Mode of action of yeast culture (YEA-SACC 1026) for stimulation of rumen fermentation in buffalo calves

The effect of daily supplementation of 5 g Saccharomyces cerevisiae yeast culture (YC, YEA-SACC 1026), 30 g NaHCO₃, supernatant from 5 g YC (YCS), 5 g autoclaved YC (YCH) or 5 g γ-irradiated YC (YCR) to the diet of buffalo calves on rumen microbial populations and fermentation pattern was examined. Addition of 30 g NaHCO₃ increased the rumen pH to the level observed with YC group. The pH and the concentrations of total, total viable and cellulolytic bacteria and total volatile fatty acids (VFA) were significantly higher while that of lactic acid, hexose-unit oligosaccharides and NH₃-N were significantly lower in the rumen fluid of YC compared with the control group. The effect of NaHCO₃ was 39·5 and 59·5% in decreasing the concentrations of lactic acid and hexose-unit oligosaccharides, 48·1, 47·2 and 45·5% in increasing the numbers of total, total viable and cellulolytic bacteria, 50·0 and 58·1% in increasing the concentrations of total VFA and protein and 51·3% in decreasing the concentration of NH₃-N of YC. The corresponding values for YCR addition in the diet were 38·6, 45·7, 48·5, 44·4, 51·5, 39·1, 48·1 and 46·5%. The effect of YCS and YCH was only marginal, but conspicuous up to 2 h after feeding, in changing the above rumen variables when compared with the YC group. The results indicated that contribution of increase in pH in changing the rumen variables was approximately 50% of YC and almost all the stimulatory activity was associated with live yeast cells. Autoclaving of YC destroyed almost all and γ-irradiation of YC retained about 50% of stimulatory activity of YC. The effect of YC on rumen fermentation, which was maximum up to 2 to 4 h after feeding, decreased with time. © 1998 SCI.     

Determination of RNA and ATP in the rumen liquid of cows fed with diets differing in forage to concentrate ratio

The effect of dietary composition on the RNA and ATP concentrations in rumen bacteria was determined. Four dry Simmental cows received two diets (H, hay only; C, hay and concentrate) and samples of rumen fluid were taken at three different times during the day. Rumen fluid was analysed for DM, N, pH, VFA, RNA, ATP and total bacterial count. There were no significant differences in RNA concentration whether it was determined in fresh or frozen samples or after having been precipitated overnight. The effect of time of sampling was almost always significant: for pH, ammonia nitrogen, propionic acid, n-butyric acid and total VFA this was particularly evident at 12:00 h in comparison with 08:00 and 16:00 h (P < 0·05). Bacterial DM, total count and ATP content decreased linearly with increasing time from the morning meal (P < 0·01), while the highest RNA content was observed at 12:00 h and the lowest at 16:00 h (P < 0·01). The bacterial content (DM basis) of RNA and the RNA:N, RNA:total count and ATP:N ratios were significantly higher with diet C, while differences for ATP (μg mg^?1 DM), nitrogen (mg per 100 mg DM) and ATP:RNA ratio were not significant. The effect of sampling time was similar for the two diets: the RNA content of bacterial cells increased from 08:00 h to 12:00 h (P < 0·05), while the RNA:N, RNA:total count and ATP:RNA ratios increased from 08:00 to 12:00 h and decreased from 12:00 to 16:00 h. The ATP content had a similar trend to that of RNA, but differences with time were not significant. Although the use of RNA and ATP as bacterial markers has to be considered with some caution, their determination together with rumen parameters, such as pH, VFA and ammonia, could contribute to useful investigations of the anaerobic fermentative process.     

Effects of intraruminal infusions of propionate and butyrate with two different protein supplements on milk production and blood metabolites in dairy cows receiving grass silage-based diet

Four cows were used in a balanced 4×4 Latin square with 2 week experimental periods to investigate the effects of intraruminal infusions of volatile fatty acids and protein source on milk production and blood metabolites. The four treatments in a 2×2 factorial arrangement were isoenergetic intraruminal infusions of propionate (500 g day⁻¹) or butyrate (417 g day⁻¹) each given with isonitrogenous protein supplementation of fish meal (FM) or barley protein (BP). The cows were fed restrictively with 9 kg dry matter day⁻¹ of formic acid treated grass silage and 8 kg day⁻¹ of concentrate. Propionate infusion increased milk yield (24·9 vs 23·4 kg day⁻¹; P<0·05), milk protein yield (832 vs 778 g day⁻¹; P=0·05) and milk lactose content (44·7 vs 43·5 g kg⁻¹; P<0·05) and yield (1113 vs 1023 g day⁻¹; P<0·01), whereas butyrate infusion was associated with a higher milk fat content (44·7 vs 39·4 g kg⁻¹; P<0·01) and yield (1033 vs 974 g day⁻¹; P<0·01). FM tended (P<0·10) to increase milk yield, but had no significant effects on milk composition or milk component yields compared with BP. Butyrate infusion increased blood ketones, plasma non-esterified fatty acids and glycine relative to propionate infusion. The concentrations of ammonia N in rumen fluid and urea in plasma and milk were similar for both protein supplements. The profile of amino acids in plasma was similar for both protein supplements except for the higher concentrations of phenylalanine, proline and tyrosine with BP. The results show that protein utilisation can be improved by increasing the supply of propionate from rumen fermentation in cows given a grass silage-based diet. © 1998 SCI.     

