Influence of growth stage and season on the energy value of fresh herbage. 2. Relationships between digestibility and metabolizable energy content and various laboratory measurements

This paper gives details of a study which has examined the effect of herbage growth type and season on the relationships of digestible organic matter in the dry matter (DOMD) and metabolizable energy (ME) contents measured in vivo to various laboratory measurements including three in vitro estimates of DOMD based on rumen fluid pepsin (RFP), pepsin cellulase (PC) or neutral detergent cellulase (NCD). Seventy herbages harvested over two years and comprising 32 spring primary growths, 14 summer regrowths and 24 autumn growths were used.
For DOMD in vivo , significantly different regression relationships were required for spring and autumn-harvested herbage. Equations based on PC were:
Spring herbage: DOMD (g kg^-1 DM) = 436 + 0·501 PC (g kg^-1 DM) ²= 76·7%; r.s.d. = 25·4
Autumn herbage: DOMD (g kg^-1 DM) = 594 + 0·195 PC (g kg^-1 DM) ²= 15·5%; r.s.d. = 23·1
For autumn herbages there were no significant relationships with ME. As with DOMD in vivo the PC method was shown to provide the most accurate relationship with ME concentration of spring herbage. The relationship was:
ME (MJ kg^-1 DM) = 6·16 + 0·0094 PC (g kg^-1 DM) ²= 69·8%; r.s.d. = 0·57
For both DOMD and ME the relationships for spring herbage based on PC were the only ones which did not differ significantly from those of an earlier study.
It is concluded that even where significant relationships for summer and autumn herbages were developed, the predictors accounted for substantially less of the variability than in spring herbages. This appeared to be largely due to reduced range in the DOMD and ME content in summer and autumn herbages.     

Comparison of two in vitro procedures using rumen liquor-pepsin or pepsin-cellulase for prediction of forage digestibility

Seventy-three samples of grass and legume herbage of known in vivo digestibility were used to compare an in vitro procedure comprising incubation with pepsin followed by cellulase (Jones and Hayward, 1975) with the Tilley and Terry (1963) procedure using rumen liquor followed by pepsin. The results obtained using the pepsin-cellulase method proved to be highly repeatable. On the basis of the residual standard deviation of the regression of in vivo dry matter digestibility (DMD) on dry matter digested in vitro (g/100 g DM), the pepsin-cellulase method was shown to be only slightly less accurate than the rumen liquor-pepsin method for combinations of both primary growth and regrowth of grasses (r.s.d. ±1.80 and ±1.46 respectively). However, the pepsin-cellulase method was noticeably less accurate than the rumen liquor-pepsin method when used on legume herbages (r.s.d. ±3.17 and ±1.91) or on grass and legume herbages combined (r.s.d. ±3.80 and ±1.60). For the rumen liquor-pepsin method one regression equation predicting DMD having the form, Y= 1.02 X? 0.41, was permissible. For the pepsin-cellulase method separate regression equations were necessary for grasses (species and growth stages combined) having the form, Y = 0.56 X+ 34.7, and for each legume species. It was concluded that the pepsin cellulase method was of value for grass samples, and, within species, for legumes because of its accuracy and precision and its speed and convenience relative to the rumen liquor-pepsin procedure; however, for legume species combined, and presumably for grass-legume mixtures, it was not sufficiently accurate.     

A TWO-STAGE TECHNIQUE FOR THE IN VITRO DIGESTION OF FORAGE CROPS

A simple technique for the determination in vitro of the dry- or organic-matter digestibility of small (0·5 g) samples of dried forages is described. It involves incubation first with rumen liquor and then with acid pepsin. Using 146 samples of grass, clover and lucerne of known in vivo digestibility ( Y ), the regression equation Y = 0·99 X– 1·01 (S.E. ± 2·31) has been calculated, where X = in vitro dry-matter digestibility. This technique has been used for the study of the digestibilities of plant breeder's material, of the leaf and stem fractions of herbage and of herbage consumed by animals.     

The digestibility of herbage selected by oesophageally fistulated cows, steer calves and wether sheep when strip-grazing together

The digestibility of herbage selected by dairy cows, milk-fed calves, weaned calves and wether sheep was examined on four occasions each day as they strip-grazed together a daily allocation of herbage. The average quality of the material selected by each group was similar. Organic matter digestibility of the herbage selected declined from 0·274 to 0·223 as the average height of the sward fell from 16 to 6 cm; this decline was slightly more rapid for the cows than for the other stock. A similar trend was also evident in samples cut from the sward to simulate the horizon removed prior to each sampling time.     

