# Life Stage-Specific Burdens and Impacts of Gastrointestinal Nematodes in Beef Cattle in the United States: A Review of Diagnostics, Impacts on Productivity, and Immune Response

## TL;DR

This review explores how gastrointestinal worms affect beef cattle at different life stages and suggests better diagnostic tools and management strategies to reduce their impact.

## Contribution

The paper provides a comprehensive review of life stage-specific impacts of gastrointestinal nematodes in beef cattle and emphasizes the need for targeted, diagnostics-driven control strategies.

## Key findings

- Young cattle suffer the most productivity losses due to gastrointestinal nematodes.
- Mature cattle contribute more to pasture contamination, highlighting the need for targeted control.
- Integrated parasite management and diagnostics can help reduce anthelmintic resistance and improve cattle health.

## Abstract

Gastrointestinal parasites are a common problem in beef cattle, reducing growth, milk production, and overall health. This review highlights how parasite burdens differ at various life stages, from young calves to mature cows, and how these differences affect productivity. It also examines modern diagnostic tools that can identify which parasite species are present and how heavily animals are infected. These methods allow for more targeted treatments, reducing unnecessary use of deworming drugs and helping prevent drug resistance. Understanding when and how parasites impact cattle can improve animal health, growth, and welfare. By summarizing current knowledge and practical strategies, this review provides guidance to producers and veterinarians for managing gastrointestinal parasites more effectively, supporting responsible livestock production.

Gastrointestinal nematodes (GINs) remain a significant challenge to productivity and sustainability in beef cattle systems in the United States, contributing to subclinical reductions in growth, reproductive performance, and overall herd health across production stages. Control programs have historically relied on routine anthelmintic use; however, increasing reports of anthelmintic resistance highlight the need for alternative management strategies. This narrative review synthesizes peer-reviewed literature identified through targeted searches of major scientific databases spanning approximately seven decades, with articles selected for relevance to GIN epidemiology, diagnostics, and control in beef cattle. Particular emphasis is placed on life stage-specific susceptibility, host immune development, and the role of diagnostic tools in guiding evidence-based interventions. The review further examines non-anthelmintic strategies such as grazing management, nutritional supplementation, selective breeding, and integrated parasite management practices adapted from small ruminant systems. Across studies, young and immunologically developing cattle experience the greatest productivity losses, while mature animals contribute disproportionately to pasture contamination, reinforcing the importance of targeted control measures. Overall, the literature supports a transition toward integrated, diagnostics-driven parasite control programs that sustain productivity and animal well-being while preserving long-term anthelmintic efficacy.