Effects of Silage Fermentation and Post-ruminal Casein Supplementation in Lactating Dairy Cows: 1—Diet Digestion and Milk Production

Two silages were prepared from the first-cut sward of timothy-meadow fescue and wilted to a dry matter (DM) content of 300 g kg^-1. One was ensiled with the addition of a formic-acid-based additive (4 litres formic acid (FA) per tonne) and the other with the addition of a bacterial inoculant (LAB) at a rate of 5×10⁶ colony forming units g^-1. Both silages were well preserved, but the extent of fermentation was greater in LAB-silage than in FA-silage as indicated by a lower concentration of water soluble carbohydrates (68 vs 177 g kg^-1 DM) and a higher concentration of lactic acid (147 vs 32 g kg^-1 DM). Four Ayrshire cows were used in a 4×4 Latin square experiment with 21-day periods to study the effects of silage fermentation and postruminal casein supplementation on silage intake, nutrient supply and milk production. The four treatments were FA-silage without casein (FA-0), LAB-silage without casein (LAB-0), FA-silage with casein (FA-C) and LAB-silage with casein (LAB-C). Both silages were given ad libitum with 8 kg day^-1 of barley without or with 400 g day^-1 of casein infused into the duodenum. Organic matter digestibility was lower (0·723 vs 0·753; P<0·01) for FA-silage than for LAB-silage. Cows offered FA-silage had a higher molar proportion of acetate and a lower proportion of propionate in ruminal fluid than cows offered LAB-silage. Microbial protein synthesis estimated from the output of purine derivatives in urine was greater (288 vs 260 g N day^-1; P<0·05) for cows given FA-silage compared with LAB-silage. Feeding LAB-treated silage tended (P<0·10) to decrease silage DM intake compared with FA-treated silage (10·61 vs 11·77 kg DM day^-1). Silage composition did not affect significantly milk yield or milk composition. Casein infusion increased milk yield (25·1 vs 27·1 kg day^-1; P<0·05), milk protein content (32·4 vs 33·8 g kg^-1; P<0·05) and protein yield (808 vs 905 g day^-1; P<0·01). The responses were similar for both silages. © 1997 SCI.     

Diurnal Variation in the Composition of Ileal Digesta and the Ileal Digestibilities of Nutrients in Growing Pigs

Diurnal variation in the chemical composition of digesta and its effect on nutrient digestibilities of diets varying in dietary fibre content was examined in pigs fitted with a PVTC-cannula at the terminal ileum. The pigs were fed three times a day (08:00, 16:00 and 24:00 h). A barley control diet and four barley-based diets containing two levels (100 or 200 g kg^-1 diet) of alfalfa meal or white clover meal and Cr₂O₃ as an indigestible marker were fed according to a 5×5 Latin square design. In each experimental period, digesta were collected for 1 h every third hour on each of two separate sampling days, covering in total a 24 h period. The concentration of dry matter (DM), crude protein (CP), ash and chromium (Cr) in the ileal digesta varied in relation to time of feeding. However, the patterns were similar after all three meals (08:00, 16:00 and 24:00 h) and independent of diet. The maximum DM, CP and ash contents were reached 4–5 h post-feeding. The highest (P < 0·05) DM concentration was found in the ileal digesta of pigs fed the barley control diet. The DM concentration decreased (P < 0·05) as the inclusion level of alfalfa meal and white clover meal was increased. The lowest DM concentration was found for the highest inclusion level of alfalfa meal. The ileal digestibilities of both organic matter and CP were lower 1–2 h post-feeding compared with those recorded 3–5 h later, indicating that the less digestible components of a diet have shorter transit times. The pooled ileal digestibilities of organic matter and CP from the three 8 h periods (08:00–16:00 h, 16:00–24:00 h, 24:00–08:00 h) did not differ (P < 0·05) from each other. Therefore, the estimate of digestibility can be based on digesta samples collected from any interval between two consecutive meals. However, care must be taken to obtain representative samples of digesta between meals. © 1997 SCI.     

