Year: 1950
Type: article
Abstract: Inbreeding, in some instances, has been an effective system of breeding for livestock improvement but never has come into very common use in purebred herds and flocks, presumably because the incidence of abnormalities and other undesired traits is higher among inbred individuals.In recent years and at the present time, inbreeding projects have been and are being initiated by many experiment stations to obtain a more conclusive answer on how to derive greater benefit from this system of mating.With few exceptions, these experiments with large animals, as well as those with laboratory animals, have resulted in reduced vigor as exhibited by slower growth, smaller size, greater mortality and lower production and fertility.The present paper reports the effects of mild inbreeding on several characteristics in a herd of Holstein-Friesian cattle. DATA AND METHOD USEDA project with registered Holstein cattle was inaugurated by the Iowa Agri~ cultural Experiment Station in 1930 to determine the consequences of mild inbreeding accompanied by selection for high production.This study is an analysis of the records accumulated in this project between 1930 and 1942.The herd was closed to outside blood in 1930 except for three proven sires used briefly in 1932 to 1935.Usually about 35 to 50 females of breeding age were maintained in the herd, the number being larger in the later years.The breeding system followed was to use sons of the best producing cows and to keep them in service until sufficient cows (30 or more) were bred to each one to be fairly certain he would have at least eight tested daughters.This resulted in most of the bulls being used for slightly over 1 yr.each.This breeding system would be expected to raise the inbreeding something like 3 per cent per generation or a little under 1 per cent per year ( 14).An analysis of the pedigrees indicates this is approximately the amount of inbreeding that did occur.Inbreeding was measured by Wright's (13) formula and was computed from pedigrees traced in all lines to animals born in 1910 or earlier.Inbreeding coefficients ranged from 0 to 28 per cent, with the majority of the animals falling in the lower third of the range.In additi6n to birth weights of both bull and heifer calves, the following measurements were taken on females at 6 too.and 1, 2, 3, 4, 5 and 7 yr. of age:
Source: Journal of Dairy Science
Authors: R.H. Nelson, J.L. Lush
Institution: Michigan State University
Language: English
Subfield: Genetics
Domain: Life Sciences
SDG: Zero hunger
Open Access status: bronze
OpenAlex ID: W2157279957