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.     

The nutritive value of concentrate feedstuffs for ruminant animals: Part III. Small intestinal digestibility as measured by in vitro or mobile bag techniques

The aim of the study was to generate a database of small intestinal digestibility (SID) of different sources of concentrate ingredients commonly offered to ruminants in European countries. 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 ruminal undegradable protein (RUP) portion of the test feedstuffs was obtained by ruminal incubation in four Friesian steers offered grass silage and concentrate. The RUP fraction was digested with pepsin and pancreatin enzymes (PPD) or placed into the duodenal cannula of two Friesian cows using the mobile bag technique, which were recovered in the faeces. The average in situ SID (g/kg) of CSM, RSM, SBM, SUN, BA, BP, PK, CO, MDG, MGF and MC was 834 (S.D. 61), 711 (S.D. 47), 978 (S.D. 9), 586 (S.D. 170), 427 (S.D. 80), 712 (S.D. 24), 767 (S.D. 53), 816 (S.D. 38), 860 (S.D. 73), 656 (S.D. 65) and 510 (S.D. 41), respectively. Corresponding in vitro SID values (g/kg) were 641 (S.D. 65), 620 (S.D. 45), 840 (S.D. 27), 606 (S.D. 155), 445 (S.D. 36), 601 (S.D. 17), 640 (S.D. 63), 686 (S.D. 69), 756 (S.D. 63), 634 (S.D. 84) and 504 (S.D. 16), respectively. These results show that the SID of feeds can vary substantially between different sources and indicates that different feeds should be screened for their nutritive value as a result. As the relationship between in situ (Y) and in vitro (X) SID is best described by the linear regression equation Y=−91.9+12.7X (r=0.91), indicating a close relationship between results obtained using both techniques, the in vitro PPD technique offers a quick and reliable method for SID of feeds to be screened on a regular basis.     

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.     

Effects of protein sources on concentrations of hydrogen sulphide in the rumen headspace gas of dairy cows

Two Latin square design experiments investigated the relationship between hydrogen sulphide concentration in the rumen headspace gas of dairy cows and the early stages of protein degradation in the rumen. In Expt 1, three protein sources differing in rumen N (nitrogen) degradability (maize gluten feed (MGF); sunflower meal (SFM); and soyabean meal (SBM)) were used, whereas in Expt 2 four different batches of the same feed (MGF) differing in colour (CIE L*, a*, b* (CIELAB) scale) were used. After allowing the concentration of hydrogen sulphide in rumen gas to decline close to zero, a fixed amount of protein sources was offered to cows and the concentrations of hydrogen sulphide were recorded in rumen headspace gas at 30-min intervals. In Expt 1, the concentration of hydrogen sulphide showed considerable variation between protein sources, with MGF having the highest concentration followed by SFM and SBM resulting in very low concentrations. The N wash losses (zero time measurements with nylon bags) ranked the feeds in the same way, from MGF (highest; 61%) to SBM (lowest; 26%). There were marked differences in the degradation of cystine and methionine between protein sources, although the degradation of cystine was always higher than for methionine. MGF (Expt 2) led to increased concentrations of hydrogen sulphide, with peak concentrations achieved between 1 and 2 h after feeding. The concentrations of hydrogen sulphide were higher for MGF1, intermediate for MGF2 and lower for MGF3 and MGF4, agreeing with colour scale. Differences in the early stages of dietary sulphur degradation corresponded with differences in hydrogen sulphide concentrations in rumen gas. The results suggest that hydrogen sulphide concentrations in the rumen headspace gas could be useful to evaluate nutritional parameters not measured by the in sacco technique, contributing to a better understanding of the response of dairy cows to different protein supplements.     

