Genetic parameters for faecal egg count, packed-cell volume and body-weight in Santa Inês lambs

Lôbo, Raimundo Nonato Braga; Vieira, L. S.; Oliveira, Adílson de; Muniz, Evandro Nevez; Silva, José M da

doi:10.1590/s1415-47572009005000032

Cited by 20 publications

(13 citation statements)

References 12 publications

(30 reference statements)

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Nieto et al [ 91 ] estimated heritability for the FEC using a threshold model as 0.08, but in this study animals found to have higher FECs were dewormed, which may have affected this result. Lôbo et al [ 75 ] found FEC heritability to be highly variable throughout the life of the animal, ranging from 0.04 to 0.27 in the first challenge and 0.01 to 0.52 during the second.…”

Section: Differences Between Breedsmentioning

confidence: 99%

Selection methods for resistance to and tolerance of helminths in livestock

et al. 2014

View full text Add to dashboard Cite

Helminthiases are among the most important livestock diseases worldwide, in particular for small ruminants, which are the focus of this review. Resource Allocation Theory implies that high-productivity farm animals proportionate insufficient resources for adequate coping with stressful conditions. Significant differences between breeds and within breeds are seen, as well as genotype vs. environment interactions. With improvement of genetic host resistance to infection, transmission of infection will be impacted. On the other hand, genetic improvement of resilience can lead to a reduction in clinical signs of disease, but not necessarily reduce transmission of infection to other animals. Faecal egg count (FEC) is the main measurement used to evaluate helminthiasis load, despite the fact that the protocols and analytical methods can affect the results, and the FEC data frequently shows aggregative, negative skewed distribution, and a high coefficient of variation. Mass selection where heritability is generally medium to low generally produces slow results and low economic returns. Many studies have been published linking resistance to nematodes in livestock to Quantitative Trait Loci and most studies have concentrated on chromosomes where the major histocompatibility complex region is located. Nevertheless, these complex traits have been seen to be affected by thousands of variants that each has a small effect. More recent studies have shown that genome-wide selection strategies can be useful in selecting animals for improved production and resistance traits in this case.

show abstract

Section: Differences Between Breedsmentioning

confidence: 99%

Selection methods for resistance to and tolerance of helminths in livestock

et al. 2014

View full text Add to dashboard Cite

show abstract

“…In the present study, the heritability estimate for FEC was 0.19±0.03. For this same trait, Riley & Van Wyk (2009) found heritabilities of 0.22±0.06 for Merino sheep, while Lôbo et al (2009) reported values ranging from 0.01 to 0.51 in the first and second exposures of Santa Inês sheep to the parasite. The later authors attributed this variation to the fact that animals challenged for the first time are not yet resistant to endoparasites; as they grow older, they become less susceptible to the pathogenic effects of nematodes.…”

Section: Resultsmentioning

confidence: 92%

“…These traits could be included as selection goals in sheep breeding programs, in order to obtain genetic gains for resistance to endoparasites. With this, the genetic selection of sires and dams that are resistant or resilient to gastrointestinal infections, i.e., of parasitized animals with the ability to maintain production, would be possible (Lôbo et al, 2009;Riley & Van Wyk, 2009 and could reduce chemotherapeutic treatments (Molento et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Estimates of genetic parameters and cluster analysis for worm resistance and resilience in Santa Inês meat sheep

Oliveira

Savegnago

Freitas

et al. 2018

Pesq. agropec. bras.