Intake and digestibility of components of forage rape (Brassica napus) by sheep

Herbage from forage rape ( Brassica napus cv. Lair), harvested in the autumn, was separated into different morphological components and offered ad libitum to weaned lambs and adult sheep in two indoor pen-feeding experiments. In vivo. digestibility and the voluntary intake of herbage components were measured and related to chemical composition and in vitro digestibility. The organic matter digestibility of all plant components, especially of petiole, was high; lamina, 0·847: petiole, 0·892; upper stem. 0·865; lower stem, 0·771. Lambs and adults digested 'leaf' (0·83) vs 0·846) or 'stem' (0·782 vs 0·789) equally well. Both lambs and adults ate much less of the components or of whole crop than would be predicted with grass crops of similar digestibility or fibre content. With the exception of lamina, intake was closely related positively to digestibility and negatively lo fibre content. Low intakes of lamina were associated with high concentrations of glucosinolates. In vitro digestibility values obtained on small samples of forage show that the process is adequate for the prediction of in vivo digestibility.     

Influence of some sward characteristics on the consumption of irrigated pastures grazed by lactating dairy cattle

Pasture variables measured in eight experiments at Kyabram, Victoria were used to quantify factors influencing the consumption of irrigated pastures grazed by dairy cows. In addition, whether intake prediction equations based on sward characteristics could be developed and applied in the field was also considered.
Herbage intake (DMI) was positively related to herbage allowance (HA) in all cases; however, the increase in daily DMI achieved for every additional kg herbage offered to a cow ranged from 015 to 0·35 kg. Herbage intake was also consistently related to residual herbage (RH). For every additional tonne herbage dry matter (DM) ha⁻¹ remaining after grazing, each cow consumed increased daily amounts of herbage ranging from 3·2 to 5·1 kg DM. However, of the other pasture variables, herbage mass (HM), pasture type (P_T) and digestibility of the herbage DM on offer (DMD) influenced herbage intake less consistently.
When the data from all experiments were included together, DMI was influenced by sward characteristics in the following manner: where LW = live weight of the cow (kg) and DE = duration of experiment (d).
When RH was considered instead of HA, only 61% of the variability in intake was accounted for compared to 80% when HA was considered:
In both of these equations, two variables other than the sward characteristics were significant; these were LW and DE. The significance of these variables in these relationships are discussed together with the possibility of using them for predicting DMI in other environments. However, it is concluded that they do not have general applicability and it is suggested that they may be useful only in the environment in which they were generated.     

Digestibility of energy and gross energy intake in fresh pastures

Several experiments were performed in spring summer over the period 1982–85 to study the relationships between digestibility of energy (DE), gross energy intake (GEI), acid detergent fibre (ADF) and dry matter (DM) content in pasture.
Wether sheep in metabolism pens and fed ad libitum with daily-cut fresh pasture were used. Two plots with different botanical composition were used to provide herbage; one dominated by Lolium perenne and the other by Holcus lanatus. A high correlation ( r = -0·91) was observed between DE and ADF. The prediction used a second-order degree polynomial.
Gross energy intake and digestibility of energy were scarcely correlated ( r = 0·50) when all cases as a whole were considered. Higher correlations between GEI and DE ( r = 0·69) were obtained when only data from pastures where Holcus lanatus prevailed were considered, and still higher ( r = 0·91) in those pastures dominated by sown species with DE values lower than 70%.
Herbage DM content had a large effect on GEI( r = 0·83) in the pastures dominated by perennial ryegrass with DE higher than 70%, the correlation between DE and GEI being low and negative ( r =-0·36). It is possible, therefore, to predict apparent digestibility of pasture energy from ADF. However, DE is closely related to GEI only in those pastures in which DE is lower than 70%, DM content being an important factor limiting the intake of those fresh pastures dominated by Perennial ryegrass when DE is above 70%.     

