Effect of sequestering agents based on a Saccharomyces cerevisiae fermentation product and clay on the ruminal bacterial community of lactating dairy cows challenged with dietary aflatoxin B_1

摘要

This study was conducted to examine the effects ofclay (CL) and Saccharomyces cerevisiae fermentationproduct (SCFP) on the ruminal bacterial communityof Holstein dairy cows challenged with aflatoxin B_1(AFB_1). A second objective was to examine correlationsbetween bacterial abundance and performancemeasures. Eight lactating dairy cows stratified by milkyield and parity were randomly assigned to 4 treatmentsin a 4 × 4 Latin square design with 2 replicatesquares, four 33-d periods, and a 5-d washout betweenperiods. The treatments included (1) control (basaldiet, no additive); (2) T (control + 63.4 μg/kg AFB_1,oral dose); (3) CL (T + 200 g/head per day of sodiumbentonite clay, top-dress); and (4) CL+SCFP [CL + 19g/head per day Diamond V NutriTek (Diamond V Inc.,Cedar Rapids, IA) + 16 g/head per day MetaShield(Diamond V Inc.), top-dress]. Cows were adapted todiets containing no AFB_1 from d 1 to 25 (predosingperiod). From d 26 to 30 (dosing period), AFB_1 wasorally dosed and then withdrawn for d 31 to 33 (withdrawalperiod). During the predosing period, comparedwith the control, feeding CL and CL+SCFP increasedthe relative abundance of the most dominant phylum,Bacteroidetes (55.1 and 55.8 vs. 50.6%, respectively),and feeding CL+SCFP increased Prevotella abundance(43.3 and 43.6 vs. 40.0%, respectively). During the dosingperiod, feeding AFB_1 did not affect the ruminalbacterial community, but the relative abundance ofFibrobacteraceae increased with CL+SCFP comparedwith T (1.45 vs. 0.97%); Fibrobacter abundance alsotended to increase with CL+SCFP compared withT and control, respectively (1.45 vs. 0.97 and 1.05%,respectively). Feeding AFB_1 with or without CL orCL+SCFP did not affect ruminal pH or concentrationsof NH_3-N, total volatile fatty acids, or individual volatilefatty acids. Milk yield and milk component yieldswere positively correlated with the relative abundanceof unclassified Succinivibrionaceae, unclassified YS2, orCoprococcus. Feed efficiency was positively correlated(r ≥ 0.30) with the relative abundance of unclassifiedYS2, Coprococcus, or Treponema. Feeding aflatoxin at63 μg/kg, a common contamination level on farms, didnot affect the abundance of dominant bacteria or rumenfermentation. When aflatoxin was fed, CL+SCFPincreased the abundance of Fibrobacter, a major fibrolyticbacteria genus. Milk yield and DMI were positivelycorrelated with abundance of Succinivibrionaceae andCoprococcus. Feed efficiency was positively correlatedwith abundance of Coprococcus, Treponema, and YS2.Future studies should speciate culture and determinethe functions of the bacteria to elucidate their roles inthe rumen and potential contribution to increasing theperformance of dairy cows.