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Expected Genetic Gain from Newly Developed Selection Indices for South African Holstein Cattle
ABSTRACT: The effect of selection on recently developed selection indices on genetic changes in milk volume (VOL), fat yield (FY), protein yield (PY), somatic cell score (SCS), calving interval (CI) and overall economic merit (ECON) were determined for South African Holstein cattle. Expected genetic change was calculated for the four pathways of selection using selection index theory. Selection based on the fluid index resulted in responses of 950.61 l, 18.73 kg, 26.33 kg, 7.64 days, and -0.02 score, per generation, for VOL, FY, PY, CI and SCS, respectively. Genetic merit for ECON increased by ZAR460.43. The corresponding genetic changes, for selection applied on the solid index, were 14.65 l, 12.22 kg, 10.92, 1.82 days and -0.11 score, respectively for VOL, FY, PY, CI and SCS, and ZAR480.49 for ECON.
Keywords:
breeding objective
economic value
selection response
index selection
