Disease & heat resistance

Identification of a suitable trait for phenotyping resistance to gastrointestinal nematode infection in Holstein cattle for genetic purposes.

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Abstract

Gastrointestinal nematode (GIN) infection is a major medical and economic concern in grazing cattle. GINs negatively impact growth in young animals and milk production in adults, and induce gastroenteritis symptoms when parasite burden are high. Infection control mainly relies on anthelmintic treatments. However, due to increasing resistance of GIN to anthelmintics and the ecological impact of their intensive use, alternative control strategies are needed. Enhancing genetic resistance of cattle represents a sustainable strategy to mitigate parasite burden. To establish an efficient genomic selection, we need to define indicator trait of GIN genetic resistance that: 1- can be easily phenotyped on a few thousand individuals each year, 2- displays genetic variability among individuals, and 3- has a high enough heritability to ensure sufficient genomic selection accuracy. In the framework of GIVERNI project funded by APIS-GENE, this study's objective was to identify such an indicator trait. Three candidate traits were investigated: the number of GIN eggs per gram of feces (EPG), the serum pepsinogen level, and the salivary anti-CarLA immunoglobulin A (IgA) level (a promising new phenotype for GIN resistance in sheep). The serum anti-GIN immunoglobulin G (IgG) level, considered as a marker of parasite exposure at the group level, was also measured. A total of 2800 Holstein heifers were sampled in western France at the end of their first grazing season. Participating herds were selected so that the animals had spent at least 4 months on pasture without any anthelmintic treatment prior sampling. Samples were analyzed in a regional veterinary laboratory for IgG, pepsinogen and EPG phenotypes and in a New Zealand laboratory for IgA levels. Heritability was estimated using WOMBAT software. Contemporary group, month and year of sampling, age (in months), grazing duration, duration between the end of the grazing season and the sampling, and type and timing of possible treatments were included as fixed effect. Phenotypic analyses demonstrated that pepsinogen and IgA levels were highly sensitive to the duration between the end of the grazing season and the sampling time, samples collected more than 2 weeks after grazing ended being uninformative. This must be taken into account in future phenotyping campaigns and will make them much more difficult to manage. Additionally, the cost of sending frozen IgA samples to New Zealand was quite prohibitive. On the contrary, EPG count was variable among individuals, including within herds with low average IgG levels (i.e. low exposure). Heritability estimates were low to moderate for EPG (0.10 ± 0.05) and pepsinogen (0.20 ± 0.06), while not different from 0 for IgA. In light of this initial study, EPG count appears to be the most promising phenotype. Further work is needed to assess the potential efficiency of selection based on this trait.

Keywords: 2026

How to Cite:

Aubriot, D., Boichard, D., Boishardy, A., Brisseau, N., Croiseau, P., Debelhoir, V., Delafosse, A., Fresco, S., Leclerc, H., Lehebel, A., Martin, P. & Ravinet, N., (2026) “Identification of a suitable trait for phenotyping resistance to gastrointestinal nematode infection in Holstein cattle for genetic purposes.”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2286298. doi: https://doi.org/10.31274/wcgalp.23911

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