Discipline: contamination; Keywords: milk, mycotoxin, silage, digestibility.
Mycotoxins are a diverse group of secondary metabolites produced by many fungi in the genera Aspergillus, Fusarium and Penicillium. They may cause toxic responses when ingested by humans and farm animals. Among the mycotoxins, those produced by Fusarium spp. are usually detected in several feeds because Fusarium molds are widespread and able to contaminate field crops in most areas. Animals develop numerous symptoms following consumption of feed contaminated with the mycotoxin deoxynivalenol (DON), including gastrointestinal problems, soft stools, diarrhea, immune suppression, and a general decrease in performance, probably due to feed refusal. The aims of the study by Dr A. Gallo and colleagues were to investigate the effects of a dairy cow diet contaminated by regularly found concentrations of different Fusarium mycotoxins on (1) feeding behaviour, rumination activity, milk yield, milk composition, milk coagulation properties, and haematological, immunological, and biochemical traits and, (2) to determine the effect of a mycotoxin-deactivating product in preventing the negative effects of these mycotoxins. The results of their study were published in the Journal of Dairy Science. Volume 103 of 2020, pages 11314 to 11331, the title being: A mycotoxin-deactivating feed additive counteracts the adverse effects of regular levels of Fusarium mycotoxins in dairy cows.
In the trial the authors examined the outcomes of the objectives in 12 lactating Holstein dairy cows using a 3-period × 3-treatment Latin square design. The experimental period was 21 days of mycotoxin exposure followed by 14 day of washout. During the treatment periods, the cows received one of three diets: (1) a control total mixed ration (TMR) diet contaminated with 340.5 μg of DON per kg of dry matter (DM) and 127.9 μg fumonisins (FB) per kg of DM (CTR); (2) a mycotoxin (MTX) diet of TMR contaminated with Fusarium mycotoxins at levels higher than CTR but below US and European Union guidelines (i.e., 733.0 μg of DON per kg of DM and 994.4 μg of FB/kg of DM); or (3) a mycotoxin-deactivating product (MDP) diet, which was the MTX diet supplemented with a mycotoxin deactivator product (i.e., 897.3 μg of DON per kg of DM and 1,247.1 μg of FB per kg of DM; Mycofix, 35 g per cow per day). During washout, all animals were fed the same CTR diet. Body weight, body condition score, DM intake, dietary nutrient digestibility, milk production, milk composition and rennet coagulation properties, somatic cell count, blood serum chemistry, haematology, serum immunoglobulin concentrations, and expression of multiple genes in circulating leucocytes were measured.
Milk production was significantly greater in the CTR group (37.7 kg per day) than in the MTX (36.4 kg per day) and the MDP (36.6 kg per day) groups. Curd firmness and curd firming time were negatively affected by the MTX diet compared with the other two diets. Furthermore, DM and neutral detergent fibre digestibility were lower when fed the MTX diet than when fed the CTR diet (67.3 vs. 71.0% and 42.8 vs. 52.3% respectively). The MDP diet had the highest digestibility coefficients for DM (72.4%) and neutral detergent fibre (53.6%) compared with the other two diets. The activities of plasma liver transaminases were higher when fed the MTX diet than when fed the CTR and MDP diets. Compared with the CTR diet, the MTX diet led to slightly lower expression of genes related to immune and inflammatory functions, indicating that Fusarium mycotoxins had an immunosuppressive effect.
The results indicated that feed contaminated with regularly found levels of Fusarium mycotoxins adversely affected the performance, milk quality, diet digestibility, metabolic variables, and immunity of the cows, and that supplementation with mycotoxin deactivator product counteracted most of these negative effects.