Food safety through fungal disease and mycotoxin mitigation on dairy farms: From field to feed and the rumen

Dairy producers are faced with a multitude of challenges regarding dairy cattle production. One such challenge common for cows fed whole-plant corn silage (WPCS) is the often negative effect of fungi. Fungi affect WPCS both in the field and post-harvest; and can cause serious issues for cows that consume it. The use of fungicide (FUN) in the field and feeding adsorbents (AD) to cows are ways to combat the negative consequences caused by fungi and their resulting toxins (mycotoxins). Fungicides work on the corn plant in the field to halt fungus growth, while AD such as clay and yeast work in the rumen to mitigate the negative effects associated with the consumption of mycotoxins on WPCS and other feedstuffs. This research aimed to delve into the consequences of foliar FUN on WPCS and of feeding AD to cows challenged by aflatoxins (AF). To examine the effects of FUN on WPCS in the field and post-ensiling, treatments were assigned to 16 3.38-ha plots in a completely randomized split-plot block design. Treatments were: brown midrib corn (BMR) or floury corn (FLY) without FUN (CON), BMR with FUN (pyraclostrobin and metconazole; Headline AMP, BASF, Florham Park, NJ), and FLY with FUN. Samples of whole corn plants were collected and separated into leaves, stalks, flag leaf, and cobs. Fresh-cut, WPCS samples were collected at harvest and sealed inside mini-silos for the duration of their respective ensiling times. Brown midrib corn plants had a greater number of green leaves than FLY with 11.81 and 11.34 ± 0.09 leaves, respectively (P = 0.001). Corn plants in CON had a greater number of yellow leaves than corn plants in FUN with 0.28 and 0.08 ± 0.02, respectively (P < 0.0001). Corn treated with FUN tended to yield more total WPCS than CON with 63,634 and 60,488 ± 1,533 kg/ha, respectively (P = 0.08). Whole plant corn silage lignin (ADL) content decreased as days ensiled increased with 31.61, 28.48, 25.48, and 22.38 ± 0.77 g/kg of DM for d 0, 30, 90, and 150 d, respectively (P < 0.0001). Floury WPCS had a greater ADL content than BMR WPCS with 31.25 and 22.72 ± 0.61 g/kg of DM, respectively (P < 0.0001). Brown mid-rib WPCS had a greater NDF digestibility at 30 h than FLY WPCS with 572.6 and 492.3 ± 6.9 g/kg of DM, respectively (P < 0.0001). Floury WPCS had greater undigested NDF than BMR WPCS with 125.3 and 96.1 ± 2.1 g/kg of DM, respectively (P < 0.0001). Brown mid-rib corn kernels had a greater kernel vitreousness score than FLY corn kernels with scores of 3.11 and 2.65 ± 0.13, respectively (P = 0.05). A variety × treatment interaction was observed for kernel vitreousness score with scores of 3.23, 2.99, 2.49, and 2.80 ± 0.14 for BMR/CON, BMR/FUN, FLY/CON, and FLY/FUN, respectively (P < 0.0001). From this study we concluded that BMR WPCS treated with FUN and ensiled for 90 to 150 d may result in the most superior WPCS when fed to dairy cows. When FUN aren’t enough to protect WPCS from fungal infestation, AD are commonly fed to cows in order to alleviate the negative effects of toxins on cows. In the first cow trial, lactating Holstein cows [(n = 76); BW (mean ± SD) = 698 ± 72 kg; DIM = 153 ± 83 d] were assigned to 1 of 5 treatments in a randomized complete block design. The trial lasted 28 d and measurements were made from d 22 to 28. From d 22 to 24 cows received an AF challenge (100 μg of AFB1/kg of diet DM administered orally). Treatments were: no AD and no AF challenge (CON); no AD plus an AF challenge (POS); 30 g per cow per d of an AD