During rainless weather following a monsoon, sorghum (Sorghum bicolor cv. SPH–280) was grown on a Vertisol either unirrigated throughout growth or irrigated for 7 weeks after emergence and rainfed thereafter. Before sowing, ammonium sulphate was applied at six rates from 0 to 150 kg/ha N. Roots were sampled every 2 weeks to determine biomass and root length density as a function of depth. Every week, soil water content in all treatments was measured gravimetrically to a depth of 0·23 m and with a neutron probe from 0·3 to 1·5 m.

Below 0·45 m, volumetric water content was a negative exponential function of time after roots arrived and the maximum depth of extraction moved downwards at 2–5 cm per day. In the dry treatment, the extraction ‘front’ lagged behind the deepest roots by c. 12 days initially but the two fronts eventually converged. Irrigation delayed the descent of the extraction front by c. 20 days but thereafter it appeared to descend faster than without irrigation. Averaged over N rates, the time constant of the exponential function was inversely related to the root length density, lv, decreasing with depth from about 20 to 10 days as lv increased from 2·5 to 4·0 km/m3.

The biomass[ratio ]water ratio was almost independent of N but increased from a mean of 5·3 g dry matter per kg water in the dry treatments to 6·9 g/kg with irrigation. When normalized by the seasonal mean difference in vapour pressure deficit within irrigated and unirrigated plots, the ratios were 13·1 and 13·3 kPa g per kg water, respectively.

In order to understand better some of the reasons for differences between forage plant species in digestibility, different parts of nine plant species in either milled or chopped (1 cm lengths) form were examined for in vitro digestibility and in milled form for neutral detergent fibre and lignin. The nine species were: Trifolium repens L., Medicago sativa L., Desmodium intortum (Mill.) Urb., Brassica napus L., Lolium perenne L., Festuca arundinacea Schreb., Chloris gayana Kunth, Cenchrus ciliaris L. and Zea mays L. In each case early harvesting was compared with later harvesting in each of two years. The plants were grown in spring–summer in a heated glasshouse.

The forage at the early harvest was, on average, 1–4% units more digestible in vitro than that at the later harvest and generally slightly lower in lignin and neutral detergent fibre content. However, the stems of Z. mays were higher in neutral detergent fibre at the early than at the later harvest.

The leaf sheaths of L. perenne and F. arundinacea were more digestible than the leaf blades. L. perenne was more digestible than F. arundinacea in both sheaths and blades. The sheaths and blades of C. gayana and C. ciliaris were less digestible and had a higher neutral detergent fibre content than those of L. perenne and F. arundinacea. The leaf blades, excluding the midribs, and the stems and leaf sheaths of Z. mays were all rather high in digestibility when milled and moderately low in neutral detergent fibre and lignin; the leaf blade midribs of Z. mays were less digestible and higher in neutral detergent fibre than the stems and similar to the stems in lignin content. The leaflets of T. repens had an appreciably lower neutral detergent fibre content than the stolons and petioles and a rather lower lignin content in dry matter and yet were, if anything, less digestible than the stolons and petioles. The stolons of T. repens were much more digestible than the stems of M. sativa and D. intortum. The digestibility of D. intortum was low in all the plant parts examined, leaflets, petioles and stems. In both D. intortum and B. napus, the leaflets or leaf blades were much lower than the stems in neutral detergent fibre and lignin and yet they were no more digestible than the stems when milled.

The digestibility of chopped leaflets and leaf blades was similar to that of milled leaflets and leaf blades, but chopping rather than milling reduced the digestibility of stems (particularly of those of Z. mays), petioles, the leaf blade midribs of Z. mays, and, to some extent, leaf sheaths.

