An investigation into the consequences of selection for growth, size and efficiency

Author: M.M. Scholtz, C.Z. Roux and S.J. Schoeman
Year: 1990
Issue: 4
Volume: 20
Page: 169 - 173

The effect of selecting for growth, size and efficiency on fitness (fertility and survival rate) and body composition was investigated by surveying a number of selection experiments which have appeared in Animal Breeding Abstracts since 1938. In the case of rodents and poultry, selection for body mass, growth rate and feed efficiency was studied in 26, 21 and 13 experiments respectively. Much less information on the relationship between growth, size or efficiency and fitness is available for beef cattle and mutton sheep. When selecting for increased body mass or growth rate in rodents and poultry, almost 90% of the experiments yielded data which demonstrated an increase in body fat, or a decrease in fitness, or both in the offspring. When selecting for increased feed efficiency, only 15% of the experiments surveyed reported un favourable results. In general, the relationship between growth rate or body mass and fertility in beef cattle tends to be negative. Animal breeding for meat should therefore not be based on selection for growth or size alone. Other selection criteria should be investigated and the principle of utilizing sire and dam lines in beef cattle should receive attention.




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