Nutritional properties of potato protein concentrate compared with soybean meal as the main protein source in feed for the double-muscled Belgian Blue bull

The objective of this experiment was to compare the nutritional properties of potato protein concentrate, a by-product of the starch industry produced entirely in Europe, with that of soybean meal (SBM), for growing cattle. The experiment was conducted on double-muscled Belgian Blue bulls, fitted with rumen, duodenal and ileal cannulas, according to a 4 × 4 Latin square design. They were fed three different iso-N and iso-net energy diets formulated according to the Dutch feed evaluation system, differing in the nature of the main protein source, which was either SBM (‘SBM’ treatment), potato protein concentrate (PPC, ‘PPC’ treatment) or an iso-N mixture of these two protein sources (‘mixed’ treatment). A fourth treatment consisted of ‘PPC’ supplemented by 9.5% digestible proteins supplied by duodenal perfusion of sodium caseinate (CAS, ‘PPC + CAS’ treatment). No significant difference was observed in the ruminal fluid pH, whereas both ‘PPC’ and ‘PPC + CAS’ had the effect of reducing the ruminal ammonia nitrogen (N-NH₃) concentration. No significant difference was observed in the apparent intestinal digestibility of the dry matter (DM), organic matter (OM) or N. Outflows of non-NH₃-N, microbial proteins and dietary proteins from the rumen were similar for ‘PPC’, ‘SBM’ and ‘mixed’, and increased with CAS infusion by 20%, 17% and 27%, respectively. On the basis of in vivo observations, the degradability of SBM and PPC proteins was estimated at 0.60 and 0.43, respectively, corresponding to the values quoted in the literature. The supply of digestible essential amino acids (EAA) was significantly greater with ‘PPC + CAS’ and did not differ among ‘SBM’, ‘mixed’ and ‘PPC’. This illustrates the difficulty of altering the amino acid (AA) pattern of digestible protein by the nature of the protein of dietary origin when an animal is fed a high nutritional value diet. N retention was not affected by replacing SBM with PPC, but increased by 10% with CAS infusion. On the basis of the plasma AA pattern, the supply of digestible Met was probably limiting with ‘SBM’, ‘mixed’ and ‘PPC’. The CAS perfusion supplemented all AA, including Met, leading to increased N retention. This improvement was limited, however, and N utilisation remained unchanged between treatments. In conclusion, despite a more favourable EAA pattern, PPC offered no advantage compared with SBM for growing bulls when diets were formulated according to the Dutch feed evaluation system.     

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.     

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.     

The effects of and interactions between the maturity of grass silage and concentrate starch source when offered as total mixed rations on the performance of dairy cows

A 2 × 2 factorial feeding experiment was conducted to examine the effects of varying the maturity level of the grass used to prepare silage and the nature of concentrate starch source and their interactions on dry matter intake (DMI), diet digestibility, energy corrected milk (ECM) production and milk composition in dairy cows. Twenty-eight multiparous Swedish Red dairy cows, 133 ± 45 days in milk (DIM), with an average milk yield of 30 ± 4 kg/day and a live weight of 624 ± 69 kg were blocked by DIM and randomly assigned to seven replicated balanced 4 × 4 Latin squares with four 21-day experimental periods. The experimental diets consisted of four total mixed rations (TMR) consisting of early-cut grass silage (EGS) supplemented with either barley- or maize-based concentrate and late-cut grass silage (LGS) supplemented with either barley- or maize-based concentrate. All TMR contained identical proportions of forage (51%) and concentrate (49%). Total tract digestibility was estimated by determining indigestible NDF (iNDF) concentrations in feeds and faeces and using iNDF as an internal marker. The feeds’ ruminal degradation parameters were determined using both in situ (nylon bag) and in vitro (gas production (GP)) techniques. Cows offered diets containing EGS had greater (P < 0.001) daily dry matter (DM) intakes, ECM yields and total tract digestibilities for DM and organic matter (OM), but these were not affected by the nature of the concentrate starch source. No interaction between the maturity of the silage and the nature of the concentrate starch source was observed for DMI, diet digestibility or ECM yield. Both grass silages and concentrates had similar rates of ruminal degradation of NDF when measured in situ. The in situ DM (P < 0.001) and starch (P = 0.001) degradation rates of barley-based concentrate were greater than those for maize-based concentrate. In vitro OM GP rates and extents were similar for both concentrate feeds. The results showed that diets containing EGS offered better animal performance and diet digestibility than diets containing LGS. The concentrate starch source did not affect animal performance, but total NDF digestibility was better with diet containing barley- than maize-based concentrate.     

