Change in amino acid composition of different protein sources after rumen incubation

Linkage of in situ ruminal degradation of crude protein with ruminal degradation of amino acids and phytate from different soybean meals in dairy cows

The objectives of this study were to determine the range in ruminal degradability of crude protein (CP) and intestinal digestibility of rumen undegradable protein in commercial soybean meal (SBM) and to investigate the range in in situ ruminal AA and phytate (InsP6) degradation and their relationship to CP degradation. An in situ study was conducted using 3 lactating Jersey cows with permanent rumen cannulas. Seventeen SBM variants from Europe, Brazil, Argentina, North America, and India were tested for ruminal CP and AA degradation, and in vitro intestinal digestibility of rumen undegradable protein. Nine variants were used to investigate the ruminal degradation of InsP6. The estimated rapidly degradable fraction (a) of CP showed an average value of 4.5% (range: 0.0%-9.0%), the slowly degradable fraction (b) averaged 95% (91%-100%), and the potential degradation was complete for all 17 SBM variants. The degradation of fraction b started after a mean lag phase of 1.7 h (1.1-2.0 h) at an average rate (c) of 10% per hour, but with a high range from 4.5% to 14% per hour. Differences in the degradation parameters induced a considerable range in CP effective degradation at a rumen passage rate of 6% per hour (CPED6) from 38% to 67%; hence, the concentration of rumen undegradable protein varied widely from 33% to 62%. The range in AA degradation between the SBM variants was high, with Ser showing the widest range, from 28% to 96%, and similar for the other AA. The regression equations showed close relationships between CP and AA degradation after 16 h of in situ incubation. However, the slopes of the linear regressions were significantly different between AA, suggesting that degradation among individual AA differs upon a change in CP degradation. The concentrations of InsP6 and myo-inositol pentakisphosphate in bag residues in the in situ study decreased constantly with longer ruminal incubation times. The ruminal degradation parameters of InsP6 ranged from 11% to 37% for fraction a, 63% to 89% for fraction b, and from 7.7% to 21% per hour for degradation rate c, with average values of 21%, 79%, and 16% per hour, respectively. The calculated InsP6 effective degradation at a rumen passage rate of 6% per hour (InsP6ED6) varied from 61% to 84% among the SBM variants. Significant correlations were detected between InsP6ED6 and CPED6 and between InsP6ED6 and chemical protein fractions A, B1, B2, B3, and C. Linear regression equations were developed to predict ruminal InsP6 degradation using CPED6 and chemical protein fractions B3 and C chosen by a stepwise selection procedure. We concluded that a high range in CP, AA, and InsP6 degradation exists among commercial SBM, suggesting that general degradability values may not be precise enough for diet formulation for dairy cows. Degradation of CP in SBM may be used to predict rumen degradation of AA and InsP6 using linear regression equations. Degradation of CP and InsP6 could also be predicted from the chemical protein fractions.

Ruminal Microbial Degradation of Individual Amino Acids from Heat-Treated Soyabean Meal and Corn Gluten Meal in Continuous Culture

Eight dual-flow continuous culture fermenters were used in three periods to study the effects of diets containing heat-treated soyabean meal (HSBM) or corn gluten meal (CGM) on ruminal microbial fermentation and the degradation of individual amino acids (AA). Treatments were a mix of non-protein nitrogen (N; urea and tryptone) that were progressively substituted (0, 33, 67 and 100%) for HSBM or CGM. Ruminal escape of AA was calculated with the slope ratio technique. Total volatile fatty acids (95.0 mM) and molar proportions (mol/100 mol) of acetate (59.3), propionate (21.8) and butyrate (10.5) were not affected by the treatments. As the level of HSBM or CGM increased, the concentration of ammonia-N and the degradation of protein decreased (p < 0.01), and the flows of nonammonia and dietary N increased (p < 0.01) quadratically. Compared with HSBM, CGM provided the highest flow (g/d) of total (20.6 vs. 18.3, p < 0.01), essential (9.04 vs. 8.25, p < 0.04) and nonessential (11.5 vs. 10.0, p < 0.01) AA, and increased linearly (p < 0.01) as the level of supplemental protein increased. Ruminal degradation of essential AA was higher (p < 0.04) than nonessential AA in CGM, but not in HSBM. Degradation of lysine was higher (p < 0.01) in both proteins, and degradation of methionine was higher in CGM. Ruminal degradation of individual AAs differ within and between protein sources and needs to be considered in precision feeding models.

