Loading...
Genetic and nongenetic factors associated with the fate of maiden ewe lambs: slaughtered without ever lambing versus retained for breeding
Citations
Altmetric:
Keywords
Date
2019-09-24
Collections
Files
Loading...
main article
Adobe PDF, 179.75 KB
Research Projects
Organizational Units
Journal Issue
Citation
McHugh, N., Pabiou, T., McDermott, K., Wall, E., Berry, D.P. Genetic and nongenetic factors associated with the fate of maiden ewe lambs: slaughtered without ever lambing versus retained for breeding, Translational Animal Science, Volume 4, Issue 1, January 2020, Pages 242–249, https://doi.org/10.1093/tas/txz156
Abstract
The decision on which ewe lamb
to retain versus which to sell is likely to vary by producer based on personal preference. What is not known, however, is if any commonality exists
among producers in the characteristics of ewe
lambs that influence their eventual fate. The objective
of the present study was to determine what
genetic and nongenetic factors associate with the fate of maiden ewe lambs. The fate of each ewe lamb born in the present study was defined as either subsequently: 1) having lambed in the flock,
or 2) was slaughtered without any recorded lambing event. A total of 9,705 ewe lamb records from 41 crossbred flocks were used. The logit of the odds of the ewe lamb being retained for lambing was modeled using logistic regression. Variance components
were then estimated for the binary trait
representing the fate of the ewe lamb using animal
linear and threshold mixed models. The genetic
correlations between fate of the ewe lamb and preweaning,
weaning, or postweaning liveweight were
also estimated. From the edited data set, 45% of
ewe lambs born entered the mature flock as ewes.
Ewe lambs reared as singles, with greater levels of
heterosis but lower levels of recombination loss,
born to dams that lambed for the first time as hoggets,
with greater breed proportion of the Belclare,
Suffolk, Texel, and Llyen breeds were more likely
(P < 0.001) to eventually lamb in the flock than
be slaughtered without ever lambing. Irrespective
of the age of the animal when weighed, heavier
ewe lambs were more likely to eventually lamb
(P < 0.001). The genetic SD and direct heritability
of fate of the ewe lamb estimated in the univariate
linear model was 26.58 percentage units and 0.31
(SE = 0.03), respectively; the heritability was 0.30
when estimated using the threshold model. The
corresponding direct heritability of fate of the ewe
lamb estimated in the bivariate analyses with liveweight
ranged from 0.29 (SE = 0.03; preweaning
weight) to 0.35 (SE = 0.04; postweaning weight).
The genetic correlations estimated between fate of
the ewe lamb and the liveweight traits were weak
to moderate but strengthened as the age of the ewe
lamb at weighing increased. Results from this study
provide an understanding of the factors producers
consider when selecting females for retention
versus slaughter which may form useful parameters
in the development of a decision support tool
to identify suitable ewe lambs for retention.