Effects of pelleting diets containing cereal ergot alkaloids on nutrient digestibility, growth performance and carcass traits of lambs

https://doi.org/10.1016/j.anifeedsci.2017.06.006Get rights and content

Highlights

  • Particle size significantly influenced analysis of total and individual alkaloids.

  • Pelleting feed may alter ergot alkaloid profiles and reduce negative impacts.

  • Feeding 433 ppb ergot alkaloids most negatively impacted lambs fed mash diets.

  • Feeding 169 ppb alkaloids in pelleted or mash diets did not affect lamb performance.

Abstract

The effects of pelleting feed containing cereal ergot alkaloids was evaluated in performance and nutrient digestibility trials using growing lambs. Defined concentrations of ergot alkaloids [Control (C), no added alkaloids but background concentrations of ∼3 ppb; Low (L), ∼169 ppb; High (H), ∼433 ppb] were achieved by substituting barley grain for ergot-contaminated screenings containing (fed basis) approximately 538 g/kg barley grain, 300 g/kg alfalfa and 160 g/kg canola meal. Diets were fed either as a mash or as a completely pelleted feed. Total alkaloid concentrations did not differ between corresponding mash and pelleted diets, but ergotamine and ergosine were 2–3 times greater in mash feeds, while ergocornine, ergocristine and ergometrine were 2–3 times greater in pelleted diets. The total collection digestibility experiment used 12 ram lambs in a crossover design with 3 experimental periods. Alkaloid dose did not affect digestibility of DM, OM, or CP, but NDF and ADF digestibilities were linearly reduced (P < 0.05) with increasing alkaloid dose. Alkaloid concentrations in feces depended upon the specific type of alkaloid measured. In preliminary results, ergocristine and ergotamine were the only alkaloids in higher concentrations (P < 0.001) in feces from lambs fed H as compared to C diets. In the growth experiment, ram and ewe lambs (live weight 24.6 ± 1.08 kg) were randomly assigned to diets, weighed weekly and fed to a slaughter weight of ≥45 kg. Dietary treatments did not affect carcass characteristics, although serum prolactin concentration was linearly reduced (P < 0.001) by increasing alkaloid dosage and was lower (P = 0.01) in lambs fed mash as compared to pelleted diets. Although pelleted diets had total alkaloid concentrations that were similar to mash diets, lambs fed pelleted diets had 60 g/d greater (P < 0.001) ADG than those fed mash diets. For H diets, lambs had lower ADG and feed conversion (P = 0.03) than those fed C or L, Based on the results of this study, pelleting diets reduced negative impacts of ergot alkaloids possibly by changing alkaloid profiles.

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.

Section snippets

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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