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

Both wool and sheep meat industries are interested in sheep that have a high reproduction performance and are resistant to internal parasites, in addition to the traditional traits. There is considerable interest in breeding sheep for wool, carcass, reproductive and internal parasite resistance traits simultaneously. The objective of this study was to estimate single trait genetic parameters for 40 traits recorded in Merino sheep, covering bodyweight, carcass, wool, reproduction and internal parasite resistance traits. This also involved determining the appropriate models. The results from this study will be used to review the genetic parameters used in the routine genetic evaluations conducted by Sheep Genetics. The most appropriate models included a maternal genetic effect and covariance between direct and maternal genetic effects for most of the bodyweight traits, greasy and clean fleece weight, fibre diameter and coefficient of variation of fibre diameter. The permanent environment due to the dam was not included for any trait. There was considerable genetic variation in most traits analysed; lowest heritabilities (0.09–0.10) were found for number of lambs born and weaned per lambing opportunity, and highest heritabilities (0.62–0.77) for fibre diameter. The estimated heritabilities and genetic variances, in combination with the estimated correlations, indicate that there is potential to make genetic improvement in most traits currently recorded in Australian Merino sheep.

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Usefulness of running animal models in absence of pedigrees: Estimation of genetic parameters for gastrointestinal parasite resistance traits in Djallonké sheep of Burkina Faso

Small Ruminant Research ◽

10.1016/j.smallrumres.2018.01.020 ◽

2018 ◽

Vol 160 ◽

pp. 81-88 ◽

Cited By ~ 6

Author(s):

Isabel Álvarez ◽

Amadou Traoré ◽

Iván Fernández ◽

Isabel Cervantes ◽

Luis Varona ◽

...

Keyword(s):

Animal Models ◽

Burkina Faso ◽

Genetic Parameters ◽

Gastrointestinal Parasite ◽

Parasite Resistance ◽

Estimation Of Genetic Parameters ◽

Resistance Traits

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Estimation of genetic parameters for disease-resistance traits in Cynoglossus semilaevis (Günther, 1873)

Journal of Applied Ichthyology ◽

10.1111/jai.13067 ◽

2016 ◽

Vol 32 (4) ◽

pp. 643-651 ◽

Cited By ~ 7

Author(s):

F. Liu ◽

Y. Z. Li ◽

X. X. Wang ◽

X. F. Liu ◽

H. F. Xing ◽

...

Keyword(s):

Disease Resistance ◽

Genetic Parameters ◽

Cynoglossus Semilaevis ◽

Estimation Of Genetic Parameters ◽

Resistance Traits

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

Journal of Animal Science ◽

10.1093/jas/skab341 ◽

2021 ◽

Author(s):

M N Boareki ◽

F S Schenkel ◽

O Willoughby ◽

A Suarez-Vega ◽

D Kennedy ◽

...

Keyword(s):

Genetic Parameters ◽

Body Condition Score ◽

Genetic Correlations ◽

Gastrointestinal Parasite ◽

Parasite Resistance ◽

Multiple Trait ◽

Fecal Egg Count ◽

Counting Methods ◽

Mean And Variance ◽

Resistance Traits

Abstract 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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PSVIII-8 Genetic parameters for parasite resistance in an endangered and heritage sheep breed from Florida

Journal of Animal Science ◽

10.1093/jas/skab235.441 ◽

2021 ◽

Vol 99 (Supplement_3) ◽

pp. 242-242

Author(s):

Zaira M Estrada-Reyes ◽

Jorge A Hidalgo Moreno ◽

Brittany N Diehl ◽

Ibukun M Ogunade ◽

Andres A Pech-Cervantes ◽

...

