Faecal egg count and food intake comparisons of Romney single‐trait selection and control lines

Morris, C. A.; Clarke, J. N.; Watson, Trevor; Wrigglesworth, A. L.; Dobbie, J. L.

doi:10.1080/00288233.1996.9513196

Cited by 16 publications

(11 citation statements)

References 10 publications

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“…The lower fleece weights in lambs and ewes in the low FEC selection line than in the high line were consistent with our preliminary results from the same flock of Perendales (Morris et al 1997b), and with the results from the equivalent Romney selection experiment in New Zealand where animals from the two FEC lines also grazed together (Morris et al 1997a). Earlier New Zealand results (all reviewed by Morris et al 2000) from Romney fleece-weight selection lines at Massey University (Howse et al 1992;Williamson et al 1995) and at Tokanui Station (Morris et al 1996) were positive in sign (lower fleece weights associated with low FEC). Paternal half-sib data for FEC and wool growth (from midside patches over the parasite challenge period) at an AgResearch property (Woodlands) also showed large positive genetic correlations, although nearzero phenotypic correlations (McEwan et al 1992).…”

Section: Correlated Responsessupporting

confidence: 81%

“…An effect with the same sign was also observed for winter weight, yearling weight, 18-month weight, and adult ewe weight (Tables 3 and 4). Earlier results from New Zealand Romney lines selected for low FEC (Morris et al 1997a;2000) or lines selected for high weight (Morris et al 1996) showed a positive relationship (unfavourable sign) between FEC and New Zealand Journal of Agricultural Research, 2005, Vol. 48 weight on some occasions; whenever the difference or the correlated response between the selection lines was significant, the sign was always positive.…”

Section: Correlated Responsesmentioning

confidence: 99%

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Direct and correlated responses to selection for high or low faecal nematode egg count in Perendale sheep

Morris

Wheeler

Watson

et al. 2005

New Zealand Journal of Agricultural Research

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A selection experiment with Perendale sheep was established in 1986, with lines selected solely on the basis of high or low faecal nematode egg count (FEC) in lambs after weaning. Ranking for FEC involved a natural mixed-species challenge in all years, although in early years this was augmented by an artificial challenge with Haemonchus contortus larvae. Faecal samples were taken from each animal for FEC on two occasions, separated by an anthelmintic drench. A total of 1840 lambs were recorded for FEC in the high and low selection lines from 1986 up to the 2002-born lamb crop. Direct responses to divergent selection for or against FEC were estimated, along with indirect responses in live weights (lambs, yearlings, and adult mixedage ewes), in fleece weights (yearlings and ewes) and in breech soiling ("dag") scores. Analyses of both lines across all years were carried out using animal-model restricted maximum likelihood techniques and also fixed-effects models. The realised heritabilities of log e (FEC + 100) at the two sampling times were 0.22 ± 0.03 and 0.16 ± 0.03; the genetic correlation estimates between log e (FEC1 + 100) and yearling live weight and fleece weight were 0.36 ± 0.17 and 0.54 ± 0. back-transformed FEC means averaged 556 and 114 eggs/g for the high and low lines, respectively, representing a 4.9-fold line difference. When exposed to equal parasite challenge, lambs from the high FEC line were heavier than low-line lambs by 6-12% (breeding ewes 8%), with all differences being significant (P < 0.001); corresponding figures for fleece weight were 24-26% (breeding ewes 15%), again with all differences significant (P< 0.001), and dag scores averaged 0.55 units higher in lowline animals (P < 0.001). It is concluded that, under natural mixed-species parasite challenge on pasture, small rates of genetic change for FEC were achieved in small, closed populations of Perendales. There were unfavourable correlated responses to selection to reduce FEC, comprising lower weights, reduced fleece weights, and more dags. The prospect of index selection to break the unfavourable genetic correlations with FEC is discussed.

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Section: Correlated Responsessupporting

confidence: 81%

Section: Correlated Responsesmentioning

confidence: 99%

Direct and correlated responses to selection for high or low faecal nematode egg count in Perendale sheep

Morris

Wheeler

Watson

et al. 2005

New Zealand Journal of Agricultural Research

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“…This was assessed on lines of sheep selected either for wool production or for meat production where faecal egg excretion or worm burdens were significantly higher as compared to values from non selected animals [36,50,77]. In addition, on a study measuring host resistance to internal parasites on lines of sheep selected for different traits of production, positive correlations calculated between lines were found between egg excretion and liveweight or wool growth [49].…”

Section: Identification Of Less Resistant/resilient Animals Related Tmentioning

confidence: 99%

Control of gastrointestinal parasitism with nematodes in dairy goats by treating the host category at risk

Hoste¹,

Chartier

Frileux

2002

Vet. Res.

