Nitrogen in vivo digestibility and in situ degradability data for estimation of lower tract N digestibility with or without correction for microbial contamination

In situ degradability and in vivo (by difference) digestibility trials were conducted to estimate lower tract residual N digestibility (LTRND) of five protein supplements. Efforts were also made to improve the in situ method of measuring protein degradability. For in situ degradability trials, soybean meal (SBM), corn gluten meal (CGM), cotton seed cake (CSC), wheat bran (WB) and corn gluten feed (CGF) were weighed into Dacron bags and incubated in the rumen of three cannulated Chios ewes. SBM, CGF and WB were degraded significantly, while CGM and CSC were least degraded. Microbial contamination (MC) resulted in a 5.3–28.3% artificially decrease in effective ruminal protein degradation of supplements. Total tract digestibility was measured using five rams in an in vivo, by difference, trial using a 5 × 5 Latin-square design. SBM had higher CP digestibility compared to WB, CGF and CSC, and higher N free extract (NFE) digestibility compared to the other feeds. CGM showed higher CP digestibility compared to WB, CGF or CSC, while CGF had higher organic matter (OM) and crude fibre (CF) digestibility compared to WB. CSC was the protein source with the lowest digestibility of OM, CP and NFE in comparison with the other feeds. LTRND was predicted as 0.928, 0.806, 0.227, 0.540, and 0.498 for SBM, CGM, CSC, WB, and CGF, respectively, or 0.931, 0.803, 0.147, 0.364, and 0.316 when the correction for MC was applied. Lower tract N digestibility could be predicted via a combination of in situ degradability and in vivo apparent digestibility data. This approach yields significant data regarding LTRND estimation of protein supplements, while diminishing animal suffering by avoiding small intestinal fistulation.     

Ruminal degradability and in vitro intestinal digestibility of sunflower meal and in vitro digestibility of olive by-products supplemented with urea or sunflower meal: Comparison between goats and sheep

The in vitro digestibility of two-stage dried olive cake (TSDOC) and olive leaves (OL) unsupplemented or supplemented with increasing amounts of urea (U) or sunflower meal (SM) (0, 1.5, 2 and 2.5 g/100 g organic matter (OM) of the by-product) was determined. Chemical and amino acid composition, in vitro digestibility, in situ rumen degradability of crude protein and amino acids, and in situ–in vitro intestinal digestibility of SM CP and amino acids was determined. The in sacco rumen degradability and in vitro intestinal availability of CP and individual amino acids were also determined. Results obtained in Granadina goats and Segureña wethers were compared. SM provides arginine, glycine and aspartic and glutamic acids. The addition of increasing amounts of U or SM improved (P<0.001) the IVDMD and IVOMD of both TSDOC and OL. There was no effect (P>0.05) of the rumen inoculum origin on in vitro TSDOC digestibility. In contrast, values for OL were higher (P<0.001) for goats versus sheep. In sacco ruminal CP degradability of SM was relatively high, and similar in sheep and goats (ED=0.78 and 0.75 for sheep and goats). Individual amino acid ruminal degradability had different values, being lowest for methionine, leucine, proline, tyrosine and cysteine. Values obtained for individual amino acids differed from those of CP. Apparent intestinal digestibility of undegraded protein (AIDUP) of SM was high (0.86 and 0.98, respectively, for sheep and goats). The intestinally absorbable protein (IADP) was low (18.9 and 24.0 for sheep and goats, respectively). Results indicate that goats and sheep have the same capacity for TSDOC digestion, but goats showed a better capacity than sheep for OL utilisation. Although the amino acids supply to the intestine from SM is not important it could be a good supplement for low degradable protein feedstuffs such as TSDOC and OL.     