Keyword(s):

Body Condition ◽

Genetic Parameters ◽

Body Condition Score ◽

Genetic Correlations ◽

The United States ◽

Parasite Resistance ◽

Southern Us ◽

Condition Score ◽

Native Sheep ◽

Resistance Traits

Abstract The Florida Native Sheep is one of the oldest sheep breeds in the United States. This heritage breed from Florida, naturally adapted to humid and hot climate conditions, is one of the most parasite resistant breeds from the Southern US. However, only approximately 1,000 individuals remain alive in the world. Therefore, conservation efforts and breeding programs are critical for survival of this breed. The objective of this research was to estimate genetic parameters for parasite resistance and body condition score in Florida Native sheep. The pedigree file contained 695 animals born between 2018 and 2020 and included 279 individuals with genotypes (38,429 SNP after quality control). The dataset contained 365 animals with phenotypic records at 38 days post-infection (natural Haemonchus contortus infection) for fecal egg count (FEC), blood packed count volume (PCV), FAMACHA score (FAM), and body condition score (BCS). Genetic parameters were estimated using a multi-trait model with a Bayesian implementation in the GIBBS3F90 program. Heritabilities were 0.38 0.07, 0.47 0.05, 0.27 0.04, and 0.52 0.07 for FEC, PCV, FAM, and BCS. Genetic correlations among parasite resistance traits were high and favorable: -0.82 0.06 (FEC-PCV), 0.83 0.07 (FEC-FAM), and -0.94 0.03 (PCV-FAM). Genetic correlations among parasite resistance traits and BCS were -0.42 0.11 (FEC-BCS), 0.75 0.09 (PCV-BCS), and -0.82 0.05 (FAM-BCS). Genetic progress for parasite resistance is possible in Florida Native sheep. The FAMACHA score is a phenotypic parameter easy to record in sheep; therefore, genetic selection for this trait can be effective to improve the remaining traits.

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Genetic relationships between internal parasite resistance and production traits in Merino sheep

Animal Production Science ◽

10.1071/an15469 ◽

2017 ◽

Vol 57 (2) ◽

pp. 209 ◽

Cited By ~ 14

Author(s):

D. J. Brown ◽

N. M. Fogarty

Keyword(s):

Genetic Parameters ◽

Genetic Correlations ◽

Production Traits ◽

Parasite Resistance ◽

Breeding Programs ◽

Sheep Breeding ◽

Breeding Values ◽

Merino Sheep ◽

Internal Parasite ◽

Australian Sheep

Breeding Merino sheep that are resistant to internal parasites alleviates the high costs associated with treatment of worm infestation and loss of production, as well as mitigating the development of anthelmintic resistance among the major worm species. Faecal worm egg count ((cube root transformation), wec) can be used in sheep as a measure of internal parasite resistance. Accurate estimates of genetic parameters for wec are required for calculation of Australian Sheep Breeding Values and inclusion of worm resistance in sheep breeding programs. This study provides updated estimates of heritability for wec and its genetic correlations with production traits. Data were analysed from a wide range of Australian and New Zealand Merino sheep in the MERINOSELECT database, which included 141 flocks with 801 flock years and up to 217 137 animals with wec recorded in at least one of four ages (W = weaning, P = post weaning, Y = yearling, H = hogget). The heritability estimates ranged from 0.16 ± 0.01 for Ywec to 0.29 ± 0.01 for Wwec, with generally high genetic correlations between the ages. Bivariate analyses estimated genetic correlations between wec at the various ages and growth, carcass quality, reproduction and wool production traits at various ages. These genetic correlations were generally small or close to zero, albeit with some significantly different from zero. The moderate heritability for wec (0.2–0.3) and its high phenotypic variation (coefficient of variation >30%) shows that relatively rapid selection response for worm resistance could be achieved. Inclusion of wec in sheep breeding programs to increase worm resistance would be expected to have little if any impact on other important production traits. These genetic parameters have been incorporated into MERINOSELECT by Sheep Genetics to provide Australian Sheep Breeding Values for wec and appropriate indices for wool and meat production. There is evidence that genotype × environment interactions may be important in some environments by reducing the accuracy of Australian Sheep Breeding Values for wec. Hence it may be prudent for breeders to implement strategies that manage the risk of any impact of genotype × environment on their breeding program.

