Sire x ecological region interaction in Bonsmara cattle

Abstract

Die moontlike interaksie tussen vaar en vier ekologiese streke waarin Bonsmara beeste in Suid-Afrika hoofsaaklik voorkom is ondersoek. Geboorte en speenrekords van 43 628 geregistreerde kalwers wat gebore is tussen 1976 en 1997 in 18 kuddes was beskikbaar. Beperkte maksimum aanneemlikheid (REML) prosedures is gebruik in die ontleding. Genetiese korrelasies en verwagte genetiese vordering as gevolg van seleksie is beraam deur dieselfde eienskap (bv speenmassa) as verskillende eienskappe in elk van die vier streke te beskou. Die resultate toon dat vir genetiese evaluasie die drie bosveldstreke as een omgewing beskou kan word. Dit sal egter beter wees om die hoeveldstreek as 'n aparte omgewing te hanteer. Die seleksie van bulle wat op die Hoeveld geteel is met die doel om genetiese verbetering in die Bosveld te bewerkstellig behoort minder effektief wees as die seleksie van bulle wat enige plek in die Bosveld geteel is en andersom. Die resultate bevestig ook weereens dat vaar x kontemporere groep (HYS) interaksie gewoonlik belangriker is as die interaksie tussen vaar en enige vasgestelde streek.

The possible interaction between sire and four ecological regions in which Bosmara cattle are mainly found in South Africa was investigated. Birth and weaning weight records of 43 628 registered Bonsmara calves born between 1976 and 1997 from 18 herds were available. Restricted Maximum Likelihood (REML) procedures were used in the analyses. Genetic correlations and expected correlated response to selection were estimated assuming the same trait (e.g. weaning weight) to be a different trait when measured in each of four different regions. The results indicate that for the purpose of genetic evaluation, the three bushveld regions need not be separated, but that it would be advisable to consider the highveld region as a separate environment. Selection of bulls bred on the Highveld for the purpose of genetic improvement in the bushveld regions is likely to be less effective than selection of bulls bred anywhere in the bushveld and conversely. The results have also, once again, confirmed that the interaction between sire and contemporary group (HYS) is usually more important than between sire and any designated region.