White clover cultivars Sacramento ladino, Sonja and Aberystwyth S.184 were assessed for dry matter (DM) yields, clover content and herbage quality in monostand and in 50:50 mixtures with grasses under cutting at Truro, Nova Scotia and Charlottetown, Prince Edward Island between 1986 and 1989. Grasses were: orchardgrass (Dactylis glomerata L.), tall fescue (Festuca arundinacea Schreb.), timothy (Phleum pratense L.) and reed canarygrass (Phalaris arundinacea L.). Dry matter yields ranged from 6158 to 11645 kg/ha and were highest in white clover/orchardgrass and white clover/timothy at Truro, and in white clover/timothy at Charlottetown. Sonja and Aberystwyth S.I84 outperformed Sacramento white clover in herbage DM and clover yield in all years at both locations. First-cut herbage contributed 39 and 29% of total yields at Truro and Charlottetown, respectively. Clover yield was highest in first-cut Sacramento/orchardgrass, but dropped by up to 73% in white clover/timothy associations over a 2-year period. Crude protein ranged from 14·4% in clover/timothy to 23·4% in clover/reed canarygrass and was positively correlated with clover content. It was concluded that choice of clover cultivar as well as grass is an important consideration in maximizing herbage yields and quality in the Atlantic region.

Electrical conductivity was evaluated for estimating the nutrient content of cattle and pig slurries. Slurry samples were collected in 1991 from the storage tanks of 48 cattle and 10 pig units on commercial farms in Ireland. Samples were analysed for NH4+ and total concentrations of Na, K, Ca, Mg and P. Electrical conductivity (EC) was measured on raw slurries (ECraw) and on slurries diluted by 10 with water (ECdilute). Relationships between EC and nutrient content were examined by correlation and linear regression analyses.

In both slurry types, NH4+ was the dominant cation with K+ second in importance on a molar basis. Within each slurry type, the concentration of each of these cations was significantly correlated with EC. Using ECdilute gave more accurate predictions of concentrations than ECraw, but even ECraw was a better predictor than dry matter (DM) content. The linear relationships between NH4+ or K+ and ECdilute explained > 82% of the variance within each slurry type. The P content in slurries was related better to DM than to EC. Since EC measurement could be by cheap, robust meters, its potential for on-farm use deserves further investigation.

Leaf appearance of contrasting potato cultivars was examined in field experiments at Cambridge, UK, between 1985 and 1990. Three experiments examined the effects of N fertilizer on the appearance and growth of leaves. Four experiments examined leaf appearance over a wide range of planting dates and in two of these experiments different physiological ages of seed were compared.

Linear regression of rate of appearance of main-stem leaves on air temperature indicated a strong dependence of rate of leaf appearance on temperature in the cultivar Maris Piper with a phyllochron of c. 31 K d/leaf but in Estima variation in rate of leaf appearance was only partly explained by differences in air temperature. The phyllochron of main-stem leaves in Estima and Home Guard was shorter for old seed than young seed but there was little effect of seed age in four other cultivars. The phyllochron of main-stem leaves was longer without N fertilizer than with N but the difference in the phyllochron between rates of applied N was small. Leaf appearance on sympodial branches was slower and more variable than on the main-stem. Growth of branches differed between cultivars, particularly with no N fertilizer. In the determinate cultivars Estima and Diana there was restricted growth of branches but in the indeterminate cultivar Cara, significant leaf area was contributed by branches. The duration of leaf appearance and longevity of individual leaves is discussed in relation to N, temperature and cultivar.

Data from the F1, F2 and F3 generations derived from four F1 hybrids of sunflower were analysed to determine the genetical control of eleven agronomically important traits namely, flowering time (FT), final height (FH), seed set (SS), fresh seed weight (FSW), dry seed weight (DSW), 25-seed weight (SSW), head diameter (HD), head angle (HA), neck width (NW), Botrylis infection (BI) and percentage oil content (PO), with the objective of assessing their potential for producing superior recombinant lines. Comparisons of means revealed significant differences between the F: generations of crosses for all the characters except FT. Model fitting indicated that these differences were attributed either to variation in the magnitude of the dominance component [h], or the projected mean of the Finfin; generation, m. Further, all the variation in the generation means was accounted for by the m and [h] parameters and epistasis was shown to be non-existent for almost all the traits. Analysis of the second degree statistics revealed the presence of additive genetic effects and most of the characters showed moderate heritability except for HD, which was highly heritable. All the crosses were predicted to produce significant numbers of transgressive segregants and consequently were expected to yield superior inbred lines and second cycle hybrids either to be released as varieties as such or to be utilized in future breeding work. The overall differences between the crosses, however, were not highly pronounced and therefore it was not possible to identify a cross which would yield markedly superior recombinant lines and F1 crosses compared to the others.

