Tip of The Day - October 13, 2016

Photo by Tom Semadeni


1988 International Evaluation of Holsteins

Paola Rozzi, et al.

Official proofs for milk and fat yields and for fat percentage for Holstein sires from Canada, the United States, and Italy were pooled and analyzed by a linear model that included effects of country of proof, genetic group of sire, sire within genetic groups, and additive genetic relationships among all sires.

Differences in genetic bases between countries were 334 kg for Canada versus Italy, and 565 kg for USA versus Italy for milk yields. For fat yields the differences were 14.4 kg and 19.6 kg, respectively, and for fat percentage were 0.05 and -0.01%, respectively. Genetic change over sire birth years (1965 to 1979) were 121, 198, and 87 kg for Canada, USA, and Italy for milk yields.

Sires generally imported into the USA from Canada are much worse than locally raised bulls implying that standards of selection on Canadian bulls is for something other than milk yield. However, Canadian dairymen select heavily on milk yield when importing bulls from the USA. Italy did not seem to select foreign bulls for milk yields.

The estimation of international sire proofs on a routine basis with a linear model was shown to be feasible, but standards for sire proofs arising from each country need to be implemented, such as the use of an animal model to properly account for non random mating of bulls.

The model used by Paola in this study assumed that the genetic correlation for milk yield between countries was unity, and thus, milk yield is the same everywhere. Also, this meant there were no genotype by environment interactions, and no biases present in sire proofs within each country. These, of course, were not valid assumptions, and led to the development of MACE.

Photo by Tom Semadeni

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