STABILITY PARAMETERS OF GENETIC GROUPS IN DUAL PURPOSE SYSTEM IN CHIRIQUI AND LOS SANTOS, PANAMA.

Abstract

The set of data for the present study came from the IDIAP-IDRC Project (1983-1989) with the purpose of studying the genetic stability in terms of total milk yield of three genetic groups within the dual purpose system. Seventeen farms were selected and distributed in five ecosystems of Chiriqui and Los Santos (GA, GB, BM, BB and LS). Each farm was monitoried during the traditional system study (T) and the improved system study (M). Based on these studies were defined the following environments: GAT, GAM, GBT, GBM, BMT, BMM, BBT, BBM, LST and LSM. Cows were grouped into three genetic groups: Cebuinos (Zebu, Brahman + Zebu), ≤50% European (with European blood equal or less than 50% of Holstein or Brown Swiss) and >50% European (with European blood more than 50% of Holstein or Brown Swiss). Stability parameters were estimated from Eberhart and Russell (1966) methodology. GAT and GAM environments were the most adverse for milk production but LSM and BBM environments were the most favourable. The genetic group >50% European was the best adapted to the ten environments in study (b = 1), in terms of milk yield per lactation, than the other genetic groups. The >50% European genetic group was best adapted to the environment with traditional system or less favourable (b < 1). The genetic group was best adapted to the environment with traditional system or less favourable (b < 1). The genetic group Cebuino had the highest productivity in environment with improved system or more favourable (b > 1). From this study, it is concluded that exists high interactionship between dual purpose genetic groups and the environment in which they are interacting.