No ecogeographical trends in body structure for Zebu (Bos indicus)

Abstract

Bergmann"s rule is an empirical generalisation concerning body size in endothermic species. It states that within a species, body size varies such that individuals occupying colder environments tend to be larger than individuals who live in warmer environments. To test this law in domestic Bos species, we performed a systemic review of the literature on 60 Zebu (Bos indicus) and Zebu-derivative crossbreeds from Africa and Asia. The following data were obtained via a literature metareview for each breed: wither height, live weight, conformation of dewlap and hump, latitude, longitude, and Köppen-Geiger climatic data. The body mass index (BMI, body weight divided by the square of height) was obtained to assess body size. No trend in BMI was found along latitude or between BMI and Köppen-Geiger data. BMI was not clearly explained by the development of dewlap and hump, either, but it tended to increase with body mass. Although the validity of Bergmann"s rule for Zebu breeds seems to be highly idiosyncratic and partially dependent on the study design, this study provides a new vision about the ecogeographical distribution of Zebu breeds.