This study was initiated to evaluate the short-term (< 3 years) ability of some selected acid-soil adapted hedgerow species when planted in alley cropping systems to improve soil properties in a newly-cleared Ultisol (Typic Kandiudult) of southern Cameroon, 1990–92. The hedgerow species selected were Senna (Senna spectabilis), Flemingia (Flemingia congesta)and Acioa (Acioa barterii). A non-alley-cropped control was also included in the trial. The greatest quantities of prunings, and hence, mulch were produced by Senna and Flemingia. Exchangeable Ca, effective CEC and water infiltration were greatly increased in the alleys of plots where either Flemingia or Senna had been planted within 2·5 years of hedgerow establishment. The large amounts of mulch produced by Senna and Flemingia did, however, result in soil temperatures greater than those of the control or Acioa plots c. 1 year after application of the prunings as mulch. Root growth of Senna in the subsoil was significantly greater than that of either Acioa of Flemingia, but that of cassava was reduced by alley cropping with all three hedgerow species. Compared to the control or alley cropping with Acioa, maize and cassava yields were greater when alley cropped with either Flemingia or Senna hedgerows.

The effects of green manuring with Sesbania aculeata, or with Leucaena leucocephala leaves and of weed incorporation on the physical properties of a clay loam soil under a rice–wheat rotation were compared at New Delhi, India, in 1986–87. Under puddled conditions, the volumetric moisture content of the saturated topsoils varied from 0·400 cm3/cm3 in the Sesbania-treated plots to 0·425 cm3/cm3 in plots receiving no green manure, but in the unsaturated soils at rice harvest the corresponding values were 0·317 and 0·271 cm3/cm3. The effects of the green manures on the water content of the soils were still evident after a subsequent wheat crop. Other soil physical properties affected by the treatments were the following (data refer to topsoils measured after the rice harvest): settling index (cm/cm), an estimate of structural instability, which ranged from 25·5% (Sesbania-treated plots), to 28·6% (weed incorporation), 29·7% (Leucaena-treated plots) and to 33·5% (NPK-fertilizer only). Soil dispersion increased from 6·0 to 10·0 g/100g through the same treatment sequence. Hydraulic conductivity in the NPK-fertilizer only plots was 31 cm/day, but increased to 4·8 cm/day in the Sesbania-trealed plots. Sesbania was superior to the other green manures for improving soil physical properties after its incorporation.

Nitrogen nutrition of two succeeding wheat crops was studied after ploughing of grassland in July 1987 on a clay soil at ADAS Drayton. The four plots of grassland had received 100, 250, 450 and 750 kg N/ha per year for 4 years from 1984 and were grazed by beef cattle at stocking densities which varied according to grass growth.

Determinations of soil mineral N taken to 60 cm every 3 weeks from July to the following May were particularly variable. However, in the first 2 years after ploughing the means of the series of mineral N measurements were directly proportional to the amounts of fertilizer N applied to the grass.

N offtake in winter wheat grain without fertilizer N was directly proportional to fertilizer N applied to grass but this had little effect on maximum grain yields. Large soil N supplies did not necessarily predispose the wheat crops to large grain N concentrations because fertilizer N caused grain N offtake to reach a similar maximum, irrespective of previous grass N.

Optimum amounts of fertilizer N for the wheat were 188, 147, 87 and nil kg/ha in 1988 and 152,130, 89 and 25 kg/ha in 1989 after 100, 250, 450 and 750 kg N/ha per year applied to the grass. Soil N supply as indicated by both the amount of fertilizer applied to grass and means of mineral N measurements accounted for almost all of this variation. Mean soil mineral N over winter was no better as an indicator of soil N supply than the amount of N applied to the grass. However, before adopting N applied to grass as a more general index of N supply, it would need to be adjusted for variation in N removed and lost during grass growth; these were controlled in this experiment.