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-Infections of the gastrointestinal tract with parasitic nematodes remain one of the main limiting factors in grazing dairy goats. The usual mode of control of these parasitic diseases has up to now been based on the repeated use of anthelmintics. However, the prevalence rates of anthelmintic resistances, in particular to benzimidazoles, are now particularly high in the French dairy goat production. This situation makes it mandatory to reconsider the usual mode of control of these nematodes and to look for short term, alternative solutions which combine the control of gastrointestinal infections and management of anthelmintic resistances. One of the possible options is to leave a part of the flock without treatment during the grazing season in order to maintain alleles of susceptibility to anthelmintics within the worm populations. Previous epidemiological observations identifying the categories of host populations at risk are presented which provide the rationale for targeted applications of treatments. The results of assays on experimental flocks and from farm surveys examining the advantages and drawbacks of selective treatments are presented. The value of these results in combination with other alternative solutions of control are discussed in order to use minimum treatments with maximum benefits. dairy goat / anthelmintic / selective treatment / anthelmintic resistance / parasitic nematode Résumé -Maîtrise des strongyloses gastro intestinales chez les chèvres laitières par l'application de traitements ciblés. Les infestations par les nématodes du tractus gastro intestinal demeurent un des principaux facteurs limitant à l'élevage des chèvres laitières au pâturage. Le mode usuel de maîtrise de ce parasitisme reposait jusqu'à présent sur un usage répété de molécules anthelminthiques. Cependant, la prévalence des lignées résistantes aux anthelminthiques, en particulier aux benzimidazoles, en éle-vage caprin laitier en France, est désormais très élevée. Ce constat oblige à rechercher rapidement des 531

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“…As a result, FEC has been widely used to estimate genetic variation in resistance to nematode infestation in sheep Morris et al, 1996;Cloete et al, 2000;Khusro et al, 2004;Yadav et al, 2006;Cloete et al, 2007;Snyman, 2007) and goats (Mandonnet et al, 2001;Olayemi et al, 2001;Chauhan et al, 2003;Mandal & Sharma, 2008). Several authors have reviewed genetic parameters for resistance to nematodes in sheep (Safari et al, 2005;Morris, 2011).…”

Section: Introductionmentioning

confidence: 99%

Genetic parameters and relationships of faecal worm egg count with objectively measured wool traits in the Tygerhoek Merino flock

Matebesi-Ranthimo¹,

Cloete²,

Wyk³

et al. 2014

SA J. An. Sci.

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The costs of internal parasite control and treatment are potentially very high in grazing sheep. Faecal worm egg count (FEC) has been suggested as a suitable criterion for selection for resistance to nematode infestation in livestock. Genetic parameter estimates for FEC and its relationship with wool traits were assessed in the current study, using data from Merino sheep from a selection experiment maintained at Tygerhoek Research Farm. Data consisted of ~7 100 animals born between 1989 and 2010. Rectal faecal samples were taken from individual sheep at 13 to 16 months of age, after drenching had been withheld for at least 10 weeks, generally in July to September. Nematode eggs were counted with the McMaster technique, with a sensitivity of 100 eggs per gram of wet faeces. The fixed effects of birth type, sex, birth year and sex x birth year interaction were included in the operational model for FEC. Only the effect of additive animal affected the data for FEC. Heritability estimates of FEC ranged from 0.10 for untransformed FEC to 0.16 for Log (FEC + 100). The genetic relationships of Log (FEC + 100) with staple strength (SS), staple length (SL), coefficient of variation of fibre diameter (CVFD) and standard deviation of fibre diameter (SDFD) were favourable. The genetic correlations of FEC with wool weight traits were unfavourable in absolute terms, but not significantly different from zero. Selection for FEC is unlikely to result in unfavourable correlated responses to wool traits in South African Merinos, with the exception of wool weights. ______________________________________________________________________________________

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Faecal egg count and food intake comparisons of Romney single‐trait selection and control lines

Cited by 16 publications

References 10 publications

Direct and correlated responses to selection for high or low faecal nematode egg count in Perendale sheep

Direct and correlated responses to selection for high or low faecal nematode egg count in Perendale sheep

Control of gastrointestinal parasitism with nematodes in dairy goats by treating the host category at risk

Genetic parameters and relationships of faecal worm egg count with objectively measured wool traits in the Tygerhoek Merino flock

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