Commercial gestation housing systems for sows generally fail to cater fully for their needs in terms of comfort or the ability to perform highly motivated behaviours, which can lead to chronic stress and an impairment to welfare. We compared a typical gestation system (CONTROL) with an IMPROVED one as regards oral stereotypies, aggressive behaviour, skin lesions, locomotion, and tear staining. Sows were mixed into 12 stable groups (six groups per treatment, 20 sows per group), 29 days post-service in pens with free-access, full-length individual feeding/lying stalls. CONTROL pens had fully slatted concrete floors, with two blocks of wood and two chains suspended in the group area. IMPROVED pens were the same but with rubber mats and a length of manila rope in each feeding stall, and straw provided in three racks in the group area. Direct observations of oral stereotypical (30 instantaneous scans per sow per day) and aggressive (all-occurrence sampling, 3 h per sow per day) behaviours were conducted 72 h post-mixing, in mid and late gestation. Skin lesions were counted 24 h and three weeks post-mixing, and in late gestation. Sows’ locomotion (locomotory ability) was scored using a visual analogue scale in mid and late gestation. Right and left eye tear staining was scored in late gestation. Indications of better welfare in IMPROVED sows included performance of fewer oral stereotypies in mid and late gestation, and lower tear stain scores. These sows performed more aggression in late gestation, which was associated with access to enrichment, but skin lesion counts were not affected. Thus, the changes made in the IMPROVED treatment benefitted aspects of sow welfare.

This study assessed the health and welfare implications of feeding pigs a dry or liquid diet when housed in either fully-slatted or straw-based accommodation. Between April and October 2002, 1024 (Large White × Landrace) × Large White pigs, housed in pens of 32, were fed ad libitum from 34 kg to slaughter at 104 kg liveweight. Data were collected on a range of welfare parameters. Feeding system affected only respiratory health losses. Lameness and tail-biting tended to be more prevalent health conditions in the fully-slatted system, while in the straw-based system pigs showed significantly more enteric and respiratory disease. There were no significant treatment effects on skin lesions or bursitis of the hock. Liquid fed pigs had poorer hygiene scores than dry fed pigs, especially in straw-based housing. Liquid feeding reduced activity level and investigatory behaviours directed towards other pigs. Pigs with straw spent a large proportion of their time manipulating it. Pigs without straw were less active and spent more time manipulating the pen hardware. In post-slaughter assessments, there were no systems differences in lung lesions or osteochondrosis, but other measures differed between housing or feeding systems; pigs with straw had more severe toe erosions on the foot, while pigs without straw had more severe heel erosions. Gastric lesions were more pronounced with dry feeding and in the fully-slatted system. The results highlight the relative health and welfare advantages and disadvantages of these systems for finishing pigs.

Cultivar mixtures of winter barley and spring barley, together with their component monocultures, were grown in field trials to assess the effect of cultivar combinations on both straw and grain yield. The overall grain yields for all trials were significantly higher for the cultivar mixtures than for the corresponding component monocultures. Also, significant decreases in rhynchosporium disease severity for cultivar mixtures were recorded for most non-fungicide treatments. The size of these responses was often significantly correlated with the component number of the mixtures. The amount of straw produced in mixtures was sometimes changed significantly, but not always in a positive direction and it was only correlated with increasing mixture component number in two environments. No correlation of straw yield potential of cultivars with performance in mixtures was found. Cultivar × cultivar mixture × environment interactions appeared to affect the relative yield of grain and straw differentially and therefore it was not possible to predict the effect of mixtures on the harvest index.

