Effects of birth-rearing type on weaning weights in meat sheep are systematically associated with differences in mean performance among flocks

Notter, D. R.; Brown, D. J.

doi:10.1186/s12711-015-0136-2

Cited by 5 publications

(8 citation statements)

References 10 publications

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“…Progeny of yearling Katahdin ewes had BWT that were 22% less than BWT of progeny of 4-through 7-yr-old ewes whereas BWT for progeny of Polypay yearling ewes were 25% less than BWT of progeny of 4-through 7-yr-old ewes (Notter et al, 2005). However, Notter and Brown (2015) reported that BWT for single and twin lambs by yearling Suffolk ewes were only 19% less than those of progeny of 3-through 6-yr-old ewes.…”

Section: Discussionmentioning

confidence: 94%

“…The 11% difference in BWT between single and twin lambs was similar to that observed in NSIP Polypay lambs by Notter et al (2005), but average BWT for triplet and quadruplet Polypay lambs were 18 and 34% less, respectively, than those of twin lambs. Notter and Brown (2015) reported that BWT of twin Suffolk lambs born in NSIP flocks averaged 18% less than those of single lambs and 18% more than those of triplet lambs. Variation in BWT across litter size classes was therefore less for Katahdin lambs than for Suffolk and Polypay lambs.…”

Section: Discussionmentioning

confidence: 99%

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Variance components for direct and maternal effects on body weights of Katahdin lambs

Ngere¹,

Burke²,

Notter³

et al. 2017

Journal of Animal Science

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The aim of this study was to estimate genetic parameters for BW in Katahdin lambs. Six animal models were used to study direct and maternal effects on birth weight (BWT), weaning weight (WWT), and postweaning weight (PWWT) using 41,066 BWT, 33,980 WWT, and 22,793 PWWT records collected over 17 yr in 100 flocks. Models included fixed effects of management group, dam age, type of birth (for BWT) or birth and rearing (for WWT and PWWT), and lamb age at weighing (fitted as a covariate for WWT and PWWT; all < 0.05). Variance components for random effects were estimated in sequentially more complex models and tested for significance with likelihood-ratio tests. A model that fitted only an additive animal effect overestimated additive variance for all BW, resulting in larger estimates of direct heritability than models that included maternal effects. Maternal effects explained variation ( < 0.05) in all BW. Heritability estimates for optimal models were 0.15 ± 0.01 for BWT, 0.18 ± 0.02 for WWT, and 0.20 ± 0.02 for PWWT. Estimates of maternal heritabilities were 0.14 for BWT, 0.10 for WWT, and 0.06 for PWWT, with SE = 0.01. Permanent environmental maternal effects explained 4 to 6% (±1%) of total phenotypic variances for these BW. Litter effects included temporary environmental effects common to littermates and a proportion of the dominance genetic variance and accounted for 16 to 19% (±1%) of phenotypic variance. Correlations between additive direct and maternal genetic effects were -0.14 for BWT, -0.23 for WWT, and -0.04 for PWWT but differed from 0 ( < 0.05) only for WWT. The total heritability predicted the total response in direct and maternal genetic effects from mass selection and was 0.23 for BWT, 0.20 for WWT, and 0.23 for PWWT. Direct and maternal additive, maternal permanent environmental, residual, and phenotypic correlations between BWT and WWT were 0.53 ± 0.05, 0.58 ± 0.06, 0.51 ± 0.06, 0.39 ± 0.01, and 0.44 ± 0.01, respectively; those between BWT and PWWT were 0.45 ± 0.06, 0.58 ± 0.08, 0.36 ± 0.08, 0.33 ± 0.01, and 0.37 ± 0.01 respectively; and those between WWT and PWWT were 0.85, 0.99, 0.92, 0.77, and 0.81, respectively, with SE ≤ 0.02. Therefore, both direct and maternal effects had an important impact on BW in Katahdin lambs. Models that included both additive and permanent environmental maternal effects as well as a temporary environmental litter effect should result in more accurate estimates of breeding values and better selection decisions.