Red clover (RC) and perennial ryegrass (PRG)-based forages were cut fresh during late spring/early summer and fed at similar levels of dry matter (DM) intake to rumen fistulated castrated red deer kept indoors in metabolism pens. RC contained higher concentrations of total N and non-protein cell contents than PRG and lower concentrations of fibre. Rumen pool size and fractional outflow rates of liquid (13·3 ν. 15·1%/h) and of paniculate matter (2·5 ν. 3·9%/h) were lower for deer fed RC than PRG. Apparent digestibility of energy and fibre, rumen fibre fractional degradation rate and rumen fractional disappearance rate of non-protein cell contents were all higher for RC than for PRG deer. Nitrogen retention was similar for deer fed both forages. However, the concentration, pool size and outflow of ammonia from the rumen, together with urinary N excretion, were all much greater for deer fed RC than those fed PRG. The acetate: propionate ratio in rumen volatile fatty acids (VFA) was lower for the RC than the PRG group. It was concluded that the greater fibre digestion in deer fed RC was due to a faster rumen fractional degradation rate and a longer particulate mean retention time in the rumen, and that the very rapid outflow of water from the rumen relative to particulate matter in deer fed RC (5·5:1 ν. 3·8:1) may explain why deer are not susceptible to rumen frothy bloat when grazing RC. One reason for the greater voluntary feed intake (VFI) of deer grazing RC than those grazing PRG may be due to its greater concentration of protein and non-protein cell contents and their more rapid degradation and removal from the rumen.

Extensive grazing experiments were conducted over four summer breeding seasons in north-west Queensland between 1984 and 1989. Ewes in the last third of pregnancy were grazed on Mitchell grass (Astrebla spp.) pastures of varying forb (herbaceous plant other than a grass) content. Pastures of low forb content (F-) were attained by stocking paddocks heavily with wethers prior to the experiment, or by selecting paddocks which already contained pastures of low forb content. Pastures of high forb content (F+) were kept without animals prior to the experimental period. Pastures comprised a range of forb biomass (29–828 kg DM/ha) and percentage forbs in total biomass (3–49%). Lamb marking percentage was found to be dependent on the biomass of forbs and proportion of forbs in the pasture, in two experiments. Ewes which grazed F+ pastures had lower lamb marking percentages than those grazing F- pastures.

Twenty pasture species collected during the experiments were analysed for the ratio of 13C: 12C and photosynthetic pathway was determined. Five forb and all three grass species had C4-dicarboxylic acid pathways, ten forbs had Calvin-C3 pathways and two forbs had crassulacean acid metabolism pathways.

Estimates of the proportion of C3 and C4 species in the diet were determined by analysing the ratio of 13C:12C in faeces. The apparent high proportion of Calvin-C3 pathway forbs in the diet of ewes compared to the proportion in the total pasture biomass indicated that ewes preferentially select C3 forbs in the diet, although there was no dependence of lambing percentage on the estimated proportion of C3 forbs in the diet. Management strategies that may improve lambing percentage in the Mitchell grass areas of north-west Queensland are discussed.

This paper reports genetic differences between 20 Mashona bulls from smallholder farms, 14 from Makoholi Research Station, three from commercial farms and two reference sires, in Zimbabwe. An animal model, fitted through the derivative free Restricted Maximum Likelihood program (DFREML), was used to analyse 707 birth weight and 623 weaning weight records. Both the mean breeding values of the reference sires and the ranch bulls were significantly (P < 0·05) higher than the mean breeding values of smallholder bulls for birth weight (by 1·6 and 1·7 kg, respectively) and weaning weight (by 10·4 and 11·0 kg, respectively). However, seven of the 20 bulls from smallholder farms were among the top 45% of bulls with high breeding values for both birth and weaning weight. The mean breeding value of bulls from Makoholi was not different from any of the other groups, for all traits studied. It was proposed that future efforts to form nucleus herds to improve the weaning weights of indigenous cattle should include the genetic pool in smallholder farms.