Influence of feeding sunflower seed and meal protected against ruminal fermentation on ruminal fermentation,bacterial composition and in situ degradability in sheep

ABSTRACT

The effects of treating sunflower seed (SS) and meal (SM), as well as of a mixture of both feeds (SSM; 45:55) with a solution of malic acid (1 M; 400 ml/kg feed) and heating for protection against ruminal degradation were studied. Four rumen-fistulated sheep were fed two mixed diets composed of oat hay and concentrate (40:60) and differing only in the concentrate, that contained either a mixture of untreated SS and SM (control diet) or treated SS and SM (MAH diet). A crossover design with two 24-d experimental periods was used, and each period included 10 d of diet adaptation, 9 d for in situ incubations of SS, SM and SSM, and 5 d for measuring ruminal fermentation characteristics and rumen emptying. From day 6 onwards a solution of (¹⁵NH₄)₂SO₄ was continuously infused into the rumen of each sheep to label ruminal bacteria. Feeding the MAH diet did not affect either ruminal pH or concentrations of total volatile fatty acids and NH₃-N, but decreased (p ≤ 0.01) the molar proportions of acetate and propionate and increased those of butyrate (p< 0.001). Organic matter and lipid contents of ruminal bacteria were lower whereas both N content and ¹⁵N enrichment were greater (p ≤ 0.05) in MAH-fed sheep. The in situ effective degradability (ED) of different fractions of SS, SM and SSM were calculated from the ruminal rates of particle comminution and passage, and values were corrected for microbial contamination. The MAH treatment decreased the ED of most fractions for all feeds and increased the supply of by-pass crude protein (CP) by 19.1% and 120% for SS and SM, respectively, and that of fat by 34% for SS. The MAH treatment also increased the in vitro intestinal digestibility of the by-pass CP for both SS (from 60.1% to 75.4%) and SM (from 83.2% to 91.0%). The simultaneous heating of both feeds (SSM) reinforced the protective effect of the MAH treatment and increased the by-pass CP without altering its intestinal digestibility, increasing the intestinally digested CP content by 16.8% compared with the value estimated from the results obtained for MAH-treated SS and SM incubated independently. These results indicate that the MAH treatment was effective to protect sunflower protein against rumen degradation and increased its intestinal digestibility.     

A simplified management of the in situ evaluation of feedstuffs in ruminants: Application to the study of the digestive availability of protein and amino acids corrected for the ruminal microbial contamination

The ruminal effective degradability (RED) and intestinal effective digestibility (IED) for dry matter, crude protein (CP) and amino acids (AA) were estimated by a simplified in situ method using pooled samples from rumen-incubated residues, which represented the ruminal outflow of undegraded feed. The effect of microbial contamination in the rumen was corrected using ¹⁵N infusion techniques. Studies were carried out for soybean meal (SBM), barley grain (BG) and lucerne hay (LH) in three wethers cannulated in the rumen and the duodenum. Uncorrected values of RED for CP obtained either by mathematical integration or our simplified method were similar in all feeds. Microbial N in the pooled samples of SBM, BG and LH were 2%, 11% and 24% of total N, respectively. However, intestinal incubation eliminated this microbial charge by 100%, 99% and 88%, respectively. With microbial corrections, RED showed an increase, and IED showed a decrease, except for SBM. With this correction, intestinal digested CP was reduced by 2% in SBM, 13% in BG and 34% in LH. Corrected IED of AA was relatively similar in SBM (97–99%). However, large variations were observed in BG (74–93%) and in LH (10–88%). Digestion in the rumen and intestine changed the essential AA pattern. Overall, our results support that AA digestion is affected by the characteristics of their radicals and their contents in plant cell wall proteins. The accurate estimation of feed metabolisable AA or protein requires effective measures that are corrected by ruminal microbial contamination. The proposed in situ method largely simplifies these tasks and allows a more complete and less expensive feed evaluation.     

Effect of different drying procedures on the nutritive value of olive (Olea europaea var. europaea) leaves for ruminants

