Quantitative aspects of the ruminating process in giraffes (Giraffa camelopardalis) fed with different diets

Giraffes are ruminants feeding on fresh browse and twigs in the wild, but in zoos, their diet is mainly based on alfalfa hay, grains, and pellets occasionally supplemented by twigs and foliage. These diets, which differ in composition and digestibility, affect the behavior of the animals, tooth wear patterns, and chewing efficiency. We quantified several parameters of the rumination process in ten zoo housed giraffes of different sexes and ages fed either with alfalfa hay, fresh browse, or a combination of both. Chewing during rumination was highly ritualized and specimens showed an even distribution of chewing directions during this process, which prevents uneven tooth wear and use of chewing muscles. During rumination of alfalfa hay, chewing cycles of the giraffes took on average 49 s and included 54 jaw movements compared to 37 s and 42 jaw movements during rumination of browse, respectively. Single jaw movements (measured as basic chewing rates) were on average significantly slower during rumination of alfalfa hay (alfalfa: 1.10 chews per second, browse: 1.17 chews per second) and intercycle times between two chewing cycles took significantly longer (alfalfa: 7.77 s, browse: 7.46 s). Our results clearly indicate that several rumination parameters are influenced by the type of diet.