The effects of four rates of fertilizer phosphorus (P) application (0, 9·8, 19·6 and 39·2 kg P/ha per year) on soil and crop P and cadmium (Cd) contents were measured in a field trial begun in 1968 and cropped each year with barley in south west England. In 1996, available and total soil P and Cd were measured in seven soil layers (0–20, 20–25, 25–30, 30–35, 35–40, 40–45 and 45–50 cm). Offtake of P in the crop was measured, or could be estimated, throughout the trial period. There was a linear relationship between P balance (total applied − total offtake) and P application rate with a balance of zero at a rate equivalent to 17 kg P/ha per year. The rate of P required for the economically optimum grain output was equivalent to 30 kg P/ha per year. No evidence was found for available P enrichment of soil layers below 25 cm. There was no evidence of Cd enrichment of either soil or crop after 29 years of P applications.

Field experiments were conducted on Alfisols in Nigeria between 1991 and 1993 to determine the residual effect of maize (Zea mays) and cowpea (Vigna unguiculata) on the growth, pod yield and N response of a succeeding okra (Abelmoschus esculentus) crop. Cowpea and maize were grown alone with 30 and 60 kg/ha of N, P and K, respectively, or intercropped with 60 kg/ha as a basal dressing. The preceding crops had a significant effect on soil nutrient changes, okra growth and yield, and N response of okra. Cowpea increased the N, P and K status of the soil in both sole and mixed stands, compared with sole maize. Leaf area, pod weight and marketable pod yield of okra after sole cowpea or the maize/cowpea intercrop were all significantly higher than after sole maize. Although the application of nitrogen to succeeding okra promoted growth and increased pod yield, this was not accompanied by an increase in the pod yield of okra after sole cowpea or the maize/cowpea treatment beyond 45 kg N/ha. The beneficial effects of the preceding maize/cowpea intercrop on soil fertility, okra pod yield and amounts of N required for okra were partly due to the higher rate of basal nutrients applied as compared to the effects following sole cowpea.

To appreciate more clearly some of the physical characteristics of forages which may be important in relation to digestibility and structural integrity, different parts of eight plant species were examined for the proportion of thick-walled, thin-walled and epidermal cells, the thickness of the cell walls and the diameter, length and volume of the cells. The eight species were: Trifolium repens L., Medicago sativa L., Desmodium intortum (Mill.) Urb., Lolium perenne L., Festuca arundinacea Schreb., Chloris gayana Kunth, Cenchrus ciliaris L. and Zea mays L. Early harvesting was compared with later harvesting in each of two years. The plants were grown in a heated glasshouse in spring–summer.

The plant parts with the lowest proportion of thick-walled cells (3–6% of cross-sectional area) were the legume leaflets and those with the highest proportion (47–57%) were the leaf blades and stems of C. ciliaris. The plant parts with the highest proportion of thin-walled cells were the legume leaflets and petioles and the Z. mays stems and leaf sheaths. The walls of the cells categorized as thick-walled were thinnest (0·9 μm) in L. perenne leaf blades and T. repens leaflets and thickest (2·0–2·3 μm) in the leaf blade midribs, leaf sheaths and stems of Z. mays and in the stems and petioles of T. repens. The thinnest outer walls of epidermal cells (0·9 μm) were recorded for the leaf blades of L. perenne.

The largest cells within the categories and plant parts examined (1 100000 μm3) were thin-walled cells in the stems of Z. mays. The longest cells recorded (180 μm) were thin-walled cells in the petioles of T. repens. The thick-walled cells were particularly small (1800–2600 μm3) in L. perenne leaf blades and sheaths and in T. repens leaflets. The largest thick-walled cells in the study were in the stems and petioles of T. repens. The epidermal cells of D. intortum leaflets, petioles and stems were particularly small (2000–3000 μm3).