Fresh, freeze-, air- and oven-dried at 60 °C and 100 °C olive leaves (OL) were studied in order to determine the effect of different drying procedures on OL chemical composition, in vitro digestibility, ruminal degradability, and intestinal digestibility. The drying procedure affected all the parameters measured except for gross energy (GE; P=0.194). Protein-bound condensed tannins (CT) decreased (P=0.001) with freeze-, air- and 60 °C drying (from 1.25 up to 0.82 g/kg dry matter, DM). Total CT were only decreased (P=0.001) by drying at 60 °C (from 10.0 to 6.24 g/kg DM). The in vitro crude protein (CP) digestibility increased (P<0.001) with drying except for oven-drying at 100 °C up to 58%. Values for CP digestibility found in freeze- and air-dried OL were not different (P>0.05). No differences (P>0.05) were observed between CP digestibility in air- and oven-dried at 60 °C OL. Effective degradability of DM and CP increased from 0.53 to 0.62 (P=0.005) and from 0.46 to 0.64 (P=0.002), respectively after treatment. The apparent intestinal digestibility of undegraded CP in the rumen was only affected (P=0.046) by oven-drying, which increased it from 0.33 to 0.39. As air-drying did not have detrimental effects on the OL nutritive value it could be an appropriate, simple and low-cost procedure for olive-leaves preservation.     

Effects of non-enzymatic browning reaction intensity on in vitro ruminal protein degradation and intestinal protein digestion of soybean and cottonseed meals

The effects of non-enzymatic browning reactions on in vitro ruminal gas production and in vitro ruminal and intestinal crude protein (CP) digestibilities of soybean (SBM) and cottonseed (CSM) meals were investigated. Non-enzymatically browned SBM and CSM samples were prepared using two xylose levels (10 or 30 g/kg dry matter), two heating lengths (30 or 60 min) and two heating temperatures (120 or 150 °C) for a total of one untreated (commercially solvent-extracted, Control) and eight treated samples for each protein source. The control SBM had higher (P<0.001) in vitro ruminal CP degradability values than the treated samples. Intestinal protein digestibility and total-tract CP digestibility of CSM and SBM were affected by the treatment (P<0.01). The results of the study indicate that not only ruminal CP degradability is reduced but also intestinal and total-tract CP digestibilities may be lowered depending on protein source and intensity of the non-enzymatic browning reaction.     

Effects of stage of harvest on the protein value of fresh lucerne for ruminants

The ruminal degradation of dry matter (DM) and crude protein (CP) and the intestinal availability of CP of four fresh lucerne (Medicago sativa L.) samples, corresponding to a 3rd growing cycle and harvested at 2-week intervals, were determined. Rumen degradability, measured by the nylon bag technique, and rumen outflow rates were determined on three rumen-cannulated wethers. Intestinal digestibility was determined by the mobile bag technique on three duodenal fistulated wethers. Both groups of animals were fed a 2:1 lucerne hay to concentrate diet at an intake level of 40 g DM x kg(-1) BW0.75. The effective degradability (ED) of DM decreased with maturity in linear and quadratic form, as a consequence of a decrease in the soluble fraction and a similar increase in the undegradable materials. The resultant values were 0.795, 0.661, 0.600, and 0.576 for harvests at 2, 4, 6, and 8 weeks. The ED of CP showed the same trend. However, the variations (values of 0.896, 0.832, 0.791, and 0.817, respectively), were moderate and mainly due to the reduction of the proportion of soluble CP. The intestinal digestibility of CP of all samples showed a downward trend with the increase in the ruminal incubation time, as modelled according to a logistic function. The undegraded CP digested in the gut (Di) and therefore the effective intestinal digestibility (EID) were derived from this function according to the rumen outflow of undegraded CP. The effects of maturity on the mean values of Di, expressed as a proportion of the original CP content, were the opposite of those recorded for the ED of CP. These values were 0.067, 0.102, 0.115, and 0.089 for samples harvested at 2, 4, 6, and 8 weeks, respectively. Nevertheless, when Di was expressed as g CP x kg(-1) DM, these values (18.0, 17.4, 17.1, and 14.3, respectively) decreased in linear form. The same trend was observed for EID values, which represent 0.641, 0.609, 0.549, and 0.488, respectively. The change of the digestion site produced by the reduction of ED of CP was also associated with an increase in the undigested CP (values of 0.037, 0.066, 0.094, and 0.094, at the four harvesting times).     

Influence of physical treatment of rape expeller,wheat, maize and maize gluten feed on degradability in the rumen and on the enzymatic in vitro digestibility of non degraded crude protein

The influence of physical treatment‐expansion and flaking‐on crude proteins degradability in the rumen was studied in maize, maize‐gluten feed, rape extracted meal and in the expanded one at 120°C and 150°C, rape cake, wheat and flaked wheat by in sacco method. The enzymatic digestibility of crude protein in the rumen undegraded residues of the above mentioned feeds was determined by an enzymatically in vitro method.