The fate of NO3- in raw and anaerobically-digested cattle slurries acidified with HNO3 was studied in a laboratory incubation experiment at the Agriculture and Food Science Centre, Belfast, in 1992. Four amounts (20, 30, 40 and 50 g) of each slurry type were acidified with five rates of HNO3 supplying 0·7, 1·4, 2·1, 2·8 and 3·5 mg N/g enriched to 10 atom% 15N. The slurries were stored in 500 ml glass jars for 7 days at 20 °C. The jars were left open to allow O2 supply by diffusion through the slurry surface to create varying degrees of aeration depending on slurry depth. Fluxes of N2 and N2O were measured from each jar for 2 h each day. The pH was measured after each gas flux measurement and HNO3--N recovery as NO3--N measured at the end of the incubation.

For raw cattle slurry, almost none of the HNO3--N was recovered as NO3--N at the 0·7 or 1·4 mg HNO3-N/g rates, but recovery was not significantly different (P > 0·05) from 100% at the 2·8 and 3·5 mg HNO3-N/g rates. At the 21 mg HNO3-N/g rate, recovery was higher when larger amounts of slurry were incubated, indicating that O2 could promote NO3-loss. Average pH during the incubation period had to be < 5·5 for recovery of HNO3-N as NO3-N to be > 90%. For digested cattle slurry, recovery was > 87% at the 0·7 mg HNO3-N/g rate and not significantly different (P > 0·05) from 100% at all other acid rates.

Fluxes of N2 and N2O were not detected from any digested slurry treatment but were measured in all raw slurry treatments. Gaseous losses occurred after incubation for 1 day, and maximum flux rates occurred after incubation for 2 days. Fluxes were highest from incubations with the intermediate amounts of slurry containing 1·4 mg HNO3-N/g. The largest observed flux from an individual jar was 322 μg N2-N/g/2 h with 40 g of slurry containing 1·4 mg HNO3-N/g, which would have accounted for a loss of 23% of the added HNO3-N during this period. Nitrous oxide and N2 were always evolved simultaneously and when the pH was between 7 and 9. On average, 90% of the total loss of N-gases was as N2.

The raw slurry contained much higher concentrations of volatile fatty acids than the digested slurry. If HNO3 is added to slurries containing such readily decomposable substrates, the NO3- is susceptible to loss as N2 and N2O by denitrification. Oxygen supply, pH and substrate availability control the rate of denitrification.

Experiments were done during 1990/91 and 1991/92 at Bangalore to estimate the reduction in yield caused by powdery mildew (Erysiphe polygoni DC) on coriander (Coriandrum sativum L.) cultivars differing widely in time to maturity. Powdery mildew resulted in smaller reductions in yield in the early maturing than the late maturing cultivars. Although the results of this study suggest that even expensive control measures can be recommended for managing powdery mildew in late maturing cultivars, because a small increase in the severity of powdery mildew infection may cause a considerable economic loss, they also indicate that such measures may not be economically viable for early maturing cultivars.

A 2–year study (1990 and 1991) was conducted at the ICRISAT (International Crops Research Institute for the Semi-Arid Tropics) Sahelian Centre, near Niamey, Niger, to select groundnut cultivars tolerant to drought and to examine selection techniques. Thirty-six cultivars known to vary in yield potential were grown under rainfed and irrigated conditions. Crop growth rate (C) and partitioning co-efficient (p) were estimated from phenological and final harvest data. The correlation between years was greater for partitioning than for pod yield (implying a higher heritability for p than for yield). Tolerance as determined by a drought susceptibility index for pod yield (SY), crop growth rate (Sc) and partitioning (Sp) to reproductive sinks showed thirteen cultivars as drought tolerant for either C or p or for both. The Sahelian cultivars 796, 55–437 and TS 32–1 were the most consistent for drought tolerance. Partitioning was the most important yield component affecting yield variation among cultivars.

