The value of recording body measurements in beef cattle
Abstract
English: Body size and shape are objectively described using body measurements in beef cattle. How
these measures of size and shape relate to the functioning of the individual is of paramount
importance to livestock producers. Changes in these parameters that lead to inefficient
animals are never welcomed by farmers. Therefore, constant checks on the relationships
between body measurements and performance traits are vital in selection programs.
To estimate heritabilities and genetic correlations among body measurements and
growth traits, data of 7 266 performance records of Bonsmara bull calves participating
in on-farm growth tests (Phase D) were used. The data set was extracted from the Integrated
Registration and Genetic Information System (INTERGIS) of South Africa. The
data covered a 25-year period i.e. from 1972 - 1996. Data were recorded from 45 herds,
with 439 sires and 5 180 dams involved. Traits analyzed were scrotal circumference (SC),
body length (BL), shoulder height (SH), birth weight (BW), weaning weight (WW), final
weight (FW) and average daily gain (ADG) from weaning to final test date.
Multivariate REML methodology was used to estimate (co)variances and genetic components
for different traits. In cases where there were more than one value for an estimate,
the values were pooled, weighting each estimate by the inverse of its sampling variance.
Different models were, however, fitted for each trait. The permanent environmental effect
was found to be important for most of the post-weaning traits, but it could, however, not
be considered in the multivariate runs. This was due to computational limitations imposed
by the data set. A simple model considering only direct animal effect and random error
was fitted for all post-weaning traits.
Heritability estimates for body measurements ranged from medium for body length
(0.27±0.05) to high for shoulder height (0.42±0.05) and scrotal circumference (0.46±0.06).
Corresponding estimates for performance traits were: direct (0.31±0.05) and maternal
birth weight (0.10±0.03), direct (0.29±0.05) and maternal weaning weight (0.04±0.02),
average daily gain (0.19±0.04) and final weight (0.30±0.05).
Generally, body measurements were favourably and positively correlated with performance
traits (0.03 to 0.83). However, scrotal circumference was found to be genetically
weakly correlated to maternal birth weight (-0.22±0.15) and average daily gain
(0.1O±O.13). A close to zero genetic correlation was found between average daily gain and
maternal weaning weight (0.03±0.17). These results suggest that selection for fast growing
bulls may not influence maternal performance at weaning.
Considering the favourable genetic correlations between body measurements and performance
traits, it could be inferred that selection for body measurements is compatible
with that of performance traits. However, a further study should be conducted to evaluate
which of those traits considered in this study are of economic importance so that an
appropriate selection index can be developed. Afrikaans: Liggaamsgrootte en -vorm van vleisbeeste kan objektief beskryf word m.b.v. liggaamsmates.
Die verband tussen hierdie mates en die funksionering van die dier is van groot
belang vir produsente. Veranderinge in hierdie parameters wat lei tot oneffektiewe diere sal
nie deur boere verwelkom word nie. Dit is dus nodig om die verband tussen liggaamsmates
en produksie eienskappe te monitor in seleksieprogramme.
Oorerfbaarhede en genetiese korrelasies tussen liggaamsmates en groei eienskappe is
bepaal. Produksierekords van 7 266 Bonsmara bulkalwers, afkomstig van 45 kuddes, met
439 vaders en 5 180 moeders, wat in op-die-plaas groeitoetse (Fase D) deelgeneem het, is
gebruik. Die data was afkomstig van die geïntegreerde registrasie en genetiese informasie
sisteem (INTERCIS) van Suid-Afrika en strek oor 'n 25 jaar periode (1972 tot 1996). Eienskappe
wat bestudeer is sluit in skrotumomvang (SC), liggaamslengte (BL), skouerhoogte
(SH), geboortegewig (BW), speengewig (WW), finale gewig (FW) en gemiddelde daaglikse
toename (ADC).
Meereienskap REML metodologie is gebruik om (ko)variansie komponente te beraam
vir die verskillende eienskappe. In gevalle waar daar meer as een beramer vir 'n komponent
was, is die waardes gepoel en geweeg deur die invers van die variansie. Verskillende
modelle is vir elke eienskap gepas. Volgens enkeleienskap analises was die permanente
omgewings effek belangrik vir meeste van die na-speense eienskappe, maar dit kon nie in
ag geneem word in die meereienskap lopies nie, weens rekenaarbeperkings veroorsaak deur
die grootte van die datastel. 'n Eenvoudige model wat slegs die direkte effek en toevallige
fout komponent in ag neem, is gepas vir alle na-speense eienskappe.
Oorerftikhede vir liggaamsmates varieer van medium vir liggaamslengte (0.27±0.05)
tot hoog vir skouerhoogte (0.42±0.05) en skrotumomvang (0.46±0.06). Ooreenstemmende
beramers vir produksie eienskappe is: direkte (0.31±0.05) en maternale geboortegewig
(0.10±0.03), direkte (0.29±0.05) en maternale speengewig (0.04±0.02), gemiddelde daaglikse
toename (0.19±0.04) en finale gewig (0.30±0.05).
Oor die algemeen is liggaamsmates gunstig en positief gekorreleer met produksie eienskappe
(0.03 tot 0.83). Skrotumomvang was geneties laag gekorreleerd met maternale geboortegewig
(-0.22±0.15) en gemiddelde daaglikse toename (0.10±0.13). 'n Genetiese korrelasie
naby nul is tussen gemiddelde daaglikse toename en maternale speengewig (0.03±0.17)
gevind. Hierdie resultate suggereer dat seleksie vir vinnig groeiende bulle waarskynlik nie
'n verandering in maternale prestasie by speen sal veroorsaak nie.
Aangesien daar 'n gunstige genetiese korrelasie is tussen liggaamsmates en produksie
eienskappe kan dit afgelei word dat seleksie vir liggaamsmates verenigbaar is met die van
produksie eienskappe. Daar word dus aanbeveel dat 'n verdere studie onderneem word om
die eienskappe wat ekonomies belangrik is, te bepaal en om 'n seleksie indeks te ontwikkel.