Direct and maternal additive and heterotic effects in crossbreeding Hereford, Simmentaler and Afrikaner cattle

Abstract

Data from purebred and crossbred cattle, consisting of the Hereford (H), Simmentaler (S) and Afrikaner (A) breeds were analysed to estimate breed additive effects, individual heterotic effects, breed maternal, and average maternal heterotic effects. The traits studied were birth mass, weaning mass, and cow productivity and cow efficiency ratios. Among breed groups, crossbred calves showed higher values than purebred calves for most traits. Both two-breed and three-breed rotational systems outperformed purebred, F₁ crosses, and backcrosses. Simmentaler additive effects, expressed as a deviation from Afrikaner, were positive (P ≤ 0.001) for all traits. Hereford additive effects were positive (P ≤ 0.05) for weaning mass and cow efficiency only. Simmentaler maternal effects exceeded those of Afrikaner, while Hereford maternal effects were negative for weaning mass (P ≤ 0.001) and cow efficiency (P ≤ 0.05). Individual heterosis were in most cases positive but varied from -1.6% for birth mass (H X S) to 16.6% for cow productivity (H X S). Average maternal heterosis was positive (P ≤ 0.01) for all traits and varied from 3.3% for birth mass to 39.4% for cow efficiency when expressed as a deviation from the purebred mean.

Data van suiwer- en kruisgeteelde beeste wat die Hereford (H), Simmentaler (S) en Afrikaner (A) insluit, is ontleed om direkte additiewe, individuele heterose, direkte materne en gemiddelde materne heterotiese effekte te bcraam. Die eienskappe wat ingesluit is, is geboortemassa, speenmassa, koeiproduktiwiteits- en koeidoeltreffendheidsverhoudings. Kruisgeteelde kalwers het tussen rasgroepe hoër waardes as suiwerraskalwers vir meeste eienskappe getoon. Beide tweeras- en drieras-rotasiekruisteeltstelsels het beter as suiwer rasse, F₁-kruisings en terugkruisings presteer. Direkte additiewe effekte vir die Simmentaler, uitgedruk as afwyking van die Afrikaner, was vir alle eienskappe positief (P ≤ 0.001). Additiewe effekte vir die Hereford was positief (P ≤ 0.05) vir slegs speenmassa en koeidoeltreffendheid. Simmentaler materne effekte het dié van die Afrikaner oortref, terwyl Hereford materne effekte negatief vir speenmassa (P ≤ 0.001) en koeidoeltreffendheid (P ≤ 0.05) was Individuele heterose was in meeste gevalle positief maar het van -1.6% vir geboortemassa (H X S) tot 16.6% vir koeiproduktiwiteit (H X S) gevarieer. Gemiddelde materne heterose was positief (P ≤ 0.01) vir alle eienskappe en het van 3.3% vir geboortemassa tot 39.4% vir koeidoeltreffendheid gevarieer, uitgedruk as afwyking vanaf die gemiddeld vir suiwer rasse.

Keywords: Beef cattle, breed additive, breed maternal, crossbreeding, heterosis