Farm Survey: Milk Fatty Acid Composition Measured by Mid-Infrared

Abstract Text: Our objectives were: 1) measure fatty acid (FA) composition of individual herd milks using new chemometric models for mid-infrared (IR) milk analysis and 2) determine if there were correlations between milk FA composition and bulk tank milk fat and protein tests. Bulk tank milks from 430 farms were tested multiple times per month for 14 months by mid-IR (Lactoscope FTA, Delta Instruments) for fat, protein, and FA composition. The IR instrument could test about 100 samples per hour. Data were organized in 2 groups: Jersey and Holstein. A variety of individual FA and groups of FA were measured. Validation of IR FA results was done by GLC. The key FA parameter that was positively correlated with bulk milk fat and protein concentration was DeNovo FA (g/100 g milk). Structural parameters of FA chain length (carbon number) and total unsaturation (double bonds /FA) were negatively correlated with fat and protein (g/100 g milk). This was true for both Jersey and Holstein. When DeNovo FA (relative % of FA) were higher, fat test was higher for both Jersey and Holstein. As DeNovo FA (g/100 g milk) increased, fat (g/100 g milk) increased (P < 0.001) at a much faster rate (i.e., higher slope) than when preformed FA (g/100 g milk) increased (slope 2.28 vs. 1.29) for Jersey and  (slope 2.16 vs. 1.22) for Holstein, for DeNovo vs. preformed, respectively. As the proportion of DeNovo increased (and fat percent increased), the measured FA chain length and double bonds per FA decreased (P < 0.001). True protein (g/100 g milk) increased as DeNovo FA (g/100 g milk) increased. We hypothesize that feeding and farm management practices influenced DeNovo FA production and milk fat and protein (g/100 g milk). A group of 20 Jersey and 20 Holstein farms of interest that had a wide range of DeNovo FA (g/100 g fat) were selected for a more in-depth field study, in the next year, to determine if there are cost effective feeding and management practices that can be used to increase fat and protein tests.  During the 14 month period of our study, the 10 Holstein and 10 Jersey low DeNovo herds averaged 3.62 and 3.97% fat and 2.99 and 3.15% true protein, while the 10 high DeNovo Holstein and Jersey herds averaged 3.92 and 4.80% fat and 3.09 and 3.62% true protein, respectively.

Keywords: mid-infared  milk analysis, DeNovo fatty acids, fat and protein concentration