Enzymic and in sacco methods to estimate rumen degradation of food protein in cattle

BACKGROUND: Two factorial studies compared enzymic and in sacco methods to estimate degradation of ruminant foods. Enzyme degradation (in vitro = enzyme) was determined from the release of leucine‐equivalent amino acid (LA) crude protein (CP) from sunflower meal (SF), maize gluten meal (MG), distillers' dark grain (DG) and field beans (FB) after their separate incubations with Streptomyces griseus enzyme for 0–24 h. In sacco crude protein (CP) degradation of these foods was estimated during washing (0 h) and rumen incubations in fistulated cows for 2–24 h. The LA data were expressed as g LA per either kg of CP (LACP) or acid‐hydrolysable LA (HLA) of each food and compared with in sacco data. RESULTS: These methods showed comparable degradation with time (P < 0.01). The in sacco and HLA were greater than LACP for all foods except MG where in sacco value was either lower or equal to LACP depending upon the incubation time (P > 0.05 or P < 0.05). Conversely, HLA was significantly (P < 0.01) greater than LACP from 2 h onwards. At 0 h, in sacco values were significantly greater than those of enzyme for SF, DG and FB (P < 0.05) but not for MG. The foods differed significantly for degradation constants (a, b, c) in each method (P < 0.05). CONCLUSIONS: Despite variations between in sacco and enzyme estimates for different foods, the relationships between these estimates suggest that the HLA enzyme method has the potential to estimate food degradation. Copyright © 2007 Society of Chemical Industry     

Dietary effects on growth,liver peroxides,and serum and lipoprotein lipids in rats fed a thermoxidised and polymerised sunflower oil

The effect on food intake, weight gain, liver lipid peroxides, lipemia and lipoprotein composition was determined in rats fed a diet with 15% sunflower oil used repeatedly for frying and containing ∽19% polar material (group 2). These dietary effects were compared over a 4 week study period with those found in rats fed a control diet that contained 15% unused sunflower oil with ∽5% polar material (group 1). Both groups had similar food and nutrient intakes (except for linoleic acid, significantly lower (P<0·01) in group 2), yet the final weight gain and food efficiency and protein efficiency ratios were significantly lower in group 2. As a consequence of thermoxidised oil ingestion, liver homogenates from group 2 presented higher (P<0·02) levels of thiobarbituric acid reactive substances (TBARS) Liver TBARS levels were significantly correlated (P<0·01) with the amount of thermoxidised substances ingested. No treatment effect was found on VLDL lipid composition. However, the LDL fraction of group 2 animals appears enriched (P<0·05) in total and free cholesterol. In group 2 rats, phospholipids, and total and esterified cholesterol were significantly increased (P<0·05) in HDL. As a consequence of the changes in the lipoprotein composition, the amount of all forms of serum cholesterol, and serum phospholipids was significantly higher (at least P<0·05) while the amount of serum triacylglycerols remained unchanged in rats fed the used oil. HDL-phospholipids were significantly correlated (P<0·02) with the amount of thermoxidised compounds ingested. The increase in serum cholesterol and phospholipids, and in HDL-cholesterol and HDL-phospholipid concentration seens in group 2 rats may be a protective mechanism against the peroxidative stress produced by the ingestion of used sunflower oil. © 1998 SCI.     

Effects of extraction and reconstitution of ryegrass juice on fermentation,digestion and in situ degradation of pressed cake silage

Primary growth of Italian ryegrass was fractionated into green juice and pressed cake (PC). PC was ensiled either directly or after reconstitution with the juice which was spray dried and then added to water before ensiling (RPC). This process was aimed at distinguishing between chemical (removal of nutrients) and physical (mechanical disintegration) effects of fractionation. Two additional wilted silages were prepared from long cut or chopped Italian ryegrass (WL and WC, respectively). The fermentative quality, digestion and in situ degradation of dry matter for the four silages were compared. WC, RPC and PC silages indicated lactate-rich fermentation while WL silage had a comparatively low lactate content. PC silage had a lower (P<0·05) pH value with lower (P<0·05) amounts of organic acids compared with WC and RPC silage, suggesting that removal of buffering components with the juice had greater effects than shredding on fermentation of PC silage. The digestibility of protein was lower (P<0·05) in PC than WL silage but the reduction was compensated for in RPC silage. Ruminal concentrations of total volatile fatty acids were the highest (P<0·05) when goats fed WL silage while those on the other silages had similar concentrations. Ruminal pH was lower (P<0·05) in goats fed PC than WC silage and the difference was not fully reversed by reconstituting the juice to PC. Juice extraction decreased (P<0·05) the soluble fraction and the rate of disappearance of dry matter in the rumen but the potential degradability was not different among treatments. These results suggest that both chemical and physical changes due to the fractionation affect the characteristics of digestion of PC silage while the removal of nutrients has a major role in the modified silage fermentation. © 1997 SCI.     

