BS in Dairy Science
Dairy Science Department
The objective of the study was to determine if citric acid levels measured in milk was related to genetic variants identified in Holstein and Jersey cows. The data used were milk samples collected from both Holstein and Jersey cows at Cal Poly, San Luis Obispo. Citric acid levels and other constituents were measured using FTIR methods with the FOSS MilkoscanTM FT2 on each sample. Genotypes were obtained for the DGAT 1 locus using polymerase chain reaction and an enzymatic digestion using the MWO I restriction enzyme. Observations were obtained on 13 Holsteins and 12 Jersey cows. Results indicated that citric acid level, as a percentage was higher for the Jersey cows than for the Holstein cows -- 0.18 and 0.14, respectively. However, when protein and percent fat were included as independent variables in the statistical model, the difference between Holstein and Jersey for citric acid level was not significant. This indicated that the between breed difference was due to usual breed milk concentration differences.