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Impact of birth and rearing type, as well as inaccuracy of recording, on pre-weaning lamb phenotypic and genetic merit for live weight1
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2017-04-01
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N. McHugh, T. Pabiou, K. McDermott, E. Wall, D. P. Berry, Impact of birth and rearing type, as well as inaccuracy of recording, on pre-weaning lamb phenotypic and genetic merit for live weight, Translational Animal Science, Volume 1, Issue 2, April 2017, Pages 137–145, https://doi.org/10.2527/tas2017.0015
Abstract
The objective of the present study was
to quantify the impact of the systematic environmental
effects of both birth and rearing type on pre-weaning
lamb live weight, and to evaluate the repercussions of
inaccurate recording of birth and rearing type on subsequent genetic evaluations. A total of 32,548 birth
weight records, 35,770 forty-day weight records and
32,548 records for average daily gain (ADG) between
birth and 40-day weight from the Irish national sheep
database were used. For each lamb, a new variable,
birth-rearing type, reflecting both the birth and rearing type of a lamb was generated by concatenating
both parameters. The association between birth-rearing type and birth weight, 40-day weight, and ADG
was estimated using linear mixed models. The repercussions of inaccurate recording of birth type were
determined by quantifying the impact on sire estimated breeding value (EBV; with an accuracy of ≥
35%), where one of the lambs born in a selection of
twin litter births was assumed to have died at birth
but the farmer recorded the birth and rearing type
as a singleton. The heaviest mean birth weight was
associated with lambs born and subsequently reared
as singles (5.47 kg); the lightest mean birth weight
was associated with lambs born and reared as triplets (4.10 kg). The association between birth-rearing
type and 40-day weight differed by dam parity (P <
0.001). Lambs reared by first parity dams as singles,
irrespective of birth type were, on average, heavier at
40-day weighing than lambs reared as multiples, but
as parity number increased, single-born lambs reared
as twins outperformed triplet-born lambs reared as
singles. Irrespective of the trait evaluated, the correlation between sire EBV estimated from the accurately
recorded data and sire EBV estimated from the data
with recording errors was strong ranging from 0.93
(birth weight) to 0.97 (ADG). The EBV for sires
with progeny data manipulated were 0.14 kg, 0.34
kg and 5.56 g/d less for birth weight, 40-day weight
and ADG, respectively, compared to their equivalent EBV calculated using accurately recorded data.
Results from this study highlight the importance of
precise recording of birth-rearing type by producers
for the generation of accurate genetic evaluations.