with proprietary composition of yeast cell wall and bentonite clay (P30); 60 g per cow per d of the same AD previously mentioned (P60); and 60 g per cow per d of a prototype AD (PROT). Blood was sampled on days 22 and 26 (n = 2 per cow), and analyzed for superoxide dismutase (SOD) concentration. Milk samples from d 22 to 26 were analyzed for AFM1 concentrations by HPLC. Fecal samples collected from the rectum on d 22 and 24 were analyzed for AFB1 concentrations via HPLC. A quadratic treatment effect (P < 0.0001) was observed for plasma SOD concentrations at 2.77, 1.99, and 1.97 ± 0.05 U/mL for POS, P30, and P60 treatments, respectively. Aflatoxin M1 transfer (11.4 and 0.00 ± 1.60 g/kg), excretion (29.52 and 0.00 ± 4.58 µg/d), and concentrations in milk (0.76 and 0.00 ± 0.16 µg/kg) were greater for POS than CON, respectively (P < 0.0001) but no differences were observed among other treatments. A tendency for a quadratic treatment effect (P = 0.08) was observed for fecal AFB1 concentrations at 6.78, 8.55, and 5.07 µg/kg for the POS, P30, and P60 treatments, respectively. Oral supplementation of yeast and bentonite clay-based AD during AF challenge resulted in quadratic changes in plasma SOD and fecal AFB1 concentrations; however, no differences were observed for DMI or milk yield. From this study we concluded that yeast cell wall and bentonite-based AD may be beneficial in reducing inflammation during an AF challenge. In a second cow study, we sought to determine the ruminal degradability of feedstuffs in response to 3 concentrations of dietary clay in lactating dairy cows. Treatments were: no clay (CON), 10, or 20 g/kg of dietary DM as clay (EcoMix®, UMG, Ukraine). Samples (8 g) of dried alfalfa hay (AH), grass hay (GH), wet brewer’s grains (WBG), ground corn (GC), corn silage (WPCS), or soybean meal (SBM) were placed into polyester bags (3 replicates per feed) and incubated for 0, 2, 4, 8, 12, 48, 72, or 96 h in 3 rumen-cannulated cows. Recovered bags were analyzed for DM, NDF, ADF, starch, and CP for all feedstuffs, as well as total fatty acids (TFA), saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), and polyunsaturated fatty acids (PUFA) for GH, WBG, and WPCS. Soluble (SF), digestible (D), and indigestible (I) fractions; and fractional rate of digestion (Kd) and effective degradability (ED), were estimated for each feedstuff, treatment, and cow combination. Dry matter SF for GH was 0.14, 0.17, and 0.12 g/100 g of DM for CON, 10, and 20 g/kg (P = 0.03). Dry matter Kd for GH was 0.026, 0.015, and 0.022 h-1 for CON, 10, and 20 g/kg (P = 0.02). Digestible DM for WBG was 0.59, 0.66 and 0.76 g/100 g of DM for CON, 10, and 20 g/kg (P = 0.04). Dry matter ED for WBG was 0.44, 0.41, and 0.31 g/100 g of DM for CON, 10, and 20 g/kg (P = 0.02). Soluble DM for SBM was 0.26, 0.34 and 0.15 g/100 g of DM for CON, 10, and 20 g/kg (P = 0.04). Dry matter ED for SBM was 0.48, 0.57, and 0.39 for CON, 10, and 20 g/kg (P = 0.002). From this study, we concluded that the addition of clay at 10 or 20 g/kg of total dietary DM increased SF of GH and SBM, ED of SBM, and D of WBG. As a whole, this research aimed to provide practical solutions to a common problem faced by dairy farmers regarding mycotoxins both in the field and in feedstuffs. In the field, FUN may improve the health and quality of corn plant and WPCS, while AD are useful for attenuating the negative effects of toxins within the cow. Lastly, the addition of a clay-based AD may improve the degradability of some feedstuffs making it effective in maximizing both health and productivity of dairy cows