The extent and nature of spread of exotic plant species to and within Alaska by shipment of hay and straw was studied. The amounts of hay and straw imported into Alaska and the amounts and types of seed in imported and locally produced hay and straw was determined We purchased alfalfa hay, wheat straw, ryegrass straw, and timothy hay produced in Washington and Oregon (WA–OR) and locally produced straw and hay. The hay and straw were shaken over screens, and the remaining fines were mixed with sterile potting soil and incubated in the greenhouse. Forty-nine plant species were identified from hay and straw, nine of which are ranked as invasive in Alaska, including downy brome, foxtail barley, hare barley, narrowleaf hawksbeard, and quackgrass—a prohibited weed in Alaska. The number of seeds ranged from 0 to 6,205 seeds kg−1, with an average of 585 seeds kg−1, and the number of species ranged from 0 to 12, with an average of 4.2 species per bale. Crop seed comprised a large proportion of the germinated seeds in ryegrass straw, wheat straw, and timothy/brome hay (98, 78, and 62%, respectively), but was less prevalent (ranging from 0 to 38%) in the other three hay and straw crop types. Hay and straw from Alaska contained more total seeds and species than hay and straw from WA-OR, but the difference was not significant when only weed seed was used in the analysis. Alaska-grown timothy/brome hay contained significantly more total seed than alfalfa hay and wheat straw from WA–OR and Alaska-grown barley straw. The grower or distributor of the hay and straw also influenced the number of seeds and species among some crop types. Results of this study document that large numbers of alien plant species are transported by movements of hay and straw into and within Alaska.

In the EU, pigs must have permanent access to manipulable materials such as straw, rope, wood, etc. Long straw can fulfil this function, but can increase labour requirements for cleaning pens, and result in problems with blocked slatted floors and slurry systems. Chopped straw might be more practical, but what is the effect on pigs’ behaviour of using chopped straw instead of long straw? Commercial pigs in 1/3 slatted, 2/3 solid pens of 15 pigs were provided with either 100 g/pig per day of long straw (20 pens) or of chopped straw (19 pens). Behavioural observations were made of three focal pigs per pen (one from each of small, medium and large weight tertiles) for one full day between 0600 and 2300 h at each of ~40 and ~80 kg. The time spent rooting/investigating overall (709 s/pig per hour at 40 kg to 533 s/pig per hour at 80 kg), or directed to the straw/solid floor (497 s/pig per hour at 40 kg to 343 s/pig per hour at 80 kg), was not affected by straw length but reduced with age. Time spent investigating other pigs (83 s/pig per hour at 40 kg), the slatted floor (57 s/pig per hour) or pen fixtures (21 s/pig per hour) was not affected by age or straw length. Aggressive behaviour was infrequent, but lasted about twice as long in pens with chopped straw (2.3 s/pig per hour at 40 kg) compared with pens with long straw (1.0 s/pig per hour at 40 kg, P=0.060). There were no significant effects of straw length on tail or ear lesions, but shoulders were significantly more likely to have minor scratches with chopped straw (P=0.031), which may reflect the higher levels of aggression. Smaller pigs showed more rooting/investigatory behaviour, and in particular directed towards the straw/solid floor and the slatted floor than their larger pen-mates. Females exhibited more straw and pen fixture-directed behaviour than males. There were no effects of pig size or sex on behaviour directed towards other pigs. In summary, pigs spent similar amounts of time interacting with straw/solid floor when long and chopped straw were provided, and most aspects of pig-directed behaviour and injuries were not affected by straw length. There was an increase in pigs with minor shoulder lesions with chopped straw, perhaps because of increased aggression. The use of chopped straw as an enrichment material for pigs warrants further investigation in larger and more detailed studies.

