High mycotoxin levels in wheat grain and their effects on beef cattle ruminal fermentation, performance, and carcass traits

Published: March 14, 2023

By: Bierworth, R.M. 1,2; Ribeiro, G.O. 1; Terry, S.A. 2; Penner, G.B. 1; McKinnon, J.J. 1; Hucl, P. 1; Randhawa, H. 2; Beauchemin, K.A. 2, Schwartzkopf-Genswein, K. 2; Yang, W.Z. 2; Gruninger, R. 2; Guan, L.L. 3; Gibb, D.4; and McAllister, T.A. 1.

Summary

Author details:

1 Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, SK; 2 Agriculture and Agri-Food Canada, Lethbridge Research and Development Centre, Lethbridge, AB; 3 Agricultural Food and Nutritional Science, University of Alberta, Edmonton, AB; 4 Gowan’s Feed Consulting, Raymond, AB.

Abstract

With the rising impact of climate change on grain crops in North America, more wheat grain has failed to meet milling grade standards and has been diverted to animal feed. A common reason for rejection is infection with F. graminearum and C. purpurea, which produce deoxynivalenol (DON) and ergot alkaloids (EA), respectively. Current allowable limits in cattle for DON are 5 ppm in Canada, while EA limits are 2 to 3 ppm. The objectives of this study were to investigate the effects of high mycotoxin levels on ruminal fermentation, growth performance, and carcass characteristics of finishing steers. The primary mycotoxin assessed was DON (5 ppm and 10 ppm), but EA were also present in the same wheat at 2.1-4.3 ppm. Forty crossbred steers (8 cannulated) were housed in individual pens, blocked by weight, and randomly assigned to 1 of 4 treatments; control-low (0 ppm), control-high (0 ppm), MYC-low (5 ppm-DON; 2.1 ppm-EA), and MYC-high (10 ppm-DON; 4.2 ppm-EA). Wheat screenings were added to control diets so as to generate diets with a chemical composition that was similar to MYC diets. Steers were fed a finishing diet consisting of 88% dry rolled wheat based-concentrate and 12% barley silage on a dry matter basis for 112 days. Ammonia and volatile fatty acid concentrations in rumen fluid did not differ among treatments. Final body weight, dry matter intake (DMI), average daily gain (ADG) and gain to feed ratio (G:F) of steers fed MYC were reduced when compared to controls (P<0.01), with DMI for controls averaging 9.67-9.85 kg/d, MYC-low at 8.38 kg/d, and MYC-high at 6.29 kg/d. ADG for controls ranged between 1.90-1.92 kg/d, MYC-low at 1.36 kg/d and MYC-high at 0.84 kg/d. Hot carcass weight and fat cover were also reduced (P<0.01), but lean meat yield was increased in MYC steers (P<0.01). No differences were noted in carcass grades. In conclusion, a combination of DON and EA, negatively impacted growth performance and carcass traits of steers. These findings illustrate the importance of knowing what toxins are present in feed wheat for finishing cattle. Adjusting approved levels of mycotoxins when two or more are present may help avoid adverse impacts on growth performance of finishing feedlot cattle.

Keywords: beef cattle, wheat, mycotoxins, performance, DON, ergot.

Introduction

Changing climatic conditions in Western Canada has led to increased amounts of wheat grain failing milling grade standards and as a result more is available as feed (He et al., 2015). One reason for wheat grain failing grading standards is infection with Fusarium graminearum and/or Claviceps purpurea, which produce deoxynivalenol (DON; Bianchini et al., 2015) and ergot alkaloids (EA; Tittlemier et al., 2015), respectively. Due to the ability of the rumen microbial population to metabolize DON to de-epoxy DON (DOM-1; Guerre, 2020), ruminants are considered less sensitive to the toxin than monogastrics (Dänicke et al., 2005; Roberts et al., 2021). Ruminants are more sensitive to EA (Rahimabadi et al., 2022) and can exhibit variable symptoms among individuals. This variation in response is attributable to complex interactions among the plant, pathogen, animal and the environment (Klotz, 2015). Generally, there are 3 types of manifestations to ergot toxicity; [1] convulsive (Rahimabadi et al., 2022) [2] gangrenous (Klotz, 2015), and [3] other (Coufal-Majewski et al., 2016). Research on possible interaction between DON and EA is scarce. The objectives of this study were to assess the effects of a mixture of DON and EA in feed wheat on ruminal fermentation, growth performance, and carcass traits of feedlot cattle.