In the Sudano-Sahelian zone of West Africa there is potential for groundnut (Arachis hypogaea L.) to be grown as a dry-season crop where irrigation is available. However, there are substantial variations in the temperatures during the post-rainy season that can be expected to influence growth and yield. An experiment at the ICRISAT Sahelian Centre was done in order to study the effect of sowing date on phenology, yield and the processes of yield determination for four groundnut cultivars under irrigation in the dry seasons of 1990/91 and 1991/92. Starting on 15 November, eight sowing dates at 2-weekly intervals were tested. Sowing date significantly affected phenology (time to emergence, flowering and maturity) with groundnut sown in November/December taking the longest time to reach these phenological stages. November and December sowings gave the highest pod yield within each year, despite the lowest crop growth rates (B), and yield declined progressively as sowing occurred later (50% decrease by March) despite increasing B. The observed responses appear to have been due to the effect of temperature differences during the pod-filling phase on partitioning. Partitioning (p) to pods was optimized at c. 30 C, with some indication of cultivar differences in partitioning response to temperature. Across all the environments, cultivars displayed substantial differences in yield stability. When sown late, yields were low and lines with high partitioning were the best. When sown early in the post-rainy season, cultivars with a high B value were the better choices. Plant habit differences and B suggest that radiation interception was a limitation to yield, particularly when the crops were sown in the cool months of the year. However, haulm yield and crop growth rates were not consistently affected by sowing date across the years, and cultivars demonstrated different degrees of stability for B. It is concluded that where pod has a price advantage over fodder, irrigated groundnut for the dry season should be sown in November to allow the crop to develop under the relatively cool temperatures that maximize pod yield. Further agronomic research is suggested to maximize B for individual cultivars for given sowing dates.

Two field experiments in Canterbury, New Zealand, were conducted during 1993–95 following the ploughing of temporary pasture leys. These experiments investigated the effects of cover crop management on the accumulation of soil mineral N and nitrate leaching during winter, and the growth and N uptake of the following spring cereal crop. The cover crops used were ryegrass (Lolium multiflorum L.), oats (Avena sativa L.), lupins (Lupinus angustifolius L.), mustard (Sinapis alba L.) and winter wheat (Triticum aestivum).

Ploughing of temporary pasture in autumn (March) resulted in extensive net N mineralization of organic N by the start of winter (June). In fallow soil, mineral N in the profile in June ranged from 98 kg N/ha in 1993 to 128 kg N/ha in 1994. When cover crops were established early in the autumn (March) in 1993, both the above-ground dry matter production (1440–3108 kg DM/ha) and its N content (50–71 kg N/ha) were substantial by the start of winter. In 1994, establishment of cover crops one month later (April) resulted in very little dry matter production and N uptake by June. In both years, compared with fallow soil, winter wheat planted in May had little effect on soil mineral N content by the start of winter.

Compared with fallow, cover crops had little effect on soil drainage over winter. Cumulative nitrate leaching losses from fallow soil were much smaller in 1993 (23 kg N/ha) than in 1994 (49 kg N/ha), mainly due to differences in rainfall distribution. Cover crops reduced cumulative nitrate leaching losses in 1993 to 1–5 kg N/ha and in 1994 to 22–30 kg N/ha. When cover crops were grazed, soil mineral N contents were increased due to the return of ingested plant N to urine patch areas of soil. Elevated soil mineral N contents under grazing persisted throughout the winter. Grazing had little effect on cumulative nitrate leaching losses, mainly because of the small amount of drainage that occurred after grazing in either year.

Compared with fallow, incorporation of large amounts of non-leguminous above ground dry matter depressed the yield and N uptake of the following spring-sown cereal crop. Where cover crops were grazed, yields of the following cereal crops were similar to those for soil fallow over the winter.

Lactating red deer (Cervus elaphus) hinds and their calves were rotationally grazed on Lotus corniculatus or perennial ryegrass/white clover pasture at an allowance of 12 kg DM/hind/day during summer 1996 in Palmerston North, New Zealand. Half the hinds suckled pure red deer calves and half suckled hybrid (0·25 elk[ratio ]0·75 red deer) calves. Measurements were made of the diet selected, voluntary feed intake of the hinds and liveweight changes of the hinds and calves.

Lotus corniculatus and perennial ryegrass constituted c. 90% of green material in the diet selected on the respective forages. Total nitrogen (N) content and organic matter digestibility (OMD) were higher for Lotus corniculatus than for perennial ryegrass/white clover pasture. Lotus corniculatus contained 21 g condensed tannin (CT)/kg dry matter (DM), whilst pasture contained only traces of CT (1·6 g/kg DM).

