Digestion of feed amino acids in the rumen and intestine of steers measured using a mobile nylon bag technique

Nutritive value and ruminal degradation of seven Chinese herbs as forage for Tan sheep

Tan sheep is an indigenous ovine breed of China known for its high meat quality and pleasing taste. Seven herbs of traditional Chinese medicine, namely, Ephedra sinica, Glycyrrhiza uralensis, Caragana korshinskii, Allium mongolicum, Thymus vulgaris, Astragalus membranaceus, and Lespedeza bicolor are commonly grazed by Tan sheep. It has been widely believed that these herbs are of high nutritive value, which may significantly contribute to the high meat quality and distinct flavor of Tan sheep. However, the nutritive values of these herbs have not been evaluated to date. In this study, samples of the seven herbs were collected from the steppe of Yanchi County of Ningxia Autonomous Region of China. The dry matter (DM), crude protein (CP), ether extract (EE), ash (Ash), calcium (Ca), phosphorus (P), neutral detergent fiber (NDF), and acid detergent fiber (ADF) of these herbs were measured using locally cultivated alfalfa as the standard forage. Digestion of the dry matter, neutral detergent fiber, acid detergent fiber, and crude protein in the rumen of Tan sheep was examined using the nylon bag method, in order to evaluate their feeding nutritional value. Our results show that all the seven herbs meet the nutritional needs of ruminants based on the standard forage alfalfa. However, Ephedra, Glycyrrhiza, Caragana, Allium, Astragalus, and Lespedeza have higher nutritive value than Thymus (P < 0.05). According to the ruminal degradation rates of dry matter, neutral detergent fiber, acid detergent fiber, and crude protein, the nutritive value of Caragana, Allium, and Lespedeza is higher than that of Ephedra, Glycyrrhiza, Astragalus, and Thymus (P < 0.05). The overall nutritive value of Allium is the highest among the seven herbs and therefore Allium is recommended to better meet the nutritional needs of Tan sheep.

Assessing availability of amino acids from various feedstuffs in dairy cattle using a stable isotope-based approach

Nitrogen efficiency in dairy cows can be improved by more precisely supplying essential amino acids (EAA) relative to animal needs, which requires accurate estimates of the availability of individual EAA from feedstuffs. The objective of this study was to determine EAA availability for 7 feed ingredients. Seven heifers (258 ± 28 kg BW) were randomly chosen and assigned to 8 treatment sequences in a 7 × 8 incomplete Latin square design. Treatments were a basal diet (BD), and 10% (on a dry matter basis) of BD replaced by corn silage (CS), grass hay (GH), alfalfa hay (AH), dried distillers grain (DDGS), soybean hulls (SH), wet brewers grain (BG), or corn grain (CG). Total plasma AA entry rates were estimated for each EAA within each diet by fitting a 4-pool dynamic model to observed plasma, ¹³C AA enrichment resulting from a 2-h constant infusion of a ¹³C algal AA mixture. Individual EAA availability from each test ingredient was determined by regression of entry rates for that AA on crude protein intake for each ingredient. The derived plasma total EAA entry rates for corn silage, grass hay, alfalfa hay, dried distillers grain, soyhulls, brewers grain, and corn grain were 30.6 ± 3.4, 27.4 ± 3.2, 31.3 ± 3.4, 37.2 ± 3.2, 26.4 ± 3.2, 37.8 ± 3.2, and 33.5 ± 3.2% (±standard error) of EAA from each ingredient, respectively. Using the previous estimate of 8.27% EAA utilization by splanchnic tissues during first pass, total rumen-undegradable protein EAA absorbed from the gut lumen was 33.4, 29.9, 34.1, 40.6, 28.8, 41.2, and 36.5% of the EAA in each ingredient respectively.

Effects of different dietary ratio of metabolizable glucose and metabolizable protein on growth performance, rumen fermentation, blood biochemical indices and ruminal microbiota of 8 to 10-month-old dairy heifers

Objective

The aim of this experiment was to evaluate the effects of different dietary ratio of metabolizable glucose (MG) to metabolizable protein (MP) on growth performance, blood metabolites, rumen fermentation parameters and the ruminal microbial community of 8 to 10-month-old heifers.

Methods

A total of 24 Holstein heifers weighing an average of 282.90 kg (8 month of age) were randomly assigned to four groups of six. The heifers were fed one of four diets of different dietary MG/MP (0.97, 1.07, 1.13, and 1.26).

Results

The results showed that the ratio of MG/MP affected the growth performance, blood metabolites, rumen fermentation parameters and the ruminal microbial community of heifers. The average daily gain of heifers was enhanced by increasing the ratio of MG/MP (p<0.05). The concentration of blood urea nitrogen, cholesterol, and low density lipoprotein cholesterol as well as the concentration of total volatile fatty acid in the rumen fluid of heifers decreased with the improvement in the ratio of dietary MG/MP (p<0.05). However, the relative amount of Ruminococcus albus and Butyrivibrio fibrisolvens in the rumen of heifers was increased significantly (p<0.05) when the dietary MG/MP increased. At the same time, with the improvement in dietary MG/MP, the amount of Fibrobacter succinogenes increased (p = 0.08).