Field experiments were carried out in Brittany (Western France) in 1993 to measure ammonia losses from surface-applied pig and cattle slurry. Experiments were conducted on grass, stubble (wheat and maize) and arable land using a wind tunnel system. Ammonia losses were followed during periods ranging from 20 to 96 h after slurry application. Rates of slurry applied varied from 40 to 200 m3/ha. In two experiments, losses from cattle slurry were respectively 75 and 54% of the ammoniacal nitrogen applied in the slurry. Ammonia emissions from pig slurry applied at a rate of 40 m3/ha, during spring and summer experiments, were higher on grass (45–63% of the total ammoniacal nitrogen applied) than on wheat stubble (37–45%). On average, 75% of the total loss in all experiments occurred within the first 15 h after spreading. Significant correlations were found between ammonia losses (kg N/ha) and mean soil temperature and slurry dry matter content (%) using simple linear regressions and stepwise procedures. The time of application was also found to influence the magnitude of ammonia loss: 83% of the total loss occurred within 6 h when the slurry was applied at midday compared with 42% when it was applied in the evening.

Low quality chaffed meadow hay, containing 10·5 g N/kg dry matter (DM), was fed to four artificially reared sambar (tropical) deer (Cervus unicolor) and four red (temperate) deer (Cervus elaphus) confined indoors in metabolism crates at Palmerston North, New Zealand, during March and April 1994. Measurements were made of DM intake (DMI), apparent digestibility, nitrogen (N) retention and the time spent eating and ruminating. Voluntary food intake (VFI), measured over days 7–11, was substantially greater for red deer than for sambar deer (67 v. 36 gDM/kgW0·75/day). Dry matter intake of red deer was then restricted, so that apparent digestibility could be better compared between the two species. Eating and ruminating time/gDMI and chews during eating/gDMI were all greater for sambar deer than for red deer. Apparent digestibility of DM, organic matter (OM) and energy were low (c. 0·42) and not different between deer species. Apparent digestibility of neutral detergent fibre (NDF) and cellulose were highest for red deer, but lignin apparent digestibility was highest for sambar deer. Both deer species lost weight and were in negative N balance. However, despite their lower N intake, sambar deer lost significantly less N and liveweight per day (– 5·6 g and – 118 g) than red deer (– 12·2 g and – 258 g). It was concluded that red deer responded to a diet of low quality roughage by increasing VFI and cellulose digestion, whilst sambar deer responded with a lower VFI but greater chewing activity, improved lignin digestion and better N conservation. Rumen mean retention time should be measured in future experiments with sambar deer and red deer fed on low quality forage diets.

A factorial experiment on Vicia faba L. cv. Alameda with three plant densities at three levels of nitrogen fertilization was done for three years (1984–87) at Granada. Yield varied markedly from 403 to 579 g/m2 between seasons. The mean increase in plant population density from 10 to 16 plants/m2 raised seed yield, but a further increase to 21 plants/m2 did not increase yield significantly. There was, however, considerable variation in the response to increasing density (Dl to D3) within each N level (N0, N1 and N2). Application of 30 kg N/ha at the start of flowering increased mean seed yield only at the lowest plant density and in 1986, but 60 kg N/ha increased yield by 135% on average over the 3 years. The highest N application rate resulted in consistently higher overall yields at each plant density. Leaf area index (LAI) showed a significant increase at 20 seeds/m2 compared with that at 10 seeds/m2 but there was no further increase at 30 seeds/m2. Harvest index (HI) was mainly affected by the annual weather conditions, and ranged from 47–4 in 1986 to 62–6 in 1987. HI was related to the mean temperature at flowering (April).

In a field experiment with transplanted rice (Oryza sativa L.) during the wet season of 1990 at the Central Soil Salinity Research Institute, Karnal, India, the effects of four rates of N application (0, 80, 120 and 160 kg N/ha), two methods of urea application (before puddling, M,, and after puddling, M2) and two presubmergence periods (none, S0, and 1 week, S1,) were evaluated on ammonia volatilization losses in a sodic soil (pH 9·0, exchangeable sodium 29%). Cumulative ammonia volatilization losses were 1·43, 18·00, 22·54 and 28·29 kg/ha following applications of 0, 80, 120 and 160 kg N/a respectively; 17·08 and 18·01 kg/ha for treatments M1, and M2 respectively; and 18·63 and 16·34 kg/ha for treatments S0 and S1 respectively. Flood-water NH4+ and pH increased during days 1–4 and then there was a sharp decline on days 4–9, followed by a gradual decline. The highest flood-water NH4+ and pH values were found for the treatments which received urea at the rate of 160 kg N/ha, after puddling (M2) and with no presubmergence period (S0).

