Recipient Organization
UNIVERSITY OF CALIFORNIA, DAVIS
410 MRAK HALL
DAVIS,CA 95616-8671
Performing Department
Population Health & Reproduction
Non Technical Summary
Mitochondrial conversion of energy as NADH and FADH to ATP is an important contributor to energy supply accounting for approximately 20-30% of resting energy requirements (Ramsey et al., 2000; Rolfe and Brown, 1997). Therefore changes in mitochondrial efficiency will have large impacts on energetic efficiency. But, it is unknown how diet, stage of lactation and disease affect energetic efficiency of mitochondria in dairy cattle. Through the process of oxidation of fuels by mitochondria, free radicals are created that will disrupt mitochondria membrane function leading to increased proton leak and decreased ATP production from NADH and FADH. Feeding antioxidants such as copper, zinc, and manganense will counteract free radical damage of mitochondria membranes and increase production of ATP leading to more energetically efficient mitochondria. Understanding the role of antioxidants in mitochondrial efficiency will lead to improved feeding recommendations to manage cattle for optimal nutrient use. More energetically efficient cattle will reduce feed intake and costs of production leading to improved dairy farm efficiency and sustainability.
Animal Health Component
20%
Research Effort Categories
Basic
60%
Applied
20%
Developmental
20%
Goals / Objectives
The objective of this research is to analyze the impact of antioxidants given as a feed supplement on mitochondrial energetic efficiency and milk production of lactating commercial dairy cows. Energetic efficiency will be measured by measuring mitochondrial oxygen consumption, membrane potential and proton leak kinetics in fresh liver biopsies to assess the relative amount of oxygen used and ATP produced in cows supplemented with two different availabilities and sources of copper, zinc and manganese.
Project Methods
Liver biopsies will be taken from 60 dairy cows at the end of the feeding period of 4 weeks. Mitochondria will be isolated from liver using slight modifications of the procedures of Chappell and Hansford (1972) and Rickwood et al. (1987) as previously described (Ramsey et al., 2004). Integrity of the mitochondrial preparations will be determined by measuring respiratory control ratios (RCR) and membrane potential. Mitochondrial oxygen consumption will be measured using previously described methods (Harper et al., 1998; Lal et al. 2001). All measurements will be completed in duplicate using mitochondria (0.5 mg/ml) in incubation medium with 5µM rotenone and 0.4 µg nigericin. Membrane potential will be measured with a methyltriphenylphosphonium (TPMP+)-sensitive electrode. The kinetic response of the proton leak to membrane potential will be determined in isolated mitochondria by titrating the electron transport chain with malonate (0.2M), an inhibitor of complex II of the respiratory chain.The above measurements will be in addition to research funded by an outside company. Therefore the following measurements are not included in the budget for this request. In brief, multiparous Holstein lactating cows, at 20-60 DIM will be fed 5 different mineral mixes in their rations. Mineral mix treatments are current dairy mineral mix of inorganic Cu Mn and Zn (control), organic sources of Cu, Mn or Zn at 3 different levels, or inorganic sources of Cu Mn or Zn for a total of 5 treatments. Each treatment will be fed to 60 cows within a pen of approximately 220 high milking cows for approximately 4 weeks. All other feeding and management practices will be identical for all treatments. Milk production will be measured every other week by DHIA and samples will be recovered from DHIA for mineral analyses. Monthly feed, water, blood, and fecal samples will be analyzed for minerals Feed intake by pen will be estimated using FeedWatch and liver samples at the beginning and end of the trial will also be analyzed for copper, zinc and manganese content to assess mineral status.Mitochondrial efficiency data will be analyzed using SAS (Version 9.2, SAS Inst. Inc.,Cary, NC) PROC Mixed, with treatment (supplements) as fixed effect to determine if mitochondrial metabolism and milk production are correlated and change with supplementation. In addition, variables associated with production, such as body condition score, milk yield, milk fat and milk protein will be tested as covariates to determine significance and if significant (P< 0.05) will be maintained in the equation. Means will be generated and partitioned using the LS-MEANS and PDIFF options.