The treatment of feed decreased significantly the original solubility and theoretical degradability of crude proteins, and the amount of undegraded crude proteins was increased. Positive influence on the amount of enzymatically digested crude protein was determined in rape expanded at 120 °C and 150 °C (60, 61 and/or 68%). Flaking of wheat had a similar effect. Enzymatic digestibility at undegraded rests where increased by 8–10% after the heat treatment and it remained almost unchanged in expanded maize‐gluten feed.     

Rumen degradability and intestinal digestibility of brewers' grains as affected by origin and heat treatment and of barley rootlets

The rumen degradability and intestinal digestibility of dry matter (DM) and nitrogen (N) of three samples of brewers' grains (BG) and three of barley rootlets (BR) were determined. Rumen degradability was determined by the nylon bag technique in three rumen fistulated wethers. Intestinal digestibility was determined by the mobile nylon bag technique in two duodenal fistulated wethers. N content ranged from 41.2 to 46.4 g/kg DM for BG, and from 42.8 to 53.7 g/kg DM for BR. N effective degradability (NED), calculated for rumen outflow rates determined in each sheep, ranged from 57.2% to 70.9% for BG and from 79.0% to 84.0% for BR. N intestinal digestibility (NID) determined on 8 h-rumen incubated residues, ranged from 84.9% to 89.8% for BG and from 67.3% to 81.3% for BR. Lower rumen degradability was partially compensated by higher intestinal digestibility, resulting in a smaller variation in the estimated amount of digestible bypass N, which ranged from 24.7% to 36.7% for BG and from 10.8% to 17.1% for BR. One BG sample was selected to study the effects of heat treatment (HT) on its chemical composition, rumen degradability and intestinal digestibility. The BG sample was either freeze-dried (UBG) or dried at 50°C (50BG), 100°C (100BG), 135°C (135BG) and 175°C (175BG). Total N content was not affected by HT, but the acid–detergent insoluble N (expressed as percentage of total N content) increased from 13.7% to 54.1%. HT reduced the NED (from 76.5% to 25.6%) and, as a consequence, the supply of undegraded N to the duodenum was increased by 1.2, 1.8, 2.4 and 3.2 times for 50BG, 100BG, 135BG and 175BG, respectively. Drying at 50°C and 100°C had no adverse effects on the NID determined on 8 h-rumen incubation residues (mean value of 84.3%), but drying at 135 and 175°C decreased it to values of 80.1 and 51.6%, respectively. As a consequence, the estimated amount of digestible bypass N was increased by 1.2, 1.8, 2.3 and 1.9 times when drying at 50°C, 100°C, 135°C and 175°C, respectively.     

In situ evaluation of the ruminal and intestinal degradability of extruded whole horse beans

Four rumen and proximal duodenum fistulated non-lactating Holstein cows were used to determine the effect of extrusion at 120 degrees C of whole horse beans (Vicia faba cv Talo) on in vitro nitrogen (N) solubility and in situ degradation of dry matter (DM) and crude protein (CP) in the rumen and intestine. Cows were fed a ration of 30% whole horse beans (WHB) and 70% Italian rye-grass hay. The degradation of DM and CP was estimated using nylon bags suspended in the rumen for 2, 4, 7, 16, 24 and 48 h; the effective ruminal degradability of DM and CP was evaluated assuming a ruminal outflow rate of 0.06/h. Bags incubated in the rumen for 16 h were introduced into the small intestine through the duodenal cannula and subsequently recovered in the feces. Extrusion of WHB reduced N-solubility in buffer solution (21.1 vs 74.9%). Processing diminished the effective rumen degradability of DM (74.6 vs 80.4%) and CP (70.2 vs 89.2%). Meanwhile, the amounts of DM and CP digested in the intestine increased: 9.6 vs 1.4% and 25.2 vs 3.0% respectively. Therefore, feeds containing extruded WHB increase the availability of dietary proteins in the intestine compared with diets containing raw WHB.     