Nutrient contents,rumen protein degradability and antinutritional factors in some colour- and white-flowering cultivars of Vicia faba beans

Six colour-flowering (Scirocco, Alfred, Carola, Condor, Tina and Herz Freya) and six white-flowering (Caspar, Albatros, Gloria, Tyrol, Vasco and Cresta) cultivars of Vicia faba were studied. The crude protein contents of colour- and white-flowering cultivars were 267±13·6 and 283±18·8 g kg⁻¹, respectively, which did not differ significantly at P<0·05. The levels of lipids, crude fibre, starch and ash varied from 14 to 22 g kg⁻¹, 88 to 143 g kg⁻¹, 407 to 485 g kg⁻¹ and 32 to 42 g kg⁻¹, respectively. The calculated organic matter digestibility (OMD) and metabolisable energy (ME) of the white-flowering cultivars were significantly higher (P<0·001) than those of the colour-flowering cultivars (OMD: 889·1±26·6 g kg⁻¹ vs 797·5±17·1 g kg⁻¹; ME: 13·97±0·49 vs 12·30±0·34 MJ kg⁻¹). In all cultivars, sulphur amino acids were lower than adequate concentration when compared with recommended amino acid pattern of FAO/WHO/UNO reference protein for a 2–5-year-old child. The in vitro rumen nitrogen degradability of colour-flowering cultivars was significantly lower (P<0·01) compared to that of white-flowering cultivars (71·4±9·3% vs 88·0±11·1%). Amongst colour-flowering varieties, the contents of total phenols (TP), tannins (T) and condensed tannins (CT) were highest in Alfred (28·3, 21·0 and 35·4 g kg⁻¹, respectively). The contents of TP and T were similar (about 15 and 10 g kg⁻¹, respectively) in Carola, Tina and Herz Freya, and the CT were in the order: Condor>Herz Freya>Carola. The CT were not detected in white-flowering varieties, T were virtually absent and TP were extremely low (4·0–4·9 g kg⁻¹). The activities of other antinutritional factors (white- and colour-flowering cultivars, respectively: trypsin inhibitor activity 3·05±0·34 and 1·85±0·09 mg trypsin inhibited g⁻¹; lectin 27·2±9·4 and 27·1±5·1 mg ml⁻¹ assay medium producing haemagglutination; phytate 15·0±2·7 and 16·6±2·3 g kg⁻¹) were very low. A strong negative correlation (r=-0·92, P<0·001) between tannins and in vitro rumen protein degradability was observed which suggested that tannins have adverse effect on protein degradability. Similarly negative correlations between tannin levels and metabolisable energy (r=-0·89; P<0·001) and organic matter digestibility (r=-0·89; P<0·001) were observed. The correlation coefficient between trypsin inhibitor activity and tannins was negative and highly significant (r=-0·88, P<0·001), whereas between tannins and saponins it was significantly positive (r=0·96, P<0·001). ©1997 SCI     

Dietary Fat Reduces Odd-Numbered and Branched-Chain Fatty Acids in Depot Lipids of Rabbits

Forty eight Californian×New Zealand White rabbits were randomly distributed in three groups of 16 animals each. A control (with no added fat) and two diets enriched at a rate of 30 g fat kg^-1 were used. Olive oil and sunflower oil were used as sources of fat for the fat-supplemented diets. Branched chain (BCFA) and n-odd-numbered carbon fatty acids (ONFA) in the perirenal fat depots of control animals were respectively 5 and 22 mg g^-1 of total fatty acids, while in fat-enriched diets they were around 3 and 16 mg g^-1, respectively. The ratio of unsaturated: saturated fatty acid in perirenal fat was 1·25:1 when the control diet was administered and around 1·80–1·95:1 in fat-enriched diet groups, which represents approximately a 50% increase (P<0·01). However the melting points of the fats showed little difference (NS) between the control group and the group with olive oil addition whilst the sunflower oil-supplemented group showed only a 5·7% lower value (P<0·01). In a second experiment in which diets with equal digestible energy and protein were used, reductions in total amounts of ONFA (P<0·01) and BCFA (P<0·05) were observed in the perirenal fat of animals receiving the fat-enriched diets. The addition of fat depressed the concentrations of ONFA and BCFA, which may act to maintain the consistency of fat in a narrow range, avoiding to some extent the production of undesirable soft and floppy carcasses. © 1997 SCI.     

