Production impacts and resistance of gastrointestinal parasites in feedlot cattle

Summary

Control of gastrointestinal parasites is fundamental to the health and productivity of cattle in feedlots. Therefore, treating internal parasites when cattle are first taken to a feedlot (induction) is integral to the Australian feedlot industry.

A study of 1,434 individual animals tested the effect of six currently available deworming protocols on production parameters of feedlot cattle, including productivity, animal health, post-mortem liver pathology, and beef yield and quality.

There was no benefit in production parameters for providing cattle with a combination treatment that contained multiple drugs, compared to dewormers that only contained a single drug compound. There were, however, significant production benefits in terms of weight gain (+0.06kg/day) and exit weight (+6.2kg) in treating animals at induction with any of the dewormer products, compared to leaving them untreated.

Objectives

• Identify the genus of gastrointestinal nematodes that commonly infect cattle during feedlot induction in Southern Queensland.
• Evaluate the effect of different treatment protocols on parasite resistance, average daily gain and carcase characteristics of feedlot cattle, including a mix of oral and injectable treatments.

Key findings

• The average faecal egg count at induction was 77.6 eggs per gram of faeces (less than 25 eggs per gram is considered optimal to reduce impacts on productivity).
• The most common genus of gastrointestinal parasite found in the feedlot cattle was Cooperia (73%) and Haemonchus was the second most common (15%). Both parasites are prevalent in grazing operations in Queensland.
• There was a consistent resistance to the injectable parasite control drug, doramectin, particularly for Cooperia. A low level of resistance to the drug albendazole was also suspected. Cattle that were treated with a dewormer gained 0.06 kg per day more than untreated cattle and exited the feedlot 6.2 kg heavier than untreated cattle.
• Carcases from cattle that received an anthelmintic were 3.3 kg heavier than cattle that did not receive an anthelmintic.
• Hydatid cysts were identified in 3.83% of livers at slaughter. The presence of hydatid cysts in livers reduced hot carcase weight by 7.2 kg.

Benefits to industry

This project confirms the productivity benefits of administering effective parasite control to feedlot cattle and the value for ongoing surveillance programs to monitor drug resistance to parasites. In addition, effective de-wormers are of benefit to the health of feedlot cattle.

MLA action

MLA has communicated results to feedlot producers through the The Quarterly Feed e-newsletter and industry veterinarians via quarterly Australian Lot Feeder Association (ALFA)-MLA meetings.

Future research

In practical terms, feedlots should:

• deworm cattle at induction with the drug of their choice, with consideration of the type of parasites that are targeted
• aim to reduce faecal egg counts to 25 eggs per gram following treatment, to prevent the impact of gastrointestinal parasites on animal health and productivity
• consider incorporating a low-intensity parasitological component into their feedlot management system to monitor the effectiveness of dewormer treatments to ensure that worm burdens do not impact productivity.