- Agronomic: barley, corn, oats, soybeans, grass (misc. perennial), hay
- Animals: bovine
- Animal Products: dairy
- Animal Production: grazing - continuous, feed formulation, feed rations, winter forage, feed/forage
- Crop Production: cover crops
- Education and Training: farmer to farmer, on-farm/ranch research, participatory research
- Farm Business Management: feasibility study
- Sustainable Communities: sustainability measures
This research assessed the concentration of conjugated linoleic acid (CLA) in milk and beef from farms that varied management systems. On-farm dairy- and beef-controlled studies compared the CLA concentration in milk and beef from cattle either pastured or fed with stored feeds and higher amount of concentrates. Intensively pastured cows produced milk with CLA concentrations that were about 3- to 4-fold greater than in milk from cows fed mostly stored feeds and concentrates.
Conjugated linoleic acid (CLA) is a collective term for a mixture of positional and geometric isomers of linoleic acid (C18:2). This fatty acid is produced as an intermediate during the biohydrogenation of linoleic acid to stearic acid by the bacterium Butyrivibrio fibrisolvens (Kepler et al., 1966), producing cis9 trans11 CLA, which is the primary isomer found in ruminant milk and meat. Vaccenic acid (C18:1, trans11) also is an intermediate product in the ruminal biohydrogenation process and is a precursor for endogenous formation of CLA via 9-desaturase activity. Endogenous synthesis is estimated to contribute about 64% of the CLA in milk fat (Griinari et al., 2000). The normal concentration of cis9 trans11 isomer in milk from cows fed a typical dairy ration is about 0.38 g/100 g of total fatty acids (Dhiman et al., 1999) and about 0.35% in beef lipids. However, this concentration can be elevated markedly by increasing the supply of precursors for CLA synthesis through nutritional manipulations. For example, inclusion of oils, extruded oil seeds, and raw oil seeds all increase CLA content in the milk. Fish oil is even more effective in increasing CLA in milk.
Pasture feeding has haspreviously been demonstrated to increase CLA concentration in milk (Dhiman et al., 1999) and beef (French et al., 2000). Pasture grasses are rich in linolenic acid, which can be converted to trans vaccenic acid during the biohydrogenation process in the rumen and then synthesized to CLA.
Although pasture feeding is a regular production protocol among organic dairy and beef producers, the intensity of grazing practice vary between farms in the U.S. We evaluated the CLA concentrations of milk and beef from a broad spectrum of largely pasture-based beef and dairy operations in northeast Iowa and southwest Wisconsin. Furthermore, we studied the effect of pasture grazing on milk and beef CLA concentrations.
Project objectives:div style="margin-left:1em;">
Determine factors affecting and optimizing CLA concentrations in milk and meat across a broad spectrum of largely pasture-based dairy and beef operations throughout the year (dairy and beef comparison studies).
Describe seasonal CLA concentration changes in milk from cows moving from winter rations onto spring pasture, determine ability of feeding supplements to enhance presumed increases, and quantify costs involved in enhancing CLA concentrations above pasture levels (dairy controlled study).
Describe seasonal CLA concentration changes in meat from steers moving from fresh pasture onto winter feeding, determine winter feeding strategies that maintain the highest CLA concentrations, and quantify costs involved (beef controlled study).
Increase awareness and knowledge of factors affecting and maximizing CLA concentrations in meat and milk from grazing systems among researchers, producers, and marketers and stimulate the application of this knowledge in additional research, management changes by producers, and marketing efforts of individual producers and the Coulee Region of Organic Producers Pool (CROPP).