Effect of supplemental yeast culture and dietary starch content on rumen fermentation and digestion in dairy cows

The objectives of this experiment were to evaluate the effect of feeding a culture of Saccharomyces cerevisiae on rumen metabolism and digestibility when cows are fed diets varying in starch content. Four lactating Holstein cows were assigned to a 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments. Treatments were low starch (LS; 23% of diet DM) and no yeast culture (YC; LS-control), LS and 15 g of YC/d (LS-YC), high starch (HS; 29% of diet DM) and no YC (HS-control), and HS and 15 g of YC/d (HS-YC). Periods lasted 28 d, with the last 9 d for data collection. Days 20 to 24 were used to determine production, nutrient flow, and digestibility. On d 25, 3 kg of corn grain DM was placed in the rumen 1 h before the morning feeding, and yields of milk and milk components were measured after the challenge. Blood was sampled −1, 3, 7, and 11 h relative to the morning feeding on d 24 and 25. Rumen pH was measured continuously on d 24 and 25. Rumen papillae were collected on d 24 and 28 to quantify mRNA expression of select genes. Supplementing YC increased yields of milk (26.3 vs. 29.6 kg/d), energy-corrected milk (ECM; 26.5 vs. 30.3 kg/d), fat (0.94 vs. 1.08 kg/d), true protein (0.84 vs. 0.96 kg/d), and ECM/dry matter intake (1.15 vs. 1.30) compared with the control but did not affect dry matter intake (22.6 vs. 22.9 kg/d). Cows fed HS had increased milk true protein percentage (3.18 vs. 3.31%) and yield (0.87 vs. 0.94 kg/d) compared with cows fed LS. Feeding HS-YC increased the proportion of dietary N incorporated into milk true protein from 24.9% in the other 3 treatments to 29.6%. Feeding HS increased the concentration of propionate (21.7 vs. 32.3 mM) and reduced that of NH₃-N (8.3 vs. 6.7 mg/dL) in rumen fluid compared with the control, and combining HS with YC in HS-YC tended to increase microbial N synthesis compared with LS-YC (275 vs. 322 g/d). Supplementing YC to cows fed HS reduced plasma haptoglobin and rumen lactate concentrations, increased mean rumen pH, reduced the time with pH <6.0, and prevented the decrease in rumen neutral detergent fiber digestion caused by HS. Cows fed HS had less total-tract digestion of organic matter (73.9 vs. 72.4%) because of reduced acid detergent fiber (57.6 vs. 51.7%) and neutral detergent fiber (60.9 vs. 56.7%) digestibility. Production performance after the challenge was similar to that before the challenge, and YC improved yield of ECM. After the challenge, supplementing YC tended to reduce rumen lactate concentration compared with the control and reduced haptoglobin in cows fed HS. Feeding HS but not YC increased expression in rumen papillae of genes for receptors (FFAR2 and FFAR3) and transporter (SLC16A3) of short-chain fatty acids but did not affect genes involved in transport of Na⁺/H⁺ or water or in inflammatory response. Supplementing YC to dairy cows improved lactation performance in diets containing low or high starch, and mechanisms might be partially attributed to improvements in rumen pH, digestion of fiber, microbial N synthesis, and reduction in acute phase response.     

The effect of feeding pods of multipurpose trees (MPTs) on the degradability of dry matter and cell wall constituents of maize stover and alfalfa incubated in the rumen of sheep

This study evaluated the effects of feeding alfalfa and pods of tree legumes on rumen pH and ammonia concentration as well as in sacco degradability of dry matter and fibre constituents of maize stover, alfalfa hay and their neutral detergent extracts. The feeds were incubated in the rumens of five South African Merino sheep fed individually in an incomplete (5 × 4) Latin square design using five diets. The diets comprised equal proportions of pasture hay and either alfalfa (Alfalfa diet) or pods of Acacia sieberiana (Sieberiana diet), Acacia nilotica (Nilotica diet) or Leucaena leucocephala (Leucaena diet). The fifth diet was composed of pasture hay alone (Hay diet) and served as a negative control. Supplementation of hay with either legume pods or alfalfa significantly (p < 0.05) increased rumen ammonia concentration from 56 to a maximum of 86 mg l^?1. The pH of the rumen fluid ranged between 6.2 and 6.5 for all diets, but variations in pH were not significant. Diet did not affect (p > 0.05) the degradability constants lag time (LT), slowly degradable fraction (B), potential degradability (PD), effective degradability (ED) and rate of degradation (C) of dry matter (DM) but significantly (p < 0.01) affected ED of the fibre constituents of the incubated feeds. The effective degradabilities of the incubated feeds differed (p < 0.001), with alfalfa and maize stover having average values of 555 and 318 g kg^?1 DM respectively. The rate of degradation of alfalfa was also higher (p < 0.01) than that of maize stover. Neutral detergent extraction improved ED of the cell wall constituents of maize stover but produced the opposite effect for alfalfa. The interactions between incubation feed and extract were significant (p < 0.01) for ED and C of neutral detergent fibre and hemicellulose. The observations show that pods from tree legumes are comparable to alfalfa in the provision of rumen ammonia but limit microbial activity in the degradability of fibre constituents. They also show that maize stover and alfalfa differ in their degradabilities and that the differences may be attributed to their cell wall chemistry. © 2001 Society of Chemical Industry     

Changes with maturity in fibre composition and levels of extractable polyphenols in Greek browse: Effects on in vitro gas production and in sacco dry matter degradation

