Effect of various silage additives applied in corn, alfalfa and whole barley on in vitro duodenum utilizable crude protein in dairy cows 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 increase utilizable crude protein at duodenum (uCP) Introduction Silages have become the necessary forage component in the ration of dairy cows over the last few decades (Khan et al., 2015). Silages are often a wise choice when selecting forages for providing fiber and energy needed to optimize rumen function (Kolver et al., 2001). Although protein concentration in silages is much lower than concentrates, dry matter intake of silages is high and therefore protein entering into the digestive tract is considerable. Hence, the importance of inclusion of additives in silages to prevent protein proteolysis is indisputable. Protein utilization in silages is poor and is related to proteolytic activity by crop enzymes and further microbial breakdown of protein during ensilage. Thus, we tested urea (nutrient additive for enrich crude protein) , Biomin® inoculants (fermentation stimulant) and formic acid (fermentation inhibitor) on in vitro duodenum utilizable crude protein in dairy cows and its effectiveness. Material & methods The whole crop corn (hybrid 700) in September 17, 2016 at the 2/3 milk-line stage of kernel maturity, whole barley forage (Hordeum vulgare L.) in April 20, 2016 at dough stage, and alfalfa forage (Medicago sativa L.) in May 10, 2016 in third cutting at the 40% bloom stage were harvested and chopped, then ensiled in laboratory mini-silos and opened after 90 days. Silage additives were urea, formic acid, and Biomin® inoculant (Biomin GmbH, Industriestrasse 213130 Herzogenburg, Austria). The Biomin® inoculant (BioStabil strains), which containing a blend of Enterococcus faecium (DSM 3530), Lactobacillus brevis (DSM 19456) and Lactobacillus plantarum (DSM 19457) was applied in liquid at least 2 x 105 colony forming units per gram for both corn and whole barley silages. Formic acid was used at about four litres per ton and 10% higher for alfalfa forage. Urea was added to corn and whole barley at 10.8 and 21.6 g/kg based on dry matter. In vitro duodenum utilizable crude protein was determined using the modified Hohenheim gas test (modHGT) based on the method described by Edmunds et al., (2012) to mimic in vivo duodenal condition. The modHGT follows procedures of the gas test with a chemical alteration of 2 g/l increase in NH4HCO3 and 2 g/l reduction in NaHCO3 in the buffer solution. Gas production (GP) was also recorded at 24 h for use in the calculation of metabolizable energy (ME). NH3-N concentration was determined by using a modified phenol-hypochlorite reaction, and used in the following calculation (Edmunds et al., 2012): uCP (g/kg DM)=((NH3-Nblank+Nsample-NH3-Nsample)/weight(mg DM)) × 6.25 × 1000), ME (MJ/kg DM) = 7.81 + 0.07559 GP - 0.00384 Ash + 0.00565 CP + 0.01898 fat - 0.00831 ADF. The Dunnett test was used between a control (untreated) and all other means (treated with additives) to compare differences within each crop. Differences among means were tested using the LSMEANS test. Results & discussion In vitro duodenum utilizable crude protein value was higher in alfalfa silage than those of corn and whole barley silages. Inclusion of urea, regardless of crops and levels, increased uCP at 8 h. and effective uCP at different assumed passage rate. Nevertheless, the ratio of uCP to CP for urea-treated corn and whole barley silages were lower than those of their controls (P< 0.05). The ratio of uCP to CP at 48 h. unlike 24 h. was higher in silages treated with 21.6 g/kg urea than respective controls (P< 0.05). These various results may be explained by variety of microbial activity to protein degradation during incubation. In vitro duodenum utilizable crude protein was not affected by formic acid in whole barley silage, although treated alfalfa silages had higher uCP than control. These results confirmed reports from researchers who noted that an increase in microbial synthesis in rumen and microbial-N flow at the duodenum with addition of formic acid to alfalfa has occurred (Jaakkola et al., 2006). On the other hand, silage treatments with acid might decrease the apparent digestibility of CP in the rumen and elevate the proportion of by-pass protein flowing to the duodenum. Applying inoculant did not result in a consistent change in uCP at 8 and 48 h after incubation in corn and whole barley silages (P>0.05), but effective uCP was influenced in treated whole barley silage. Metabolizable energy was lower in formic acid treated-alfalfa silage, but inclusion of urea and inoculant had no significant effect on metabolizable energy. Conclusion In conclusion, urea and formic acid additives may improve animal performance by increasing utilizable CP entering at intestine. Acknowledgements Researchers gratefully acknowledge funding from department of animal science, Ferdowsi University of Mashhad, Iran. References Edmunds B, Sudekum KH, Spiekers H, Schuster M and Schwarz FJ 2012. Animal Feed Science and Technology 175, 106-113. Jaakkola S, Kaunisto V and Huhtanen P 2006. Grass Forage Science 61, 282-292. Khan NA, Yu P, Ali M, Cone JW and Hendriks WH 2015. Food Science and Agriculture 95, 238-252. Kolver ES, Roche JR, Miller D and Densley R 2001. Proceedings of the New Zealand Grassland Association. New Zealand. 63,

Keywords