Hinds grazing Lotus corniculatus tended to have higher voluntary feed intake, and calf liveweight gain (485 v. 399 g/day) and weaning weight (52·6 v. 48·1 kg) were greater than for deer grazing perennial ryegrass/white clover pasture. Hybrid calves grew faster than pure red deer calves (P<0·01), with hybrid calves grazing lotus having very high liveweight gain (c. 520 g/day). Liveweight gain of hinds grazing Lotus corniculatus also tended to be higher (91 v. 20 g/day) than for hinds grazing perennial ryegrass/white clover pasture. CT was bound more strongly during chewing by red deer than had been found in comparable studies with sheep and the nutritional significance of this is discussed. Nutritional reasons for the superior performance of deer grazing Lotus corniculatus are discussed.

Experiments to evaluate the optimum plant population density and sowing date for winter peas, semi-leafless cv. Rafale, were sited on free draining sandy loam soils at Thornhaugh, Cambridgeshire in 1993/94 (Expt 1), 1994/95 (Expt 2) and 1995/96 (Expt 3). Peas were sown at the end of October, in mid-November and early December, at seed rates to achieve final plant densities in spring of 50, 70 or 90 plants/m2. Seed rates were calculated allowing for 20% seedbed loss and plant loss due to winter kill in Expt 1, and 15% in the other two years.

Peas sown in warmer seedbeds in October emerged in early December or before, November-sown peas did not emerge until mid-January and December-sown peas from late February to mid-March. The growth stage of October-sown peas was thus more advanced than the later sowings over the winter and spring period. Winters were mild for Expts 1 and 2, but there were more frost periods during Expt 3.

The yield of winter peas was dependent on sowing date. Yields of Rafale sown in October were highest in Expt 1, but lower than November-sown peas in 1995 (Expt 2), as a result of damage from late frosts during flower initiation in April, and in 1996 (Expt 3) due to plant losses after a more severe winter, frost periods and very cold winds in March. In Expts 1 and 2, yields of December-sown peas were significantly lower than November-sown peas, probably because they were adversely affected by drought stress during the sensitive flowering period. Therefore the optimum time for sowing winter pea cv. Rafale to achieve reliable yields appears to be mid-November. In some years, however, conditions may be too wet for late drilling, particularly on heavier soils.

The highest plant population densities of 90 plants/m2 gave the highest yields in Expts 2 and 3, but there was little increase between 75 and 90 plants/m2. Bearing in mind financial return and seed costs, the optimum target suggested is 75–80 plants/m2.

A grazing experiment was carried out using 18 Holstein/Friesian dairy cows at the Scottish Agricultural College, Crichton Royal Farm in 1991, to investigate the use of n-alkanes for estimating supplementary grass silage intake by grazing dairy cows. Two groups of animals grazed perennial ryegrass swards and were offered a supplement, consisting of a perennial ryegrass silage, twice daily after milking. Mean group silage intakes were measured daily during the last 5 days of a 12-day experimental period and individual silage intakes were estimated using n-alkanes. Animals were dosed twice daily with paper pellets containing dotriacontane (C32). The silage was marked with hexatriacontane (C36). The mean silage intake, estimated by weighing, was 6·8 kg DM per day. The mean estimated silage intakes were 6·9, 8·7 and 8·3 kg DM per day respectively using odd-chain n-alkanes in the C27−C35 range of naturally occurring alkanes, the odd-chain n-alkanes in the C27−C35 range with C36, and C36 by itself. No significant differences were found due to sampling routine (morning or afternoon) when using the naturally occurring n-alkanes but significant differences did exist when using the C36 alkane in the calculation of supplement intake. The results indicate that the n-alkane technique can be used to estimate the supplementary silage intake of grazing dairy cows using naturally occurring n-alkane patterns.

