Peter Udén

The determination of digesta particle size in some herbivores

Methods for determining and describing digesta and faecal particle size were studied. Higher mean particle size values were demonstrated for wet sieving as compared to dry sieving. Equines had larger faecal particle size than ruminants and rabbits. Particle size decreased with body weight in rumen-reticulum and facese for the ruminants. The fibre particle size was the same in rabbit hard and soft faeces and similar to sheep and goat faeces. The excretion pattern of Cr-mordanted fibre in sheep was shown to be influenced by the fraction that was labelled in the rumen. Retention time in the rumen and whole tract increased with increasing particle size. In rabbits, 300 μ Cr-mordanted fibre particles gave similar marker retention times.

The effect of grinding and pelleting hay on digestibility, fermentation rate, digesta passage and rumen and faecal particle size in cows

Abstract High-quality grass hay was either chopped (CH) or ground and pelleted (PH) and given to two rumen-fistulated cows at about the maintenance level. Digestibility in vivo was measured as well as neutral detergent fibre (NDF) rate and extent of fermentation in sacco. Solids and liquid marker excretions in faeces were measured after a pulse dose in the rumen of Cr-mordanted NDF and LiCoEDTA. A 3-pool model with lag was fitted to the data and retention times were calculated for individual pools and for the total digestive tract. Core samples were taken from the rumen three times daily for particle size analysis by wet sieving. Faecal and feed mean particle size (MPS) was determined. Pelleting lowered dry matter and NDF digestibility from 0.73 to 0.67 and from 0.79 to 0.68, respectively. Fermentation rate decreased from an average of 0.094 to 0.051 h −1 and the unavailable NDF fraction was increased from 0.23 to 0.37 by pelleting. Digesta liquid retention was unaffected by pelleting, but total solids retention decreased from 73 to 54 h. The effect of pelleting on retention in different pools varied between the animals. Rumen MPS was largest, and faecal MPS smallest, when feeding on CH. Hay PH gave the lowest MPS after evening feeding and the highest before morning feeding. The opposite was observed for CH. The decrease in fermentation rate, increase in unavailable fibre and decrease in rumen digesta retention are believed to be the main factors responsible for decreased digestibility in vivo.

The effect of intake and hay: Concentrate ratio upon digestibility and digesta passage

Hay:concentrate ratios and level of intake were varied in dairy cow rations to study the effects on digestibility, metabolic faecal output and digesta retention. The hay contained >80% grasses and the concentrate mix consisted of 40% barley and 40% oats. A total of 22 dry or lactating dairy cows was used, half of which received approximately 19 g DM/kg body weight, of which 30–100% was hay dry matter. The remaining cows were given a diet with 50% hay and 50% concentrates at levels of 14–32 g DM/kg BW. Organic matter digestibility (OMD), neutral detergent fibre digestibility (NDFD) and metabolic faecal output (MFO; % of intake) were measured, as well as the rate of NDF disappearance in sacco. Passage of liquid was measured with CoEDTA, concentrates with Cr-labelled barley hulls and hay with Cr-labelled hay. Linear regressions of OMD (%), NDFD (%) and MFO (%) on hay level (%) were significant (P < 0.05) with slopes of −0.14, 0.18 and 0.033, respectively, but digesta retention was unaffected by hay:concentrate ratio. Intake had no significant effect on digestibility and MFO, but affected total mean retention time (h) of liquid, concentrates and hay significantly, with slopes of −0.24, −1.4 and −1.6 (P < 0.05), respectively. Incubations in sacco showed that NDF in hay was more rapidly degraded than in concentrates (0.0971 vs. 0.0469 h−1; P < 0.001), whereas residual NDF at infinite time was similar (38.9 and 41.7%, respectively). NDFD seemed to be relatively unaffected by concentrate level and intake in the regions of 0–30% concentrates and <20 g DM/kg BW, respectively. Relative depression in NDFD (observed NDFDin vivo - potential NDFDin sacco) vs. concentrate level and intake, excluding observations <30% concentrates and < 20 g DM/kg BW, gave significant regression lines with slopes of −0.31 and −0.89 percentage units per 1% increase in concentrate level (P < 0.05), respectively.

Relationship between condensed tannin structures and their ability to precipitate feed proteins in the rumen

BACKGROUND Tannins can bind to and precipitate protein by forming insoluble complexes resistant to fermentation and with a positive effect on protein utilisation by ruminants. Three protein types, Rubisco, rapeseed protein and bovine serum albumin (a single high-molecular weight protein), were used to test the effects of increasing concentrations of structurally different condensed tannins on protein solubility/precipitation. RESULTS Protein type (PT) influenced solubility after addition of condensed tannins (P < 0.001) in the order: Rubisco < rapeseed < BSA (P < 0.05). The type of condensed tannin (CT) affected protein solubility (P = 0.001) with a CT × PT interaction (P = 0.001). Mean degree of polymerisation, proportions of cis- versus trans-flavanol subunits or prodelphinidins versus procyanidins among CTs could not explain precipitation capacities. Increasing tannin concentration decreased protein solubility (P < 0.001) with a PT × CT concentration interaction. The proportion of low-molecular weight rapeseed proteins remaining in solution increased with CT concentration but not with Rubisco. CONCLUSIONS Results of this study suggest that PT and CT type are both of importance for protein precipitation but that the CT structures investigated did not allow identification of parameters that contribute most to precipitation. It is possible that the three-dimensional structures of tannins and proteins may be more important factors in tannin-protein interactions.