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Section: Discussionmentioning

confidence: 94%

Section: Discussionmentioning

confidence: 99%

Variance components for direct and maternal effects on body weights of Katahdin lambs

Ngere¹,

Burke²,

Notter³

et al. 2017

Journal of Animal Science

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“…Another consideration for fitting an extra interaction is that there should be enough observations in each subclass to be able to fit it. Otherwise, the estimate will be affected by sampling errors (Notter and Brown 2015). In the data used by this study, there were enough observations in each flock or flock by sex by age subclass to estimate the interactions effect well.…”

Section: Correlation Of Ebvsmentioning

confidence: 99%

Investigation of methods for inclusion of systematic environmental effects in weaning and post-weaning weights for meat sheep in large-scale genetic evaluation

et al. 2022

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Context. Genetic evaluation of Australian sheep is conducted for millions of animals for more than 100 traits. Currently, the Australian sheep genetic-analysis software (OVIS) applies a pre-adjustment of phenotype for fixed effects rather than fitting all fixed and random effects jointly in a linear mixed model to estimate breeding values. However, the current correction factors might be outdated and potential interactions among fixed effects not accounted for, which could lead to bias in estimated breeding values (EBVs). Aims. This study aimed to assess whether correction factors used in OVIS for early bodyweights recorded in meat sheep breeds are appropriate, so as to explore whether the pre-adjustment method is still suitable and how this compares with a linear mixed model, and to estimate the significance of interactions between fixed effects. Methods. Correlations between EBVs from different models and regression slopes from forward prediction were calculated, using weaning-weight data on 365 956 White Suffolk and 370 649 Poll Dorset sheep and post-weaning weight data on 292 538 White Suffolk and 303 864 Poll Dorset sheep. Key results. The current OVIS procedure resulted in regression slopes of progeny performance on sire EBVs (averaged over breeds) of 0.37 and 0.35 for weaning and postweaning weights respectively. Updated pre-adjustment factors improved the regression slopes to 0.40 and 0.38 respectively. Analysis with a linear mixed model produced significantly better regression slopes than did pre-adjustment (0.47 and 0.44 respectively). Further, regression slopes obtained from the linear mixed model with flock by sex by age interaction averaged over breeds were 0.48 for weaning and 0.46 for post-weaning weight respectively, which was a moderate improvement over the current OVIS model. Including a flock by sex by age interaction produced significantly better improvement in Poll Dorset sheep and modest improvement in White Suffolk sheep than did linear mixed model without interaction. Conclusions. Using a linear mixed model with a flock by sex by age interaction significantly improves the utility of estimated breeding values for weaning and post-weaning weight in predicting the performance of future progeny. Implications. To account for systematic environmental effects, a linear mixed model should be used in OVIS to jointly estimate the fixed effects and EBVs.

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“…Thus, proper recording of both birth and rearing type of the lamb, as well as the respective appropriate adjustment in the genetic evaluation model, is required to achieve accurate genetic evaluations for growth. The appropriate adjustment is necessary because the pre-weaning growth potential of a lamb is affected by whether the lamb was born or reared as a singleton or multiple ( Safari et al, 2007 ; David et al, 2011 ; Notter and Brown, 2015 ), and birth type can account for up to 31% of the phenotypic variance in pre-weaning growth ( Hagger, 1998 ). Nonetheless, lambs born into a multiple litter are at greater risk of mortality ( McHugh et al, 2016 ) and, where mortality may have occurred, a reduced litter size may not actually be recorded by the producers.…”

Section: Introductionmentioning

confidence: 99%

Impact of birth and rearing type, as well as inaccuracy of recording, on pre-weaning lamb phenotypic and genetic merit for live weight1

McHugh

Pabiou²,

McDermott³

et al. 2017

Translational Animal Science

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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.

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Effects of birth-rearing type on weaning weights in meat sheep are systematically associated with differences in mean performance among flocks

Cited by 5 publications

References 10 publications

Variance components for direct and maternal effects on body weights of Katahdin lambs

Variance components for direct and maternal effects on body weights of Katahdin lambs

Investigation of methods for inclusion of systematic environmental effects in weaning and post-weaning weights for meat sheep in large-scale genetic evaluation

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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