Herbage intake and liveweight gain of bulls and steers continuously stocked at fixed sward heights during autumn and spring

Two experiments were conducted to examine the relationship between sward surface height, herbage intake and liveweight gain in beef cattle grazed on pasture. In Experiment 1, two 'animal types' (18 Charolais × Angus steers and 18 Friesian bulls) were continuously grazed for 22 days during the late autumn on replicated swards maintained at sward surface heights of 6, 10 and 15 cm. Herbage intakes, assessed from the faecal concentration of chromium delivered from an intraruminal controlled release capsule and the in vitro digestibility of hand-plucked herbage samples, were curvilinearly related to sward height (r = 0·76, p <0·0·01). Average liveweight gains were 0·02, 0·61 and 1·31 kg d^-1 ( P <0·05) and increased linearly ( r = 0·84, P <0·001) with sward height. The maintenance organic matter intakes of the steers and bulls, with initial mean (± s.e.) live weights of 225 ± 15 kg and 172 ± 15 kg respectively, were estimated to be 3·6 and 3·5 kg d^-1 respectively. In Experiment 2 (spring) 36 cattle, including 35 of those used in Experiment 1, were reallocated to sward heights of 5, 10 and 15 cm using the same design as for Experiment 1. Average liveweight gains were 0·94, 1·57 and 1·68kg d^-1 ( p 0·05) and were curvilinearly related to sward height ( r = 0·093, p <0·05). Maintenance intakes could not be reliably extimated for the cattle in Experiment 2 because few animals had liveweight gains close to zero. These trials confirm that liveweight gain in continuously grazed finishing steers and bulls increases with sward surface height to maximum of 8–10cm with spring ryegrass/white clover pastures while, in autumn, swards of 12–15cm height are required to achieve maximum performance.     

Bovine faeces as a source of micro-organisms for the in vitro digestibility assay of forages

The aim of this study was to investigate whether bovine faeces could replace rumen liquor collected from fistulated sheep in the determination of organic matter digestibility (OMD) of forages in vitro . The first experiment compared two inocula that had been prepared by mixing 83 and 333 g of cattle faeces with 1 litre of artificial saliva according to the first stage of the in vitro technique of Tilley and Terry ( Journal of the British Grassland Society, 18, 104–111, 1963). Inocula made from 333 g of faeces gave higher values of OMD than that prepared from 83 g of faeces and was used in subsequent studies. When a 48-h acid pepsin digestion, the second stage of the Tilley and Terry (1963 ) technique, was included, the OMD values and the ease of filtering of undigested residues were increased. The second experiment compared digestibility determined with inocula produced from faeces with that produced from rumen liquor. The OMD of a ryegrass hay determined with an inoculum prepared from faeces was 0·468 compared with 0·528 when using an inoculum prepared from rumen liquor. The third experiment investigated the accuracy of estimating the OMD of eight contrasting forages determined using rumen liquor from three sheep ( y ) and faeces from two cows ( x ). All regressions were significant ( P  < 0·001) and had residual standard deviations (r.s.d.) of between ±0·019 and ±0·022. The final study compared faeces collected from cattle fed with either hay or concentrates. The OMD of forage was higher from the hay-fed animals, but the r.s.d. values of the regressions were similar. It was concluded that cattle faeces shows potential as an alternative to rumen liquor collected from rumen-fistulated sheep for use in the in vitro digestibility assay of forages.     

Identifying suitable temperate grass species and cultural practices for herbage production in the mountain regions of North Vietnam

In North Vietnam, during winter, shortage of herbage constrains the profitability of dairy farming. The first objective of this study was to evaluate the potential of alternative temperate (C₃) forage species, namely common oat ( Avena sativa L.), lop-sided oat ( Avena strigosa Schreb.), Italian ryegrass ( Lolium multiflorum L.) and a commercial forage mixture (Avex), to address the shortage of herbage during winter in the mountain regions of North Vietnam. The second objective was to measure the effects of cultural practices (sowing rate, harvest interval and irrigation level) on yield of dry matter (DM), chemical composition, digestibility of DM and metabolizable energy (ME) concentration of herbage from the best adapted C₃ species previously tested (lop-sided oat). Four experiments were conducted. Oat species proved to be the best adapted species and produced the highest annual yield of herbage (7600 kg DM ha⁻¹) with a high nutritive value. Yields of DM of lop-sided oat were not affected by sowing rate of seed but increased as the length of harvest intervals increased from 30 to 45 and 60 d ( P  <   0·001). Crude protein concentration, digestibility of DM and ME concentration decreased as the harvest interval increased ( P  <   0·01). Irrigation increased the yields of DM of lop-sided oats by 1·3 ( P  <   0·05) but had no effect on the nutritive value of herbage. It is concluded that both common oat and lop-sided oat are suitable species to provide herbage in the winter for the mountain regions of North Vietnam.     