Rumen fermentation,nutrient flow to the duodenum and digestibility in bulls fed calcium soaps of rapeseed fatty acids and soya bean meal coated with calcium soaps

Three Polish Friesian bulls fitted with rumen and duodenal canulas were used in a 3 × 3 Latin square experiment to study the effect of Ca soaps of rapeseed fatty acids (CSRFA) on rumen fermentation, nutrient and fatty acid (FA) flow to the duodenum, and to investigate in vivo the possibility of using CSRFA as a means of protecting soya bean meal protein against degradation in the rumen. Treatments were (1) control, no fat (2) CSRFA, at 2% of dietary DM and (3) SBM protein coated with CSRFA (CSRFA:SBM, 1:1, wt/wt), at 4% of dietary DM. The animals were fed isonitrogenous diets, containing 45% meadow hay, 10% fodder beet and 45% concentrate mixture on a DM basis. Intake was limited to 80 g DM d⁻¹ kg^−0.75. There were no treatment effects on rumen fermentation, rumen liquid turnover rate or volume, suggesting that CSRFA were inert in the rumen. A slight decrease in ammonia concentration in the rumen fluid from the CSRFA:SBM diet and the degradability data do not confirm the protection of SBM protein by CSRFA. Treatments did not affect apparent OM digestibility in the rumen, total N and NAN (non-ammonia nitrogen) flow into the duodenum or microbial protein synthesis. However, rumen degradability of protein was increased by feeding CSRFA. Feeding CSRFA significantly increased the duodenal flows of C18:0, C18:1 and total FA, but when expressed as a percentage of intake, there were no significant treatment differences. The average duodenal flow of total FA was 81.7% of intake. Extents of biohydrogenation of unsaturated FA were decreased in diets containing CSRFA. Estimated net biohydrogenation of C18:2, C18:3 and total unsaturated C18 FA of CSRFA was 43.3, 60.4 and 59.4%, respectively. Postrumen and total tract digestibility of total and individual FA were not different between treatments     

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.     

Adjusting homestead feeding to requirements and nutrient intake of grazing goats on semi-arid, subtropical highland pastures

Intensive livestock grazing can largely deplete the natural fodder resources in semi-arid, subtropical highlands and together with the low nutritional quality of the pasture vegetation limit the growth and production of grazing animals. To evaluate the contribution of homestead feeding of grazing goats to rangeland conservation and animal nutrition, two researcher-managed on-farm trials were conducted in a mountain oasis of Northern Oman. Goats' feed intake on pasture in response to four rations containing different levels of locally available green fodder and concentrate feeds was determined in six male goats each (35 ± 10.2 kg body weight (BW)). Total feed intake was estimated using titanium dioxide as external fecal marker as well as the diet organic matter (OM) digestibility derived from fecal crude protein concentration. The nutritional quality of selected fodder plants on pasture was analyzed to determine the animals' nutrient and energy intake during grazing. The pasture vegetation accounted for 0.46 to 0.65 of the goats' total OM intake (87 to 107 g/kg0.75 BW), underlining the importance of this fodder resource for the husbandry system. However, metabolizable energy (7.2 MJ/kg OM) and phosphorus concentrations (1.4 g/kg OM) in the consumed pasture plants were low. Homestead feeding of nutrient and energy-rich by-products of the national fishery and date palm cultivation to grazing goats increased their daily OM intake (R2 = 0.36; P = 0.005) and covered their requirements for growth and production. While the OM intake on pasture was highest in animals fed a concentrate-based diet (P = 0.003), the daily intake of 21 g OM/kg0.75 BW of cultivated green fodder reduced the animals' feed intake on pasture (R2 = 0.44; P = 0.001). Adjusting homestead supplementation with locally available feedstuffs to the requirements of individual goats and to the nutritional quality of the pasture vegetation improves animal performance and eases the grazing pressure exerted on the natural vegetation. This management strategy therefore appears to be a valuable alternative to intensive livestock feeding in zero-grazing systems and may contribute to sustainable livestock production in ecologically fragile, semi-arid mountain regions.     

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.     