Acetyl and phenolic acid substituents in timothy of different maturity and after digestion with rumen microorganisms or a commercial cellulase

Abstract Timothy grown in northern Sweden was harvested at varying maturity. Residues were prepared by extraction with ethanol or incubation in vitro, using rumen liquor or a commercial cellulase. The content of acetyl and phenolic ( p -coumaric- and ferulic acid) substituents increased with maturity in all residues. Incubation with rumen liquor caused removal of a higher proportion of the substituents than the cellulase treatment. It was notable that ferulic acid was removed to a much greater extent than p -coumaric acid substituents. Acetyl and p -coumaric acid substituents, assumed to be linked mainly to the xylans, were proportionally less digestible in rumen liquor than xylose.

Comparison of laboratory methods on precision and accuracy of predicting forage organic matter digestibility

Abstract Three methods of estimating digestibility were tested using different incubation times. A modified one-stage in-vitro method (VOS), an in vitro true digestibility (IVTD) at two incubation times and an in sacco true digestibility (ISTD) method, also at two incubation times were examined for precision and accuracy of prediction. Forages ( n = 21) consisting of straws, hays and silages, grown in Sweden and of known in vivo organic matter digestibility (OMD) running from 0.300 to 0.809 were used. Incubations of single samples replicated on 3 different days were used. Fermentation times were 96 h (standard) for the VOS and 48 h (standard) and 72 h for the IVTD and ISTD methods. Results showed higher mean OMD at 72 h (0.78) than at 48 h (0.75) and higher values for ISTD (0.79) than for IVTD (0.74) and for VOS (0.70). The reliability of the results (precision) was poorest with the in sacco methods. Variations in precision among the in vitro techniques were small. The intercepts decreased and the slopes of the regression equations increased, when incubation time changed from 48 to 72 h. The accuracy of predicting in vivo digestibility was lowest with IVTD and ISTD incubated at 72 h followed by ISTD and IVTD at 48 h and highest with VOS.

Promising tropical grasses and legumes as feed resources in Central Tanzania IV. Effect of feeding level on digestibility and voluntary intake of four herbaceous legumes by sheep

An experiment involving comparison of 4 legumes fed at 5 levels was conducted to study the effect of the level of feeding on digestibility and voluntary intake by Blackhead persian rams. The legumes were Neonotonia wightii cv. Mpwapwa (NWM), Stylosanthes scabra cv. Seca (SSS), Macrotyloma axillare cv. Archer (MAA) and Macroptilium atropurpureum cv. Siratro (MAS). The forages were cut at 8 weeks and dried in the sun. Sixteen sheep were used and fed 600, 900, 1200, 1500 and 1800 g/day in a split plot design. Among the species compared, SSS and NWM had higher (P < 0.05) organic matter (OM) digestibility than MAA and MAS. Differences in intakes among species were observed, with MAS having lower OM intakes (P < 0.05) than the other species. Increasing feeding level allowed the selection of more leafy diet with significant improvement (P < 0.05) in OMD in SSS, and MAA, but not of MAS and NWM. Significant improvement (P < 0.05) in intakes of OM and digestible OM were observed in all species, as feeding level was raised from 600–1800 g per day, to allow for the selection. The level of feeding allowing maximum intakes of OM with the least refusal was, on the average, 1200 g with 19.6% refusals, ranging from 900 g per day with refusals of 10.3% for MAS, to 1500 g per day with refusals of 29.4% for SSS. The maximum OM intakes were 20.5 g kgW−1 d−1 and 25.5 g/kg BW/day for MAS and SSS, respectively. Estimated maximum intake at infinite feeding level was, on the average, 26 g/kg BW/day. A realistic value for SSS could not be obtained, but was, probably, considerably higher than that for the others. To obtain a maximum value for animal production, refusals of approximately 40% would be required. Among the legumes studied, SSS seems to be the most promising species for the semiarid areas of Central Tanzania.