Neutral and acid detergent fibre (NDF, ADF), lignin, crude protein (CP), total extractable phenols (TEPH), tannins (TETa), condensed tannins (vanillin assay TECTa; proanthocyanidins TEPAs) in the leaves of spring Phyllirea media (SPRG) or early summer (ESUM) and early autumn (EAUT) Carpinus duinensis, Quercus coccifera and Fraxinus ornus were studied. Gas production (in vitro) and dry matter (DM) degradation (in sacco) were also studied after incubation for up to 96 h. Concentrations of TEPH, TETa, TECTa, TEPAs and the fibre components were variable (P < 0·05) among species and except for CP were not consistently changed with degree of maturity. CP content varied from 70·5 to 132·9 (g kg^?1 DM) but was always decreased by 15–25% at maturity, whereas levels of TECTa and TEPAs were increased (P < 0·05) in C duinensis and Q coccifera but not in F ornus (P > 0·05). Concentrations of phenolics were related negatively but more significantly to gas production than to DM degradation (in sacco). Therefore, the gas test was considered to be more efficient than the nylon bag technique for the identification of feeds with antinutritive factors. Based on their phenolic content and gas production or DM degradation, the nutritive value of P media = F ornus (ESUM and EAUT) > C duinensis = Q coccifera (ESUM) > C duinensis = Q coccifera (EAUT). It was concluded that the decline in CP with maturity could make nitrogen the factor limiting intake and digestibility. This would be accentuated with an increase in the concentration of phenolics, particularly tannins.     

Comparative composition of aerial and subterranean potato tubers (Solanum tuberosum L)

The composition of aerial and subterranean tubers of two potato genotypes cvs Desiree (red skin) and Epicure (white skin) was compared immediately after harvest using a range of analytical methods. Irrespective of genotype, aspartic acid, arginine, glycine, glutamic acid, histidine, leucine, serine, threonine and total amino acid concentrations were significantly higher (P<0·05) in aerial compared with subterranean tuber tissue. Significant increases (P<0·05) in valine in aerial tubers, but no significant differences in alanine, tyrosine and iso-leucine, when compared with subterranean tubers of cv Desiree, were found. In cv Epicure, alanine, tyrosine and iso-leucine were significantly higher in aerial tubers (P<0·05); however, no significant differences in valine were recorded. There was no significant increases in lysine and phenylalanine between tuber types. Regardless of genotype α-solanine, α-chaconine, chlorogenic acid, chlorophyll and crude protein concentrations were significantly higher in aerial tubers compared with subterranean ones (P<0·01). No significant increases in total lipids between tuber types were found. In cv Desiree, ascorbic acid content was not significantly different between aerial and subterranean tuber tissue, but in cv Epicure concentrations were significantly higher (P<0·01) in aerial tubers. Starch concentrations were significantly higher in subterranean tubers of both cultivars (P<0·05). Sugar content was significantly higher in aerial tubers of cv Epicure (P<0·01), but not significantly different between aerial and subterranean tubers of cv Desiree. Regardless of genotype, phosphorus, magnesium, potassium, zinc, manganese and sodium concentrations were significantly higher (P<0·05) in aerial tubers. Iron and copper concentrations were significantly higher in aerial tubers of cv Desiree (P<0·01), but significantly less in cv Epicure compared with subterranean tubers (P<0·01, P<0·05). Calcium concentrations were not significantly different between aerial and subterranean tubers of cv Desiree, but significantly higher in aerial tuber tissue of cv Epicure (P<0·01). Total gross energy (mJ kg⁻¹ FW) was higher in aerial tubers of cv Desiree compared with subterranean tubers (P>0·05), but not significantly different between aerial and subterranean tubers of cv Epicure. The potential applications of aerial tubers for industrial purposes are discussed. © 1997 SCI.     

Dietary manipulation of the yield and composition of milk: Effects of dietary inclusions of barley and oats in untreated or formaldehyde-treated forms on milk fatty acid composition

Eight 1st-lactation cows were given four dietary treatments in a duplicated 4×4 Latin square experiment. Diets consisted of hay and soya bean meal together with barley, formaldehyde-treated barley, oats or formaldehydetreated oats (approximately 34:12:54 on a dry matter basis). Barley diets supplied 211 g fatty acids d^?1, oats diets supplied 537 g d^?1. The fatty acid composition (g kg^?1 total fatty acids) for barley diets was: 300 (16:0); 20 (18:0); 150 (18:1); 470 (18:2); 60 (18:3). Corresponding values for oats diets were 180, 20, 390, 380 and 30 g kg^?1. Formaldehyde treatment of the cereals tended to increase milk yield and reduce milk fat content (P<0·01 for barley) but did not affect milk fatty acid composition. Feeding oats in replacement for barley significantly (P<0·05) increased milk yield and lactose yield and reduced milk fat content (P<0·05 for the untreated cereals) and protein contents (P<0·01) without significant effects on milk fat or protein yields. Oats diets led to significant (P<0·001) reductions in the content of 8:0–16:0 fatty acids in milk fat with associated increases (P<0·001) in the content of 18:0 and 18:1. Changes in milk fat content of 18:2 and 18:3 acids were small. The results show the inclusion of oats in the cow's diet to be a means of reducing the saturated fatty acid content of milk fat thereby improving the nutritional value of milk and milk products and their appeal to the health-conscious consumer.     