Effects of linseed lipids fed as rolled seeds, extruded seeds or oil on organic matter and crude protein digestion in cows

Effects of fatty acids of linseed in different forms, on ruminal fermentation and digestibility were studied in dry cows fitted with ruminal and duodenal cannulas. Four diets based on maize silage, lucerne hay and concentrates (65/10/25 dry matter (DM)) were compared in a 4 × 4 Latin square design experiment where the diets were: control diet (C), diet RL supplied 75 g/kg DM rolled linseeds, diet EL supplied 75 g/kg DM extruded linseeds, and diet LO supplied 26 g/kg DM linseed oil and 49 g/kg DM linseed meal. The diets did not differ in total organic matter (OM) and fibre digestibility, in forestomach and intestinal OM digestibility, and in duodenal N flow. Microbial N duodenal flow tended to be lower for RL versus C diet (P<0.1). Extrusion did not reduce ruminal crude protein (CP) degradation in vivo and in situ. Volatile fatty acid concentration and pattern, and protozoa concentration in the rumen, did not vary among diets. Results confirm the absence of a negative effect of a moderate supply of linseed on rumen function, as well as no effect of extrusion on its ruminal CP degradability.     

In situ intestinal digestibility of dry matter and crude protein of cereal grains and rapeseed in sheep

The ruminal degradation and intestinal digestibility (ID) of dry matter (DM) and crude protein (CP) of different feed samples were measured in two trials by using nylon bag and rumen outflow rate techniques in three wethers cannulated in the rumen and in the duodenum. In trial 1, three samples of grains of wheat, barley, and corn treated by cooking (TW, TB, and TC, respectively) were studied together with a sample of untreated corn grains (CG) of different origin. In trial 2, these studies were carried out on a sample of rapeseed (RS) and on a mix of this same sample and rapeseed meal (in proportions 70:30) treated by cooking (TR). In both trials, the animals were fed at the same intake level (40 g DM x kg(-1) LW0.75) with 2:1 (DM basis) forage to concentrate diets. Rumen degradation rates of DM were high in the treated cereals (between 11.0 and 14.2% x h(-1)) and low in the CG (6.35% x h(-1)), whereas for CP these rates were low in all cereals. For DM, in all cereals, ID decreased linearly as the ruminal incubation time increased. The values of intestinal effective digestibility (IED), calculated from these functions and from the rumen outflow, were respectively: 86.4, 62.1, 51.5, and 67.9%. For CP, ID was unaffected by the ruminal incubation time in corn samples, whereas in TW and TB a reduction of these values was only observed for the time of 48 h. The values of IED of CP for CG, TW, TB and TC were: 82.6, 88.9,82.5, and 91.6%, respectively. Rumen degradation rates of the RS and TR samples were 8.35 and 8.23% x h(-1) for DM and 12.0 and 9.59% x h(-1) for CP. In RS, the ID of DM and CP showed a downward trend with an increase of the ruminal incubation time, as modelled according to an exponential function. This same trend was observed for TR after a lag period estimated at 7.53 and 6.51 h for DM and CP, respectively. The values of IED of RS and TR were respectively 56.5 and 50.8% for DM and 71.9 and 80.1% for CP. These same results were also determined by a simplified method using a sample pooled to be representative of the rumen outflow of undegraded feed. The respective values for RS and TR were 54.8 and 51.6 for DM and 65.8 and 78.9% for CP. This method seems to be a promising technique to estimate IED, although more studies are needed to improve its accuracy.     