Nitrate loss in drainwater and cultivated layer flow was measured over 5 years on two pairs of hydrologically isolated plots, one pair with cereal straw incorporated for 4 years and burnt in the fifth, and the other with straw burnt in all 5 years. Although straw incorporation decreased nitrate leaching and probably decreased net mineralization of soil organic matter in the first winter, these effects were apparently diminished or even reversed in later winters, and the straw had no benefit on cereal yields or N-uptakes. The results suggest that the present practice on UK farms of regularly incorporating cereal straw is unlikely to decrease nitrate losses and in the long term may increase them, especially on clay soils and in wet winters after long dry periods. On clay soils it is also unlikely to increase crop yields in the short or medium term.

In order to understand more about the nature of forage particles before they enter the rumen and about the degradation of cell walls in the rumen, particles of different plant parts produced by sheep when eating each of eight plant species were described in terms of volume and exposed surface area and in terms of numbers of cells and volume and surface area of cell wall. Estimates were made of the extent to which the walls would be degraded in the rumen. The eight species were: Trifolium repens L., Medicago sativa L., Desmodium intortum (Mill.) Urb., Lolium perenne L., Festuca arundinacea Schreb., Chloris gayana Kunth, Cenchrus ciliaris L. and Zea mays L. In each case early harvesting was compared with later harvesting in each of two years. The plants were grown in a heated glasshouse.

The plant parts which were chewed to the smallest particle size during eating, and which produced particles with the largest proportion of total cell wall area exposed on the outside of the particle (6–10%), were the legume leaflets and the grass leaf blades and sheaths. The proportion of total cell wall area exposed on the outside of chewed particles derived from stems was only 3–4%. The number of thick-walled cells per mm3 of chewed particle was greatest in particles derived from the leaf blades and stems of C. ciliaris, the leaf blades and leaf sheaths of L. perenne and the stems of C. gayana. The average number of thick-walled cells per particle was 860000 in particles derived from the stems of C. gayana and C. ciliaris and 260000 in particles derived from L. perenne leaf blades and sheaths. The volume and surface area of walls of thin-walled cells per mm3 were greatest in particles derived from legume leaflets. The total surface area of walls of epidermal cells per mm3 was greatest in particles derived from leaflets and leaf blades and least in those derived from stems. The estimated percentage of wall thickness of thick-walled cells which would be degraded in the rumen was relatively high in the case of leaf blades, sheaths and stems of C. ciliaris, leaf blades of Z. mays, leaf sheaths of L. perenne and F. arundinacea and stems of C. gayana, relatively low in the case of petioles of T. repens and stems of D. intortum and M. sativa and close to zero in legume leaflets. The estimated percentage of wall thickness which would be degraded did not seem to be related to the concentration of lignin in the walls, either in grasses or in legumes.

Four, 4-week old Friesian calves (BW=50±3 kg), fitted with duodenal, portal and jugular catheters and duodenal electrodes, were used to study the metabolism of duodenally infused betaine (Bet) or choline (Chol) and their effects on blood sulphur amino acids and duodenal myoelectrical migrating complexes (MMC). Animals were fed milk replacer at 5% BW twice daily, but were starved overnight prior to the experimental procedure. Animals received a saline infusion for 2 h at 1 ml/min followed by a 1 h infusion of 1·2 or 3·6 mmol of either Bet or Chol. Infusion of saline was continued for another 2 h after the cessation of the amino acid infusion. Duodenal MMC were measured with a computer-based data acquisition system (MacLab, ADI, Australia). There were no differences in measured blood metabolites between the jugular and portal vein; therefore, only average values were presented. Plasma Met concentrations increased from 20 μm, 20 min after initiating Bet infusion, whereas a lower dose of Chol decreased plasma Met and a higher one had no effect. The highest plasma methionine (Met) concentration (29 μm) occurred 45 min after the onset of the Bet infusion (1·2 mmol). Compared to the 3·6 mmol Bet infusion, the intraduodenal infusion of 1·2 mmol of Bet resulted in a greater area (P<0·001) under the plasma Met concentration curve (281·6 v. 73·3 mmol). A similar pattern was observed for plasma cystine concentrations. Infusion of Bet or Chol did not change the duration of MMC but Bet increased the number of spikes during the phase of low spiking activity (37·5 v. 14·6 pre-infusion, spikes/min; P<0·01). Chol had the same effect but only after the infusion ceased (29·3 v. 11·5 spikes/min; P<0·01). The velocity of migration of regular spiking activity (RSA; related to digesta transport) increased as a result of infusion (16·4 pre-infusion v. 31·3 Bet, 25·2 Chol cm/min; P<0·01). Chol caused an immediate increase in the velocity of migration of RSA, whereas with the Bet infusion an increase was observed after cessation of infusion. Increased concentrations of sulphur amino acids during Bet infusion could indicate that labile methyl groups may be limited in calves. Postruminal Bet and Chol supplementation may cause a decrease in nutrient absorption in the small intestine by increasing digesta transport.