Nitrogen in browse species: ruminal degradability and post-ruminal digestibility measured by mobile nylon bag and in vitro techniques

This study determined nitrogen degradability and digestibility of rumen undegradable nitrogen using mobile nylon bag (MNB) and pepsin/pancreatin in vitro technique (IV) of 40 browse species. Thirty Ethiopian highland sheep fitted with rumen cannulae were used in nitrogen (N) degradability studies. Six steers fitted with rumen cannulae were used in preparation of 16-h and 24-h ruminal undegraded residues and four steers fitted with distal abomasal cannulae were used in MNB technique. The browses varied widely in nitrogen solubility (15–468 g kg⁻¹), potential degradability (223–976 g kg⁻¹), rate of degradation (0·13–24% h⁻¹) and effective degradability (135–821 g kg⁻¹). The apparent N digestibility (ND) of the rumen undegraded residues differed significantly (P<0·05) among browse species. No significant difference (P>0·05) was observed in ND of 16-h and 24-h residues. The ND of the 16-h residue varied from -218 to 759 g kg⁻¹ and 169 to 851 g kg⁻¹ for MNB and IV methods, respectively. Browse species with high tannin contents such as Acacia hockii, A horrida, A melanoxylon, A persiciflora, A salicina, A saligna and Flemingia macrophylla had high rumen by-pass and a low ND, while Sesbania spp and A nilotica with low tannin contents underwent rapid and extensive dry matter and nitrogen degradation in the rumen. Acacia sieberiana, Chamaecytisus palmensis, Erythrina spp, Gliricidia sepium, Samanea saman and Enterolobium cyclocarpum had high proportions of protein escaping rumen degradation (BP ) and with a high proportion of the by-pass protein digested in the intestine, therefore these browses had a high potential as protein supplements. The ND measured with the MNB were significantly lower (P<0·001) than by the IV method. The correlation between MNB and IV was high and significant (R²=0·89, P<0·0001) as also indicated by the regression equation (SE in parentheses): MNB=-22·8 (4·55)+1·0 (0·08)IV (RSD=10·56, R²=0·79, n=40, P<0·001). The intercept of the linear relationship obtained was different from zero while the slope was not different from unity. Multiple regression analysis suggested that some of the unexplained variation could be accounted for by either nitrogen, acid detergent fibre, total phenolics or neutral detergent fibre bound tannin levels in browses. The IV method is accurate for estimating digestibility of ruminally undegradable N, and hence its use would considerably reduce the need for delicate surgery and the elaborate procedures involving the MNB technique. © 1998 SCI.     

Chemical characterisation and ruminal nutrient degradability of hulled and hull-less oats

The objectives of this study were to determine the chemical and ruminal nutrient degradability characteristics of two hulled (Calibre and AC Mustang) and one hull-less (AC Belmont) oat varieties. Ruminal nutrient degradability characteristics of the oat varieties were determined relative to barley using one ruminally fistulated cow. Neutral (NDF) and acid (ADF) detergent fibre levels were higher (P < 0·05) in hulled than hull-less oats. Hulled AC Mustang had higher (P < 0·05) NDF and ADF content than hulled Calibre. Starch content was higher (P < 0·05) in AC Belmont (590 g kg⁻¹) than Calibre (457 g kg⁻¹) and was higher in Calibre than AC Mustang (415 g kg⁻¹). Crude protein was higher (P < 0·05) in hull-less than hulled oat. Both hulled varieties had similar CP content (average 124 g kg⁻¹). Estimated digestible energy value was highest (P < 0·05) for AC Belmont (16·94 MJ kg⁻¹), intermediate for Calibre (14·18 MJ kg⁻¹) and lowest for AC Mustang (13·34 MJ kg⁻¹). Ruminal dry matter and NDF degradability were higher (P < 0·05) in hull-less than barley and was higher in barley than hulled oats. Ruminal starch degradability exceeded 900 g kg⁻¹ for all tested feeds and had the order AC Belmont = barley > Calibre = AC Mustang. It was concluded that oat varieties used in this study varied considerably in their chemical composition and ruminal degradability. When compared with barley, hulled oats had lower while hull-less oats had higher ruminal degradability. © 1998 SCI.     