Hereford (H × H), Brahman × Hereford (B × H), Simmental × Hereford (S × H) and Friesian × Hereford (F × H) females born over a 5-year period (1973–77) were placed on pastures of high, medium or low nutritive value at Grafton, New South Wales, Australia, at weaning (7–8 months of age). The first mating of heifers on high pasture was at 15 months (1974) while that on medium and low pastures was delayed until 27 months of age (1975). This paper reports the reproductive performance of these cows up to 5 years of age and the preweaning growth of their calves which were sired by Hereford bulls at Grafton, Australia. In total, 1222 calving records were analysed.

Most traits were subject to interaction between genotype and other main effects (pasture, year of birth of cow, cow age and sex of calf). Eyelid pigmentation was an exception, with calves from B × H cows having more than calves of other genotypes (73 v. 43%). There were significant genotype differences in calving difficulty among 2-year-old heifers only, with H × H (33%) requiring more assistance than F × H (15%) and SxH (10%) heifers, while B × H heifers did not require any assistance. Genotype differences in percentage of calves born and weaned were observed on low pastures only, where B × H (66% born, 65% weaned) exceeded H × H (48%, 39%) and S × H (39%, 38%) cows, with F × H (58%, 50%) cows being intermediate. Calves by H × H cows were the slowest-growing and were the lightest at weaning on all pastures, with mean gains of 759, 604 and 340 g/day, and mean weaning weights of 212, 188 and 110 kg, on high, medium and low quality pastures, respectively. F × H and S × H cows produced the fastest-growing calves on high quality pasture (966 and 936 g/day, respectively) while B × H cows produced the fastest-growing calves on medium (823 g/day) and low (679 g/day) quality pastures. F × H cows weaned the heaviest calves on high quality pasture (274 kg) while F × H and B × H weaned the heaviest calves on medium (230 and 229 kg, respectively) and low (162 and 169 kg, respectively) quality pastures. Differences in body measurements followed a pattern similar to weaning weight.

The objectives of this study were (i) to evaluate a new surgical procedure to catheterize hepatic vessels as well as the posterior aorta and vena cava, (ii) to test a modification of a downstream dilution technique in order to measure blood flows through splanchnic tissues and hindquarters in rapid succession, and (iii) to improve the reliability of splanchnic blood flow measurements using paraamino hippuric acid (PAH). Ten adult ewes were used. The transhepatic surgical approach used proved successful; it was relatively easy to set up and a good recovery of hepatic functions was obtained. The attempt to measure splanchnic and hindquarters blood flow in rapid succession by alternating the sites of PAH infusion was unsuccessful, probably because of transient modifications in infusion rates due to different blood pressures in veins and arteries. Indeed, arterial PAH concentrations changed with infusion site. Finally, a better reproducibility of splanchnic blood flow measurements was obtained in sheep, fed every 3 h, by infusing the required amount of PAH partly via the mesenteric vein and partly via a ruminal vein.

A surgical preparation was developed to measure uptake of amino acids from the small intestine into the cranial mesenteric vein (CMV) of lambs. Results from this preparation were compared with those from the traditional hepatic portal vein (PV) preparation in the same lambs. Necropsy revealed that, in contrast to the PV preparation which included all portal-drained viscera, the CMV preparation drained primarily small intestine (0·84–0·92 small intestinal mass). The CMV preparation contributed 0·238 of blood flow from and 0·307 of oxygen consumption by the PV preparation. Venous-arterial differences for alpha-amino nitrogen (AAN), phenylalanine (Phe) and tyrosine (Tyr) were three- to fourfold greater in the CMV than in the PV preparation, indicating that the CMV preparation is more sensitive for measuring amino acid uptake. The ratio CMV/PV for uptake of AAN was 0·61 (P< 0·001), but this ratio was much closer to unity (mean 0·84) for Phe and Tyr. Since the CMV preparation drains primarily the small intestine, through which all amino acid absorption occurs, it should prove to be extremely valuable for studying absorption from and metabolism within this organ using a combination of arteriovenous and isotopic tracer techniques.

