Meta-analysis of the effects of supplementing hydroxychloride compared with sulfate sources of trace minerals on...

The objectives of this study were to review the literature and use meta-analytical methods to determine the effects of supplementing hydroxychloride (HTM) compared with sulfate (STM) sources of Cu, Mn, and Zn on production performance of dairy cows. The literature was systematically reviewed, searching for randomized experiments that replaced STM with HTM in diets fed to lactating dairy cows. A total of 7 experiments met the inclusion criteria, of which 5 were Latin square designs and 2 were continuous designs, representing 283 unique cows and 518 experimental units. The individual cow data were obtained from investigators and data were computed as means per experimental unit. Responses of interest included intake of DM and trace minerals, yields of milk and milk components, feed efficiency, body weight, body condition score, and mineral concentrations in tissues. Predictors included treatment, if STM or HTM, the experimental design, if Latin square or continuous, and the experiment itself. Dietary ingredients were entered into the NASEM (2021) software to estimate the NEL content of each diet to calculate energy balance. Data were analyzed using mixed-effects models including the fixed effects of treatment, experimental design, and the interaction treatment and experimental design, and the random effect of experiment nested within experimental design. Treatment did not affect the daily intakes of DM (STM = 24.5 vs. HTM = 24.9 ± 0.9 kg/d), Cu (STM = 494 vs. HTM = 500 ± 27 mg/d) and Zn (STM = 2,235 vs. HTM = 2,272 ± 213 mg/d); however, cows fed HTM consumed 118 ± 22 mg/d more Mn than those fed STM (STM = 1,754 vs. HTM = 1,872 ± 95 mg/d). Yields of milk, fat, and true protein tended to increase 1.0 ± 0.6, 0.044 ± 0.023, and 0.031 ± 0.016 kg/d, respectively, in cows fed HTM compared with STM, whereas yield of ECM and the amount of net energy secreted as milk increased 1.1 ± 0.5 kg/d and 0.76 ± 0.39 Mcal/d, respectively, in cows fed HTM compared with STM. Source of trace mineral did not affect feed efficiency, body weight, body condition score, or net energy balance of cows. Source of trace minerals did not affect the concentrations of Cu, Mn, or Zn in serum of cows. There was no evidence of an interaction between source of trace mineral and design of experiment for any of the responses evaluated. Furthermore, there were no indication of heterogeneity or publication bias. These results suggest that supplementing HTM compared with STM as sources of Cu, Mn, and Zn in diets of lactating dairy cows benefits production performance.