A field trial on alley-cropping was conducted at the University of Ibadan research farm in the 1990/91 cropping season to assess the contributions of arbuscular mycorrhizal (AM) fungi and hedgerow woody legumes to the yield and nutrient uptake of cassava (Manihot esculenta Crantz) as an intercrop in an infertile soil. The trial also investigated the influence of AM fungi on the interplanting of a non-nodulating woody legume Senna siamea (syn. Cassia siamea) with a nodulating woody legume (Leucaena leucocephala).

AM contributions to cassava were greater than the hedgerow contributions, which demonstrated that AM associations are an essential component in the nutrition of cassava. In contrast to cassava, AM inoculation only influenced the leaf dry weight and uptake of nutrients of non-interplanted woody legumes but not the above-ground biomass and P uptake of interplanted woody legumes. However, non-inoculated interplanted Leucaena benefited more from indigenous AM fungi than the competing Senna. The negative contributions to the nutrient uptake (K, Ca and Mg) of cassava by hedgerows and the lack of response to AM inoculation in interplanted hedgerow woody legumes could be attributed to root competition among the different plant species growing in close proximity to each other. The present results show that cassava benefits more from AM association than Leucaena which in turn benefits more than Senna in an alley-cropping system.

The effects of oversowing introduced grasses and legumes, tree killing and stocking rate on simulated diet quality and feed intake of cattle were studied in an open eucalypt woodland in the semi-arid tropics of north-eastern Australia in 1990. Rainfall during the experimental period was above average, producing good conditions for pasture growth, which resulted in little influence of stocking rate on pasture or dietary attributes. During the growing season, forage quality, as measured by nitrogen concentration and in vitro digestibility, was higher in sown pasture than in native pasture, and higher in plots with live trees than in plots with killed trees. Treatment differences in herbage quality disappeared later in the year when pastures senesced. In sown pasture treatments, there was no effect of tree killing on legume (Stylosanthes spp.) quality. However, Stylosanthes made a greater contribution to the diet of cattle grazing in wooded paddocks than in paddocks where trees had been killed. The proportion of Stylosanthes in the diet reached a peak in May and then declined. Oversowing increased both diet quality and feed intake while, to a lesser extent, killing trees resulted in generally lower diet quality and feed intake.

Estimates of liveweight change were made from the quantities of energy and protein consumed by the cattle. As expected, large increases in liveweight gain were predicted to occur in oversown pastures compared with native pastures. However, estimates indicated that animal performance may be better where trees are left intact rather than killed. While carrying capacity is greatly increased with the removal of trees, this may be at the expense of individual animal performance. Possible reasons for this significant negative response in dietary attributes and predicted liveweight gain to tree killing are discussed.

Lime loss rates were determined for 11 agricultural soils across England (1987–92) under arable cropping (six sites) and grassland management (five sites), receiving commercial rates of fertilizer inputs. Lime additions in the range 0–1500 kg ha−1 CaCO3 (250 kg ha−1 CaCO3 increments) were made annually to the sites. Soil pH (water and 0·01 m CaCl2) and exchangeable calcium concentrations were measured annually. The annual lime loss rates were calculated as the amount of lime needed to maintain the initial site pH or exchangeable Ca concentrations.

