Effect of source of trace minerals in either forage- or by-product–based diets fed to dairy cows: 2. Apparent absorption and retention of minerals

Abstract

Eighteen multiparous cows were used in a split-plot replicated Latin square with two 28-d periods to evaluate the effects of source of supplemental Cu, Zn, and Mn (sulfates or hydroxy) on apparent absorption of minerals when fed in either a forage- or by-product-based diet. The by-product diets were formulated to have greater concentrations of NDF and lesser concentrations of starch, and specific ingredients were chosen because they were good sources of soluble fiber and β-glucans, which bind trace minerals in nonruminants. We hypothesized that hydroxy trace minerals would interact less with digesta and have greater apparent absorption compared with sulfate minerals, and the difference in apparent absorption would be greater for the by-product diet compared with the forage-based diet. During the 56-d experiment, cows remained on the same fiber treatment but source of supplemental trace mineral was different for each 28-d period; thus, all cows were exposed to both mineral treatments. During each period cows were fed no supplemental Cu, Zn, or Mn for 16 d, followed by 12 d of feeding supplemental minerals from either sulfate or hydroxy sources. Supplemental minerals for each of the mineral sources fed provided approximately 10, 35, and 32 mg/kg of supplemental Cu, Zn, and Mn, respectively, for both fiber treatments. Total Cu, Zn, and Mn dietary concentrations, respectively, were approximately 19, 65, and 70 mg/kg for the forage diets and 21, 85, and 79 for the by-product diets. Treatment had no effect on dry matter intake (24.2 kg/d) or milk production (34.9 kg/d). Cows consuming the by-product diets had greater Zn (1,863 vs. 1,453 mg/d) and Mn (1,790 vs. 1,588 mg/d) intake compared with cows fed forage diets, but apparent Zn absorption was similar between treatments. Manganese apparent absorption was greater for the by-product diets compared with the forage diets (16 vs. 11%). A fiber by mineral interaction was observed for Cu apparent absorption, as cows fed hydroxy minerals with forage diets had greater apparent absorption compared with cows fed sulfate minerals; however, the opposite was observed with the by-product diets. Source of supplemental trace minerals and type of fiber in diets affected availability of Cu and Mn and should be considered in ration formulation.

The influence of supplemental zinc and dietary fiber concentration on mineral retention of beef steers1

“…This study utilized both inorganic and AA complexed Zn sources in the SUPZN treatment. Recent work suggests that ruminally soluble sources of Zn may negatively affect fiber digestion ( Garg et al, 2008 ; Faulkner et al, 2017 ; VanValin et al, 2018 ); however, fiber digestion was unaffected by SUPZN in this study. As mentioned previously, fiber provided by the FIBER diets was highly digestible, which may not have been the case in previous studies displaying depressed fiber digestibility with the addition of Zn, potentially resulting in greater undegraded fiber available to bind ruminally solubilized Zn.…”

“…Utilizing the same Zn supplementation method, Carmichael et al (2018) noted increased N retention regardless of ractopamine hydrochloride inclusion. These previous studies utilized relatively low-fiber finishing diets (~20% NDF) and recently supplemental mineral inclusion has been shown to impact fiber digestibility ( Faulkner et al, 2017 ; Faulkner and Weiss, 2017 ; VanValin et al, 2018 ). Faulkner et al (2017) noted differential impacts of fiber from by-products vs. forages such as corn silage on trace mineral absorption by dairy cows, and a large amount of by-product (modified distillers grains) were fed in previous studies examining the combination of Zn–AA complex and Zn sulfate ( Genther-Schroeder et al, 2016a ; Carmichael et al, 2018 ).…”

“…These previous studies utilized relatively low-fiber finishing diets (~20% NDF) and recently supplemental mineral inclusion has been shown to impact fiber digestibility ( Faulkner et al, 2017 ; Faulkner and Weiss, 2017 ; VanValin et al, 2018 ). Faulkner et al (2017) noted differential impacts of fiber from by-products vs. forages such as corn silage on trace mineral absorption by dairy cows, and a large amount of by-product (modified distillers grains) were fed in previous studies examining the combination of Zn–AA complex and Zn sulfate ( Genther-Schroeder et al, 2016a ; Carmichael et al, 2018 ). Therefore, the objective of this study was to evaluate the impact of low- or high-fiber finishing diets on nutrient digestibility and Zn retention when Zn supplementation is similar to industry rates ( Samuelson et al, 2016 ).…”

“…In addition, Carmichael et al (2018) found that increasing supplemental Zn concentrations positively impacted N retention in finishing beef steers that receive a low-fiber diet (~19% NDF). Recently, some have determined that feeding supplemental trace minerals may influence fiber digestibility ( Faulkner et al, 2017 ; Faulkner and Weiss, 2017 ; VanValin et al, 2018 ). Regardless, few studies have been conducted evaluating the relationship of fiber and Zn supplementation exceeding current recommendations ( NASEM, 2016 ).…”

Effect of source of trace minerals in either forage- or by-product–based diets fed to dairy cows: 1. Production and macronutrient digestibility

“…Apparent absorption of minerals is discussed in the companion paper (Faulkner et al, 2017). No fiber by mineral interactions were observed for apparent digestibility of any nutrient (P > 0.34).…”