Making use of the relationship between the productive and reproductive traits of cows to improve the efficiency of selection indices
1997
Amin, A.A. | Toth, S. | Gere, T. (Godolloi Agrartud. Egyet., Gyongyos (Hungary). Mezogazd. Foisk. Kar)
A data set of first lactation records of Holstein-Friesian was used to analyse the relationship between daily milk yield and reproductive performance. Reproductive traits were age at first calving (AFC), days open (DO), number of services per conception (NOS) and productive traits, daily milk yield per lactation (AV), daily milk yield per calving interval (AVCI), minimum daily yield (MIN) and maximum daily yield (MAX). Reduced-restricted selection indices, restricted-selection subindices, and multi-trait selection indices were constructed. Heritability for reproductivity and productivity were ranged between 0.11 to 0.38 and 0.26 to 0.79, respectively. Genetic and phenotypic correlations between daily milk yield and either NOS or DO were high and positive. Restriction on AV brought about reduction in NOS by 2.1 services, in DO by 35 days, in daily costs by 10.5 HUF and 37.9 HUF. On the other hand by restriction on both NOS and DO the most improvement was achieved in AV, AVCI, MIN and MAX by 0.6, 0.8, 0.3, and 1.2 kg, respectively. Average increase of the daily milk yield was 0.73 kg and this caused an increase in total milk yield by 730 kg and total income by 4380 HUF per lactation
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