Two experiments of randomized block design were carried out at the Agricultural Research Institute of Northern Ireland in 1991/92 involving groups of 20 pigs fed ad libitum from single-space feeders with built-in water supply from 37 kg to slaughter at 91 kg liveweight.Treatments were replicated 16 and 6 times respectively in Experiments 1 and 2. In the first experiment, one feeder perpen was compared with two feeders per pen positioned side by side. Two feeders increased feed intake (P < 0·05) but had no significant effects on growth rate or feed conversion. With two feeders, the total time that feeders were occupied and the number of visits to feeders were both increased, while the number of enforced withdrawals from feeders and the amount of queuing were both decreased compared with the single feeder. In the second experiment, placing two feeders 2 m or more apart instead of side by side had no significant effects on feed intake or growth rate but improved feed conversion efficiency by 4%. This improvement was associated with fewer and longer visits to feeders but no difference in enforced withdrawals or queuing. In both experiments all treatments showed broadly similar patterns of diurnal feeding behaviour with two peaks of activity daily, a smaller peak pre-midday and a larger one in the afternoon. This pattern was influenced more by number of visits to feeders than by the mean duration of each visit. It is recommended that two single-space feeders are used in pens of 20 finishing pigs when non-pelleted diets are offered ad libitum and that feeders are sited some distance apart, not side by side.

The preweaning growth of the progeny of mature cows grazing high, medium or low quality pasture was evaluated. The cows were 5–9 years of age at the beginning of the study and were either purebred Hereford (H x H), first-cross Brahman x Hereford (B x H), Simmental x Hereford (S x H) or Friesian x Hereford (F x H). Hereford and Brahman bulls were mated to these cows for three mating seasons commencing in 1982, at Grafton, New South Wales, Australia. Records on 634 calves born over three consecutive years were used.

Most traits were subject to significant sire breed or dam breed effects or their interactions with one or more of the other main effects (pasture, year of birth of calf, cow age and sex of calf). The incidences of calving difficulty and stillbirths were exceptions. Stillbirths (mean of 3·8%) were not affected by any of the effects studied, while calving difficulty was affected only by sex of calf effect (males, 3·9%; females, 0·8%). The mean calving date of Brahman-sired calves was 11·4 days later (P < 0·05) than that of Hereford-sired calves. Differences between Brahman-sired and Hereford-sired calves for weaning weight were not significant for S x H (Brahman, 237 kg; Hereford, 232 kg) and FxH (Brahman, 238kg; Hereford, 238kg) dams. For HxH dams however, calves sired by Brahman were heavier at weaning (205 kg) than those sired by Hereford (193 kg) bulls, while for B x H dams the reverse was true (Brahman, 222 kg; Hereford, 231 kg). For calves with B x H dams average daily gain (ADG) was the same (957 g/day) for each sire breed, while for the other dam breeds, Brahman-sired calves had a higher ADG than Hereford-sired calves (862 v. 779, 1014 v. 946 and 1022 v. 950 g/day for H x H, S x H and FxH, respectively). Calves sired by Brahman bulls had > 90% eyelid pigmentation while Hereford-sired calves had 44–74%. On high quality pasture, the weaning weights and ADG of calves of F x H and S x H dams were higher than those of B x H and HxH dams. On medium quality pasture, weaning weight of calves of crossbred dams (B x H, S x H and FxH) were similar but higher than those of H x H dams. On low quality pasture, mean weaning weight of calves of B x H was higher than those of S x H and F x H dams, which in turn, were higher than that of H x H dams.