Straw possesses many characteristics that make it attractive to pigs and can therefore be effective in preventing negative penmate-directed behaviours. However, straw is difficult to handle in current vacuum slurry systems under most commercial conditions and can therefore only be used in limited amounts. To occupy pigs effectively, straw must remain attractive to pigs throughout the whole day; hence, have a certain degree of novelty. We investigated the penmate-directed behaviour of liquid-fed growing pigs in a production herd, assigned to five experimental treatments: 1×25, 1×50, 1×100, 2×50 and 4×25 g of chopped straw/pig per day, with 20 replicates of each treatment (pen was regarded as experimental unit). Behaviour was observed at two different growth stages; ~40 and 80 kg live weight of the pigs. Activity and exploratory behaviour directed at penmates, straw, pen components and the slatted floor were registered continuously for 15 min of each hour during day time (0600 to 2200 h) by use of video observation of three focal pigs per pen. The pigs were active for about one-third of the day corresponding to ~5 h/day. Of the active time, an average of 7% (35 min) was spent on penmate-directed behaviour. The pigs were more active and increased their straw-directed behaviour when provided with 100 g straw/pig per day compared with 25 and 50 g (P<0.001). However, penmate-directed behaviour was not reduced with an increased amount of straw (P>0.05), and there was no effect on pigs’ behaviour when straw provision was increased per day (P>0.05). Pigs became less active and reduced their straw-directed activities when their weight increased from 40 to 80 kg live weight (P<0.001), but the amount of penmate-directed behaviour was similar (P>0.05). Further, the residual straw results indicated that perhaps a more frequent straw provision could help establish a more even level of fresh available straw during the day. However, the frequent straw provision did not occupy pigs more than one daily allocation did. In conclusion, there was no difference in penmate-directed behaviour of the pigs when given 25 or 50 g of straw/pig per day compared with 100 g of straw/pig per day, nor were there any difference when 100 g of straw/pig per day was provided more frequently.

A series of 24-h video studies on four commercial Danish pig herds investigated the behaviour of pregnant sows kept in dynamic groups (72 to 200 sows) with electronic sow feeding (ESF). The herds mainly differed with respect to provision of a layer of unchopped straw as bedding material, the frequency of introduction/removal of animals, space allowance in the lying area, group size and number of feeding stations, and starting times for the feeding cycle. All herds had one feeding cycle per 24 h. Six 24-h video recordings in the most settled period with respect to rank relationships (2 to 12 days after the last introduction) were collected from each herd and analysed according to activity and aggressive interactions. In two of the four herds recordings were collected in two separate periods with different starting times for the feeding cycle. In all herds peaks of activity in the morning and in the afternoon were evident. Furthermore, the diurnal variation was overlaid by an increase in activity at the start of the feeding cycle. The activity and aggression in the feeding area as well as the duration per sow of the period with high feeder occupation were lowest in herds where a layer of straw bedding was provided. Changing feeding start from day time to night time was accompanied by a reduced feeder occupation in the period following start of the feeding cycle. However, in herd 1 (characterized by no litter, high stocking density and high frequency of grouping) the level of aggression was reduced, whereas it was increased in herd 2 (characterized by straw in lying area, low stocking density, low frequency of regrouping). Number of regroupings and space allowance apparently had no obvious effects on the average frequency of aggression or the aggression per sow at risk in periods between introduction of new animals, but space allowance may have improved social function by weakening the association between activity and aggression. Due to the small number of herds included the present results were descriptive rather than conclusive. However, the study supports the suggestions that provision of unchopped straw as bedding material and starting the feeding cycle in the evening for overnight feeding may improve behaviour in dynamic group housing systems with ESF. However, the benefits of starting the feeding cycle in the evening may depend on low disturbance in daytime from other management procedures.

