Genetic trends for the South African Charolais are available only for those traits which were included in the latest BLUP analysis, namely birth weight, weaning weight, yearling weight and 18-month weight, recorded in Phase A and B of the National Beef Cattle Improvement Scheme of the ARC-Animal Improvement Institute.
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In the past, performance testing was not easily accessible for small breeders. Phase D1-tests requires for example at least 15 bulls per test group for accurate comparisons within the group. Furthermore, Phase D1-test data is not directly comparable between different herds. It is therefore possible for an animal with a GDT-index of 110 in a low quality herd to be weaker than an animal with a GDT-index of 95 in an excellent herd. An index calculated on an animal's own performance test data does not always offer a very high prediction of the probability that the animal will transfer its traits to its progeny.
Phase D2 offers overall better comparison value by allowing multi-herd comparisons, thus making it possible for groups of breeders to work together by having their bulls tested simultaneously.
This makes it possible for smaller breeders to combine their bulls into groups of 30 or 40 to obtain more accurate and sensible test results. This also indicates how participating herds compare amongst themselves.