Utility of buckwheat (Fagopyrum esculentum Moench) as feed: Effects of forage and grain on in vitro ruminal fermentation and performance of dairy cows

Buckwheat is of high value in crop rotations and overall agricultural ecology because of strong rooting and intensive flowering properties, but it is rarely cultivated and information on its nutritional value to ruminants is scarce. The contents of net energy for lactation (NEL), as estimated with the Hohenheim Gas Test (n = 3), were 4.3, 4.9 and 7.5 MJ NEL/kg dry matter (DM) for fresh and ensiled whole buckwheat plants and buckwheat grain, respectively. In two experiments with the Rumen Simulation Technique (Rusitec), ruminal fermentation characteristics of buckwheat forages and buckwheat grain (n = 4/diet) were evaluated. In the first experiment, 0, 300 or 600 g/kg of a pure hay diet were replaced by either fresh or ensiled buckwheat to create five diets. Neither form of buckwheat forages had effects on in vitro ruminal degradability and short chain fatty acid (SCFA) concentrations and composition. The use of fresh buckwheat reduced ruminal ammonia concentrations and enhanced estimated microbial N growth efficiency. These differences did not occur with silage, indicating a change in nutritional value by ensiling. Fresh buckwheat reduced the number of bacteria in the incubated fluid, while ensiled buckwheat reduced that of holotrich protozoa. Methane formation was not influenced by the buckwheat forages. In the second experiment, wheat meal (400 g/kg dietary DM), was replaced stepwise (0.5 and 1.0) by buckwheat grain meal. This did not cause differences in parameters of nutrient degradability, relative N efficiency and total amount and composition of SCFA. Holotrich protozoa counts increased, but total gas formation decreased with increasing dietary level of buckwheat grain. In a final experiment, cows yielding about 40 kg milk/day were fed mixed silage-concentrate diets (n = 4). A control diet contained no buckwheat. In a second diet, maize silage was partly substituted by buckwheat silage (98 g/kg dietary DM). In a third group, part of the energy concentrate was substituted by buckwheat grain meal (94 g/kg). There were no effects on feed intake, milk yield and milk composition. Buckwheat proved to be a plant that offers different feeds of a quality sufficient to be considered suitable in ruminant nutrition.     

In vitro digestion and fermentation characteristics of canola co-products simulate their digestion in the pig intestine

Canola co-products are sources of amino acid and energy in pig feeds, but their fermentation characteristics in the pig intestine are unknown. Thus, we determined the in vitro fermentation characteristics of the canola co-products Brassica juncea solvent-extracted canola meal (JSECM), Brassica napus solvent-extracted canola meal (NSECM), B. napus expeller-pressed canola meal (NEPCM) and B. napus cold-pressed canola cake (NCPCC) in comparison with soybean meal (SBM). Samples were hydrolysed in two steps using pepsin and pancreatin. Subsequently, residues were incubated in a buffer solution with fresh pig faeces as inocula for 72 h to measure gas production. Concentration of volatile fatty acids (VFA) per gram of dry matter (DM) of feedstuff was measured in fermented solutions. Apparent ileal digestibility (AID) and apparent hindgut fermentation (AHF) of gross energy (GE) for feedstuffs were obtained from pigs fed the same feedstuffs. On DM basis, SBM, JSECM, NSECM, NEPCM and NCPCC contained 15, 19, 22, 117 and 231 g/kg ether extract; and 85, 223, 306, 208 and 176 g/kg NDF, respectively. In vitro digestibility of DM (IVDDM) of SBM (82.3%) was greater (P<0.05) than that of JSECM (68.5%), NSECM (63.4%), NEPCM (67.5%) or NCPCC (69.8%). The JSECM had greater (P<0.05) IVDDM than NSECM. The IVDDM for NSECM was lower (P<0.05) than that for NEPCM, which was lower (P<0.05) than that for NCPCC. Similarly, AID of GE was greatest for SBM followed by NCPCC, JSECM, NEPCM and then NSECM. Total VFA production for SBM (0.73 mmol/g) was lower (P<0.05) than that of JSECM (1.38 mmol/g) or NSECM (1.05 mmol/g), but not different from that of NEPCM (0.80 mmol/g) and NCPCC (0.62 mmol/g). Total VFA production of JSECM was greater (P<0.05) than that of NSECM. Total VFA production of NSECM was greater (P<0.05) than that of NEPCM or NCPCC, which differed (P<0.05). The ranking of feedstuffs for total VFA production was similar to AHF of GE. In conclusion, in vitro fermentation characteristics of canola co-products and SBM simulated their fermentation in the small and large intestine of pigs, respectively. The 30% greater VFA production for JSECM than NSECM due to lower lignified fibre of JSECM indicates that fermentation characteristics differ between canola species. The NSECM had the highest fermentability followed by NEPCM and then NCPCC, indicating that fat in canola co-products can limit their fermentability in the hindgut.     

