P.PSH.1321 - Investigating animal health and disease in Australian lamb feedlots - Fact sheet

Summary

Specialist lamb finishing systems (feedlots) are increasingly being utilised by Australian lamb producers to combat the seasonal fluctuations of nutrient supply in extensive pasture-based systems. The practice involves removing lambs from pastures and crops and feeding groups of them in confined pens in accordance with regulated standard and guidelines.

For more comprehensive information regarding the standards that feedlots need to abide by, please see www.mla.com.au/contentassets/769ad90825574c27bb1b3873f03e3ed0/l.lsm.0022_-_national_procedures_and_guidelines_for_intensive_sheep_and_lamb_feeding_systems.pdf.

Lot feeding energy dense diets is a practical method to realise the potential of high growth genotype lambs. By meeting market specifications at younger ages, total nutrient intake decreases and feed resources can be prioritised elsewhere, improving overall production efficiency. Lot feeding lambs has increased in popularity due to consistently high lamb prices making the practice profitable despite considerable sources of production loss remaining unresolved.

The practice of lot feeding lambs inherently occurs after lambs are weaned from their dams, which is a known period of stress in lambs (Freitas-de-Melo et al., 2022). Furthermore, dietary changes, transport and mixing of lambs of different age groups and origins, as is often the case when feed lotting, exacerbates this stress in the initial days of induction into a feedlot (Navarro et al., 2020). Under these circumstances, certain infectious agents such as species of coccidia or respiratory tract pathogens, which may be present in healthy animals may cause disease in these stressed lambs.

Nutrient intake is the primary driver of lamb growth rate and feed efficiency, consequently, any cause of reduced intake threatens to decrease production and profitability. Many common diseases in lamb feedlots initially result in decreased intake and frequently result in removal of lambs from the feedlot environment and in extreme cases mortality.

The incidence of certain diseases in lamb feedlots is largely unknown, due primarily to a lack of diagnostics and reporting at a farm level. Previous surveys conducted with lamb feedlot operators have identified acidosis and shy feeding as the major contributors to production loss; however, without accurate diagnostics many producers are possibly attributing unknown deaths to common causes.

Objectives

The aims of this project were to
• Conduct a literature review to determine the most significant health concerns in feedlots and establish gaps in the literature.
• Conduct prospective cohort monitoring to determine the incidence of health conditions within feedlots and to determine risk factors associated with these conditions.
• Develop an appropriate resource to aid producers in managing health issues in Australian feedlot systems.
The results from prospective cohort monitoring and the producer resource are presented in this report.

Further to this, an honours student joined the project team at the end of 2022 to further examine the risks of shy feeding in Australian lamb feedlots and to conduct an economic analysis to determine the cost of shy feeding to the lamb feedlot industry. The results of these analyses are presented in this report.

Key findings

The mean mortality rate was 2.9% for the 21 cohorts surveyed. Acidosis, urolithiasis, pulpy kidney, salmonella and pneumonia contributing to the highest incidence within this project. Time of year and low space allocation (<2.1m2//lamb) have been identified as two key risk factors. Antibiotic usage was not common practice; however, multidrug antibiotic resistance was found within one pneumonic lung sample which highlights the need for further research into more effective preventive measures when it comes to bacterial infections.

Benefits to industry

This project has provided:
• Industry benchmarking data on the causes of lamb mortality within sheep feedlots.
• Improved understanding of risk factors for disease related lamb mortality to inform industry best-practice management recommendations for lot fed lambs.
• Improved understanding of how veterinarians can aid livestock producers with their sheep management through their diagnostic expertise.
Findings from this study will inform guidelines for improved lamb survival within feedlots

MLA action

MLA using the outcomes of this project to inform new investments, and create adoption material for industry to help improve resources available for sheep feedlots.

Future research

Further research is required to understand the mechanisms and development of best practice guides for the key animal health ailments identified within this project.

- Respiratory conditions
Further research is recommended into understanding pneumonia and pleurisy including:
• Examination of data from pedigree-recorded flocks in Australia with a high incidence of severe pneumonia and pleurisy to enable more accurate estimates of genetic parameters, and subsequent correlations with production and disease traits;
• Investigating antibiotic use as a treatment for pneumonia in feedlots and the efficacy of these treatments with a strong focus on resistance issues with antibiotic use;
• Development of a multi-valent vaccine against organisms known to cause pneumonia in lambs.

- Salmonella
Further research into effective salmonella prevention strategies is pertinent given the high incidence of the disease identified in this study and the serious risk of antibiotic resistance development without judicial use.

- Urolithiasis (water belly):
Further investigation into investigating the role of dietary magnesium levels in feedlot rations as a cause of urolith formation is required. In addition investigating the role of ammonium chloride in reduced growth rates in lot fed lambs.

- Shy feeders:
Whilst a lot of research has been conducted in this space, conflicting results between studies regarding shy feeding in feed lot settings highlight the need for further research to develop practical and reliable methods for the early identification of the most vulnerable animals in feedlots.