Evaluation of source of corn silage and trace minerals on rumen characteristics and passage rate of Holstein cows

摘要

The effects of source of corn silage and trace mineralon rumen fermentation, turnover, and particle passagerates were evaluated with 8 ruminally cannulated Holsteincows averaging 83 (standard error = 5) days inmilk in a replicated 4 × 4 Latin square design with a2 × 2 factorial arrangement of treatments and 28-dperiods. The diets consisted (dry basis) of 55% conventional(CON) or brown midrib-3 (BM3) corn silage, 2%chopped wheat straw, and 43% grain mix with eithersulfate (STM) or hydroxy (HTM) source of Cu, Zn,and Mn trace minerals. The targeted supplementalamount of Cu, Zn, and Mn was 194, 1,657, and 687mg/d, respectively. The dietary treatments were (1)CON-STM, (2) CON-HTM, (3) BM3-STM, and (4)BM3-HTM. Dietary nutrient composition of BM3 dietsaveraged 32.1% amylase neutral detergent fiber on anorganic matter basis (aNDFom) and 6.9% undigestedneutral detergent fiber at 240 h of in vitro fermentation(uNDF240om; % of dry matter), and CON dietsaveraged 36.2% aNDFom and 8.6% uNDF240om (%of dry matter). Data were summarized by period andanalyzed as a replicated Latin square design with fixedmodel effects for corn silage, trace mineral, corn silageand trace mineral interaction, period within replicatedsquare, and replicated square using the MIXED procedureof SAS (version 9.4, SAS Institute Inc., Cary, NC).Cow within replicate was a random effect. Daily mean,standard deviation, minimum, and maximum for rumenpH were unaffected by corn silage or trace mineralsource. Cows fed the CON diets had greater rumen acetatepercentage than cows fed the BM3 diets (65.7 vs.64.7 molar %). In contrast, cows fed the BM3 diets hadgreater rumen propionate percentage than cows fed theCON diets (21.4 vs. 20.4 molar %). Total volatile fattyacid concentration was lower for cows fed STM versusHTM in BM3 diets, but not for the cows fed the CONdiets. Cows fed the BM3 diets had faster turnover rateand shorter turnover time for uNDF240om than cowsfed the CON diets (3.12 vs. 2.86%/h and 33.3 vs. 36.5h, respectively). Cows fed the BM3 diets had a fasterpassage rate of small and medium corn silage neutraldetergent fiber particles than cows fed the CON diets(5.73 vs. 5.37%/h and 4.74 vs. 4.31%/h, respectively).We observed a corn silage by source of trace mineralinteraction on organic matter and uNDF240om rumenpool size and organic matter turnover. Overall, sourceof corn silage had a pronounced influence on rumendynamics presumably related to greater in vitro neutraldetergent fiber digestibility and lower uNDF240omcontent of BM3 corn silage that allowed for faster turnoverof indigestible neutral detergent fiber and greaterpassage rate of corn silage particles. In contrast, thesource of trace mineral had much less significant effectson rumen fermentation, turnover, and particle passagerates. Corn silage-based diets intended to enhance rumenfiber fermentation, turnover, and passage are moreaffected by source and digestibility of neutral detergentfiber than source of dietary trace minerals.