Heritability estimates for pre-weaning growth traits in the Adelaide Boer goat flock

Abstract

Data consisting of records from 3 040 animals, born of 59 sires and 597 dams, were collected from 1978 to 1991 and analysed to estimate variance components for birth weight, weaning weight, average daily gain (ADG) and Kleiber ratio. Birth year, age of dam, sex and rearing status (a combination of birth and weaning status) were included in the analysis as fixed effects. Methods employed were Henderson's Method 3 , fitting a sire model, and Restricted Maximum Likelihood, using a derivative-free algorithm and fitting four different animal models. The following ranges of heritabilities were obtained from the different models: 0.162 - 0.327 for birth weight; 0.162 - 0.350 for weaning weight; 0.176 - 0.257 for ADG; and 0.130 - 0.231 for Kleiber ratio. Estimates from animal models which excluded maternal genetic effects were biased upwards, while the inclusion of maternal genetic effects resulted in lower and presumably more realistic variance components. Maternal effects were large for birth weight and small for the other three traits. Selection for weaning weight or average daily gain is suggested.

Produksiedata wat bestaan uit rekords van 3 040 diere, die nageslag van 59 vaars en 597 moeders, is van 1978 tot 1991 van die Boerbokkudde op Adelaide Proefstasie versamel en gebruik om variansiekomponente vir geboortemassa speenmassa, gemiddelde daaglikse toename (GDT) en die Kleiberverhouding te beraam. Vier vaste effekte, naamlik geboortejaar, ooiouderdom, geslag en meerlingstatus ('n kombinasie van geboorte- en speenstatus), is in die ontleding ingesluit. Verskillende metodes is toegepas, naamlik Henderson se Metode 3, vir die passing van 'n vadermodel, asook Beperkte Maksimum Waarskynlikheid (REML), vir die gebruik van 'n afgeleide vrye algoritme en die passing van vier verskillende dieremodelle. Die volgende reeks erfbaarhede is met die verskillende modelle verkry: 0.162-0.327 vir geboortemassa; 0.162-0.350 vir speenmassa; 0.176 - 0.257 vir GDT; en 0.130 - 0.231 vir die Kleiberverhouding. Beramings met dieremodelle wat nie materne effekte in ag neem nie, het opwaartse sydigheid getoon, terwyl die insluiting van materne effekte laer en waarskynlik meer realistiese beramings tot gevolg gehad het. Die invloed van materne komponente was groot op geboortemassa en klein op die ander drie eienskappe. Seleksie vir speenmassa of GDT word voorgestel.

Keywords: Boer goats, heritabilities, variance components