511 Session 5: Feed resources and sustainable diets The impact of silage additives on undigested NDF and potential digestible NDF of corn, whole barley and alfalfa silages Mohsen Danesh Mesgaran, Seyyed Mohsen Hosseni, Alireza Vakili, Abbasali Nasserian Dept. Animal Science, Ferdowsi University of Mashhad, Mashhad, Iran E-mail: danesh@um.ac.ir Take home message Inclusion of urea and formic acid to silages decreases undigested NDF (uNDF) and increases potential digestible NDF (pdNDF). Introduction Silage fermentation is a dynamic process that leads to loss of nutrients; however, it is affected by a variety of biological and technological factors (Kung, 2010). In recent years there has been a focus to enhance silage quality and minimize nutrient losses during ensiling. A critical component for assessing silage quality is fiber digestibility. Increasing fiber digestion results in reduced physical gut fill in the rumen and is related to greater dry matter intake, as well as energy density and milk yield (Oba and Allen, 2000). We hypothesized that Biomin® inoculant, formic acid and urea may alter uNDF and pdNDF. Thus, the effect of silage additives for corn, whole barley and alfalfa on fiber digestion were tested. Material & methods The whole crop corn (hybrid 700) in d 17 September 2016 at 2/3 milk line of kernel maturity stage, whole barley forage (Hordeum vulgare L.) in d 20 April 2016 at dough stage, and alfalfa forage (Medicago sativa L.) at d 10 May 2016 in second cutting at 40 % flowering, were harvested and chopped. They were then ensiled in laboratory mini-silos, 4-L polyvinyl tubes, and were immediately sealed by polypropylene screw cap on top with a rubber seal. Silage additives were Biomin® inoculant, formic acid and urea. The Biomin® (BioStabil strains) inoculant, was applied in liquid at 800 and 9600 colony forming units per kilogram (cfu/kg) to corn and 800 cfu/kg for whole barley crops. Formic acid was used within the range of four litres per ton in fresh alfalfa. Urea was added to corn and whole barley at 10.8 and 21.6 g/kg based on dry matter. Undigested NDF was determined at intervals of 30 (fast pool), 120 (slow pool), and 240 h. The procedure has been fully described by Goeser and Combs (2009). Undigested NDF was calculated as 100 – IVNDFD (in vitro NDF digestibility) where IVNDFD, % NDF = [1 − (NDFresidual− NDFblank)/ NDFsample] ×100, the amount of pdNDF is calculated from the difference of total NDF and uNDF (pdNDF % DM = (100 – % uNDF240 h) × % NDFsample). Data were analyzed by the generalized linear model (PROC GLM; SAS 9.2). The Dunnett test was used between a control (untreated) and all other means (treated with additives) to compare differences within each crop. The least significant difference in means of uNDF and pdNDF were obtained using the PDIFF option of LSMEANS statement. Results & discussion Data of undigested NDF and potential digestible NDF of corn, whole barley and alfalfa silages are presented in Table 1. The inclusion of urea to corn and whole barley silages improved fiber digestion by decreasing uNDF concentration at 30 h and increasing potential digestible NDF to corn. Addition of formic acid to the alfalfa silages increased pdNDF at 30 and 240 h. During ensiling, partial hydrolase of fiber with acids may alter ruminal digestibility. So this pre-hydrolase caused NDF to readily be digested in the rumen by increasing surface area available for microbial attack. Weimer (1996) suggested that the buffering effect of silage additive on rumen pH might be a possible explanation for the beneficial effects on fiber digestibility. Inoculation of Biomin did not affect both uNDF and pdNDF at different times of incubation. There were no detectable differences for uNDF240h among silages with various additives. Table 1: The effect of silage additives on undigested NDF and potential digestible NDF of corn, whole barley and alfalfa silages Items Corn silage Alfalfa silage Whole barley silage CS0.0 CSU10.8 CSU21.6 CSB800 CSB9600 SEM AS0.0 AS4.0 SEM BS0.0 BSU10.8 BSU21.6 BSB800 S E M uNDF30 51.6 48.9* 48.8* 52.4 50.8 1.0 67.7 64.4 1.9 59.2 57.8 55.7* 59.0 1.0 pdNDF30 26.7 29.1* 29.4* 26.7 27.0 0.7 14.1 16.6 * 0.2 22.9 23.3 22.2 22.7 0.2 uNDF120 42.6 40.9 41.5 43.8 40.8 1.0 54.7 53.8 0.8 51.0 52.1 48.8* 51.5 0.9 pdNDF120 31.9 33.6* 33.6* 31.6 32.4 0.6 21.8 22.1 0.5 27.5 26.6 28.5 26.9 0.7 uNDF240 31.2 29.9 28.5 31.8 31.2 1.7 46.2 45.7 1.8 39.4 39.2 36.7 39.2 2.2 pdNDF240 38.2 39.9 41.1 38.8 37.9 0.7 24.0 25.0 * 0.3 34.1 33.8 35.2* 34.8 0.3 * Within a column, means with an asterisk differ significantly from control (P< 0.05). SEM= standard error of means. Conclusion Inclusion of urea and formic acid as an additive to silages may decrease uNDF and increase pdNDF by providing more energy through a more rapid rate of fermentation. However, it seems that Biomin® inoculant did not influence fiber digestibility. Acknowledgements Researchers gratefully acknowledge funding from Ferdowsi University of Mashhad, Iran. References Goeser JP and Combs DK 2009. Dairy Science 92, 3833-3841. Kung L 2010. Department of Animal and Food Sciences, University of Delaware Newark, DE, 19717-1303. Oba M and Allen MS 2000. Dairy Science 83, 1333-1341. Weimer PJ 1996. Dairy Science 79, 1496-1502.

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