I suppose that you are interested in species of Barbus sensu lato, i.e. the subfamily Barbinae, like in your other question [the former genus Barbus has been split into several different genera within that subfamily; see the Catalog of Fishes online for details]. Many papers have been published on this topic; you may wish to consult some of the papers listed below.
Balirwa, J. S. 1979. A contribution to the study of the food of six cyprinid fishes in three areas of the Lake Victoria Basin, East Africa. Hydrobiologia 6 (1): 65-72.
Bănărescu, P. M. and N. G. Bogutskaya (eds.) 2003. The freshwater fishes of Europe. Vol. 5/II. Cyprinidae 2. Part II: Barbus. Aula-Verlag, Wiesbaden: i-x + 1-454.
Khalaf, A. N., Al-Jafery, A. R. & Sadek, S. E. 1985. Food and feeding habit of Barbus belayewi (Menon) from Diyala River, Baghdad, Iraq. Acta Ichthyologica et Piscatoria 15 (2): 119-127.
Khumar, F. & Siddiqui, M. S. 1989. Food and feeding habits of the carp Labeo calbasu Ham., in North Indian waters. Acta Ichthyologica et Piscatoria 19 (1): 33-48.
Moghraby, A. I. el & Abd el Rahman, A. 1984. Food and feeding habits of Labeo niloticus (Pisces, Cyprinidae) in Jebel Aulia Reservoir, Sudan. Hydrobiologia 110: 327-332.
Spataru, P. & Gophen, M. 1985. Food composition of the barbel Tor canis (Cyprinidae) and its role in the Lake Kinneret ecosystem. Environmental Biology of Fishes 14 (4): 295-301.
Nasir, N.A., A.K. Naama and A. Al-Saboonchi. 1989. The distribution, length-weight relationships, food and feeding of the cyprinid fish Barbus sharpeyi from Al-Hammar Marsh, Iraq. Fisheries Research. Vol. 7(1–2): 175-181.
Magalhãtes, M. F. 1992. Feeding ecology of the Iberian cyprinid Barbus bocagei Steindachner, 1865 in a lowland river. Journal of Fish Biology. Vol. 40 (1): 123-133.
Although some of them are not in English, you could find interesting the linked pdfs.