View full text Add to dashboard Cite

The objective of this work was to estimate genetic parameters for traits related to resistance to endoparasites in Santa Inês sheep, for a possible inclusion in sheep breeding programs, as well as to evaluate the additive genetic pattern of the animals using cluster analyzes, in order to assess whether there are groups within the population that can be used as candidates for selection for resistance to endoparasites. The studied traits were: Famacha score, fecal egg counts (FEC), packed cell volume (PCV), total plasma protein (TPP), body condition score (BCS), and body weight (BW). Heritability estimates ranged from 0.17 (0.05) for TPP to 0.31 (0.07) for BCS. The cluster analyzes based on the breeding values identified four clusters. Famacha and BCS can be recommended as selection criteria for resistance to hematophagous endoparasites because they can respond to selection and are easy to be measured. Animals from cluster 1 have great potential as candidates for selection because of their additive genetic pattern, taking into account body weight and endoparasite resistance due to higher breeding values for BW, BCS, PCV, and TPP and lower breeding values for Famacha and FEC.

show abstract

“…However, it may not be as directly applicable to dryland conditions in the Mediterranean part of South Africa (Cloete, Mpetile & Dzama 2016 ), leaving FWEC as the main criterion available for selection against gastrointestinal helminths. Heritability estimates of FWEC reported in literature range from 0 to 0.52 (Greeff, Karlsson & Harris 1995 ; Lôbo, Vieira & Oliveira 2009 ; Mpetile et al 2015 ). Breeding for a reduced FWEC has been successful in Australia (Greeff, Karlsson & Besier 1999 ; Greeff, Karlsson & Underwood 2006 ; Karlsson & Greeff 2006 ) and New Zealand (Morris et al 2005 ).…”

Section: Introductionmentioning

confidence: 99%

Genetic variation in and relationships among faecal worm eggs recorded in different seasons of the year at the Tygerhoek farm in South Africa

Mpetile

Dzama

Cloete

2017

J. S. Afr. Vet. Assoc.

View full text Add to dashboard Cite

Gastrointestinal nematodes result in severe economic and production losses to the sheep industry. An increase in resistance of the nematodes to chemicals used for control, as well as a demand of consumers for meat products free from chemicals, has fostered research on alternative control strategies. Breeding for resistance to nematodes offers an alternative to control parasitism but its effectiveness depends on genetic variation in faecal worm egg count (FWEC), an indirect measure of parasite resistance. A historic dataset of FWEC from four Merino lines subjected to natural parasite challenge was used to estimate genetic parameters for FWEC in three seasons (autumn, winter and spring) using a repeated records animal model, followed by a three-trait animal model analysis treating FWEC in different seasons as separate traits. The effects of selection line, birth year, sex, the sex x birth year interaction, season and the season x year interaction were significant when using 4994 records recorded from 1997 to 2000 (p < 0.001). The heritability of log-transformed FWEC amounted to 0.09 ± 0.02, with no contribution from the animal permanent environmental variance to the between animal variation across seasons. Three-trait heritability estimates for log-transformed FWEC amounted to 0.07 ± 0.05 in autumn, 0.13 ± 0.05 in winter and 0.19 ± 0.05 in spring. These results suggest sufficient genetic variation in FWEC to support selection for lower log-transformed FWEC. However, the best time to record data for selection is after the break of the season in winter and in spring, when sheep are stimulated by a greater intake of infective larvae from the pasture after the first rains. Genetic correlations among FWEC in the respective seasons were moderate to high, ranging from 0.55 to 0.89. Phenotypic correlations, on the other hand, were significant but lower in magnitude, ranging from 0.09 to 0.16. These results provide useful information for developing strategies for the genetic improvement of ovine resistance to gastrointestinal nematodes under Mediterranean conditions in South Africa by using FWEC as an indicator trait.

show abstract

Genetic parameters for faecal egg count, packed-cell volume and body-weight in Santa Inês lambs

Cited by 20 publications

References 12 publications

Selection methods for resistance to and tolerance of helminths in livestock

Selection methods for resistance to and tolerance of helminths in livestock

Estimates of genetic parameters and cluster analysis for worm resistance and resilience in Santa Inês meat sheep

Genetic variation in and relationships among faecal worm eggs recorded in different seasons of the year at the Tygerhoek farm in South Africa

Contact Info

Product

Resources

About