In a previous experiment the provision of straw to group-housed pigs increased the number of daily feeder visits. This effect of straw is comparable with conditions of reduced social competition for access to the feeder. The aim of this experiment was to investigate if changing straw provision within a pen resulted in similar and reversible effects in this behaviour. One hundred and twenty male pigs (41·1 (s.e. 0·43) kg) were used in three blocks each of four pens of 10 pigs. In each block of 42 days duration one pen had no straw throughout (treatment 1); one pen had no straw for 21 days (period 1) followed by straw for 21 days (period 2) (2); one pen had straw followed by no straw (3) and one pen had straw throughout (4). The pens were situated in a naturally ventilated building with light from 06.00 to 20.00 h. Each pen had a kennel, a lying area and a single-space computerized feeder for recording feeding behaviour. The pigs’ activity was recorded on video in the 2nd and 5th weeks of each block. The number of feeder visits was slightly higher for pigs with straw (1: 9·69 v. 4: 10·46) but this was not significant (P > 0·05). The effect was more marked for treatment 2 where the visits increased (P < 0·01) from period 1 (8·52) to period 2 (10·64) and for treatment 3 where they decreased (11·20 v. 10·10). Pigs without straw (treatment 1) spent more time in the kennel than those with straw (treatment 4) (P < 0·05). For treatment 2 the proportion of time spent in the kennel fell from 0·607 in period 1 to 0·288 in period 2 (P < 0·01). There was a general trend for more activity and more lying outside the kennel when straw was provided. The effect of straw provision was not as marked as that seen previously; nevertheless changing straw provision (treatments 2 and 3) did result in an increase in feeder visits with straw, probably related to the increase in general activity and lying outside in the area adjacent to the feeder.

The dry-matter (DM) intake and growth rate in male lambs were predicted from rumen degradability characteristics, rumen DM losses at different times, neutral- or acid-detergent fibre (NDF or ADF) contents and DM apparent digestibility of roughages. Four different straws consisting of wheat, barley, oat and rice were each offered ad libitum to 24 Merino male lambs with 200 glday concentrate for 4 weeks to determine DM intake and growth rate. Apparent digestibilities of the straws were measured with three Merino male sheep. Measurements were made during the last 10 days of each 20-day period. The degradation characteristics of the straws were measured by incubating samples in nylon bags for 8, 16, 24, 48, 72 and 96 h in the rumens of three Merino male sheep fitted with rumen cannulae. The exponential model p = a + b(l - er^) was fitted to the data. Potential degradabilities of DM (defined as a + b) and apparent digestibilities of DM ranged from 530 to 679 and 440 to 560 g/kg, respectively. The mean DM intake of the straws varied from 543 to 745 glday, the digestible DM intake from 236 to 417 glday and growth rate from 17 to 95 glday. Using the degradation characteristics A, B and c in a multiple regression analysis, the correlation coefficients with DM intake and growth rate were 0·79 and 0·70, respectively. NDF and ADF were related to DM intake (i = 0·65; r = 0·64) and growth rate (r = 0·55; r = 0·56). The correlation coefficient between DM apparent digestibility and DM intake was 0·76. It is concluded that the rumen degradation characteristics have potential for predicting intake of straws and growth rate in sheep.

The effect of ammonia treatment of straw on both the rumen environment and the extent of its microbial fermentation was studied. Four rumen cannulated sheep were randomly given 700 g/day of untreated straw plus urea (US), ammonia-treated straw (TS) and alfalfa hay (AH) in a change-over design with three periods. Rumen pH was lower and ammonia-nitrogen and total volatile fatty acid (VFA) concentrations were higher (P < 0·001) with AH than with US or TS. With the straw diets, TS promoted a lower pH than US (P < 0·05), but differences were less than 0·3 units and the mean pH was never below 6·5. There were no differences between the straw diets in ammonia-nitrogen or VFA concentration (P > 0·05). When untreated barley straw (BS) and treated straw (TS) were incubated in situ disappearance of dry matter (dDM) at 12, 24 and 48 h (P < 0·01) and neutral-detergent fibre (dNDF) at 48 h (P < 0·001) were higher with TS. In vitro incubation showed a higher gas production with TS only after 36 h (P < 0·05) whereas gas from BS fermentation was higher up to 14 h (P < 0·05). Among diets, dDM, dNDF and gas production with US were numerically higher than with TS or AH throughout, although few significant differences were observed, except for a higher dDM at 12 (P < 0·01) and 24 (P < 0·10) h and a higher dNDF at 12 h (P < 0·10). Particle-associated enzymes were extracted from BS and TS incubated in the rumen for 4, 8, 22 and 24 h. Results ofxylanase and cellulase activities support those of straw incubation, with a drop between 4 and 8 h in TS diet. The concentration of residual phenolics per unit of incubated straws after 12 and 24 h show that phenolics release to the media was higher with the TS diet. Daily changes of phenolic concentration into rumen liquid was also higher with TS than with US (P < 0·001). The increased release of straw phenolics by ammoniation reduced the potential for rumen degradation of straw, mainly in the first hours of the fermentation period.

