Abstract #M305

# M305
Total fatty acid and rumen unsaturated fatty acid load variation in commercial TMR, forages, and corn grain.
J. P. Goeser*1,2, J. Karlen1, D. Meyer1, A. L. Lock3, 1Rock River Laboratory Inc, Watertown, WI, 2University of Wisconsin-Madison, Madison, WI, 3Michigan State University, Lansing, MI.

Risk of dietary-induced milk fat depression and troubleshooting low milk fat tests may be partially alleviated when the fatty acid (FA) content and profiles for individual feeds are known. Our first objective was to expand on feed library FA data by describing population statistics for total FA content (TFA, % DM) and rumen unsaturated FA load (RUFAL) for commercial dairy farm feeds. Our second objective was to determine if knowing TFA and feed type was sufficient to predict RUFAL (% DM and % TFA). Commercial farm legume and/or grass hay (n = 69) and silage (n = 129), corn silage (n = 115), corn grain (n = 35), and small grain silages (n = 46) were selected for FA analyses from samples submitted from across the US for routine nutritional analysis based upon near-infrared spectral diversity. Total FA concentration and profile was determined by gas-liquid chromatography. TFA (% DM) was calculated by summing individual FA concentrations and RUFAL determined by summing unsaturated 18-carbon FA. RUFAL was expressed as both % DM and % TFA to explore the variation across feeds and within FA content. Data were analyzed by SAS JMPPro v11. RUFAL (% TFA and % DM) was related to TFA and feed type using backward elimination. Population statistics for TFA and RUFAL are presented in Table 1. RUFAL (% DM) was related to TFA (linear and quadratic effects), feed, a TFA interaction with feed (each with P < 0.001; model adj. R2 = 0.99). RUFAL (% TFA) was related to TFA (linear and quadratic effects) and feed (each with P < 0.001; model adj. R2 = 0.77). The coefficient of variation (percentage; Table 1) suggest that TFA varies greater than FA profile. Results suggest that feed TFA (% DM) can predict RUFAL (% DM), however relationships may not be linear and are feed dependent. Table 1. Commercial farm forage and grain population descriptive statistics
Legume/grass hay0.920.2627.952.37.0313.50.490.17
Legume/grass silage1.260.5140.363.810.015.70.840.42
Corn silage1.540.3220.675.24.626.101.180.29
Corn grain2.890.6723.184.41.762.092.450.59
Small grain silage1.110.4035.664.79.1714.20.740.32

Key Words: milk fat, fatty acid, nutrition