Encapsulation of soybean meal with fats enriched in palmitic and stearic acids: effects on rumen-undegraded protein and in vitro intestinal digestibility

Fat coating of soybean meal (SBM) can reduce its protein degradability in the rumen, but the encapsulation of SBM with palmitic (PA) and stearic acids (SA) has not yet been investigated, despite both fatty acids are common energy sources in dairy cow diets. This study aimed to evaluate the effects of applying a novel method, using either 400 or 500 g fat/kg (treatments FL40 and FL50, respectively), which was enriched in PA and SA at different ratios (100:0, 75:25, 50:50, 25:75 and 0:100), on physical and chemical characteristics, ruminal degradability, solubility and in vitro intestinal protein digestibility (IVIPD) of the obtained products. Encapsulation of SBM in fat resulted in greater mean particle size and lower bulk density and protein solubility than unprotected SBM (USBM). Treatment FL50 resulted in increased (p < 0.01) rumen-undegraded protein (RUP) compared to USBM. There were no differences in RUP of SBM when different PA: SA ratios were used. The mean RUP content of treatments FL40 and FL50 (306 and 349 g/kg, respectively) was greater compared to USBM (262 g/kg, p < 0.05), but lower than that for a standard heat-treated SBM (431 g/kg). Values of IVIPD did not differ among SBM, heat-treated SBM and FL40 and FL50 samples, all being greater than 97.8%. In conclusion, encapsulation of SBM with fats enriched in PA and SA proved to be effective in reducing protein solubility and increasing RUP without depressing protein digestibility in the intestine. For validation of the method, in vivo research to investigate the effects of these products on the production of dairy cows is warranted.     

Use of the mobile nylon bag technique to determine the digestible energy content of traditional and non-traditional feeds for swine

The following experiment was conducted using the mobile nylon bag technique (MNBT) to determine dry matter and energy digestibility in traditional feeds as well as non-traditional feeds in order to calculate digestible energy (DE) values for use in ration formulation programmes. A total of 22 ingredients were tested in this experiment including the traditional cereal grains barley, corn, oats and wheat, as well as secondary cereal grains such as normal and low viscosity rye, low lignin and high fat oat groats, wheat heavies and # 1 wheat screenings and a new bread wheat designated as CDC Teal. Three legumes (lupines, peas and dehydrated alfalfa), three varieties of canary seed (CDC Maria, dehulled CDC Maria and Keet), and raw and micronized canola seed were tested as protein sources. Finally, three oilseed meals obtained from the Chinese feed industry (Chinese rapeseed meal, Chinese cottonseed meal and extruded full-fat soybean meal) were also included. After simulating gastric digestion the nylon bags were inserted into the duodenum of five barrows through simple duodenal T-cannulae. Eight bags were administered to each pig daily. Ten nylon bags were prepared for each feed with two bags being inserted into each of the five barrows. A total of 220 bags were inserted over a 7-day period. The overall results of this experiment indicate that the MNBT has great potential for use in determining the digestible energy content of swine feeds. For the most part, values obtained in the present experiment compared favourably with previously published values. Four feedstuffs produced digestible energy values that differed by greater than 5% from previously reported values. However, variation in chemical content provided a reasonable explanation for these discrepancies. The MNBT has several advantages compared with conventional digestibility methods in that many feeds can be tested in a relatively short duration of time with significantly fewer animals being used, only small amounts of feed are required and the test allows for energy measurements in feedstuffs that would not normally be fed to pigs as a single ingredient. Additional research on a wider variety of feedstuffs should be conducted to confirm the potential of the MNBT as a tool to accurately determine DE values for swine.     