Conclusion

A diet with an optimal ratio (1.13) of MG/MP was beneficial for the improvement of growth, rumen fermentation, dietary protein and energy utilization of 8 to 10-month-old dairy heifers in this experiment.

How Integrated Management Strategies Promote Protein Quality of Cotton Embryos: High Levels of Soil Available N, N Assimilation and Protein Accumulation Rate

Cottonseed is widely used as a source of ruminant feed and for industrial purposes. Therefore, there is a tremendous need to improve the nutritional value of cotton embryos. In this study, a conventional management (CM) and two integrated cotton management strategies (IMS1, IMS2) were performed at two soil fertility levels to study the relationships among soil N, N assimilation, embryonic protein accumulation and protein quality. The levels of proteins, essential amino acids, and semi-essential amino acids, especially those of glutamate, lysine, and methionine, were higher in IMS1 and IMS2 embryos than in CM embryos. These changes were significantly positively correlated with the soil-available N content, glutamine synthetase activity and peak value of protein accumulation rate and were negatively correlated with the free amino acid level. These results illustrated that integrated management strategies, especially the rates and timing of N application, raise the level of soil available N, which is beneficial for N assimilation in developing cotton embryos. The protein content was limited by the rate of protein accumulation rather than by the free amino acid content. The combination of target yield fertilization, a growth-driven N application schedule, a high plant density and the seedling raising with bio-organic fertilizer can substantially improve protein quality in cotton embryos, especially at a soil with low soil organic matter and total nitrogen.

Duodenum has the greatest potential to absorb soluble non-ammonia nitrogen in the nonmesenteric gastrointestinal tissues of dairy cows

In cattle, dietary protein is gradually degraded into peptide-bound amino acids (PBAAs), free amino acids (FAAs), and ultimately into ammonia by the rumen microbes. Both PBAA and FAA are milk protein precursors, and the rumen and small intestines are the main sites where such precursors are produced and absorbed. This work was designed to investigate the expression of the peptide transporter PepT1 and the AA transporters ASCT2, y(+)LAT1, and ATB(0,+), and the concentrations of PBAA, FAA, and soluble protein in the rumen, omasum, and duodenum of dairy cows. Tissues and digesta were collected from six healthy Chinese Holstein dairy cows immediately after the animals were slaughtered. The expression of transporters was analyzed by real-time quantitative polymerase chain reaction (PCR). The FAA concentration was assessed using an amino acid (AA) analyzer, PBAA concentration by quantification of AA before and after acid-hydrolysis by 6 mol/L HCl, and soluble protein concentration by quantification of the bicinchoninic acid content. The results showed that the relative abundance of mRNA of the transporters and the soluble non-ammonia nitrogen (SNAN) concentration of each fraction were greater in the duodenum than in the rumen or omasum. These results indicate that the duodenum is the predominant location within the nonmesenteric digestive tract for producing milk protein precursors. In addition, PBAA was the largest component of SNAN in the digesta from the rumen, omasum, and duodenum. In conclusion, the duodenum has the greatest concentrations of SNAN and PBAA, and the greatest potential for absorption of SNAN in the form of PBAA in the nonmesenteric gastrointestinal tissues of dairy cows.

Rumen Degradability and Small Intestinal Digestibility of the Amino Acids in Four Protein Supplements

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.

Ruminal degradability and intestinal digestibility of individual amino acids in mixed diets with different crude protein levels measured by the modified in vitro three-step and mobile nylon bag technique

The ruminal degradability and intestinal digestibility of dry matter (DM), crude protein (CP) and amino acids (AA) in three total mixed rations with different CP levels were estimated using the modified in vitro three-step procedure (TSP) and mobile nylon bag (MNB) technique on growing lambs. The ruminal effective degradability of DM and CP did not respond with increasing dietary CP level. However, the intestinal digestibility of DM was significantly increased with increasing dietary CP level estimated by TSP (P < 0.05) or MNB method (P < 0.01). Intestinal digestibility coefficients of CP determined by TSP were lower than those of the MNB method. Histidine was extensively degraded by rumen micro-organisms, while tyrosine was the most anti-degradable AA among the samples. The ruminal AA degradability exhibited no significant differences except for threonine, tryptophan, alanine, aspartic acid and proline for the three diets. Similarly, only a few AAs (i.e. histidine, methionine, tryptophan, aspartic acid and cysteine in TSP; histidine, tryptophan, aspartic acid and serine in MNB) had significant differences in their intestinal digestibility; in addition, values of MNB were lower than that of the TSP method, indicating that intestinal digestibility of DM seems to be overestimated in TSP, while that of CP might be overestimated in the MNB method.

Measurement of the Intestinal Digestibility of Rumen Undegraded Protein Using Different Methods and Correlation Analysis

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.

