The selection of dairy bulls for artificial insemination

Abstract

A numerical model of AI selection procedures has been constructed in an attempt to assess the efficiency of current selection methods and to examine possibilities for their improvement. The results indicate that (1) present selection methods are relatively efficient in their utilization of test resources, but much less efficient in their usage of tested bulls. Additional investments in bull testing are likely to profit the dairy industry. (2) The main effects of improved bull utilization are (a) to permit increases in selection pressure with no increase in cost over current selection procedures and (b) to extend the limits to profitable selection. (3) The adoption of alternative stud management systems, in which bulls are slaughtered early in life, are likely to require excessively large investments in semen processing and storage.

Performance test procedures for meat production amongst dairy bulls used in AI

“…in the rate of selection. This value was substantially larger than that previously observed (£25 thousand) in relation to similar changes in the rate of selection for milk yield (Hinks, 1970). This may be attributed to the relative effect of changes in the rate of selection for milk yield and yearling performance on bull requirements.…”

“…An annual intake of 100 yearling bulls was considered sufficient to maintain a population of this size in the absence of a performance test (Hinks, 1970). Table 1 indicates the number of bull calves needed to provide 100 yearling bulls for AI following the imposition of different rates of selection for yearling performance.…”

“…Year • growth response (1) herd replacements from Fi females (2) herd replacements from sons in AI In order to standardize all responses at current market values, a conversion factor (t) was applied to discount the value of future genetic gains at a rate of 8% per annum (Hinks, 1970). Estimates of the numbers of offspring obtained from different sources were affected by the assumption that cows calved once every 13 months (i.e.…”

“…IN an earlier paper (Hinks, 1970) an attempt was made to examine the efficiency of current testing and selection methods for dairy bulls used in AI and to assess the potential benefits obtainable from intensified selection for milk yield. In the present paper, the costs and genetic consequences of alternative performance test procedures for meat production during the first year of a bull's life have been examined and contrasted with those of intensified!…”

Effect of including major gene information in mass selection: a stochastic simulation in a small population

“…Discounting is a classical tool used by geneticists (Poutous and Vissac, 1962;Hill, 1974;Cunningham and Ryan, 1975;Smith, 1977;Miller and Pearson, 1979) for taking into account the time when genetic gains are obtained and it has been applied to numerous selection schemes (Soller et al, 1966;Hinks, 1970;Danell et al, 1976). (Falconer, 1981;Larzul et al, 1997 (see fig 2b).…”