Rape (Brassica campestris) was labelled, during cultivation, with 15N and then prepared into rapeseed meal (RSM) and rapeseed straw (RSS). Three non-lactating cows, equipped with ruminal and Tshaped duodenal cannulae, were used to incubate both feeds in the rumen for various periods of time in mobile bags contained within larger mesh bags. Some of the mobile bags were then inserted into the duodenum and collected from the faeces. The effects of rumen incubation time and contamination by non-feed N during the rumen incubation and subsequent intestinal digestion on the intestinal feed N digestion values so obtained were assessed. The intestinal digestion of intact RSM nitrogen was also measured in vivo by dosing directly into the duodenum and measured as the net loss of excess 15N not recovered in the faeces.

With RSM, microbial contamination did not affect the disappearance values of feed N from mobile bags in the rumen, the difference in the disappearance between 15N and total N (NT) being negligible. However, the decrease in the disappearance from the mobile bags in the intestine with increasing rumen incubation time tended to be smaller with 15N than with NT, resulting in significantly increasing differences between 15N and NT with increasing rumen incubation time. The average in vivo net loss within the intestine of 15N of labelled RSM was much lower (50·0%) than the 15N disappearance from the mobile bags (80·9%).

With RSS, the disappearance values of 15N and NT from the mobile bags in the rumen were different. The disappearance of 15N was always higher than that of NT, and it also increased significantly more with increasing incubation time. The disappearance of 15N from the mobile bags within the intestine decreased with increasing rumen incubation time, but that of NT remained rather constant.

It is concluded that the intestinal N digestion of a feed may vary significantly depending on the degree of preceding rumen degradation. Therefore, constant intestinal digestion coefficients may not be applied in the modern protein evaluation systems. With protein-rich feeds, such as RSM, the influence of non-feed N is small and does not interfere with the estimation of intestinal N digestibility by the mobile-bag method. With fibrous feeds with low N, such as RSS, intestinal N digestion values are seriously confounded by non-feed N. The present study with RSM did not confirm the correspondence between the value obtained by the mobile-bag method and that in vivo.

The chewing behaviour of red deer (Cervus elaphus) during eating and the effectiveness of chewing on feed comminution was studied in two experiments. In Expt 1, deer were fed long or chopped lucerne (Medicago sativa) hay, and feed intake and chewing activity were recorded. In Expt 2, the rumen was emptied and test meals of fresh chicory (Cichorium intybus cv. Puna), lotus (Lotus corniculatus cv. Grasslands Goldie), ryegrass (Lolium perenne cv. Ruanui) forage and long lucerne hay were given, chewing activity recorded and the ingested forage quantitatively removed from the rumen. In Expt 1, the chopped hay was eaten more quickly than long hay (11·4 v. 8·3 g dry matter/min), and required fewer chewing bites per g dry matter eaten. In Expt 2, the four forages were consumed at similar rates (mean 4·3 g organic matter/min) and there was no significant difference in the chewing required to consume either total organic matter (OM) or cell wall OM. Deer chewed more quickly when eating lucerne hay than when eating lotus, and it was estimated that a greater number of chewing bites were required to form a bolus of lucerne hay than to form a lotus bolus. The proportion of ingested OM which was comminuted so as to pass a 1 mm sieve (efficiency of chewing) was greater for lotus (0·485) and lucerne hay (0·.518) than for chicory (0·.267). The efficiency of chewing ryegrass (0·.366) was intermediate and not significantly different from any other forage. For all forages, the main effect of chewing during eating appeared to be the release of cell contents, rather than the comminution of cell wall. Physical breakdown to particles which passed a 1 mm screen but were retained on an 0·25 mm screen was low for fresh forages (0·074–0·086) but was slightly higher for lucerne hay (0·127). Deer reduced feed particle size during eating with a similar efficiency to sheep, but were less efficient than goats.

It is suggested that the chewing effort associated with forage consumption by red deer is related to the need to form a bolus. The amount of chewing may be as much influenced by the physical characteristics of the forage (e.g. leaf size and shape) as by its chemical composition, and the extent of comminution during eating may be determined by the processing needed to form a bolus and the resistance of the feed to bolus formation.