The nutritive value of concentrate feedstuffs for ruminant animals: Part II: In situ ruminal degradability of crude protein

The objective of the study was to generate a database of in situ ruminal degradability of crude protein (CP) from different samples of a range of concentrate feedstuffs comprising protein, energy or protein+energy feeds commonly offered to ruminant animals in European countries. The in situ disappearance of CP was calculated using the in situ nylon bag technique where the test feedstuffs were subject to ruminal incubation in four Friesian steers offered grass silage and concentrate. Disappearance of CP from the test feeds from the rumen was measured at 0, 2, 4, 8, 14, 24 and 48 h. The exponential model of Ørskov and McDonald (1979) was used to measure degradation kinetics of CP. Test protein feeds were sunflower meal (SUN), rapeseed meal (RAP), soyabean meal (SBM) and cottonseed meal (CSM). Test energy feeds were palm kernel meal (PK), pollard (PO), barley (BA) and beet pulp (BP). Test protein+energy feeds were maize distillers grains (MDG), maize gluten feed (MGF), copra meal (CO) and malt combings (MC). The effective degradability of CP (EDP) in the protein feed SBM, where outflow rate (k)=0.02 was not influenced (P>0.05) by the sample of feed used. For the energy feeds, the EDP in PO for k=0.05 h⁻¹, 0.06 h⁻¹ and 0.08 h⁻¹ and EDP in BA for k=0.08 h⁻¹ were not significantly affected (P>0.05) by the sample of feed used. The data has shown that for the majority of feeds examined in this study, the different samples of any one feed are not equal in nutritive value and it is necessary to screen feeds for nutritive value before using them in ration formulation systems.     

Degradability characteristics of dry matter and crude protein of forages in ruminants

Twelve corn silages, 22 grass silages and 14 grass hays, obtained from various farms located in the lower Fraser Valley region of British Columbia, and 16 alfalfa hays, grown primarily in the Columbia basin of central Washington State, were evaluated using both the rumen and the mobile nylon bag in situ techniques. Nylon bags containing each forage were incubated in duplicate for 0, 2, 4, 8, 12, 24, 48, 72, or 96 h in two of six non-lactating Holstein cows fitted with rumen and duodenal cannulae. All forage types were evaluated in terms of the following dry matter (DM) and crude protein (CP) digestion characteristics: soluble fraction A, degradable fraction B, degradation rate, lag phase, and effective degradability. The mobile nylon bag technique was used to determine intestinal disappearance of DM and CP from the forages following pre-incubation in the rumen for 12 h. Significant (P < 0.05) differences in degradation characteristics occurred within all forages with regard to the soluble and potentially degradable DM and CP fractions. Soluble CP content in the rumen varied from 44.08 to 75.37% and from 18.74 to 65.38% in the corn and grass silages, respectively, and from 48.27 to 75.43% and from 30.13 to 65.95% in the alfalfa and grass hays, respectively. Significant differences within each forage type were also observed for the degradable CP in fraction B: 10.89 to 45.28% for corn silage, 20.72 to 82.77% for grass silage, 16.67 to 44.88% for grass hay and 25.44 to 62.93% for alfalfa hays. Significant differences (P > 0.05) were observed in fractional rates of ruminal DM degradation of the grass hays and corn silages. Significant differences did exist in the fractional rates of ruminal CP degradation within all forage types with the exception of alfalfa hays. Effective degradabilities of DM and CP were also significantly different between samples of a particular forage type. The mobile nylon bag data indicated that approximately 20% of the original CP in the grass silage, grass hay and alfalfa hay samples disappeared in the intestine and that there was significant variation between individual samples. On average, in the corn silage samples more than 10% of the original nitrogenous material disappeared in the intestine. The results presented in this study clearly demonstrate that the use of tabulated values for describing individual batches of forages in terms of their degradability characteristics is inaccurate since they may not reflect the particular forage being used in the ration and thus may lead to errors in diet formulation.     

Prediction of the degradability of sugarcane celulosic residues by indirect methods

The effect of mild NaOH treatments on sugarcane cellulosic wastes (bagasse, pith, and straw) to increase their biological degradability has been studied. At a level of 8% NaOH (on a dry matter basic) 60% digestibility measured by the in vitro technique was achieved for all materials tested. Indirect methods to predict the digestibility of treated materials such as the bacterial degradability, enzymatic degradability, hot-water solubility, and chemical oxygen demand were tried as alternative methods to the rumen fluid technique. High correlation coefficients for all materials were obtained with all alternative techniques. The minimal r value was 0.96 while the highest was 0.99. An important reduction of time and reagents is achieved by the utilization of the solubility and chemical oxygen demand tests.     

