Evaluation of liver mitochondrial oxygen consumption of lactating Holstein dairy cows supplemented with Cobalt, Copper, Manganese and Zinc in organic and inorganic forms

Abstract Text:

Production of reactive oxygen species (ROS) at mitochondrial level may cause membrane damage impacting energetic efficiency by yielding less ATP. The objective of this study was to evaluate the impact of different concentrations of organic and inorganic forms of Co, Cu, Mn and Zn (Bioplex Co, Cu, Mn, and Zn; Alltech, Inc.) on liver mitochondrial respiration of lactating dairy cows at a commercial dairy.  Fifty lactating Holstein dairy cows (70 DIM) were randomly assigned to five treatments: Control, Organic75, Organic100, Organic125, Inorganics (CuSO₄.5H₂O,MnSO₄. H₂O and ZnSO4. H₂O supplemented at the same amount as Organic100) (Table 1). Minerals were supplemented on top of control diet to individual cows daily with an oral solution of the mineral for 28 d (24 d for adaptation and 4 d of sample collection). On the last day of treatment, 1 g of liver tissue was biopsied to measure O₂ consumption in isolated mitochondria. Statistical analysis was performed in R (version 2.15.1) using ANOVA. State 3 respiration (maximum ATP stimulated respiration), State 4 respiration (maximum leak-dependent respiration) and respiratory control ratio (RCR= State 3 / State 4) did not differ among treatments, (P = 0.72, P = 0.38 and P= 0.76, respectively) which may be related to high variation in mitochondrial respiration among cows. Numerically, Organic100, 75 and inorganics had the greatest oxygen consumption for ATP production and the greatest rates of oxygen consumption during proton leak dependent respiration. If only considering oxygen consumption results, greater mitochondrial efficiencies would be expected for cows with less oxygen consumption during State 4 and greater oxygen consumption during State 3 respiration. In the present study, supplementation of Co, Cu, Mn and Zn in Organic125 and control cows had the least oxygen consumption during State 4 respiration, however data on individual cow’s feed intake may change these results. Concentration of minerals for Organic125 could be acting as antioxidants by decreasing the incidence of ROS and protecting mitochondria from oxidative damage. Limiting oxidative damage by feeding greater concentrations of antioxidants may prevent mitochondrial membrane damage increasing the efficiency of ATP production and potential increase on milk production and feed efficiency.

Keywords: dairy, mitochondria, minerals

Table 1. Amount of minerals supplemented on top of control diet for each treatment.

	Control	Organic75	Organic100	Organic125	Inorganics
			(mg/d)
Co	2.96	14.70	19.60	24.50	19.60
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