A total of 79687 (after editing) first lactation records for milk (MY), butterfat (BFY) and protein (PRY) yield, as well as butterfat (BFP) and protein (PRP) percentages were obtained from the South African Holstein Society for animals that were registered and participating in the South African National Dairy Animal Improvement Scheme. The records cover a period of 21 years (1980 to 2000). Variance components, heritability, the genetic and phenotypic correlation estimates were obtained by REML procedures using an animal model. Heritability estimates for MY, BFY, PRY, BFP and PRP were 0.37, 0.29, 0.33, 0.47 and 0.60 respectively. The genetic correlation estimates of MY with BFY, PRY, BFP and PRP were 0.72, 0.89, -0.49 and -0.45, respectively, while those of BFY with PRY, BFP and PRP were 0.85, 0.24 and -0.02. The genetic correlations of PRY with BFP and PRP were -0.25 and -0.04, while the correlation estimate between BFP and PRP was 0.62.
"Experientia docet" - Experience is the best teacher