A study was conducted to compare the effects of ammoniation and protein supplementation of barley straw on rumination behaviour of sheep. Four wethers were allocated to four diets offered ad libitum in a 4 × 4 Latin-square design. The diets were, untreated barley straw + molasses meal (diet 1), untreated barley straw + soya-bean meal + molasses meal (diet 2), ammonia-treated barley straw + molasses meal (diet 3) and ammonia-treated barley straw + soya-bean meal + molasses meal (diet 4). Animals were kept in metabolism crates throughout each 16-day experimental period and allowed free access to water and a mineralized salt lick. The first 11 days of each period were for adaptation to the harnesses and diets while the last 5 days were used for rumination studies. Animals given diets 3 and 4 had slower eating rates compared with those given diets 1 and 2. Rumination index and duration of each rumination period was lower for sheep consuming diets 3 and 4 than for those on diets 1 and 2 but not significantly so (P > 0·05). Rumination time per 100 g neutral-detergent fibre (NDF) intake was significantly lower (P < 0·01) for diets containing ammoniated straw. Animals given ammoniated straw diets also regurgitated fewer boluses per unit NDF intake than did those on untreated straw diets. The results showed that increased intake and digestibility, which is usually associated with ammoniated straws, was due to sheep doing less work per unit of time to break down straw for digestion. In this way, potentially digestible tissues within a given amount of straw is more readily exposed. The foregoing suggests that ammonia treatment results in less rumination so that ruminants given ammonia-treated straw diets do less work ruminating.

An experiment was conducted to examine the effect of ammonia treatment or soya-bean meal supplementation on rumen and lower tract digestion and urinary purine-derivative excretion in sheep given barley straw-based diets. Four wethers each fitted with simple rumen and duodenal cannulae were randomly allocated to four diets in a 4×4 Latin-square design. The diets were, untreated barley straw + molasses meal (diet 1), ammonia-treated barley straw + molasses meal (diet 2), untreated barley straw + soya-bean meal + molasses meal (diet 3) and ammonia-treated barley straw + soya-bean meal + molasses meal (diet 4). Dry-matter (DM) intake, total tract neutral- and acid-detergent fibre apparent digestibility and faecal nitrogen (N) output were higher for diets 2 and 4. Microbial protein yield, determined from total urinary purine-derivative excretion, was also high in sheep on diets 2 and 4. However, supplementation with soya-bean meal in diet 4 reduced DM and fibre digestion but increased intake and microbial synthesis. Despite the lower microbial protein synthesis for diet 3, total tract N digestion was high for the diet, an indication of higher nutrient absorption in the lower tract. The above results indicated that there was a substantial increase in rumen microbial N yield from ammoniated straw-based diets. However, not all the N was made available to the animals. Some of the microbial N absorbed in the lower tract may have been overestimated by the use of the purine derivative-microbial N evaluation method. On the other hand, when protein supplements were given the amount of microbial protein available to the ruminant through absorption in the lower tract may have been underestimated by urinary purine derivatives.

