Phenotypic Dairy Cattle Trait Expressions in Dependency of Social-Ecological Characteristics along Rural–Urban Gradients

The aim of the present study was to infer phenotypic trait expressions via mixed modeling considering both social and ecological continuous descriptors simultaneously. In this regard, we selected a challenging heterogeneous social-ecological environment, with focus on the rising megacity Bangalore, located in southern India. Dairy traits from 517 dairy cattle were recorded in 121 herds, equally distributed along a southern and a northern rural–urban gradient of Bangalore, distinguishing between urban, mixed, and rural areas. Repeated records from three visits per herd included production traits (daily milk yield in liter: MY), energy efficiency indicators (body condition score: BCS), cow wellbeing indicators (udder hygiene score: UddHS, upper leg hygiene score: ULHS, hock assessment score: HAS, rectal temperature in °C: RT), and health traits (locomotion score: LS, subclinical mastitis: SubMast). Associations between a continuous rural–urban gradient and phenotypic trait expressions were analyzed via mixed modeling, additionally considering “classic” environmental explanatory variables such as climatic conditions. MY and BCS were higher in urban than in rural areas, associated with reduced SubMast and improved hygiene scores for UddHS and ULHS. Scores for wellbeing indicators HAS and LS were unfavorable for cows in urban areas, indicating poor leg health conditions in that area. In rural areas, least-squares means for RT were quite large, probably due to the scarcity of shading and heat insulation of the barns. To the best of our knowledge, this is the first study disentangling phenotypic trait expressions in the context of social-ecological heterogeneity, contributing to a deeper understanding of physiological mechanisms underlying genotype by environment interactions.