In vitro techniques to replace in vivo methods for estimating amino acid supply

Expressing the protein value of a food involves measurements of several of its characteristics. Many in vivo studies have shown, that the protein degradability in the rumen varies substantially both between and within foods and therefore estimation of protein degradability in the rumen is an important task in protein evaluation. The most common method used has been the in situ (in sacco, nylon bag) method but many in vitro methods have been introduced and are based on use of either buffer solubility, chemical methods, rumen fluid or enzymes. None of these in vitro methods has proven to be of general use. In further development of in vitro methods as well as the in situ method a major problem is lack of a set of samples with a ‘true’ in vivo degradability which can be used for calibration of alternative methods. Microbial protein synthesis in the rumen has to be related to food characteristics which can be analysed easily. In vitro methods which can predict organic matter digestibility in foods are available and can be used to predict microbial protein synthesis in the rumen. Intestinal digestibility of undegraded dietary protein varies substantially both between and within foods and easy methods to estimate intestinal digestibility are therefore essential. The mobile bag method is easy to use and seems to give reliable results on most foods but requires access to duodenal cannulated animals which prevents this method from being routine. Alternative in vitro methods have been developed but further research is required for validation of these methods on a wide range of foods before they can be accepted for general use.

Digestion of feed amino acids in the rumen and small intestine of dairy cows measured with nylon-bag techniques

The disappearance of total N, non-protein-N and amino acid-N after washing, rumen incubation and intestinal passage of sugarbeet pulp, maize-gluten feed, maize feed meal, palm kernel meal, soyabean hulls, soyabean meal, grass silage, maize silage and concentrate was measured in four dairy cows using nylon-bag techniques. Disappearance of amino acid-N after washing varied between feedstuff's from 14 to 69% of feed amino acid-N, and was lower than disappearance of non-protein-N. For sugarbeet pulp, grass silage and maize silage, washing had a considerable effect on the amino acid profile. Disappearance of amino acid-N after rumen incubation was also lower than non-protein-N and varied between feedstuffs from 25 to 73% of feed amino acid-N. Rumen incubation had only a small effect on the amino acid profile of the residue after washing. Disappearance of amino acid-N in the intestine varied between feedstuffs from 70 to 99% of rumen undegraded amino acid-N, and was higher than the disappearance of non-protein-N. Intestinal incubation showed a considerable effect on the amino acid profile for all feedstuffs. It was concluded that protein that was assumed to escape rumen degradation and was absorbable in the intestine was higher in amino acids and methionine, and lower in non-amino acid-N and glutamic acid and proline compared with protein in the feedstuff.

Protein value for ruminants of a sample of whole cottonseed

The effective ruminal degradability (ED) of dry matter (DM), crude protein (CP) and amino acids, and the effective intestinal digestibility (IED) of DM and CP of a sample of whole cottonseed was measured using in situ and rumen outflow rate techniques in three wethers cannulated in the rumen and duodenum. The microbial contamination of rumen incubated residues was corrected by a continuous rumen infusion of15NH3as microbial marker and rumen solid associated bacteria as reference sample. Microbial contamination resulted in an overestimation of the undegradable fraction of DM (0·291v. 0·275;P<0·05) and CP (0·071v. 0·037;P<0·01) and a small underestimation of ED of DM (0·500v. 0·512;P=0·09) and CP (0·755v. 0·779;P=0·052). A proportion of 0·1 of the ruminal undegraded CP was of microbial origin and for essential amino acids this proportion varied from 0·042 to 0·150. Differences in ED between amino acids modified the amino acid profile, with an important reduction (0·2;P<0·01) in the proportion of lysine. Apparent intestinal digestibility of the insoluble fraction of this food, measured with the mobile nylon bag technique, showed large reductions (P<0·001) with the increase of the ruminal incubation time between 0 and 72 h: from 0·392 to 0·026 for DM and from 0·851 to 0·099 for CP. These evolutions fitted an exponential function with a previous lag. The IED was estimated either by integration of these equations and those describing the ruminal degradation and rumen outflow or by incubation through the intestines of a sample pooled to be representative of rumen flow of the undegraded food. The two methods gave similar values for both DM (0·222v. 0·203) and CP (0·659v. 0·658).

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

The disappearance of dry matter (DM), crude protein (CP), and amino acids (AA) in steers after rumen incubation and intestinal passage of alfalfa hay, barley hay, corn silage, barley grain, corn grain, wheat bran, meat meal, fish meal, cottonseed meal, and soybean meal were measured in 3 steers using a mobile nylon bag technique. Ruminal degradation of individual AA differed between feedstuffs. For barley hay and corn silage, the ruminal disappearance of total AA was higher and lower than the other feedstuffs, respectively. The intestinal digestibility of total AA in alfalfa hay was lower than the digestion of CP. The intestinal digestibility of Arg and His was higher than that of total AA in alfalfa hay, meat meal, cottonseed meal, soybean meal, barley hay, and wheat bran. In addition, the intestinal digestibility of Lys was higher than that of total AA in alfalfa hay, meat meal, cottonseed meal, soybean meal, barley hay, corn silage, and wheat bran. The intestinal disappearance of CP in most cases was higher than that of DM. The results indicated that feedstuffs with lower ruminal disappearance of DM, CP, total AA, essential AA, and nonessential AA generally had a higher intestinal disappearance, resulting in a relatively constant total tract disappearance. These results could be used to improve the current system of diet formulation in ruminants.

