Assessment of mycotoxin occurrence in feed samples from the Belgian veal calf industry and the influence of roughage provision

Abstract

INTRODUCTION: The Belgian white veal industry specializes in raising predominantly male surplus dairy calves to white veal meat. This is obtained by intensive feeding of low-iron diets, historically dominated by liquid milk replacer, containing vegetable protein sources. Consequently, veal calves only had very limited ruminal development and function. Only recently, the share of roughage and concentrates has expanded for welfare and feed-technical reasons, leading to more mature rumen development. Both milk replacer and solid feeds contain grain products, concomitant with possible mycotoxin contamination. Mycotoxins are naturally occurring secondary fungal metabolites that can be produced in crops and other feed commodities both pre- and post-harvest. It is suggested that an optimal rumen functioning is responsible for the biotransformation and detoxification of several Fusarium mycotoxins, including deoxynivalenol (DON), making ruminants less sensitive to these toxins. In the first part of this study, we aimed to evaluate the mycotoxin contamination of feed samples in the Belgian veal industry. Subsequently, we investigated the impact of ruminal development on the biotransformation of DON and its acetylated derivatives, 3- and 15-acetyl-DON (3- and 15-ADON), in calves using a comparative toxicokinetic approach. METHODS: Survey: 45 feed samples were collected from 15 different veal farms. On each farm three to six samples per feed component, respectively milk replacer, roughage (straw or corn silage) and concentrate feed, were collected and subsequently pooled per feed component. Samples were analysed by validated multi-mycotoxin (UHP)LC-MS/MS methods (Monbaliu et al., 2010; Van Pamel et al., 2014). Toxicokinetic study: two ruminating and two non-ruminating male calves each received respectively a bolus of DON (120 µg/kg bodyweight (BW)), 3-ADON (25 µg/kg BW), and 15-ADON (50 µg/kg BW) by intravenous (IV) injection or per os (PO) in a cross-over design, respecting a wash-out period of 96h. Concentrations were based on average feed intake and maximum contamination levels of the feed based on the survey. Following mycotoxin bolus administration, blood and urine was collected at different time points post administration. DON, 3-ADON, 15-ADON as well their metabolites, namely de-epoxy-DON, DON-3-glucuronide, DON-3-sulfate, DON-15-sulfate, 3-ADON-15-sulfate, 15-ADON-3-sulfate and DON-3,15-di-sulfate, in plasma and urine samples were analyzed by LC-MS/MS. RESULTS: Survey: About 13% of the milk replacer samples were contaminated with fumonisin B1 and FB2, with an average contamination level of respectively 32 ± 7 and 13 ± 1 µg/kg. No other mycotoxins were found in these samples. However, all roughage and concentrate feed samples were contaminated with at least one mycotoxin. DON was most prevalent, contaminating 80% of the roughage samples and all 15 concentrate samples. Also the DON acetylated derivatives 3- and 15-ADON were present in 40% of the roughage and concentrate samples. It remains to be determined whether 3- and 15-ADON contribute to the total DON contamination, e.g. by possible in vivo hydrolysis upon ingestion. Besides DON, also enniatin B was highly prevalent (73% of the samples). Toxicokinetic study: Results will be presented at the conference. DISCUSSION: The survey demonstrates a multi-mycotoxin contamination of the feed for veal calves, mainly present in roughage and concentrate feed. The results of the toxicokinetic study will determine the balance between mycotoxin exposure and ruminal biotransformation of the toxins in veal calves. The increased exposure of veal calves to mycotoxins, by the provision of large amounts of solid feed, can negatively affect veal performance, gastro-intestinal health and susceptibility for infectious diseases. However, the provision of large amounts of solid feed stimulates ruminal development, which can make the veal calves less sensitive to mycotoxins. REFERENCES Monbaliu S. , Van Poucke C., Detavernier C., Dumoulin F., Van De Velde M., Schoeters E., Van Dyck S., Averkieva O., Van Peteghem C., De Saeger S. (2010) Occurrence of mycotoxins in feed as analyzed by a multi-mycotoxin LC-MS/MS method, J. Agric. Food Cem. 58, 66-71. Van Pamel E., Antonissen G., Valgaeren B., Croubels S.,Daeseleire E. (2014) A multi-mycotoxin UHPLC-MS/MS method for the detection, quantification and identification of mycotoxins in milk replacer, 36th Mycotoxin Workshop, Göttingen, June 16-18