Inter-breed relationships of birth weight and maternal and paternal weight in cattle

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Abstract
The inter-breed relationship of birth weight and maternal and paternal weight in cattle was examined using published data on over 200 different breeds from a total of over 500 experiments. This collection of data was far from optimal for estimating genetic between-breed regressions and should have contained fewer breeds and more experiments on the same breed. Nevertheless, it was established that the mean mature weights of bulls and cows maintained a constant ratio throughout the range of breed size but mean calf weight declined relative to mean sire and mean dam weight as breed size increased.When considered in conjunction with other results on litter weight at birth, the best relationship to use appeared to be that of proportionality to dam weight to the power 0·83, which could uniformly be applied to both breeds and species. The constant of proportionality found for cattle was 0·197 which can be compared with estimates of 0·183 for sheep, 0·185 for dogs and 0·165 on average for mammalian species.