Effects of pelleting diets containing cereal ergot alkaloids on nutrient digestibility, growth performance and carcass traits of lambs
Introduction
Mycotoxins are toxic secondary metabolites of fungi impacting important agricultural commodities under a wide range of climatic conditions, with livestock often exposed to feed containing more than one mycotoxin (Songsermsakul and Razzazi-Fazeli, 2008, Fink-Gremmels, 2016). In western Canada, contamination of grain with Claviceps purpurea has increased markedly over the past 10 years (Tittlemier et al., 2015), although few studies have evaluated impacts of cereal ergot on livestock. The agronomic characteristics of cereal ergot, Claviceps purpurea, are similar to the ergot of tall fescue, Lolium arundinaceum (Fink-Gremmels, 2008, Lovell, 2013). Alkaloid types differ across species of ergot (Porter and Thompson, 1992), with both type and concentration of alkaloids influencing animal impacts (Klotz, 2015). In Canada, maximum allowable concentrations of ergot alkaloids in feed are the same for cattle and sheep (2–3 ppm; CFIA, 2017) and are at least an order of magnitude greater than the <0.1 ppm that has been reported to reduce growth rate in cattle (Shelby, 1999, Evans et al., 2003). As well, ergotism may be less severe in sheep than in cattle consuming the same concentration of ergot in the diet (Evans et al., 2003).
Due to concerns based on anecdotal evidence from the feed industry that pelleting increases negative impacts of cereal ergot alkaloids on livestock performance, the primary objective of this study was to evaluate pelleted and mash diets with increasing concentrations of alkaloids for impacts on growth performance, carcass traits and nutrient digestibility of lambs. A secondary objective was to evaluate the impact of particle size on assay of alkaloids in order to identify and control sources of variation in this methodology.
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Materials and methods
Lamb feeding and digestibility experiments were conducted at the Lethbridge Research and Development Centre (LRDC) of Agriculture and Agri-Food Canada, between May and September of 2015. Protocols for these experiments were approved by the LRDC Animal Care Committee according to the guidelines of the Canadian Council on Animal Care (2009).
Alkaloid analyses
Analyses of screenings revealed that ergocristine, ergotamine and ergocryptine were the dominant alkaloids (Table 2). Analyses of mash and pelleted C diets showed that they contained 3.4 ppb and 2.0 ppb of ergot alkaloids, respectively, consisting mainly of ergometrine and ergocristine. In spiked diets, overall alkaloid concentrations were similar regardless of preparation, averaging 153 ppb for ML, compared to 185 ppb for PL, while MH averaged 434 ppb and PH averaged 342 ppb. Although total
Discussion
The majority of studies investigating the impact of ergot alkaloids on ruminants have focused on tall fescue toxins, in which Neotyphodium coenphialum is the primary etiological agent (Burns, 2009). Fewer studies have investigated the impact on ruminants of cereal ergot alkaloids produced primarily by Claviceps purpurea (Evans et al., 2003). The types of alkaloids present in cereal ergot differ from those in tall fescue, with diversity of alkaloid profiles contributing to the variety of broad
Conclusions
An increased prevalence of ergot in western-Canadian cereal grains is related to higher rainfall due to climate change and increases the urgency of re-evaluating acceptable concentrations of ergot alkaloids in feed. Based on results of the present study, assays for alkaloids first require sample preparation standardization, in conjunction with procedural standardisation prior to the generation of recommendations of allowable concentrations of cereal ergot alkaloids in feeds. Pelleting may have
Conflict of interest
No conflict of interest existed among authors for this work. Additionally, the funding agencies did not influence this study.
Funding
This work was supported by Alberta Livestock and Meat Agency (grant number 2015R030R) and the Alberta Lamb Producers. The funders did not influence this study.
Acknowledgements
The advice and technical assistance from H. Zahiroddini, C. Barkley, W. Smart, G. Duke and M. Huenerberg is gratefully acknowledged. The support of A. Middleton and the sheep team and A. Pittman and crew at the feed mill of the LRDC is also gratefully appreciated. Thank you to the team at PDS and Susan Cook at the Endocrine Lab at the University of Saskatchewan, for conducting the alkaloid and prolactin analyses. Thanks also to Mary Lou Swift of Hi-Pro Feeds for advice regarding study design.
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