Two studies were conducted between 1991 and 1993 to assess the impact of grazing improved v. natural pasture at different stocking densities on animal and vegetation responses. In the first grazing season, goats of the West African Dwarf (WAD) breed were grazed at four stocking densities – 1·90, 2·86, 3·86 or 4·71 TLU/ha (Tropical Livestock Unit = 250 kg liveweight). Wet-season grazing lasted for 14 weeks while assessment was continued until kids were weaned at 120 days of age. There were significant (P < 0·05) changes in the content of legume and forbs in response to variations in stocking density. Liveweight gain per head was significantly (P < 0·05) higher at low than at high stocking density. The same trend was maintained with most aspects of reproductive performance. Goats at low stocking density were of a higher (P < 0·05) body condition score at parturition and had larger litter sizes than does stocked at high stocking density. Kid birth weight and liveweight gain were significantly (P < 0·001) higher at low than at high stocking density. The overall weight loss in does during nursing was similar at the different stocking densities.

In the following year, comparisons were made between three stocking densities, 2·11, 3·17 and 4·23 TLU/ha, on improved and unimproved pastures. Over 14 weeks of wet-season grazing, there was a significant (P < 0·01) decline in available dry matter except at the lowest stocking density on both pasture types. Weight gain per head decreased with increase in stocking density while the reverse was true for weight gain per unit of land. No significant differences were observed for reproductive performance between pasture types or stocking densities. Kid growth rate up to weaning declined with increase in stocking density (P < 0·001) while kid mortality rose with increase in stocking density (P < 0·01). Weight losses in nursing does were higher (P < 0·05) at low than at high stocking density.

Grazing sambar and red deer in New Zealand were offered a free choice of seven different plant species (forage legumes, browse and grasses) in 1992 and 1993 and dietary preference rankings were determined. Nutritive value of plants on offer and diet selected, plant height, plant species purity and stem diameter selected (browse only) were also determined. Total nitrogen (N) and organic matter digestibility (OMD) were highest for red clover, lowest for grasses and intermediate for browse species (willow, poplar and lupin). Top dietary preference ranking was willow for sambar and red clover for red deer in both years, with Yorkshire fog and prairie grass being lowly preference ranked with both deer species. Sambar selected willow stems up to 38 mm in diameter and poplar stems up to 54 mm in diameter. When the plants were grouped into browse, grass and forage legume categories, both deer species showed a similar preference ranking for grasses. Relative to grasses, sambar showed a strong preference for browse and a low preference for forage legumes, whilst red deer showed a strong preference for forage legumes of high nutritive value and a very low preference for browse. It was calculated that sambar selected a total diet higher in condensed tannins and lignin but lower in nitrogen than that selected by red deer, with similar values for total fibre and OMD. Differences in dietary preference between the two deer species may be linked with the greater ability of sambar deer to neutralize some plant secondary compounds and their more efficient rumination pattern compared with red deer. Both sambar and red deer can be classified as intermediate feeders, having a similar preference for grasses, but differing preferences for forage legumes and browse.

A multivariate linear model was developed to evaluate dairy cow body weight (BW) during lactation on a commercial dairy farm. The model was calibrated separately for first, second and greater than second parities, and also for winter and summer calvers, fed a total mixed ration of 65% concentrates. Average weekly BW was predicted using the following variables on a weekly basis: 4% fat-corrected milk (FCM) yield, time of conception (PREG), time from calving (w), initial body weight (1BW) measured within 2 days after calving, and weeks remaining until the end of the calving season (SWR). The ability of the model to predict mean BW along lactations was tested in the same herd following calibration and during the same period. The prediction capacity of the model for average BW of groups of cows was examined on two timescales: (i) time from calving (physiological timescale) and (ii) any time during the year (calendar timescale). Results indicated that predicted mean BW deviated from measured values either by 1–2% with a maximal deviation of c. 5% on the physiological timescale or by up to 2% on the calendar timescale.

The voluntary food intake (VFI) and apparent digestibility of chopped timothy hay by six Scottish Blackface (BF), Shetland (SH) and Dorset Horn (DH) non-breeding ewes were assessed in summer and winter. In two experiments VFI was higher in summer than in winter but did not differ between the breeds. In Expt 1, the seasonal difference in VFI was greater in BF and SH than in DH ewes and the apparent digestibility of dry matter (DM), organic matter (OM) and total nitrogen was consistently higher in all three breeds in summer than in winter. The higher digestibility of DM of the hay in summer than in winter was confirmed in Expt 2, in which the whole tract mean retention time (MRT) of the undigested residues was measured using 103ruthenium-phenanthroline as a marker. The MRT was lower in all three breeds in summer than in winter. In a third experiment, following at least 6 months ad libitum feeding on the hay, for all three breeds the contents of DM and liquid in the reticulorumen were smaller in summer, and the liquid fraction formed a greater proportion in summer than in winter. The results contrast with the expectation that intake and digestibility within a given forage type are negatively correlated. Although an increase in digestibility may facilitate a higher VFI in summer (BF and SH) it does not necessarily do so (DH).