Evaluation studies in the development of a commercial bacterial inoculant as an additive for grass silage

Two 2×2 factorial experiments are described in which a bacterial inoculant being developed as a silage additive and containing a strain of Lacto-bacillus plantarum (Ecosyl, ICI plc) was evaluated at two harvests (18 July and 30 September 1985) of two swards (perennial ryegrass and permanent pasture) in difficult ensiling conditions. On each occasion erbage was ensiled with and without inoculant using two 0·5–t capacity steel tower silos per treatment. The contents of the two replicate silos per treatment were combined for feeding to cross-bred wethers in digestibility and metabolizable energy (ME) partition studies.
Overall, inoculated herbage declined in pH post-harvest at a faster rate than control herbage (p<0·001) and three out of the four inoculated silages had lower pH, ammonia-N, acetate and alcohol and higher residual soluble carbohydrate content (p<0·001) than control. Significantly higher digestibility of nutrients (P<0·05) was found in three of the inoculant-treated silages and these also had significantly higher ME values than control (P<0·001), (10·58 and 8·77 MJ kg tol DM⁻¹ for the treated and untreated silages respectively). The use of inoculant on herbage of only moderate ensiling potential therefore, produced significant improvements in fermentation quality and feeding value over control.     

The effect of herbage allowance on daily intake by Creole heifers tethered on natural Dichanthium spp. pasture

Two experiments were carried out in Guadeloupe to estimate the organic matter intake (OMI) and digestibility (OMD) of a Dichanthium spp. sward, grazed by tethered Creole heifers [mean live weight (LW) 202 ± 2·0 kg], at three daily herbage allowances. Experiment 1 examined herbage allowances of 16, 25 and 31 kg of dry matter (DM) d^–1 on a fertilized sward at 21 days of regrowth whereas, in experiment 2, lower allowances of 11, 15 and 19 kg DM d^–1 were examined on the same sward, which was unfertilized and grazed at 14 days of regrowth. In each experiment, the herbage was grazed with three groups of two heifers in a 3 × 3 Latin square design. Sward characteristics were described before grazing. OMI was calculated from total faecal output, and OMD was predicted from the crude protein (CP) content of the faeces. The amount of herbage defoliated by the heifers was also estimated on tillers selected at random.
Organic matter intakes were on average 26 g and 19 g OM kg^–1 LW, and OMD values were 0·740 and 0·665 for Experiments 1 and 2, respectively, and were not affected by allowance. In Experiment 1, the herbage quality was high [0·50 of leaf and 116 g CP kg^–1 organic matter (OM)] for a tropical forage, whereas in Experiment 2, the quality of the herbage (0·27 of leaf and 73 g CP kg^–1 OM) was lower. These differences were reflected in differences in intake and digestibility in the two experiments.
The experimental tropical Dichanthium spp. swards can have intake characteristics similar to those of a temperate sward.     

PREDICTING ORGANIC-MATTER DIGESTIBILITY FROM IN VIVO AND IN VITRO DETERMINATIONS OF DRY-MATTER DIGESTIBILITY

The DM digestibility (DMD) and organic matter digestibility (OMD) of 36 tropical grass samples were determined both in vivo and in vitro. Regressions relating OMD to DMD were calculated. In vivo OMD=1·02 in vivo DMD+ 0·1, r=0·99. In vitro OMD=1·05 in vitro DMD—4·7, r=0.99. At the same DMD, the in vitro method predicted OMD 2·8 to 3·4 percentage units lower than the in vivo method. This difference was caused by the difference in mean apparent digestibility of the ash, in vitro 71%, in vivo 47%. In vivo DMD was correlated (r=0·92, P<0·01) with in vitro DMD and the regression relating these two factors had a residual standard deviation of ±1·42 digestibility units. This deviation was reduced to ±1·9 digestibility units when OMD was determined. For both DMD and OMD significant differences were found between grass species in the relation between in vivo and in vitro digestibility. To overcome biased estimates of OMD it was suggested that conversion equations should be avoided, and that the in vitro method be standardized with samples of known in vivo OMD as similar as possible to those being tested.     

