15-methyl Palmitic acid is a methylated fatty acid that has been found in bacteria, bovine milk fat, one-humped camel (C. dromedarius) meat and fat, and in rabbit perirenal lipids. [1][2][3][4]It is also found in human breast milk and levels are decreased in mature breast milk compared to colostrum[5]

Reference
[1]. Nickels, J.D., Chatterjee, S., Mostofian, B., et al. Bacillus subtilis lipid extract, a branched-chain fatty acid model membrane. J. Phys. Chem. Lett. 8(17), 4214-4217 (2017).
[2]. Henke, A., Westreicher-Kristen, E., Molkentin, J., et al. Effect of dietary quebracho tannin extract on milk fatty acid composition in cows. J. Dairy Sci. 100(8), 6229-6238 (2017).
[3]. Rawdah, T.N., El-Faer, M.Z., and Koreish, S.A. Fatty acid composition of the meat and fat of the one-humped camel Camelus dromedarius. Meat Sci. 37(1), 149-155 (1994).
[4]. López-Bote, C., Rey, A., Isabel, B., et al. Dietary fat reduces odd‐ umbered and branched‐chain fatty acids in depot lipids of rabbits. J. Sci. Food Agric. 73(4), 517-524 (1999).
[5]. Jie, L., Qui, C., Sun, J., et al. The impact of lactation and gestational age on the composition of branched-chain fatty acids in human breast milk. Food Funct. 9(3), 1747-1754 (2018).