Farm residues with high C:N ratios are difficult to use because of their low economic value and excessive volume. Composting is ideal for upgrading such residues, but was not thought possible without co-composting or lowering of the C:N ratio. We developed a low-input method to compost perennial ryegrass straw on-farm by forming windrows and turning them either zero, two, four, or six times throughout the year with a commercial, straddle-type turner. No water beyond normal rainfall and no N other than that contained in the straw was added. The volume of straw was reduced by up to 88% with four or six turns over 20 to 24 weeks. The average internal temperature of straw windrows reached a maximum of 54°C with four turns. The ability to compost these residues will help in the development of sustainable farming systems by allowing recycling of straw waste.

Six cereal straws and two traditional hays were used to study the relationship between voluntary dry matter (DM) intake and chemical composition and ruminal degradation characteristics. The voluntary DM intake was measured during 60 days using Barbarin adult ewes given food individually in four groups of six animals. The forages were offered to the ewes twice daily and were supplemented with 10 g DM of soya-bean meal per kg M0·75 per day and 30 g per ewe per day of a commercial mixture of minerals and vitamins. The chemical composition and the leaf/stem (L/S) ratio of the forages were determined. Their ruminal degradation characteristics were measured by using the nylon bag technique according to the exponential model Dg = a + b (1 – e−ct). Crude protein contents of straws ranged from 22 to 35 g/kg DM and that of hays from 35 to 57 g/kg DM. The corresponding values of L/S ratio varied from 0·68 to 0·88. The voluntary DM intake was highly variable and the hays were ingested at greater amounts than the straws, although their degradable (b) and their rate of digestion (c) were not significantly different (P > 0·05).

Significant relationships were established between voluntary DM intake and the neutral-detergent fibre (R2 = −0·72; P < 0·001), acid-detergent fibre (R2 = −0·75; P < 0·001) and a values (R2 = 0·83; P < 0·001). The precision of the prediction was significantly improved using ruminal degradation characteristics (Syx = 4·42) compared with the chemical composition (Syx = 5·60).

This study was aimed at evaluating (1) the dry matter (DM) and nitrogen (N) degradabilities (by sheep) of Sesbania sesban leaves, Acacia albida (Faidhabia albida), A. siberiana and A. tortiris frazfs and (2) the effect of feeding a mixture of oilseed cake and tanniferous browses on the degradability of teff (Eragrostis tef) straw and oilseed cake and on particulate and liquid passage rates. Thirteen rumen cannulated sheep in a randomized complete-block design experiment were given teff straw ad libitum supplemented (DM per day) with 155 g oilseed cake (50: 50 mixture of noug (Guizotia abyssinica) and groundnut cake; oilseed cake diet) or with 92 g oilseed cake plus either 118 g S. sesban (sesbania diet) or 179 g A. albida fruits (albida diet). Diets were formulated to supply 10·5 g supplementary N per day.

Sesbania had the highest DM washing loss, potential degradability and fastest DM degradation rate compared with the acacias. The N washing loss (g/kg) was highest for A. siberiana (500) followed by A. albida (431), A. tortilis (431) and sesbania (241). The potential N degradability (g/kg) was greater (P < 0·05) for sesbania (978) than for A. albida (848), A. tortilis (865) or A. siberiana (785). The degradation rates of oilseed cake-N and teff straw-DM, particulate and liquid passage rates, basal intake and DM digestibilities were similar among diets, but organic matter intake was highest for the albida diet. At the present levels of offer, supplementation with mixtures of oilseed cake and browses does not significantly reduce rumen degradation rates of oilseed cake-N or teff straw DM.

