Abstract
Data, consisting of a total of 400542 first lactation records completed in 1975 through 1982, were utilised for development of a model for ranking sires. Using the principle of direct sire comparison method(BLUP), sire evaluations were calculated assuming three models. Model 1 included random terms for sires and maternal grandsires (MGS) of cows, fixed sire and MGS groups within the three breeds and fixed two-year classes within herds. A two-year period within a herd was used to increase the number of records in a class. In model 2 genetic groups were only for breeds. Model 3 included fixed breed groups and herd-year classes. Relationships among bulls were used in all models. About 83, 13 and 2 % of cows making the records were of the Finnish Ayrshire (FAy), the Finnish Friesian (FFr) and the Finncattle (Fc), respectively, while about 2 % were of various crossbreds. About 20 % of the herd-year classes had cows of more than one breed. Practically all of the male ancestors of bulls and about 70 to 85 % of maternal grandsires of cows were identified in recent years. About 7 % of the total variation for fat corrected 305-day milk (FCM) production was accounted for by years within herds. The fraction of records lost in editing was 4 % for models 1 and 2, and 11 %for model 3. Assuming model 3, the average numbers of daughters for bulls of the FAy-, FFr- and Fc-breeds were 130, 152 and 44, respectively. Average number of records in a herd-year class was about 3.6 in recent years. The additive genetic superiority of the FAy-breed in FCM-production to the FFr- and Fc-breeds was 84 and 860kg, respectively. Joint use of bull groups and relationships among males (model 1) tended to underevaluate the youngest bulls and overevaluate the oldest bulls belonging to previous generations. Based on the results and the breeding structure in theFinnish dairy cattle population, model 3 was chosen to be used in official sire evaluation.
Highlights
A variant of the herdmate comparison method replaced the daughter-dam comparison in dairy sire evaluation in Finland in 1950
The objective of this paper is to present the structure of data and results from the comparison of three alternative models, and to propose a model suitable for ranking sires in the Finnish dairy cattle population
About 83, 13 and 2 percents of the cows making the records were of Finnish Ayrshire (FAy), Finnish Friesian (FFr)- and Fc-breeds, respectively, while about 2 percent were of various crossbreds (Table 1)
Summary
A variant of the herdmate comparison method replaced the daughter-dam comparison in dairy sire evaluation in Finland in 1950. The operational model is largely dictated by the structure of the population. It is questioned whether groups for sires and grandsires are necessary in the model under the Finnish data structure. After a poor fodder crop in the year of 1981, it was questioned whether the H2Y-effect should be replaced with the herd-year effect. This assumes that year effects share an important portion of the total variation for milk production records. On the other hand, replacing the H2Y-class by the HY-class, variance of error of prediction for sire proofs may increase because of loss of more records, and because the number of records for a young bull to be proved as well as in a herd-year subclass would decrease
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