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Improving Dairy Cattle by Breeding. I. Current Status and Outlook¹

Department of Animal Husbandry, Iowa State University, Ames

ABSTRACT

For brevity, I will speak in terms of improving production, although the dairyman's ideal involves also efficiency of feed use, type, longevity, etc.—these often being combined in complicated ways. High producing ability is always more desirable than low producing ability. Other things being equal, the higher producing cow will make her owner more profit (or at least will cause him less loss) than the low producing one, no matter what may be the general level of profitability or unprofitability of dairying as an enterprise compared with alternative enterprises.

PRESENT RATES OF PROGRESS

Genetic improvement can approach 1% per year if we concentrate entirely on production, cull the lowest producers as fast as we can spare them, and use in natural service only the sons of the highest producing cows. The argument, somewhat oversimplified, runs about as follows and is illustrated numerically in Figure 1.

Progress () per generation, as a result of mass selection, is the product of three factors: = (accuracy) (genic variability) (intensity).

¹ Presented in a Symposium at the American Dairy Science Association's Meeting at Urbana, Illinois, June 17, 1959. Journal Paper No. J-3780 of the Iowa Agricultural Experiment Station. Project No. 1053.

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