The urinary excretions of creatinine, allantoin and total purine derivatives by Merino ewes were compared with predictions based on the assumptions that creatinine excretion scaled to liveweight (the creatinine coefficient) was constant and was not affected by diet. The creatinine coefficient varied between individuals and was found to be affected by diet (P<0·01). As a result, there were systematic deviations (p<0·01) in the predictions of allantoin and total purine derivative excretion. If predictions of purine derivative excretion are to be made for individual animals in the absence of total urine collections, prior determination of individual creatinine coefficients is required and predictions may be confounded by diet effects on creatinine excretion. Predictions for groups on the basis of general relationships between the creatinine coefficient and liveweight may be subject to errors between diets of > 10%.

During 1991/93, young sambar (5 months old) and red deer (7 months old) were confined indoors in individual pens in New Zealand and fed a pelleted concentrate diet (12 MJ ME/kgDM; 2·9% N) ad libitum for 21 months. Seasonal patterns of voluntary feed intake (VF1), liveweight gain (LWG), scrotal circumference and plasma concentrations of prolactin (PRL), luteinizing hormone (LH), testosterone (T) and progesterone (P) were compared using five stags and three hinds of each species.

Red deer showed a strong pattern of seasonality, with high VFI and LWG in summer and low VF1 and LWG in winter and with peak plasma T and scrotal circumference in stags in early autumn. Compared with red deer, sambar showed weaker seasonal patterns of VFI and LWG, with maximum values in autumn and minimumvalues in spring. Over a complete 12-month cycle, sambar deer gained similar amounts of liveweight to red deer but consumed substantially less feed, thus demonstrating a more efficient conversion of feed tobodyweight. Metabolizable energy (ME) requirements for both maintenance and gain were substantially lower for sambar than for red deer. Scrotal circumference and plasma T values in sambar stags attained their highest values during late autumn, winter and spring, but with a lower magnitude than peak values for red stags. Plasma PRL concentrations were seasonal in both species, with highest values in summer and lowest values in winter. Rapid increase of plasma P was first detected in red hinds in autumn and sambar hinds in spring when they weighed 96 and 90 kg respectively, and were aged 17 and 14 months. Rapid increase of plasma T was first detected in red stags in early autumn and sambar stags in mid-autumn whenthey weighed 117 and 101 kg, and were aged 16 and 15 months respectively.

It was concluded that sambar deer had endogenous cycles of VFI, body growth and hormone secretion, which were of lesser amplitude and with different seasonality from those of red deer. Young sambar deer were more efficient feed converters than red deer, and attained sexual maturity at an earlier age and lower liveweight.

Isoenergetic diets containing grass silage and concentrates in the ratios 75:25; 50:50 and 30:70 on a dry matter (DM) basis were offered to 42 beef heifers, which were initially 361 kg liveweight, for 115 days in 1987 at Hillsborough, Northern Ireland. Half of the animals given each forage concentrate ratio were given one of two crude protein (CP) intakes in a 3 × 2 factorial design. The silage contained 152 g CP/kg DM, 94 g ammonia-N/kg total N and 734 g digestible organic matter/kg DM. Concentrates were based on barley and soyabean meal and were formulated to equalize CP intakes for the three forage: concentrate ratios. For diets containing 75, 50 and 30% silage, metabolizable energy intakes were 94, 92 and 87 MJ/day; liveweight gains 0·99, 1·07 and 1·12 (S.E. 0·051) kg/day; carcass gains 0·61, 0·64 and 0·67 (S.E. 0·033) kg/day; carcass lean concentrations (estimated from dissection of fore-rib joints) 636, 642 and 648 (S.E. 4·7) g/kg and carcass fat concentrations 204, 199 and 194 (S.E. 5·3) g/kg. Increasing protein intake did not affect performance, but increased carcass fat concentration at all three forage concentrate ratios. It was concluded that increasing the proportion of concentrates in grass silage-based diets increased carcass weight gain per MJ of metabolizable energy consumed and tended to reduce carcass fatness. Contrary to previous findings with young growing cattle, increasing protein intake did not alleviate the problem of greater fat deposition in finishing cattle given high-silage diets, but rather significantly increased carcass fat concentration.