Effect of soybean meal and canola meal treated with various levels of tannin extracted from Pistachio hulls on crude protein fractions based on CNCPS system

Treatment of a dietary protein such as soybean meal (SBM) to decrease its solubility and thus, its hydrolysis to ammonia in rumen fluid should increase the amount of the dietary protein that bypasses ruminal degradation without sacrificing nitrogen required for ruminal microbial growth (Nishimuta et al. 1974). Protection of dietary protein from ruminal microbial degradation increases the supply of amino acids to the small intestine (Stern, 1981). Thus, the efficiency of protein utilization by the animal should be improved (Driedger and Hatfield 1972). Using suitable and practical processing methods for improving the nutritive value of feedstuff in ruminant nutrition have an important role in reducing production costs and improving production performance of ruminant animals. The aim of this study was to investigate the effects of various levels of tannin extracted from pistachio hulls on crude protein (CP) fractionation of soybean meal (SBM) and canola meal (CM) based on the Cornell Net Carbohydrate and Protein System (CNCPS). Material and Sun dried pistachio hulls were ground through a 0. 5 mm screen and soaked in water at a ratio of 1:10 (w/v) for 24 h. Then the pistachio extract was filtered and boiled to achieve pistachio extract concentrate (PEC) containing 11% total phenol and 7. 13% total tannin on a dry matter (DM) basis. The rates of PEC treatment were determined based on the previous in vitro findings of Dentinho et al. (2007), who found that treatment of SBM with crude extract from Cistus ladanifer L. caused a decrease in rumen degradation of SBM protein, even at relatively low phenolic doses (12. 5, 25 and 50 g total phenol per kg SBM). A total amount of 1 kg dried SBM and CM were ground through a 1 mm screen for each treatment. Both soybean meal and canola meal were treated with 0, 5, 10, 15, 20 and 30 % of PEC tannin. Finally, treated SBM and CM were airdried for 12 h to reach DM content of about 90% in whole product. The protein fractions of treated SBM and CM were determined according to CNCPS system. Analysis of phenolic compounds was conducted in three replicates as described by Makkar (2000). Total phenol was determined by Folin-Ciocalteu’s reagents, and the concentration was measured as tannic acid equivalent using tannic acid (Merck, Germany) as standard. Total tannins were measured as described by Makkar (2000). A completely randomized design with 6 treatments and 3 replicates was used for the study. The data were analyzed with general linear model procedure of SAS. Significance in the data was established when P<0. 05. Effects of SBM and CM treated with various amounts of PEC on chemical composition indicated that, adding PEC decreased DM, organic matter, neutral detergent fiber (NDF( and acid detergent fiber (ADF) content, but did not affect concentrations of CP for both SBM and CM proteins relative to its control groups. Vahdani et al. (2016) reported decreased NDF content of CM protein treated with tannin extracts from tea and pistachio. On the basis of the results, the lowest amount of soluble fraction (Sum of A and B1) was observed for CM at the level of 5% PEC tannin. There was no significant difference among treatments relative to control group in B2 fraction. Inclusion of PEC increased B3 fraction compared to control and 20% level has showed the highest B3 fraction. There was a reduction in C fraction by increasing level of PEC. The  lowest soluble fraction of CP followed by the highest escaped protein (B2+B3) elicited to recommend 5% level as the best treatment for CM, in lab scale. For SBM, the level of 30% PEC tannin increased bypass fractions of protein compared to other levels (P<0/05). This treatment changed the soluble (A and B1) (12. 37%) and insoluble fractions (B2, B3 and C) (87. 62 %) in SBM compared to the control and other levels of PEC supplementation. The results suggest that PEC supplementation decreases ruminal degradation of SBM, but increased rumen degradability of CM protein. There are some methods to decrease protein degradation in rumen such as using tannins. Tannins have been shown to decrease ruminal degradation of crude protein and increase the amount of CP that reaches the abomasum and small intestine (Alipour and Rouzbehan 2010). When using SBM treated with 10 to 250 g of quebracho tannins per kg, Frutos et al. (2000) also observed a decrease in in vitro intestinal digestibility of protein at the greatest treatment rate. Further research will be needed to determine if tannin treatment of dietary protein improves its digestibility. It has been demonstrated that feeding SBM-treated PEC increases average daily gain and feed efficiency in Holstein bulls (Jolazadeh et al. 2015). Overall, it seems that the tannin extracted from pistachio hull have different effect on CP degradability of SBM and CM. However, further research is necessary to investigate in vivo effects of these treatments