Estudios genéticos y su aplicación en el mejoramiento de la ganadería

Abstract

The progress made in the last decade in techniques of genetic improvement of livestock are retiened. In reference to selection, the advantages of the "total score" method over the "independent calling levels and over the "tandem" methods are discussed, the last one being the least satisfactory of the three. Selection indices and then application in various classes of livestock are also discussed, and the manner in ubich bevitability indices are used in selection programs is indicated. Concerning methods of reproduction, the improvement uithin local types, grading-up, and the creation of new types or breeds taking into consideration local conditions of climate, nutrition, and management, are emphasized. The work in New Zealand is cited as an example in measuring the rate of improvement on a national basis In that country, butter fat production was increased 61 pounds per cow over the 25 year period from 1918 to 1943. Of this increase, 33 per centuas due to elimination of low producers, 25.2 per cent to use of better sires, and 574 per cent to improved nutritional levels and management practices.