The variance due to sire-herd interactions for production traits was estimated in the five major dairy breeds in the United Kingdom (UK). First lactation records were analysed using an animal model, with a
 repeatability model used to analyse the first five lactations. Data consisted of40066, 17674, 7245,19994 and 16850 heifer records for the Holstein/Friesian, Jersey, Shorthorn, Ayrshire and Guernsey breeds respectively. The analysis on the first five lactations consisted of 111408 Holstein/Friesian, 20964 Shorthorn, 55044 Jersey, 58310 Ayrshire and 51008 Guernsey records. Data were obtained from the files of National Milk Records for cows bom in the period 1980-1985. Heritabilities for milk, fat and protein yields in first lactation ranged from 0.26 to 0.44. The heritabilities for the five lactations were lower and ranged from 0.24 to 0.34. The estimates of the variance due to sire-herd interaction (c2) in the first lactation varied from 0.024 to 0.063 and amounted on average to about half of the respective sire components. Log transformation of yield records resulted in a reduction of about 25% in c2 values for the Holstein/Friesian breed but there was no change in the Jersey breed. The c2 values from the first five lactations were lower than those of the first and ranged from 0.020 to 0.040. The c2 estimates were considered important and should be accounted for in sire evaluations to minimise bias due to preferential treatment and to avoid over estimating the accuracy of proofs of sires with daughters in one or a limited number of herds. It was concluded that a c2 estimate of 0.04 was appropriate for all breeds in the UK evaluation procedure.

R. A Mrode, G. JT Swanson

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 17. Genetics and breeding of dairy and beef cattle, swine and horses, , 19–22, 1994
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