Developing breeding schemes for pasture based dairy production systems in Kenya I. Derivation of economic values using profit functions

Economic values for milk production (milk yield, MY and fat yield, FY), reproductive (age at first calving, AFC and calving interval, Q, growth (preweaning daily gain, DG; postweaning daily gain, PDG; and mature live weight, LW), survival (preweaning survival rate, SR and postweaning survival rate, PSR) and longevity (productive lifetime, PLT) traits were calculated for a pasture based dairy production system in Kenya. Parameters in the profit functions reflected the production circumstances of pasture based dairy production systems, but can be modified to fit other production situations. Two evaluation bases were considered; fixed herd-size and fixed pasture-input. Within each of these evaluation bases, economic values were estimated under two situations of payment of milk; based on milk volume (VOLUME) and on volume and fat content (FAT). With a fixed herd-size and under VOLUME, economic values were KSh 18.93 (MY, kg), -2.76 (FY, kg), -2.72 (AFC, days), 2.65 (Cl, days), 1.04 (DG, g/day), 3.40 (PDG, g/day), 7.95 (LW, kg), 9.96 (SR, %), 45.15 (PSR, %) and 0.07 (PLT, days). Under FAT, changes in the economic values were only observed for MY (KSh 16.05 per kg) and FY (KSh 79.44 per kg). With a fixed pasture-input, there was a significant reduction in the economic values for MY, FY and LW under both payment systems. Under VOLUME, economic values for MY, FY and LW were KSh 15.29, -140.46 and -43.15 per kg, respectively. The respective values were KSh 12.25, -62.76 and -45.03 per kg under FAT. Sensitivity analysis indicated that economic values for MY and FY increased significantly with higher prices of milk volume and fat content, respectively. With higher feed prices, the economic values for the fertility traits and longevity increased but decreased for milk production traits, survival traits and LW. This study suggests that genetic improvement of milk production, growth, fertility, survival and longevity traits will have a positive effect on profitability of pasture based dairy production systems in Kenya, especially when the availability of pasture is not limited. (C) 2003 Elsevier B.V. All rights reserved.