Utilization of year-round data in the estimation of genetic parameters for internal parasite resistance traits in Dorper sheep

Ngere, L.; Burke, J.M.; Herring, A. D.; Craig, T.M.; Wyk, J.A. Van; Riley, David G.

doi:10.1016/j.smallrumres.2017.04.005

Cited by 6 publications

(9 citation statements)

References 21 publications

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“…Estimates of (co)variance components for BW were reported and discussed by Ngere et al (2017a). In the current study, a moderate and negative genetic correlation between WFEC and BW at weaning and postweaning was in the desired direction, suggesting that lambs with greater potential for postnatal growth also had lower WFEC.…”

Section: Discussionmentioning

confidence: 47%

“…Litter, residual, and phenotypic correlations between WFEC and PWFEC were 0.25 ± 0.21, 0.15 ± 0.04, and 0.29 ± 0.02, respectively. Estimates of correlation coefficients among BW were also consistently large and positive (Ngere et al, 2017a).…”

Section: Estimates Of Genetic Parametersmentioning

confidence: 83%

“…Heritability estimates of 0.18 for WFEC and 0.23 for PWFEC from animal models were similar to the average heritability of FEC of 0.27 reported by Safari et al (2005) and estimates of 0.19 to 0.26 in Merino sheep (Brown and Fogarty, 2017), 0.26 ± 0.01 in Romney sheep (Morris et al, 2010), and 0.25 in Uruguayan Merino sheep (Goldberg et al, 2012). However, lower estimates of 0.10 in lambs of 50% Dorset, 25% Rambouillet, and 25% Finnsheep ancestry (Vanimisetti et al, 2004a) and 0.10 ± 0.03 in Dorper sheep (Ngere et al, 2017a) were also reported.…”

Section: Discussionmentioning

confidence: 95%

“…Bivariate models for WFEC and PWFEC included only significant random effects on FEC. Models for BW in bivariate analyses included the same fixed effects that were fitted for FEC, as well as random direct additive, maternal additive, maternal permanent environmental, litter, and residual effects (Ngere et al, 2017a).…”

Section: Statistical Analysesmentioning

confidence: 99%

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Genetic parameters for fecal egg counts and their relationship with body weights in Katahdin lambs

Ngere

Burke

Morgan³

et al. 2018

Journal of Animal Science

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Reliance on anthelmintic drugs to control internal parasites in sheep is no longer sustainable because of the development of resistance to these drugs in parasite populations. Genetic selection may offer an alternative long-term solution, as differences in parasite resistance exist both within and among sheep breeds. However, selection for parasite resistance may have correlated effects on other production traits. The objectives of this study were to estimate genetic parameters for weaning (WFEC) and postweaning (PWFEC) fecal egg counts (FEC) and assess their relationship with birth (BWT), weaning (WWT), and postweaning (PWWT) BW in Katahdin lambs. The study used WFEC (n = 2,537), PWFEC (n = 3.421), BWT (n = 12,869), WWT (n = 10,961), and PWWT (n = 7,812) from 12,869 lambs measured between 2003 and 2015 in 13 flocks enrolled in the U.S. National Sheep Improvement Program. Animal and sire models were fitted to the data using the ASReml statistical package. Records were corrected for fixed effects of dam age, joint effect of type of birth and rearing, and management group (defined by joint effects of flock, sex, and birth year and season); lamb age in days at each measurement time was fitted as a covariate. Maternal additive and maternal permanent environmental effects were not significant (P > 0.05), but litter effects influenced (P < 0.01) both WFEC and PWFEC. Heritability estimates ranged from 0.18 to 0.26 for WFEC and 0.23 to 0.46 for PWFEC, depending on the model used. Heritability estimates from sire models were higher than estimates from animal models. Direct additive, litter, residual, and phenotypic correlations between WFEC and PWFEC were 0.82, 0.25, 0.15, and 0.29, respectively. Bivariate analyses revealed low to moderate correlations between BW and FEC. Moderate heritabilities for FEC in this study indicated that genetic progress for this trait can be achieved in Katahdin lambs and that selection for low FEC should have little or no effect on BW.

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Section: Discussionmentioning

confidence: 47%

Section: Estimates Of Genetic Parametersmentioning

confidence: 83%

Section: Discussionmentioning

confidence: 95%

Section: Statistical Analysesmentioning

confidence: 99%

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Genetic parameters for fecal egg counts and their relationship with body weights in Katahdin lambs

Ngere

Burke

Morgan³

et al. 2018

Journal of Animal Science

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“…In Burkina Faso, heritability reported ranged from 0.21 to 0.34 ( Álvarez et al, 2018 ). Higher heritability estimates for FAMACHA score (0.33 to 0.41) were reported in Dorper Sheep in South Africa ( Ngere et al, 2017 ). The sheep in this study did not have large parasite loads and did not show disease symptoms.…”

Section: Resultsmentioning

confidence: 81%

Comparison between methods for measuring fecal egg count and estimating genetic parameters for gastrointestinal parasite resistance traits in sheep

Boareki

Schenkel

Willoughby

et al. 2021

Journal of Animal Science

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Fecal egg count (FEC) is an indicative measurement for parasite infection in sheep. Different FEC methods may show inconsistent results. Not accounting for inconsistencies can be problematic when integrating measurements from different FEC methods for genetic evaluation. The objectives of this study were to evaluate the difference in means and variances between two fecal egg counting methods used in sheep, the Modified McMaster (LMMR) and the Triple Chamber McMaster (LTCM); to estimate variance components for the two FEC methods, treating them as two different traits; and to integrate FEC data from the two different methods and estimate genetic parameters for FEC and other gastrointestinal parasite resistance traits. Fecal samples were collected from a commercial Rideau-Arcott sheep farm in Ontario. Fecal egg counting was performed using both Modified McMaster and the Triple Chamber McMaster methods. Other parasite resistance trait records were collected from the same farm including eye score (FAMACHA ©), body condition score (BCS), and body weight (WT). The two FEC methods were highly genetically (0.94) and phenotypically (0.88) correlated. However, the mean and variance between the two FEC methods were significantly different (P < 0.0001). Therefore, re-scaling is required prior to integrating data from the different methods. For the multiple trait analysis, data from the two fecal egg counting methods were integrated (LFEC) by using records for the LMMR when available and replacing missing records with re-standardized LTCM records converted to the same mean and variance of LMMR. Heritability estimates were 0.12 ± 0.04, 0.07 ± 0.05 , 0.17 ± 0.06, and 0.24 ± 0.07 for LFEC egg count, FAMACHA ©, BCS, and WT, respectively. The estimated genetic correlations between fecal egg count and the other parasite resistance traits were low and not significant (P>0.05) for FAMACHA © (r= 0.24 ± 0.32) and WT (r= 0.22 ± 0.19), and essentially zero for BCS (r= -0.03 ± 0.25), suggesting little to no benefit of using such traits as indicators for LFEC.

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Genetic parameters for resistance to gastrointestinal nematodes in sheep: a meta-analysis

Hayward

2022

International Journal for Parasitology

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Utilization of year-round data in the estimation of genetic parameters for internal parasite resistance traits in Dorper sheep

Cited by 6 publications

References 21 publications

Genetic parameters for fecal egg counts and their relationship with body weights in Katahdin lambs

Genetic parameters for fecal egg counts and their relationship with body weights in Katahdin lambs

Comparison between methods for measuring fecal egg count and estimating genetic parameters for gastrointestinal parasite resistance traits in sheep

Genetic parameters for resistance to gastrointestinal nematodes in sheep: a meta-analysis

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