Evaluation of mineral excretion of lactating Holstein dairy cows supplemented with Copper, Manganese and Zinc in organic and inorganic forms

Abstract Text:

Forms of minerals, organic and inorganic, impact the amount of mineral available for intestinal absorption. However, in the ruminant, when inorganic minerals dissociate they can associate with feed components decreasing their availability for intestinal absorption. The objective of this study was to evaluate the impact of level of feeding organic and inorganic forms of Cu, Mn and Zn (Bioplex Cu, Mn, and Zn; Alltech, Inc.) on mineral fecal excretion of lactating dairy cows on a commercial dairy.  Fifty lactating Holstein dairy cows (70 DIM) were randomly assigned to five treatments: Control, Organic75, Organic100, Organic125, and Inorganics (CuSO₄*5H₂O, MnSO₄*H₂O and ZnSO4* H₂O) (Table 1). Therefore control cows received only the levels of minerals present in the TMR based on NRC. Minerals were given by daily dosing individual cows with an oral solution of the mineral treatment for 28 d (24 d for adaptation, and 4 d of sample collection). Fecal samples were collected rectally twice a day (am and pm), combined for a 24h sample and sent for analysis of mineral content and composition. For 11 d, Cr was supplemented (10g/d) with minerals to estimate total fecal output. Statistical analysis was performed in R (version 2.15.1) using ANOVA.  No differences were observed for fecal output (kg/d) (P = 0.35) and manganese excretion (g/d) (P = 0.23) among treatments. Copper and zinc excretion levels did differ among treatments (P< 0.001). Averages (g/d) for copper excretion were 0.48, 0.66, 0.68, 0.76 and 0.58 for Control, Organic75, Organic100, Organic125 and Inorganic, respectively; and averages for zinc excretion were 2.70, 3.21, 3.04, 3.42, 2.78 for Control, Organic75, Organic100, Organic125 and Inorganic, respectively.  Greatest concentrations of mineral excretion were observed in cows supplemented with 25% above NRC requirement levels of Bioplex Cu and Zn while lowest levels of mineral excretion were observed in cows dosed with control and Inorganics. In conclusion, this study shows that mineral form only affects copper and zinc excretion. However, treatment comparisons are not corrected for contributions of minerals from other dietary components (DMI), so conclusions on levels of mineral fecal excretion may change when considering apparent absorption.

Table 1.Levels of minerals supplemented on top of TMR (control diet) for each treatment

	Control	Organic75	Organic100	Organic125	Inorganics
			(mg/d)
Mn	354.00	125.07	166.76	208.45	166.76
Cu	472.00	215.07	286.76	358.45	286.76
Zn	1,409.00	375.88	501.18	626.48	501.18

Keywords: minerals, fecal excretion, dairy cattle