The herbage intake and performance of set-stocked suckler cows and calves

Groups of eight Hereford × Friesian cows and their South Devon cross calves were set stocked over a 24-week grazing season at 3·23 (low), 3·21 (medium) or 4·24 (high) cows ha^-1 together with their calves. For the first 8 weeks only two-thirds of the total area was grazed. Increasing the stocking rate from low to medium reduced daily milk yield and cow and calf liveweight gains by 1·2, 0·24 and 0·29 kg d^-1 respectively, and from medium to high by 1·2, 0·24 and 0·23 kg d^-1. The main sward factor influencing faecal output and herbage intake was the quantity of organic matter on the pastures but the digestibility of the herbage selected also exerted a significant effect on the intake of cows. Major depressions in the herbage intake of cows occurred once the average sward height fell below 7 cm. Output of calf live weight was 628, 658 and 743 kg ha^-1 for the 3 stocking rates from low to high, and for cows 246, 179 and 30 kg ha^-1. It was concluded that decisions on pasture management should be taken in relation to the cow rather than the calf on set-stocked swards.     

The voluntary intake and in vivo digestibility of herbage harvested from indigenous hill plant communities

Voluntary intake and in vivo digestibility of herbage harvested from five indigenous communities– Agrostis-Festuca, Nardus and Molinia grasslands and Eriophorum vaginatum- and Trichophorum caespitosum -dominated varieties of blanket bog–and also from sown Lolium perenne and Trifolium repens swards were measured over two years. First growths of each sward were harvested at three stages of maturity and stored at — 20°C before feeding. Voluntary intake was measured while feeding ad libitum to 15% excess of the intake on the previous day and digestibility when feeding at 80% of voluntary intake.
There was a common positive relationship (r²= 0·86***) between intake (adjusted for year of feeding, range 72·8–16·7 g organic matter (kg LW)^0·75 d^-1) and organic matter digestibility (range 0·796–0·371), covering Lolium perenne and most of the indigenous communities. However, there were significant differences between the regressions of intake on the concentration of neutral detergent fibre for ryegrass and the indigenous communities, and also between the regressions for individual communities.
The results demonstrated the general value of organic matter digestibility as a predictor of intake potential, and the high digestibility and intake potential of immature vegetation from the grass and grass heath communities.     

Comparative sheep production and herbage characteristics on four perennial ryegrass varieties in the uplands

Ewe and lamb performance, herbage production and feed quality components on four late-flowering perennial ryegrass ( Lolium perenne L.) varieties were assessed under a fixed stocking management at an upland site (305 m OD) in mid-Wales. Averaged over four years (1981–84) there was no significant difference (P>0·05) between Aberystwyth S23, Aberystwyth Ajax, Perma and Meltra (tetraploid) in ewe and iamb liveweight gains. There were, however, considerable differences between varieties during individual years and their relative ranking also changed substantially over the four years. Lamb production on Perma was 22% more than on S23 in the first year but by the fourth year it was 21 % less than on the latter variety.
Differences between varieties were observed in herbage production. Net herbage accumulation was 15% more on Meltra than on Ajax whilst the calculated quantity of OM consumed was 19% higher from Meltra than from both Ajax and S23. Net animal liveweight gains were positively correlated with herbage production (r = 0·95, P < 0·05) and DOM consumed (r=0·96. P<0·05).     

Sward dynamics of a smooth-stalked meadowgrass dominantwhite clover sward rotationally grazed by cattle and/or sheep

This experiment was carried out to study the responses of sward components (particularly white clover, Trifolium repens ) to grazing management in a natural sward dominated by smooth-stalked meadowgrass ( Poa pratensis ) syn. Kentucky bluegrass. Treatments during two grazing seasons (1989–90) were: cattle grazing alone (C); cattle grazing followed by topping (CT); cattle grazing followed by sheep grazing (CS); and sheep grazing alone (S). Mean target pre- and post-grazing herbage masses were 2200 and 1100 kg DM ha⁻¹, estimated by single-probe electronic capacitance meter. Sward component dynamics were monitored using turf dissections, marked white clover stolons, and ring-toss white clover leaf counts. Component and sward data for the C, CT, CS and S treatments respectively, were: number of white clover leaves m⁻², 1295, 1384, 1408, 900 (s.e. ± 108); number of leaves per growing point, 3·2, 3·4, 3·0, 2·8 (s.e. ± 0·2); herbage accumulation (t DM ha⁻¹), 5·16, 5·02, 5·87, 8·28 (s.e. ±0 08); rejected herbage (% pasture area) 39·7, 7·7, 16·0, 0 (s.e. ± 75); and annual net herbage production (t DM ha⁻¹) 3·39, 4·35, 4·99, 8·28 (s.e. ± 0.07). Swards grazed by sheep alone contained less white clover, but regrew quicker and produced more herbage than other treatments. Close topping or grazing by sheep following dairy cattle grazing decreased sward rejection by cattle. These treatments maintained more of the pasture in better condition for subsequent cattle grazing, resulting in greater net herbage production than where no post-cattle grazing treatment was used.     