A study was conducted on eight preparturient camels which were kept in individual stalls adjacent to the Cairo abattoir during 1989. Four novel phenomena are described in this paper: (i) a significant (P < O·05) prepartum decrease in plasma concentrations of progesterone evident over the 48 h preceding parturition; (ii) a remarkably consistent increase in total plasma unconjugated oestrogens, commencing 2–4 days prior to parturition and peaking in excess of 200 pg/ml for c. 2 h before delivery; (iii) a tenfold increase to 5·4±0·19 ng/ml (mean±S.E.) in plasma concentrations of 13, 14-dihydro-15-keto-prostaglandin F2α (PGFM) between days –10 and – 1, showing a sudden and large increase during the 5 h prior to delivery; and (iv) three peaks of total plasma corticosteroids during the 4 h preceding delivery, with the third peak showing the greatest magnitude (24·0±3·11 ng/ml). These results suggest that the dromedary camel is an example of a species in which luteal secretion of progesterone, especially 3α-dihydroprogesterone, is required throughout pregnancy and in which cessation of luteal function, associated with a rapid increase in the oestrogen: progesterone ratio and the secretion of prostaglandin F2α (PGF2α), is a requirement for parturition.

The quantity of imbibed water that bypassed the rumen directly or rapidly effluxed from the rumen was investigated in four steers offered water marked with CrEDTA. Water was offered for short periods designed to simulate the drinking patterns that occur under extensive grazing conditions. Animals were fed either low quality pangola hay in the long form or a concentrate diet. Bypass of imbibed water was calculated by difference from marker imbibed and that present in the rumen on emptying after water had been imbibed. It thus represents the passage of marked water directly to the omasum/abomasum and that which rapidly effluxed from the rumen before emptying. Bypass of imbibed marked water was 19·0 and 25·3% for animals consuming pangola and concentrate respectively (significantly different from zero but no significant diet effect). Imbibed water entering the rumen mixed rapidly so that liquid from a posterior site in the rumen had a similar concentration of Cr to that from an anterior site in the proximity of the reticulum and cranial sac by about 1 h after drinking. There was no effect of rumen sampling site on the fractional outflow rate of CrEDTA (from imbibed marked water) from the rumen. It was concluded that most water which is drunk after a period of water deprivation will enter the rumen, mix rapidly and have a fractional outflow rate similar to other fluid in the rumen. The values derived may be used to calculate the amounts of supplement needed in drinking water if the target site is the rumen or intestines of cattle with intermittent access to water under extensive grazing conditions.

Thirty-six 4-year-old Border Leicester × Romney (BR), Poll Dorset × BR (PBR) and Suffolk × BR (SBR) ewes balanced for litter size were assigned, 6 days after the mid-point of lambing (29 June 1989), to one of three sward surface height (SSH) treatments replicated twice (six ewes/1 ha paddock). The mean SSH during the 54 days of the trial were 2·6, 4·4 and 7·8 cm. Herbage organic matter intake (OMI) was measured using intraruminal chromium controlled release capsules during weeks 3, 4, 7 and 8 of lactation. Ewe OMI was not influenced by SSH during week 3 of lactation. During weeks 4 and 7 of lactation, ewe OMI increased with SSH up to a SSH of 7·8 cm. In week 8 of lactation there was no significant difference in OMI between ewes grazing the 4·4 or 7·8 cm SSH treatments, suggesting maximum intake at this stage of lactation is reached at 4·4 cm SSH. A maximum OMI of 2·6±0·1 and 3·0±0·1 kg OM/ewe per day (P < 0·05) was reached in week 4 of lactation on the 4·4and 7·8 cm SSH treatments, respectively. Ewes grazing the 2·6 cm swards had a relatively constant OMI throughout the experiment (range 1·8±0·1 to 2·0±0·1 kg OM/ewe per day). However, these ewes lost 10·5 kg of liveweight while those on the 4·4 and 7·8 cm SSH treatments maintained a constant liveweight. Sward surface height had no effect on ewe midside wool growth rate or mean fibre diameter (measured at day 60 of lactation) or on lamb liveweight gain. Ewe breed cross had no effect on ewe OMI or midside wool growth. Lambs reared by SBR ewes were heavier (20·4±0·5 kg) at day 60 of lactation than lambs reared by PBR (18·7±0·6 kg) or BR (18·4±0·6 kg) ewes (P < 0·05). These results suggest that for Winter(June)-lambing ewes in good condition a SSH of 4·0 cm under continuous stocking should ensure near to maximum ewe and lamb performance. However, ewes in good body condition at lambing stocked on a SSH down to 3 cm will rear lambs to acceptable weaning weights but at the expense of ewe liveweight loss and possible long-term carry-over effects on future productionif compensatory weight gains are not achieved during the spring pasture growth period.