Two experiments were designed to examine the effects of ammonia treatment of barley straw on rumen environmental conditions for fibre degradation, and to determine the effect of treatment on the soluble and insoluble fractions of straw. In experiment 1, rumen pH, and ammonia-nitrogen and volatile fatty acid concentrations in the rumen of sheep receiving untreated (US1) or ammonia-treated (TS1) straw were recorded. Also, both straws were incubated in the rumen of both groups of animals. There were no significant differences (P > 0·05) within rumen parameters, except for butyrate proportion, which was higher (P < 0·01) with TS1. Dry matter and neutraldetergent fibre disappearances of TS1 were higher (P < 0·001) than those of US1 at all the incubation times. Degradation of both straws in US1-fed sheep was not smaller, and in some periods of incubation was even greater, than in TS1-fed animals. In experiment 2, samples of untreated (US2) and treated (TS2) straw were incubated in wethers offered a mixture (50:50) of alfalfa hay and straw. Samples of US2 and TS2 were soaked in autoclaved rumen fluid to measure their solubility. It was clear that, although treatment increased the soluble fraction of US2 and TS2 by 52 and 65 g/kg respectively, from 0 to 72 h of incubation, increasing the differences between straws from 45 to 58 g/kg in that period, actual microbial action on the treated roughage was the more important factor, accounting for a difference between US2 and TS2 of 131 g/kg after 72 h incubation.

The effects on animal performance of barley-urea (BU), maize gluten (MG) and rapeseed meal (RSM) offered with ad libitum winter wheat straw, were examined with 138 pregnant Hereford (♂ × Friesian ♀ cows over two winters (1987/88 and 1988/89). In each year, seven young cows and 16 old cows per treatment were offered respectively 3·0 or 1·5 kg fresh weight per head per day, of BU, MG or RSM for 167 days. There were no treatment effects on live weight, condition score or calf birth weight. In terms of animal performance BU, MG and RSM were equally effective.

Straw-Flow is a novel housing system for growing pigs which simplifies the handling of bedding and manure by allowing pigs to take unchopped straw from dispensers. Three groups of 50, 50 and 60 Large-White × Landrace pigs were housed in Straw-Flow pens from 5 to 90 kg. They were supplied daily with 50 to 100 g unchopped straw per pig and given food ad libitum. From 30 to 90 kg, mean growth rate was 863 g/day and food conversion ratio was 2·56 kg food per kg growth. The pigs' behaviour was divided approximately into: 0·820 lying, 0·100 active, 0·075 feeding and 0·005 drinking (on a proportional basis). There were no differences (P > 0·05) between groups or different weights for any of the behaviour categories. The pigs were less active before noon than after noon (P < 0·05). The daily number of visits to the drinker between weights 5 and 25 kg fell from 23·7 to 11·0 (P < 0·05). A single drinker, of new design, appeared to be adequate for a group of 50 to 60 pigs.

Four sheep (live weight 39 to 42 kg) fitted with rumen cannulas were offered ammonia-treated barley straw alone (control) or supplemented with unmolassed sugar-beet pulp or rolled barley at 0·20 or 0·40 of the total diet on a fresh weight basis (SBP20, SBP40, B20 and B40, respectively) using a 4 × 5 randomized block design. Total diet intakes were 710, 873, 1054, 843 and 1021 g dry matter per day for control, SBP20, SBP40, B20 and B40 respectively. The intake of straw was depressed significantly with SBP40 and B40 (P < 0·05). Rumen pH and ammonia concentration decreased, and total volatile fatty acid concentrations increased (P < 0·05) with increasing level of supplementation for both supplements. Rumen liquid outflow rate was affected little by the supplementation although this measurement for B40 was significantly higher than that for the other treatments. Microbial protein supply, estimated from urinary excretion of purine derivatives, increased significantly with the increasing amounts of supplements (4·5, 6·7, 8·5, 7·1 and 9·0 (s.e.d. 0·73) g N per day for control, SBP20, SBP40, B20 and B40 respectively) (P < 0·05). The calculated efficiency of microbial protein production was 12·8, 14·2, 14·3, 15·7 and 14·5 (s.e.d. 1·45) g N per kg digestible organic matter intake (DOMI) for the five treatments. Although this value was lowest with the control, differences between treatments were not significant (P > 0·05). It seems that microbial protein yield per unit DOMI for a diet based on ammonia-treated straw could not be improved substantially by supplementation with sugar-beet pulp or barley.