THE USE OF CATTLE WITH OESOPHAGEAL FISTULAE IN GRASSLAND EXPERIMENTS

Oesophageal-fistulated calves and cattle were used in various experiments during 1963 to 1966; results for 1966 are reported.
The method of inserting the fistula, the routine care of the animals and the methods of sampling through the fistula, are described.
Individual stall-feeding experiments in 1966 gave recovery values of 99.7% for herbage extruded through the fistulae, in relation to herbage eaten. The in vitro organic-matter digestibility of the grass offered and of the extrusa samples were identical. The digestibility of the grass fed in these experiments was high, but was comparable with that of herbage used in the grazing experiments reported. Grazing studies on grass/white clover pastures are reported. The digestibility was determined on all samples and they were separated into various plant fractions. Results obtained were compared with herbage samples cut at the same time. In most cases the digestibility and % N of the extrusa sample was higher than that of the corresponding herbage sample. The quantity of dead material present increased, and more was eaten, as the season advanced; it was of low digestibility. Results of intake studies with grazing animals are presented and the use of oesophagea-istulated cattle as an aid in such studies is discussed.     

A plate meter inadequately estimated herbage mass in a semi-arid grassland

A resting plate meter was tested in the laboratory and on a field site to determine its effectiveness for estimating peak herbage mass on semi-arid grasslands. In laboratory tests, data from the plate meter closely predicted the herbage mass of four perennial bunch grasses (thirteen of sixteen tests with r ² ≥ 0·90) but the closeness of the prediction varied with the pressure of the plate. Field tests took place on a southern Arizona, USA semi-arid grassland in 2005, 2006, 2007 and 2008. Twenty teams of two or three people sampled the site; five teams in each year measured eight to thirteen plate heights and clipped the vegetation beneath. Consistent with a need for yearly calibration, a significantly different ( P  <   0·05) linear relationship was detected between 3 of the 4 years which was associated with differences in average herbage mass of dry matter (DM) (1525 kg ha⁻¹ for 2005, 2093 kg ha⁻¹ for 2006, 1338 kg ha⁻¹ for 2007 and 1370 kg ha⁻¹ for 2008). Plate height poorly predicted herbage mass within years ( r ²  = 0·21, 0·51, 0·49 and 0·41 respectively) with plate heights explaining half or less of the variability in field herbage mass and having a mean prediction error of 466 kg DM ha⁻¹. The plate meter technique had limited potential for estimating peak herbage mass in semi-arid grasslands.     

Anatomical structure and digestibility of reed canarygrass cultivars and hybrid ryegrass

Anatomical structure and fibre chemistry influence the digestibility of forage grasses. The objective of this study was to evaluate the anatomical structure, digestibility, and fibre composition of leaf blades from a high alkaloid and two low alkaloid cultivars of reed canarygrass ( Phalaris arundinacea , L.) and one cultivar of tetraploid hybrid ryegrass ( Lolium hybridum , Hausskn.). Cultivars were grown in a greenhouse in a randomized complete block design with four replications. Leaf blades were either cut into 10-mm sections or dried and milled to disrupt anatomical structure.
Reed canarygrass had smaller cells and airspaces and slower tissue digestion than ryegrass. The in vitro disappearance of ryegrass sections in buffered rumen fluid was 60% greater ( P <0·01) than that of reed canarygrass after 6, 12 and 24 h of digestion. By contrast, the in vitro disappearance of milled ryegrass was similar to or less ( P <0·05) than that of reed canarygrass. In vitro dry matter digestibility and fibre composition of the grasses were similar except for acid detergent fibre, which was greater ( P <0·01) in ryegrass than in reed canarygrass. Reed canarygrass cultivars were similar in anatomical structure, digestibility, and fibre composition. It was concluded that the digestion of reed canarygrass, relative to ryegrass, was reduced by the compact arrangement of tissues and that alkaloid content did not influence the digestion of reed canarygrass cultivars.