Amino acid profile of escaped feed protein after rumen incubation and their intestinal digestibility

The crude protein content and amino acid profile of seven feedstuffs (linseed meal, maize gluten meal, rapeseed meal, rapeseed meal protected, soybean meal, fullfat soybean extruded and sunflower meal) were determined before and after ruminal incubation for 16 h in three bulls with large rumen cannulas. The intestinal disappearance of amino acids was measured using mobile bag technique. Ruminal incubation affected amino acid profile of all experimental feedstuffs. Crude protein degradation varied from 29.3% for maize gluten meal to 86.4% for rapeseed meal. A tendency towards increased disappearance was observed for glutamic acid, histidine, lysine and proline and decreased disappearance for branched-chain amino acids. The intestinal crude protein digestibility was higher than > 80%, except rapeseed meal (66.4%) and sunflower meal (77.8%). The least digestible individual amino acids were methionine and isoleucine in rapeseed meal, histidine and methionine in rapeseed meal protected and arginine in sunflower meal. In general, the lowest amino acid digestibilities were found in feedstuffs with the highest fibre content. The feedstuffs show that they have different potential for supplying of limiting amino acids. Of particular value are the feedstuffs with low crude protein degradability in the rumen and high intestinal digestibility of amino acids.

Effects of processing method on degradation characteristics of protein and carbohydrate sources in situ

Two ruminally cannulated Holstein cows in early lactation were used to determine the effects of heat treatment and particle size on fractional degradation rates and ruminal degradabilities of DM, CP and total nonstructural carbohydrate of dry shelled corn and soybeans. A randomized complete block design with cows as blocks was used. Carbohydrate sources were cracked corn, chick cracked corn, finely ground corn, and steam-flaked corn. Protein sources were soybeans that were roasted at 144 degrees C, cracked, or ground through a 4-mm screen and raw soybeans that were cracked or ground through a 4-mm screen. Reduction in particle size increased both degradability of total nonstructural carbohydrate in the rumen. Heat treatment decreased degradability of CP and increase degradability of total nonstructural carbohydrate in the rumen for both protein and carbohydrate sources. Roasting of soybeans decreased degradability of all AA except Lys. However,reduction in particle size had a stronger effect than heat treatment on ruminal degradability of CP and AA of soybeans, but had the opposite effect on total nonstructural carbohydrate degradability from corn. Methionine, Leu, and Thr had the lowest ruminal degradability across all soybean sources, and Lys and Val were the most degradable. The AA profile of the RUP fraction of soybeans differed from that of the original feed-stuff and was affected by processing method.

Influence of moist heat treatment on ruminal and intestinal disappearance of amino acids from canola meal

Three mature Angus steers fitted with large ruminal cannulas and three Holstein steers each fitted with T-shaped cannulas in the proximal duodenum and reentrant cannulas in the terminal ileum were used to study the effect of moist heat treatment on AA digestion of canola meal in each segment of the digestive tract. Canola meal was treated with moist heat at 127 degrees C for 15 or 45 min. Degradation of AA in the rumen was estimated using small nylon bags incubated for .1, 8, 16, and 24 h in the rumen. Digestion of AA in the small and large intestines and total tract were estimated using separate sets of bags in a sequence of ruminal in situ incubation, in vitro incubation in an acid-pepsin solution, and a mobile bag technique. Heat treatment for 15 or 45 min reduced concentrations of Lys by 15.9 and 29.2% and Arg by 8.0 and 15.2%, respectively. Heat treatment for 15 or 45 min significantly reduced the degradation of AA in the rumen; the availability of AA in the small intestine increased in proportion to the decreased ruminal degradation. Digestion of AA in the large intestine was 5 percentage points higher after heat treatment for 45 min than with no heat treatment. Apparent digestion of AA in the total tract was unaffected by 15 min of heating; however, 45 min of heating reduced digestion.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino acid profile and intestinal digestibility in dairy cows of rumen-undegradable protein from various feedstuffs

Three lactating cows fitted with rumen cannulas and three cows fitted with proximal duodenal cannulas were used to determine the effect of in situ rumen degradation on the AA profile of rumen-undegraded protein of 12 feedstuffs. Intestinal digestibility of rumen-undegraded protein was determined using the mobile bag technique. The absorbable AA profile of rumen-undegraded protein for each feedstuff was compared with profiles of the original feedstuff and the rumen-exposed undegraded protein. Branched-chain AA in particular seemed to be rather resistant to degradation in the rumen, as was Phe. Lysine concentrations decreased in the undegraded protein fraction in 9 of 12 feedstuffs; the degradation of Met depended on the feedstuff. The absorbable AA profiles of undegraded protein, in general, closely reflected the AA profiles of the rumen-exposed residues, which suggests that rumen degradation had a greater influence than postruminal digestion on the postruminal provision of specific absorbable AA. Intestinal digestibility of undegraded protein varied from 37.8% for Eragrostis curvula hay to 98% for soybean meal; the constant digestibility factor used by most protein systems should be reconsidered.