The supplementation of livestock feed with animal protein is a present cause for public concern, and plant protein shortages have become increasingly prominent in China. This conflict may be resolved by fully utilizing currently available sources of plant protein. We estimated the rumen degradability and the small intestinal digestibility of the amino acids (AA) in rapeseed meal (RSM), soybean meal (SBM), sunflower seed meal (SFM) and sesame meal (SSM) using the mobile nylon bag method to determine the absorbable AA content of these protein supplements as a guide towards dietary formulations for the dairy industry. Overall, this study aimed to utilize protein supplements effectively to guide dietary formulations to increase milk yield and save plant protein resources. To this end, we studied four cows with a permanent rumen fistula and duodenal T-shape fistula in a 4×4 Latin square experimental design. The results showed that the total small intestine absorbable amino acids and small intestine absorbable essential amino acids were higher in the SBM (26.34% and 13.11% dry matter [DM], respectively) than in the SFM (13.97% and 6.89% DM, respectively). The small intestine absorbable Lys contents of the SFM, SSM, RSM and SBM were 0.86%, 0.88%, 1.43%, and 2.12% (DM basis), respectively, and the absorbable Met contents of these meals were 0.28%, 1.03%, 0.52%, and 0.47% (DM basis), respectively. Among the examined food sources, the milk protein score of the SBM (0.181) was highest followed by those of the RSM (0.136), SSM (0.108) and SFM (0.106). The absorbable amino acid contents of the protein supplements accurately reflected protein availability, which is an important indicator of the balance of feed formulation. Therefore, a database detailing the absorbable AA should be established.

Four methods were adopted, including the mobile nylon bag (MNB) method, modified three-step in vitro (MTS) method, original three-step in vitro (OTS) method, and acid detergent insoluble nitrogen (ADIN) estimating method, to evaluate the intestinal digestibility of rumen undegradable protein (DRUP) of 10 types of concentrates and 7 types of roughages. After correlation analysis to determine the DRUP values using the MNB, MTS, OTS, and ADIN methods, the study aimed to find out appropriate methods to replace the MNB method due to its disadvantages such as high price, long time period, and use of a duodenal T-fistula. Three dairy cows with a permanent ruminal fistula and duodenal T-fistula were used in a single-factor experimental design. The results showed that the determined DRUP values using the MNB method for soybean meal, cottonseed meal, rapeseed meal, sunflower meal, corn germ meal, corn, rice bran, barley, wheat bran, corn fiber feed, Alfalfa (Zhao dong), Alfalfa (Long mu 801), Alfalfa (Long mu 803), grass (North), Grass (Inner Mongolia), corn silage and corn straw were 98.13%, 87.37%, 88.47%, 82.60%, 75.40%, 93.23%, 69.27%, 91.27%, 72.37%, 79.03%, 66.72%, 68.64%, 73.57%, 50.47%, 51.52%, 54.05%, and 43.84%, respectively. The coefficient of determination (R2 = 0.964) of the results between the MTS method and the MNB method was higher than that (R2 = 0.942) between the OTS method and the MNB method. The coefficient of determination of the DRUP values of the concentrates among the in vitro method (including the MTS and OTS methods) and the MNB method was higher than that of the roughage. There was a weak correlation between the determined DRUP values in concentrates obtained from the ADIN method and those from the MNB method, and there was a significant correlation (p<0.01) between the determined DRUP values of the roughage obtained from the MNB method and those obtained from ADIN method. The DRUP values were significantly correlated with the nutritional ingredients of the feeds. The regression equation was DRUP =100.5566+0.4169CP − 0.4344SP − 0.7102NDF − 0.7950EE (R2 = 0.8668, p<0.01; CP, crude protein; SP, soluble protein; NDF, neutral detergent fiber; EE, ether extract). It was concluded that both the MTS method and the OTS may suitable to replace the MNB method for determining the DRUP values and the former method was more effective. Only the ADIN method could be used to predict the values of the roughages but conventional nutritional ingredients were available for all of the samples’ DRUP.

The objective of this trial was to examine the effect of applying sodium dehydroacetate on the fermentation of blue-grass silage. Whole plant blue-grass was ensiled in laboratory bags after treated with sodium dehydroacetate at three rates, 0.05% of fresh weight (SD1), 0.1% of fresh weight (SD2), and 0.2% of fresh weight (SD3), LuproMix NC as a positive control (0.35% of fresh weight), or no additive (untreated). The each SD treatment had lower the fi nal pH than the untreated (P<0.05), but the difference was not signifi cant compared with positive control (P>0.05). All the three SD treatments had lower ammonia nitrogen (as % total nitrogen) than the untreated (P<0.05), and the signifi cant differences in ammonia nitrogen between SD3 treatment and LuproMix treatment were observed (P<0.05). Lactic acid bacteria count (cfu/g) after ensiling were unaffected by application rates of SD, but yeast/mold counts were lower for SD treatments than both controls. The SD3 treatment had the greatest the lactic acid concentration and ratio of lactic acid:acetic acid, while LuproMix had the lowest the lactic acid concentration and the ratio. Except for SD3, there were no differences in the lactic acid concentration among all the treatments. Thus, it is concluded that blue-grass silage quality can be improved by using SD3 as a antifungal additive to reduce the growth of detrimental bacteria.

An in vitro fermentation was conducted to determine the effects of hainanmycin on protein degradation and populations of ammonia-producing bacteria. The substrates (DM basis) for in vitro fermentation consisted of alfalfa hay (31.7%), Chinese wild rye grass hay (28.3%), ground corn grain (24.5%), soybean meal (15.5%) with a forage: concentrate of 60:40. Treatments were the control (no additive) and hainanmycin supplemented at 0.1 (H0.1), 1 (H1), 10 (H10), and 100 mg/kg (H100) of the substrates. After 24 h of fermentation, the highest addition level of hainanmycin decreased total VFA concentration and increased the final pH. The high addition level of hainanmycin (H1, H10, and H100) reduced (p<0.05) branched-chain VFA concentration, the molar proportion of acetate and butyrate, and ratio of acetate to propionate; and increased the molar proportion of propionate, except that for H1 the in molar proportion of acetate and isobutyrate was not changed (p>0.05). After 24 h of fermentation, H10 and H100 increased (p<0.05) concentrations of peptide nitrogen and AA nitrogen and proteinase activity, and decreased (p<0.05) NH3-N concentration and deaminase activity compared with control. Peptidase activitives were not affected by hainanmycin. Hainanmycin supplementation only inhibited the growth of Butyrivibrio fibrisolvens, which is one of the species of low deaminative activity. Hainanmycin supplementation also decreased (p<0.05) relative population sizes of hyper-ammonia-producing species, except for H0.1 on Clostridium aminophilum. It was concluded that dietary supplementation with hainanmycin could improve ruminal fermentation and modify protein degradation by changing population size of ammonia-producing bacteria in vitro; and the addition level of 10 mg/kg appeared to achieve the best results.