The use of a tannin crude extract from Cistus ladanifer L. to protect soya-bean protein from degradation in the rumen

Cistus ladanifer L. (CL) is a perennial shrub abundant in dry woods and dry land of Mediterranean zone, with high level of tannins. Tannins bind to protein, preventing its degradation in the digestive compartments. This tannin/protein complex may be advantageous when partially protecting good-quality feed protein from excessive rumen protein degradation. The objective of this trial was to use a CL phenol crude extract to prevent excessive rumen degradation of soya-bean meal protein. The phenolic compounds were extracted using an acetone/water solution (70:30, v/v). Soya-bean meal was then treated with this crude CL extract, containing 640 g of total phenols (TP) per kg of dry matter (DM), in order to obtain mixtures with 0, 12.5, 25, 50, 100 and 150 g of TP per kg DM. Three rumen-cannulated rams were used to assess in sacco rumen degradability of DM and nitrogen (N). The three-step in vitro procedure was used to determine intestinal digestibility. Increasing extract concentrations quadratically decreased the N-soluble fraction a (R² = 0.96, P = 0.0001) and increased the non-soluble degradable fraction b (R² = 0.92, P = 0.005). The rate of degradation c linearly decreased with CL extract doses (R² = 0.44, P = 0.0065). For the effective rumen degradability of N, a linear reduction (R² = 0.94, P < 0.0001) was observed. The in vitro intestinal digestibility of protein (ivID) quadratically decreased (R² = 0.99, P < 0.0001) with TP inclusion and the rumen undegradable protein (RUP) showed a quadratic increase (R² = 0.94, P = 0.0417). Total intestinal protein availability, computed from the RUP and ivID, linearly decreased with TP inclusion level (R² = 0.45, P = 0.0033).     

Effect of heat or formaldehyde treatment on the rumen degradability and intestinal tract apparent digestibility of protein in soya-bean meal and in rapeseed meals of different glucosinolate content

Three Hereford × Friesian/Holstein heifers were each fitted with rumen and simple T-piece duodenal cannulae. They were used in an experiment of latin square design to study the rumen degradability and intestinal apparent digestibility (using the mobile dacron bag technique) of protein in soya-bean meal (SBM) and in low and high glucosinolate rapeseed meals (LgsRSM and HgsRSM, respectively) each in untreated (UT), heat treated (HT) and formaldehyde treated (FT) forms. For rumen incubation times of 24 h there were no significant protein source × processing treatment interactions for either degrability of protein in the rumen (dgN) or for the proportion of food protein undegradable in the rumen and digestible in the small intestine (DUDN). At this time dgN values for FT, HT and UT were 0.263, 0.374 and 0.418 (SEM 0.0078; P < 0.001) respectively and DUDN values for SBM, LgsRSM and HgsRSM were 0.320, 0.348 and 0.386 (SEM 0.0078; P < 0.001) respectively. Compared with UT, and to a lesser extent HT, FT at all times after 0 h incubation significantly decreased dgN values and increased DUDN values for all three protein sources. Compared with UT, HT significantly decreased dgN. Apparent digestibility of the protein of SBM in the intestines was greater than that of LgsRSM and HgsRSM, and overall the values of available undegraded protein for FTLgs and HgsRSM, but not of FTSBM, were similar to or greater than for the UT sources. FT tended to decrease the total tract apparent digestibility of the protein sources.     

In vivo and in situ measurements of the digestive characteristics of sainfoin in comparison with lucerne fed to sheep as fresh forages at two growth stages and as hay