Lime loss rates based on soil water pH varied between 40 and 1270 kg ha−1 CaCO3, on the basis of CaCl2 pH between 0 and 1370 kg ha−1 CaCO3, and exchangeable Ca between 0 and 1540 kg ha−1 CaCO3. There was a positive relationship between the lime loss rate (based on water pH) and initial soil pH value (r=0·75; P<0·01), and a negative relationship with soil organic matter content (r=0·63; P<0·05) was based on soil pH, organic matter content and nitrogen (N) fertilizer input. Lime loss rates were approximately double those predicted by previous models developed in the 1970s, reflecting the greater quantities of inorganic N fertilizer now being applied to agricultural land.

Two experiments were carried out in order to study the effect of the ash content of poultry litter (PL) on its nutritional value. In Expt 1, broiler PL was incorporated in the proportions of 30 and 45% into diets based on wheat straw supplemented with 20% maize grain. The PL was either fresh (containing 19% ash) or had been heated in a stack (giving 26% ash). There were also two additional diets containing 45% fresh PL to which either ground limestone or wood ash had been added to provide the same ash content as the diets containing 45% stored, high ash PL. An in vivo digestibility and nitrogen balance trial was carried out. Storing the PL, which resulted in heating and an increase in ash content, reduced dry matter intake significantly. The largest and most significant effect on the digestibility of dry matter, organic matter and crude protein can be ascribed to the freshness of the PL. Stored, heated PL had a highly negative effect on crude protein digestibility and on nitrogen retention. No negative effect of adding extrinsic ash was recorded. In Expt 2, the nutritional value of layer PL (LPL), compared with that of broiler PL (BPL), was examined using ten beef cows before and after calving. The diet was composed of 45% PL, 35% wheat straw (WS) and 20% maize grain. Daily dry matter intakes were 12·7 and 16·2 g/kg liveweight (LW) before calving and 15·5 and 22·8 g/kg LW after calving, for cows fed LPL and BPL, respectively. Owing to the combined effect of the lower dry matter intake, lower gross energy content and lower digestibility of LPL, the digestible energy intake of BPL diets was almost three-fold, and nitrogen absorption (g/kg LW0·75) on the BPL was 2·4-fold higher than on the LPL diets. Because the ash intake of both diets was similar, it is suggested that the main inhibiting factor of intake after calving was the rumen's ability to mobilize the large amounts of ash-rich complexes of ash and organic matter to the reticular omasal orifice and, consequently, out of the rumen.

The feeding behaviour of Mamber dairy goats grazing on Mediterranean woodland in the Upper Galilee mountains of Israel was studied throughout a year (1991/92). The percentages of crude protein (CP), neutral detergent fibre (NDF), acid detergent fibre (ADF), acid detergent lignin (ADL) and condensed tannins (CT) were determined in samples collected by hand to simulate the plant parts selected by the goats. Total feed intake was evaluated by using Cr-sesquioxide as an external marker to determine the amount of faeces excreted, and 48 h in sacco degradability to assess the digestibility of samples. Overall, more time was spent by goats in feeding on ligneous material (tree and shrub foliage) than herbaceous vegetation (60 and 40% of total feeding time, respectively, P<0·05). The main ligneous species consumed by the goats were Quercus calliprinos, Sarcopoterium spinosum and Calicotome villosa (20, 13 and 7% of total grazing time, respectively). There was considerable variability in the 48 h dry matter (DM) in sacco degradability, and in the concentration of CP, NDF, ADF, ADL and CT, within and between seasons and plant species. Although requirements for nutrients varied according to the physiological stage of the goats, 48 h in sacco DM degradability and the concentration of non-ADF linked (available) CP, NDF, ADF, ADL and CT in the diet did not vary greatly: respective ranges were 45·0–49·4; 9–12·5; 44–53; 33–39; 12–17 and 3·5–4·7%. It is concluded that Mamber goats (i) may not select the best quality diet available, but may avoid wide variations in nutrient content of their diets throughout the year; and (ii) may not select a diet consistent with maximization of milk yield, but rather with optimization of body condition at the onset of the mating season.