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Genetic parameters for liveweight, wool and worm resistance traits in multi-breed Australian meat sheep. 1. Description of traits, fixed effects, variance components and their ratios

Animal Production Science ◽

10.1071/an14787 ◽

2016 ◽

Vol 56 (9) ◽

pp. 1442 ◽

Cited By ~ 10

Author(s):

D. J. Brown ◽

A. A. Swan ◽

J. S. Gill ◽

A. J. Ball ◽

R. G. Banks

Keyword(s):

Genetic Variation ◽

Fixed Effects ◽

Genetic Parameters ◽

Eye Muscle ◽

Internal Parasite ◽

Internal Parasites ◽

Genetic Evaluations ◽

Meat Sheep ◽

Breed Sheep ◽

Resistance Traits

Sheep breeders in Australia that focus on lamb production simultaneously breed sheep that have higher growth rate, improved carcass quality and are resistant to internal parasites. The objective of this study was to estimate genetic parameters for 11 traits recorded in Australian meat sheep, covering liveweight, carcass and internal parasite resistance traits. As the population of meat sheep in this database have become increasingly crossbred this study also investigates the genetic variation within and between breeds. The data comprised 1 046 298 animals from 149 Poll Dorset, 17 Suffolk, 24 Texel and 118 White Suffolk flocks. The results are averages of analyses of 10 datasets constructed by randomly sampling 25% of these flocks. There was considerable genetic variation in all traits analysed: the lowest heritabilities (0.12) were found for weaning weight and the highest heritabilities (0.31–0.32) for eye muscle depth. There were also significant differences between breeds for most traits, which breeders appear to be utilising through crossbreeding. Direct heterosis effects were small and only significant for the liveweight traits ranging from 2% to 3.4% of the phenotypic means. Maternal heterosis was not significant for any trait studied. The inclusion of heterosis effects in the model did not significantly influence the estimated genetic parameters. The results from this study have been used to review the genetic parameters used in the LAMBPLAN routine genetic evaluations conducted by Sheep Genetics.

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PSIII-8 Difference between two fecal egg count methods and estimation of genetic parameters for gastrointestinal parasite resistance traits in sheep

Journal of Animal Science ◽

10.1093/jas/skaa278.426 ◽

2020 ◽

Vol 98 (Supplement_4) ◽

pp. 232-233

Author(s):

Mohammed N Boareki ◽

Olivia Willoughby ◽

Delma Kennedy ◽

Aroa Suarez-Vega ◽

Larry Schaeffer ◽

...

Keyword(s):

Genetic Parameters ◽

Body Condition Score ◽

Genetic Correlations ◽

Gastrointestinal Parasite ◽

Parasite Resistance ◽

Multiple Trait ◽

Fecal Egg Count ◽

Mean And Variance ◽

The Difference ◽

Resistance Traits

Abstract 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 between two FEC methods, the Modified McMaster (LMMR) and the Triple Chamber McMaster (LTCM); estimate the genetic and phenotypic correlations between records from two methods; and estimate genetic parameters for FEC and other gastrointestinal parasite resistance traits. A total of 1,676 fecal samples were collected from a commercial sheep farm between 2012 and 2019. Fecal egg counting was performed using the Modified McMaster (n = 998) and the Triple Chamber McMaster (n = 678) 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 mean and variance between the two FEC methods were significantly different (P < 0.0001), but phenotypic and genetic correlations between them were high (0.88 and 0.94, respectively). Therefore, pre-adjustment is required prior to integrating data from the different methods. For multiple trait analysis with other parasite resistance traits, data from the two fecal egg counting methods were integrated (LFEC) by using records for the LMMR when available and replacing missing records with standardized LTCM records for mean and variance of LMMR. Heritability estimates were 0.12, 0.07, 0.17, and 0.24, for LFEC, FAMACHA©, BCS, and the WT, respectively. Estimated genetic correlations between fecal egg count and the other parasite resistance traits were low with FAMACHA© (0.24), BCS (-0.03), and WT (0.22), suggesting little to no benefit of using such traits as indicators for LFEC.

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