Effect of variety and harvest date on nutritive value and ruminal degradability of ensiled maize ears

The nutritive value of whole crop forage maize is influenced by the proportion of ears and stover in the whole crop and by the nutrient composition and digestibility characteristics of the plant parts. An experiment investigating the impact of variety, harvest date and year on the nutritive value of ensiled maize ears was carried out in three consecutive years (2007, 2008 and 2010). Nine different maize varieties were harvested at three different maturity stages (50, 55 and 60% dry matter (DM) content in the ears). After harvest, ears and stover were ensiled separately and afterwards nutrient composition and ruminal nutrient degradability (organic matter (OM), crude protein (CP) and non-fibre carbohydrates (NFC)) were analysed. Variety had a significant influence on content of CP and effective ruminal degradability (ED) of OM at low passage rates, whereas ED of CP and NFC was not affected by variety. In contrast, harvest date and year significantly influenced nutrient composition and ruminal degradability of ensiled maize ears. The content of NFC increased and the content of fibre components as well as ED of OM, CP and NFC declined with processing maturity of the maize plants. At a passage rate of 5% h^?1, ED of OM declined from 75.9% to 68.4%, ED of CP from 82.5% to 73.8% and ED of NFC from 88.0% to 82.3% between the early and late harvest date. The results of this study indicate that the nutrient composition and ruminal degradability of ensiled maize ears are affected mainly by maturity stage at harvest and by year, whereas variety has only little influence.     

Effects of dietary supplementation of rumen-protected folic acid on rumen fermentation,degradability and excretion of urinary purine derivatives in growing steers

The present experiment was undertaken to determine the effects of dietary addition of rumen-protected folic acid (RPFA) on ruminal fermentation, nutrient degradability, enzyme activity and the relative quantity of ruminal cellulolytic bacteria in growing beef steers. Eight rumen-cannulated Jinnan beef steers averaging 2.5 years of age and 419 ± 1.9 kg body weight were used in a replicated 4 × 4 Latin square design. The four treatments comprised supplementation levels of 0 (Control), 70, 140 and 210 mg RPFA/kg dietary dry matter (DM). On DM basis, the ration consisted of 50% corn silage, 47% concentrate and 3% soybean oil. The DM intake (averaged 8.5 kg/d) was restricted to 95% of ad libitum intake. The intake of DM, crude protein (CP) and net energy for growth was not affected by treatments. In contrast, increasing RPFA supplementation increased average daily gain and the concentration of total volatile fatty acid and reduced ruminal pH linearly. Furthermore, increasing RPFA supplementation enhanced the acetate to propionate ratio and reduced the ruminal ammonia N content linearly. The ruminal effective degradability of neutral detergent fibre from corn silage and CP from concentrate improved linearly and was highest for the highest supplementation levels. The activities of cellobiase, xylanase, pectinase and α-amylase linearly increased, but carboxymethyl-cellulase and protease were not affected by the addition of RPFA. The relative quantities of Butyrivibrio fibrisolvens, Ruminococcus albus, Ruminococcus flavefaciens and Fibrobacter succinogenes increased linearly. With increasing RPFA supplementation levels, the excretion of urinary purine derivatives was also increased linearly. The present results indicated that the supplementation of RPFA improved ruminal fermentation, nutrient degradability, activities of microbial enzymes and the relative quantity of the ruminal cellulolytic bacteria in a dose-dependent manner. According to the conditions of this experiment, the optimum supplementation level of RPFA was 140 mg/kg DM.     

Effects of isobutyrate on rumen fermentation, urinary excretion of purine derivatives and digestibility in steers

The objective of this study was to evaluate the effects of isobutyrate supplementations on rumen fermentation, urinary excretion of purine derivatives and feed digestibility in steers. Eight ruminally cannulated Simmental steers were used in a replicated 4 x 4 Latin square experiment. On DM basis, diet consisted of 60% corn stover and 40% concentrate. Dry matter intake (averaged 9 kg/d) was restricted to 90% of ad libitum intake. The four treatment groups received a daily dose of 0 (control), 8.4, 16.8 or 25.2 g isobutyrate per steer. With increasing isobutyrate supplementation total VFA concentration (range 64.2-74.0 mM) was significantly enhanced. The ratio of acetate to propionate (range 2.72-4.25) was also significantly increased due to the increase in actate production and decrease in propionate production. With increasing isobutyrate supplementation the ruminal degradation of NDF from corn stover was improved but the CP degradability of soybean meal was decreased. Furthermore, the isobutyrate supplementation caused a significantly increased urinary excretion of purine derivatives. Similarly, digestibilities of OM, NDF and CP in the total tract were significantly increased. The present results indicate that dietary supplementation with isobutyrate improved rumen fermentation and feed digestion in beef cattle in a dose-dependent manner. According to the conditions of this experiment, the optimum daily dose of isobutyrate was about 16.8 g/animal.