In each of two experiments, eight silages supplemented with concentrates containing a high proportion of either starch or digestible fibre were given to rumen-cannulated sheep. The silages constituted c. 65% of the total dry matter and differed widely in chemical composition, reflecting differences in the extent of fermentation in the silo.

Rumen pH was lower (P < 0·01 and P < 0·001 for Expts 1 and 2 respectively) and the concentration of total volatile fatty acids (VFA) in the rumen was higher (P < 0·001 for Expt 2) for the starchy concentrate. Silages differed in their effects on ruminal proportions of acetate (P < 0·001 and P < 0·01 for Expts 1 and 2 respectively) and, inversely, of propionate (P < 0·001 for Expt 1). There was evidence of a strong relationship between the molar proportion of propionate in the rumen and the concentration of lactic acid in the silage. The results indicate that the production of propionate during the metabolism of silage lactic acid by the rumen microbial population was the predominant influence on rumen fermentation pattern.

It is suggested that this relationship is the basis of some of the differences in milk production reported for silages showing restricted as opposed to extensive fermentation.

In the first two of four experiments, sheep were fed, ad libitum, sorghum stover supplemented with graded levels of foliage of the shrub leucaena (Leucaena leucocephald) or mulga (Acacia aneura), which provided between 0 and 0·34 or between 0 and 0·43 of the dietary dry matter (DM) respectively. A second treatment (with or without urea) was superimposed in a factorial design. The effect of treatments on liveweight (LW) was explainable by their effects on voluntary intake of apparently digestible organic matter (DOMI). D0M1 was increased by mulga, largely due to an increase in the total voluntary intake of organic matter (OM). Leucaena increased DOMI by increasing the ration OM digestibility and, at low levels of inclusion, intake of the basal diet. Roughage intake was greatest when leucaena provided 0·15–0·20 of the dietary DM. Leucaena increased rumen ammonia, and whenever roughage intake was increased by urea, leucaena also increased it.

In the third experiment, when diets were made isonitrogenous with urea, roughage intake was slightly greater when leucaena, rather than its ash or a mineral mixture, was supplemented. Total OM intake and DOMI were greatest when leucaena was fed.

In the final experiment, sheep were fed one of ten treatments: three basal diets (two of sorghum stover and the third of native pasture hay) each supplemented with legumes (leucaena to the hay and one stover diet and cowpea straw to the second stover diet), ash of the respective legume and formaldehyde-treated casein. The tenth treatment was sorghum stover plus urea. For sorghum stover diets with leucaena-based or cowpea straw-based supplements, DOMI responded linearly to the nonurea nitrogen concentration of the diet. On the other hand, for native hay with leucaena-based supplements, the response of DOMI to non-urea N was negligible. It was noted that the native hay (predominantly Flinders grass, Iseilema vaginiflorum), contained lower concentrations of polyphenols than sorghum stover.

It was concluded that browse foliage can increase the voluntary DOMI of sheep consuming low quality roughages by providing nitrogen and sometimes minerals and OM of greater digestibility. The slowly-degradable proteins in leucaena, cowpea straw or formaldehyde-treated casein are more effective with polyphenol-rich sorghum stover than with native hay of otherwise similar composition.