The main aim of this study was to estimate the genetic parameters of test day records of British Holstein-Friesian heifers and to determine how best to use these parameters for generic prediction of lactation performance from test day records. The possibility of reducing the frequency of recording to less often than monthly and procedures for the inclusion of part records in genetic evaluations were also investigated. Estimates of genetic parameters of test day and lactation records were obtained from data on 47736 heifers in 7973 herds, progeny of 40 proven and 707 young sires, using multivariate restricted maximum likelihood methods with a sire model. Average values of heritability estimates for test day records of milk, fat and protein yields and fat and protein contents were 0.36, 0.23, 0.29, 0.36 and 0.36, respectively. Generally, heritability estimates for test day records were lowest at the start and highest in mid and late lactation. Heritability estimates for lactation records of these traits wre 0.49, 0.39, 0.43, 0.63 and 0.47, respectively. Average values of genetic correlations between adjacent TD records of these traits were high (0.92 to 0.97), and the correlations decreased as the interval between tests increased. Genetic correlations of lactation milk yield with fat and protein yields and contents were 0.72, 0.94, -0.56 and -0.53, respectively. Estimates of genetic correlation of test day records with corresponding lactation traits were also high (0.76 to 0.99), being highest in mid lactation.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:660308 |
| Date | January 1992 |
| Creators | Pander, Banwari Lal |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/12748 |
Page generated in 0.0024 seconds