It is possible to estimate diet composition from an analysis of n-alkanes in the faeces of ruminant animals. The method requires the estimation of the concentrations of n-alkanes in the plants and faeces and then the solving of a system of simultaneous equations. There are at least three places in which significant measurement error may be introduced. First, there may be error in the determination of the concentrations of the n-alkanes in the herbage. This error may be the result of analytical error in the chemical analysis, or in the gathering of the representative sample of herbage. In either case, error in this estimate may be particularly important, since this estimate is not independently repeated for each animal in the study, but is conducted once and used throughout the study. Error may also be introduced in the estimates of digestibility of the n-alkanes themselves. The n-alkane method might be ideal if in fact the n-alkanes were completely indigestible – they are not and, furthermore, they are differentially digestible. Lastly, there may be measurement error in the estimate of the n-alkane concentrations in the faeces, which utilize the same analytical procedures that are used on the herbage. That is, if measurement error exists in the herbage estimates, it is quite possible that it also exists in the faeces estimates. We address these issues through the use of Monte Carlo simulation to investigate the likely effects of measurement error on diet composition and digestibility estimates obtained using the n-alkane method. Our results suggest the following conclusions: (1) in the face of any sort of measurement error, estimates of digestibility are likely to be unreliable; (2) when measurement error exists, one of the diet components will usually be under-estimated and the other will usually be over-estimated; (3) any sort of progressive bias in the n-alkane recovery estimates will probably have large and very significant effects on the results; and (4) if measurement error in the estimates of the n-alkane concentrations in the herbage and in the faeces are similar in expectation, then their effects tend to cancel each other out.

Growth, body composition and distribution of carcass tissues were compared in Omani sheep and goats. Animals had ad libitum access to Rhodes-grass hay (8 % CP) and a concentrate diet (16% CP) from weaning until slaughter. The two species had similar birth weights but sheep had higher preweaning (181 g/day), postweaning (175 g/day) and overall (179 g/day) growth rates than goats (120, 102 and 111 g/day, respectively) and thus they reached slaughter weights earlier. Sheep had higher slaughter weight (22·26 kg), empty body weight (20·39 kg), hot carcass weight (12·48 kg) and dressing out percentage (55·94%) than goats (21·17, 18·82, 11·48 kg and 53·97%, respectively). Sheep also had higher proportions of skin, liver and lungs and trachea (P<0·01) than goats, which had higher proportions of head, feet and gut contents. As proportions of carcass weight, sheep had higher fat (25·08%) but lower muscle content (57·24%) than goats (15·72 and 65·88%, respectively). There were no significant differences between the two species in proportion of carcass bone (13·76 and 14·17%). These effects resulted in sheep having a lower muscle: bone ratio (4·19 and 4·68) and higher fat: muscle ratio (0·44 and 0·24). Sheep had higher proportions of non-carcass, carcass and total body fat in the empty body weight (EBW) than goats. However, sheep had less non-carcass but more carcass fat than goats when fats were expressed as proportions of total body fat. Sheep had higher proportions of muscles in the proximal hind limb, distal hind limb (P<0·01), around the spinal column, connecting forelimb to thorax and high-priced muscle group (P<0·05), but lower proportions of muscles in the abdominal wall, proximal forelimb (P<0·05), distal forelimb (P<0·01), connecting neck to forelimb, intrinsic muscles of neck and thorax (P<0·05) and total forequarter muscles (P<0·01) than goats. As proportions in carcass bone, sheep had higher axial skeleton (P<0·05) but lower forelimb than goats. Among species/sex/slaughter weight groups, castrated male and female goats had the lowest growth rates. Castrates and female sheep, particularly at heavier liveweights, had higher carcass and non-carcass fat contents than intact males and goats of all sexes. Although Omani goats produced leaner carcasses and had higher proportions of some non-carcass offals than Omani sheep, they had slower growth rates and a less attractive muscle distribution. This may negatively affect their potential for large scale meat production under Omani conditions.