Effects of peripartal yeast culture supplementation on lactation performance,blood biomarkers,rumen fermentation,and rumen bacteria species in dairy cows

Feeding yeast culture fermentation products has been associated with improved feed intake and milk yield in transition dairy cows. These improvements in performance have been further described in terms of rumen characteristics, metabolic profile, and immune response. The objective of this study was to evaluate the effects of a commercial yeast culture product (YC; Culture Classic HD, Phibro Animal Health) on performance, blood biomarkers, rumen fermentation, and rumen bacterial population in dairy cows from −30 to 50 d in milk (DIM). Forty Holstein dairy cows were enrolled in a randomized complete block design from −30 to 50 DIM and blocked according to expected calving day, parity, previous milk yield, and genetic merit. At −30 DIM, cows were assigned to either a basal diet plus 114 g/d of ground corn (control; n = 20) or a basal diet plus 100 g/d of ground corn and 14 g/d of YC (n = 20), fed as a top-dress. Cows received the same close-up diet from 30 d prepartum until calving [1.39 Mcal/kg of dry matter (DM) and 12.3% crude protein (CP)] and lactation diet from calving to 50 DIM (1.60 Mcal/kg of DM and 15.6% CP). Blood samples and rumen fluid were collected at various time points from −30 to 50 d relative to calving. Cows fed YC compared with control showed a trend for increased energy-corrected milk (+3.2 kg/d). Lower somatic cell counts were observed in YC cows than in control. We detected a treatment × time interaction in nonesterified fatty acids (NEFA) that could be attributed to a trend for greater NEFA in YC cows than control at 7 DIM, followed by lower NEFA in YC cows than control at 14 and 30 DIM. In the rumen, YC contributed to mild changes in rumen fermentation, mainly increasing postpartal valerate while decreasing prepartal isovalerate. This was accompanied by alterations in rumen microbiota, including a greater abundance of cellulolytic (Fibrobacter succinogenes) and lactate-utilizing bacteria (Megasphaera elsdenii). These results describe the potential benefits of supplementing yeast culture during the late pregnancy through early lactation, at least in terms of rumen environment and performance.     

The effect of addition of mixtures of amino acids on the intake of grass silage by sheep and cattle

A mixture of 15 amino acids was either added to the basal silage diet (sheep and cattle) or infused intraruminally (cattle) to determine the role of amino acids in the control of silage intake. Neither dietary addition nor intraruminal infusion of the amino acid mixture in sheep or cattle had a significant effect on intake compared to the control (P > 0·05). However, in cattle, dietary addition of the amino acid mixture increased intake compared with intraruminal infusion of the amino acid mixture (P < 0·01). It was concluded that the amino acid content of the basal silage is not involved in the control of silage intake by sheep or cattle. © 1998 SCI     

Response of nutrient digestibilities to feeding diets with low and high levels of soybean trypsin inhibitors in growing pigs

Studies were carried out to determine the effect of dietary soybean trypsin inhibitor (SBTI) content on nutrient and energy digestibilities in growing pigs. Six barrows, average initial body weight (BW) 47·8±4·0 kg, were fitted with a simple T-cannula at the distal ileum and fed two diets according to a crossover design. Two maize starch-based diets were formulated to contain 200 g crude protein (CP) kg⁻¹ from either Nutrisoy (a food-grade defatted soy flour) or autoclaved Nutrisoy. The contents of SBTI in the Nutrisoy and autoclaved Nutrisoy diets were 13·4 and 3·0 g kg⁻¹, respectively. The experiment consisted of two periods of 12 days each. The average BW at the start of the first and second experimental periods were 53·3±3·7 and 61·0±5·1 kg, respectively. The average BW at the conclusion of the experiment was 71·8±7·6 kg. The ileal digestibilities of dry matter (DM), organic (OM), energy, CP and all amino acids measured were higher (P<0·01) in pigs fed the autoclaved Nutrisoy diet. The energy digestibility increased from 66·0 to 77·9%, and the CP digestibility increased from 37·4 to 77·1%. The increases in ileal digestibilities of the indispensable amino acids ranged from 27·0 (methionine) to 49·2 (leucine) percentage units. The increases in ileal digestibilities of the dispensable amino acids ranged from 30·2 (aspartic acid) to 50·8 (tyrosine) percentage units. The faecal digestibilities of all criteria measured were also higher (P<0·01) in pigs fed the autoclaved Nutrisoy diet. Furthermore, there was a greater (P<0·01) net disappearance (g kg⁻¹ DM intake) of DM, OM, CP, energy and all amino acids in the large intestine of pigs fed the Nutrisoy diet. In conclusion, feeding diets containing high levels of SBTI decreased both ileal and faecal digestibilities of all criteria measured. The formation of SBTI-enzyme complexes is likely to be responsible for the reduction in protein digestion and amino acid absorption. © 1998 SCI.