (P = 0.12) between treatments but overall pregnancy rate was greater (P=0.05) for heifers supplemented with ORG. Under the conditions of this experiment results suggest that supplementation with ORG contributed to higher pregnancy rates in heifers.