The influence of leaf and stem particle size in vitro and of sample size in sacco on neutral detergent fibre fermentation kinetics

Four particle sizes, chopped, ground to pass a sieve of 4.5 mm (coarse ground), 1 mm (medium ground) and 0.25 mm (fine ground) of early and late cut winter wheat were separated into leaf and stem fractions and incubated with rumen fluid in vitro for 0–148 h in a first experiment. In a second experiment, grass hay (GH) and wheat straw (WS), ground to pass a 2 mm sieve were incubated in sacco for 0–185 h. Sample size varied from 3.75 to 22.5 mg cm−2 bag surface area for GH and from 7.5 to 22.5 mg cm−2 bag surface area for WS. An exponential model with and without lag was fitted to the curves in both experiments using relative values of residual neutral detergent fibre (NDF). Treatments were tested for effects on curve displacement (any curve parameter differences) and on rate and lag of fermentation. Results from the first experiment showed a higher average rate of degradation for leaves over stems and a negative effect of cutting date. Undegradable NDF was lower for early cut stems and higher for late cut stems. Particle size had a significant effect on curve displacement in all cases. Specific effects on lag were significant in all cases except for early cut stems and on rate only for early cut leaves. The greatest effect on lag (P < 0.001) and rate (NS) was seen in late cut stems. In sacco WS rate was approximately half that of GH and undegradable NDF was 0.38 as compared with 0.21 for GH. Sample size in sacco had a significant effect on both rate and curve displacement for GH but not for WS. There seemed to be no effect on undegradable NDF in either experiment.

Effect of replacing a rice bran–soya bean concentrate with Jackfruit (Artocarpus heterophyllus) or Flemingia (Flemingia macrophylla) foliage on the performance of growing goats

Abstract Eighty weaned goats (pure Bachthao or F1 of Barbari×Bachthao or Jamnapari×Bachthao) with initial weights of 11.1 to 12.4 kg and ages ranging between 3.0 and 3.5 months were used in a study to evaluate the foliages of Jackfruit ( Artocarpus heterophyllus ) or Flemingia ( Flemingia macrophylla) as a source of protein in diets based on chopped whole sugar cane ( Sacharatum sp.) and Para grass ( Brachiaria mutica ) for growing goats. Eight goats were allocated to each of 10 treatments in a completely randomised block design and offered Para grass, chopped whole sugar cane, concentrate and foliage for 3 months. The concentrate was replaced by foliage of Jackfruit or Flemingia at five levels: 0, 25, 50, 75 and 100%, based on the protein content of the feeds. The growth rates at the five levels of inclusion were 57, 53, 58, 44 and 30 g/day for the goats fed Jackfruit compared to 56, 49, 31, 25 and 22 g/day for the goats fed Flemingia, respectively. For Jackfruit there were no differences in feed intake or growth rate up to a replacement level of 50% of the protein in the concentrate. Increasing the amount of Flemingia as a replacement for the protein in concentrate resulted in a reduced dry matter intake and decreased live weight gain compared to the control diet. The content of total tannins was similar for the two foliages and the content of condensed soluble tannins lower in Flemingia than in Jackfruit. Four castrated male goats (one each of the four breeds Bachthao, Jamnapary, Barbary and Beetal) with mean live weights of about 19 kg were used in a 4×4 Latin Square design to study the digestibility of the four forages: chopped whole sugar cane, Para grass, Jackfruit foliage and Flemingia foliage. The dry matter digestibility coefficients of chopped whole sugar cane, Para grass, Flemingia and Jackfruit were 0.67, 0.67, 0.51 and 0.53, respectively and the digestibility coefficients for crude protein −0.68, 0.70, 0.62 and 0.45, respectively. The results show that both Jackfruit and Flemingia can be potential supplements for goats offered tropical grass and chopped whole sugar cane. Jackfruit can replace up to 100% of a concentrate based on protein content. The practical level will be a question of economics. Flemingia showed a poorer potential as a supplement for goats and replacement levels should not exceed 25% of the protein in the concentrate or 17% of dry matter for growing goats.

Indigenous browse leaves as supplements to dual purpose goats in central Tanzania

Abstract The objective of the present study was to evaluate the digestibility of Albizia harveyi (AH), Delonix elata (DE) and Grewia similis (GS) dried leaves and the effect of feeding the leaf meals on the performance of goats fed low quality hay. The four treatments consisted of the three browse species combined with Cenchrus ciliaris (CC) hay and a control with concentrate + CC hay or pure CC hay. Data from twelve bucks in the digestibility experiment and twelve does with single kids in the production experiment were analyzed. All the browse species had high crude protein contents (17–20.4%) and low content of neutral detergent fibre (31.3–60.7%) and acid detergent fibre (17.9–34.7%). AH had the highest fibre content of the browses but lower than that of grass hay. Results indicate that irrespective of the higher concentration of phenolic compounds, DE leaves were better digested than leaves from AH and GS. Supplementation of low quality hay with GS leaves and concentrate increased total DM and nutrient intake but reduced DM intake of the basal diet. Does fed with GS leaves had significantly higher milk yield and kid weight gains. The poor performance of the DE supplemented goats could be associated with the presence of the relatively high levels of total soluble and soluble condensed tannins in the leaves, whereas in the case of AH, leaf dust and hair could have lowered leaf intake.