Methods and Materials

Forty crossbred steers (8 cannulated) were housed in individual pens, blocked by weight, and randomly assigned to 1 of 4 treatments; control-low (0 ppm), control-high (0 ppm), MYC-low (5 ppm-DON; 2.1 ppm-EA), and MYC-high (10 ppm-DON; 4.2 ppm-EA). Steers were fed a finishing diet consisting of 88% dry rolled wheat-based concentrate, 12% barley silage on a dry matter basis for 112 days. Wheat screenings were added to control diets so as to generate diets with a chemical composition that was similar to MYC diets, consequently producing two different control diets (high and low). This was to account for poor quality of the mycotoxin infected wheat in the treatment diets in a non-MYC control. Weigh-backs were collected weekly from troughs to estimate dry matter intake (DMI). Steers were weighed on 2 consecutive days at the beginning and end of the trial, and at 28-d intervals. Ruminal pH loggers were placed in the rumen for 7 days and upon removal rumen digesta was collected (~300 ml) and strained through two layers of cheese cloth and the filtrate was placed in either sulfuric acid for NH3, or metaphosphoric acid for VFA and stored at -20 ⁰C. Steers were marketed after 112 d on feed to Cargill Foods (High River, AB, Canada). Hot carcass weight, dressing percentage, back fat thickness, rib-eye area, lean meat yield, and quality grade were determined. Livers were scored and checked for cirrhosis, hyperplasia and tumours. PROC MIXED and PROC GLIMMIX were used to analyze data (SAS Int. Inc., Cary, NC). Models included DON and EA as fixed effects, and individual animal as a random effect.

Results and Discussion

The DMI of steers fed MYC-L and MYC-H treatments was reduced (P < 0.001) by 14.1% and 35.6%, respectively, when compared to control fed steers. Consequently, ADG (P < 0.001) and G:F (P = 0.001) for MYC (L and H) fed steers were linearly reduced, showing a 28.8% (L) and 56.0% (H) decrease for ADG, and 16.5% (L) and 31.8% (H) decrease for G:F. These findings are in agreement with Coufal-Majewski et al. (2017), where ergot alkaloids fed at a concentration of 0.4 ppm reduced ADG and G:F of lambs. However, when comparing similar studies in dairy cattle using DON, performance losses were not reported (Charmley et al., 1993; Ingalls, 1996), even when it was present in feed at 12 ppm. Ammonia and VFA concentrations did not vary among treatments, although total VFA concentrations approached significance (P = 0.06). This tendency could be explained by reduced DMI (Schären et al., 2016) observed in MYC fed steers. Mean ruminal pH was higher (P =0.018) for MYC steers, which could be explained by lower DMI, due to reduced digestion and production of VFA’s. Higher pH could also be a result of feed sorting (Miller-Cushon and DeVries, 2017) and refusals as these steers favoured the consumption of silage. Refusal of the wheat-based concentrate resulted in a reduced intake of fermentable carbohydrates and consequently higher ruminal pH (Owens and Pioneer, 2015). Hot carcass weights were linearly reduced (P < 0.001) in MYC steers as mycotoxin concentrations increased. Steers fed MYC diets also exhibited decreased (P = 0.001) average fat cover as compared to control steers. These observations reflected the reduced ADG and G:F of these steers. Meat yield (P = 0.041) and lean meat yield (P = 0.011) were increased in MYC fed steers as compared to control fed steers, which is likely a result of the reduced DMI, promoting lower ADG and leaner carcasses due to less energy available for fat deposition. There were no significant differences in carcass grades or liver scores.

Conclusions

Feed wheat contaminated with DON and EA decreased growth performance and carcass quality in feedlot steers but increased mean ruminal pH. When comparing similar levels of DON or EA in previous studies, DON was reported to have little to no negative impacts on cattle, even at concentrations of 12 ppm. EA was reported to negatively impact ruminants at 0.4 ppm and this impact increased linearly as concentrations increased. The results seen in previous EA studies are in agreement with the results of our study. However, more research is needed to determine if these results reflect the impact of a combination of DON and EA, or just EA. These findings illustrate the importance of knowing what the types and concentrations of mycotoxins are in feed wheat fed to finishing cattle, so as to avoid substantial monetary losses for producers.

Presented at the 2022 Animal Nutrition Conference of Canada. For information on the next edition, click here.

References

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Content from the event:

High mycotoxin levels in wheat grain and their effects on beef cattle ruminal fermentation, performance, and carcass traits

Introduction

Methods and Materials

Results and Discussion

Conclusions

Priya Chemicals

Evonik Animal Nutrition