The genetics of perinatal behaviour of Merinos in relation to lamb survival and lambs weaned per ewe mated

Cloete, S.W.P.; Burger, Marelee; Scholtz, A. J.; Cloete, J.J.E.; Nel, Cornelius L.; Gilmour, A.; Wyk, J.B. van

doi:10.1016/j.applanim.2021.105217

Cited by 7 publications

(2 citation statements)

References 64 publications

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“…In contrast to the developments of Sheep Genetics Australia (Brown et al, 2007, 2018) or Sheep Improvement Limited in New Zealand (Newman et al, 2000, 2010), no traits indicative of animal resilience or fitness are currently recorded by the National Small Stock Improvement (NSIS) in South Africa (Cloete & Olivier, 2010). Currently, the recording of difficult to measure traits is limited to within resource flocks only, reporting useful components of genetic variation for traits such as faecal worm egg count (Cloete et al, 2007; Matebesi‐Ranthimo et al, 2014), absence of breech strike (Scholtz et al, 2010), lamb survival (Cloete et al, 2009), or maternal behaviour (Cloete et al, 2021).…”

Section: Discussionmentioning

confidence: 99%

Including genomic information in the genetic evaluation of production and reproduction traits in South African Merino sheep

Nel,

Gurman,

Swan

et al. 2023

J Animal Breeding Genetics

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Genomic selection (GS) has become common in sheep breeding programmes in Australia, New Zealand, France and Ireland but requires validation in South Africa (SA). This study aimed to compare the predictive ability, bias and dispersion of pedigree BLUP (ABLUP) and single‐step genomic BLUP (ssGBLUP) for production and reproduction traits in South African Merinos. Animals in this study originated from five research and five commercial Merino flocks and included between 54,072 and 79,100 production records for weaning weight (WW), yearling weight (YW), fibre diameter (FD), clean fleece weight (CFW) and staple length (SL). For reproduction traits, the dataset included 58,744 repeated records from 17,268 ewes for the number of lambs born (NLB), number of lambs weaned (NLW) and the total weight weaned (TWW). The single‐step relationship matrix, H, was calculated using PreGS90 software combining 2811 animals with medium density (~50 K) genotypes and the pedigree of 88,600 animals. Assessment was based on single‐trait analysis using ASREML V4.2 software. The accuracy of prediction was evaluated according to the ‘LR‐method’ by a cross‐validation design. Validation candidates were assigned according to Scenario I: born after a certain time point; and Scenario II: born in a particular flock. In Scenario I, the genotyping rate for the reference population between 2006 and the 2013 cut‐off point approached 7% of animals with phenotypes and 20% of their sires. For reproduction traits, about 20% of ewes born between 2006 and 2011 cut‐off were genotyped, along with 15% of their sires. Genotyping rates in the validation set of Scenario I were 3.7% (production) and 11.4% (reproduction) for candidates and 35% of their sires. Sires were allowed to have progeny in both the reference and validation set. In Scenario I, ssGBLUP increased the accuracy of prediction for all traits except NLB, ranging between +8% (0.62–0.67) for FD and +44% (0.36–0.52) for WW. This showed a promising gain in accuracy despite a modestly sized reference population. In the ‘across flock validation’ (Scenario II), overall accuracy was lower, but with greater differences between ABLUP and ssGBLUP ranging between +17% (0.12–0.14) for TWW and +117% (0.18–0.39) for WW. There was little indication of severe bias, but some traits were prone to over dispersion and the use of genomic information did not improve this. These results were the first to validate the benefit of genomic information in South African Merinos. However, because production traits are moderately heritable and easy to measure at an early age, future research should be aimed at best exploiting GS methods towards genetic prediction of sex‐limited and/or lowly heritable traits such as NLW. GS methods should be combined with dedicated efforts to increase genetic links between sectors and improved phenotyping by commercial flocks.

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Section: Discussionmentioning

confidence: 99%

Including genomic information in the genetic evaluation of production and reproduction traits in South African Merino sheep

Nel,

Gurman,

Swan

et al. 2023

J Animal Breeding Genetics

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“…In this respect it has been suggested that the hypothalamus-pituitary-adrenal axis of sheep in the H line was adapted to better cope with stress compared to the L line (Hough et al, 2015). Behavioural observations also indicated that H line progeny found flock-isolation in a contrived arena test less stressful than L line contemporaries, as indicated by fewer urination and defecation events as well as a willingness to approach a stationary human situated between the tested animal and its flock mates closer in comparison to L line contemporaries (Cloete et al, 2017). A later, more comprehensive study reported that the line difference in urination and defecation events persisted while H line progeny also bleated less than L line contemporaries .…”

Section: The Effect Of Selection Linementioning

confidence: 99%

The effects of divergent selection for reproduction and sex on quantitative and qualitative slaughter traits in Merinos

Cloete

Naudé

Cloete

et al. 2021

Small Ruminant Research

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Genetic and environmental parameters for birth weight and neonatal behaviour of Merino lambs in relation to cold stress

Steyn,

Nel,

Cloete

et al. 2025

Applied Animal Behaviour Science

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The genetics of perinatal behaviour of Merinos in relation to lamb survival and lambs weaned per ewe mated

Cited by 7 publications

References 64 publications

Including genomic information in the genetic evaluation of production and reproduction traits in South African Merino sheep

Including genomic information in the genetic evaluation of production and reproduction traits in South African Merino sheep

The effects of divergent selection for reproduction and sex on quantitative and qualitative slaughter traits in Merinos

Genetic and environmental parameters for birth weight and neonatal behaviour of Merino lambs in relation to cold stress

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