In vivo and in situ digestive characteristics of sainfoin (Onobrychis viciifolia L., a tannin-rich forage) and lucerne (Medicago sativa L., a tannin-free forage) were compared to evaluate the effects of condensed tannins (CT) and growth stage (vegetative v. early flowering) in experiment 1. In experiment 2, the hays of the two forages, harvested at early flowering, were compared. Ingestibility, organic matter digestibility (OMD) and nitrogen (N) retention were measured in sheep fed sainfoin and lucerne fresh forages and hays. The loss of dry matter (DM) and N from polyester bags suspended in the rumen, abomasum and small intestine was also measured using rumen fistulated sheep and other intestine fistulated sheep. Nitrogen content was lower in sainfoin than in lucerne. Content of CT in sainfoin decreased with growth stage (3.5 to 2.5 g CT/kg DM) and was lower for sainfoin hay (0.6 g CT/kg DM). Ingestibility and OMD did not differ between fresh-fed forage species. Total N tract digestibility in vivo was much lower for sainfoin than for lucerne fresh forages (mean value 0.540 v. 0.721, P < 0.001) and for sainfoin hay than lucerne hay (0.464 v. 0.683, P < 0.001). In both species, N digestibility was not altered by growth stage. The rumen degradation of N was lower in sainfoin than in lucerne, resulting in a lower proportion of N intake excreted in urine. The intestinal digestibility of sainfoin was also lower than that of lucerne, resulting in a higher N excretion in faeces. Hence the efficiency of N utilisation by sheep (ENr) was similar (mean value 0.205 and 0.199 g N retained/g N intake for fresh sainfoin and lucerne, respectively). The coefficient of N retention by the animal was higher for sainfoin at the vegetative stage than for all the other forages. Nitrogen degradability in the rumen determined by the nylon bag technique (DegN) was lower for sainfoin than for lucerne when forages were studied both fresh (mean value 0.608 and 0.818, respectively) and as hays (0.631 and 0.767). The efficiency of forage N digestion (ENd) was higher for sainfoin at the vegetative stage. Compared with lucerne, sainfoin greatly increased the in situ estimate of forage N escaping the rumen but decreased its intestinal digestibility.     

The digestion in the small intestine of young bulls of the protein of rapeseed meal treated or untreated with formaldehyde

Twelve bulls of approximately 140 kg bodyweight were each fitted with simple cannulae in the rumen and abomasum and a re-entrant cannula in the terminal ileum. They were kept in individual pens and given daily 1.8 kg of a basal diet containing dried maize meal (whole plant), dried sugarbeet pulp and a urea/mineral preparation in the proportions 0.80, 0.18 and 0.02. Four animals received this diet alone, four received in addition 198 g daily (11 g N) of rapeseed meal by infusion into the abomasum and the remaining four the basal diet plus the same amount of formaldehyde-treated rapeseed also by infusion.The concentration of ammonia-N in the rumen fluid of animals given the untreated rapeseed meal was higher (P < 0.05) than for those on the other two treatments. The pH of the rumen and abomasal fluid was similar on all treatments. Coefficients for the apparent disappearance in the small intestine of the dry matter and nitrogen of untreated rapeseed meal infused into the abomasum were 0.76 and 0.75, respectively. In contrast formaldehyde-treated rapeseed meal was poorly digested. It is suggested that procedures for the treatment of rapeseed meal that will minimise the degradability of its protein in the rumen, yet prevent depression of its digestion and absorption in the abomasum and small intestine have still to be defined.     

Protein value of cereals and cereal by-products for ruminants: a comparison between crude protein and protein-based estimates

In situ estimates of ruminal undegraded fraction (RU) and effective intestinal digestibility (EID, corrected for microbial colonisation) of dry matter (DM), crude protein (CP) and total analysed amino acids (TAA) of rye, wheat and corn grains, wheat bran, wheat and barley distillers’ dried grains with solubles (DDGS) and corn gluten feed were measured on three rumen and duodenum cannulated wethers using ¹⁵N labelling techniques and considering ruminal rates of particle comminution (k_c) and outflow. Results indicate that not considering k_c and microbial colonisation led to considerable overestimations of RU which increased with feed ruminal degradation. Microbial colonisation may be also associated with overestimations of EID, whose estimates for DM, CP and TAA were predicted from parameters related with the ruminal escape of intestinally indigestible materials. The RU estimates were higher for TAA than for CP in grains, but the opposite was observed in by-products, whereas EID estimates were higher for TAA in all feeds. To obtain accurate protein values in these feedstuffs, it is required to consider both k_c and ruminal microbial colonisation. The CP-based results underestimate the intestinally digested protein in grains and the opposite is evidenced in cereal by-products. Microbial protein synthesised in the rumen is largely the major fraction of the feedstuff protein value with the exception of DDGS.