Rumen Degradability and Post-ruminal Digestion of Dry Matter, Nitrogen and Amino Acids of Three Protein Supplements

This study evaluated the in situ ruminal degradability, and subsequent small intestinal digestibility (SID) of dry matter, crude protein (CP), and amino acids (AA) of cottonseed meal (CSM), sunflower seed meal (SFSM) and distillers dried grains with solubles (DDGS) by using the modified three-step in vitro procedure. The ruminal degradability and subsequent SID of AA in rumen-undegradable protein (RUP-AA) varied among three protein supplements. The result show that the effective degradability of DM for SFSM, CSM, and DDGS was 60.8%, 56.4%, and 41.0% and their ruminal fermentable organic matter was 60.0%, 55.9%, and 39.9%, respectively. The ruminal degradable protein (RDP) content in CP for SFSM, CSM, and DDGS was 68.3%, 39.0%, and 32.9%, respectively, at the ruminal solid passage rate of 1.84%/h. The SFSM is a good source of RDP for rumen micro-organisms; however, the SID of RUP of SFSM was lower. The DDGS and CSM are good sources of RUP for lambs to digest in the small intestine to complement ruminal microbial AA of growing lambs. Individual RUP-AA from each protein source was selectively removed by the rumen micro-organisms, especially for Trp, Arg, His, and Lys (p<0.01). The SID of individual RUP-AA was different within specific RUP origin (p<0.01). Limiting amino acid was Leu for RUP of CSM and Lys for both RUP of SFSM and DDGS, respectively. Therefore, different protein supplements with specific limitations should be selected and combined carefully in growing lambs ration to optimize AA balance.

Intestinal digestibility of amino acids in rumen undegradable protein estimated using a precision-fed cecectomized rooster bioassay: I. Soybean meal and SoyPlus

The objectives of this experiment were to measure intestinal digestibility of AA in rumen undegradable protein (RUP-AA) in soybean meal (SBM) and expeller SBM (SoyPlus, West Central, Ralston, IA; SP) and to determine if these feeds contain a constant protein fraction that is undegradable in the rumen and indigestible in the small intestine, as assumed in the French Institut National de la Recherche Agronomique (Paris, France) and Scandinavian AAT-PBV (AAT = AA absorbed from small intestine; PBV = protein balance in the rumen) models. Three samples of SBM and 3 samples of SP were obtained from the Feed Analysis Consortium Inc. (Savoy, IL). To obtain the RUP fraction, samples were ruminally incubated in situ for 16 h in 4 lactating cows, and the collected rumen undegraded residues (RUR) were pooled by sample. Subsamples of the intact feeds and RUR were crop intubated to 4 cecectomized roosters, and total excreta were collected for 48 h. Intact feeds, RUR, and excreta were analyzed for AA. Basal endogenous AA loss estimates were obtained from fasted birds and were used to calculate standardized digestibility of AA in the intact feeds and RUP-AA. Indigestibility coefficients of the intact feeds were calculated as (100 - % standardized AA digestibility), and indigestibility of the RUR was calculated as [(100 - % ruminal degradation of AA) x [(100 - % standardized RUP-AA digestibility)]/100]. Results indicated that standardized digestibility of feed-AA was similar to standardized digestibility of RUP-AA for SBM and SP samples and that standardized digestibility of individual AA differed within samples. Standardized feed-AA and RUP-AA digestibility values were lowest for Lys and Cys and highest for Trp and Met. Results also indicated that SBM and SP did not contain a constant protein fraction that was both undegradable in the rumen and indigestible in the small intestine. Indigestibility values of RUR were lower than in intact feeds, suggesting that SBM and SP contain a protein fraction that is indigestible in the intestine but partly degradable in the rumen, digestible in the intestine after ruminal incubation, or both.

Rumen and post abomasal disappearance of amino acids and some nutrients of barley grain treated with sodium hydroxide, formaldehyde or urea in lactating cows

Four rumen and duodenum cannulated, Holstein lactating cows were used in a change-over design to determine the effects of NaOH, Formaldehyde or Urea treated barley on disappearance of Dry Matter (DM), Crude Protein (CP), Amino Acids (AA), NDF, ADF, hemicelluloses and starch in rumen, Post Abomasal Tract (PAT) and total tract by mobile nylon bag technique. Experimental treatments were coarse milled barley, barley treated with 3.5% NaOH, barley treated with 0.4% formaldehyde and barley treated with 3.5% urea that all chemical treated barley milled coarse before feeding. NaOH Treatment reduced concentrations of Lysine and Cystine in the barley grain. All chemical treatments decreased rumen disappearances of barley CP but only NaOH and Formaldehyde treatments also decrease total AA and some of the AA disappearances in the rumen. All chemical treatments increased DM, OM, CP, starch, NDF, ADF and hemicellulose disappearance of barley in the PAT. But only NaOH and Formaldehyde treatments increased total AA and most of AA disappearances in the PAT. Effect of chemical treatments on increase of disappearance of starch, Met and Gly in the total tract was significant (p < 0.05). Rumen disappearance of TAA was lower than CP but PAT disappearance of TAA was more than CP and finally total tract disappearance of TAA was more than CP. Individual AA in barley disappeared at different rates in the rumen and PAT. Consequently, the proportion of digesta CP and AA entering the intestine must be considered.