Pieces of proximal colon taken from lambs during the first 2 weeks of postnatal life were incubated in vitro for measurement of short-circuit current and unidirectional glucose fluxes.

The short-circuit current of colons taken from newborn and 1-day-old lambs was increased significantly in the presence of 5 mM D-glucose. This is taken as evidence for the presence of an active transport system for monosaccharides in this tissue. No such effect was seen using colons taken from 2-week-old lambs.

Direct measurement of glucose transport showed a net absorption to take place across the proximal colon of newborn and 1-day-old lambs. There was no net movement across colons taken from lambs aged 1 week and over. Essentially similar results were obtained when measuring the amount of glucose influx inhibited by 10−5 M phloridzin.

Colonic decline of glucose transport follows a time course different from that reported previously for the small intestine. It probably arises from rapid maturation of the colonic mucosa postnatally rather than from any gradual absence of substrate occurring during rumen development.

The effect of drought on the growth and subsequent recovery of container-grown perennial, Italian and hybrid ryegrass plants was assessed in a glasshouse. Dry-matter production and percentage of water-soluble carbohydrates were measured, and nondestructive measurements of growth components (leaf extension, leaf appearance and tillering) were made.

Drought had an effect upon all the variables recorded. Italian ryegrass was most severely affected by drought in terms of tillering, leaf extension and subsequent recovery. Selecting for improved recovery growth was considered to be of more economic importance than selecting for improved growth during drought.

It was concluded that subjecting pot-grown plants to drought, although in many ways unrealistic, was a very useful technique when screening a large number of different genotypes for drought tolerance and recovery.

The effects of a range of environmental factors on the performance of six varieties of sugar beet at 62 trial sites are considered with special reference to the identification of those environmental factors important in explaining observed variety × environment interactions.

Soya bean, mung bean, Bengal gram and lentil grown in nitrogenless sand culture and sprayed with suspensions of different strains of Rhizobium showed increases in dry weight, chlorophyll and N-content. In a few cases the performance of Rhizobium applied to the phyllosphere was almost as good as a seed inoculation treatment. The beneficial effect of spraying Rhizobiumstrains was independent of the specificity of cross-inoculation groups. Nitrogenase activity as indicated by acetylene reduction by the Rhizooium-leaf association varied between 460 and 723 nmol/g leaf/h.

Hindlimbs of pigs were dissected at 4-week intervals from 9 to 29 weeks after birth. Allometric growth ratios of the gluteal muscles, biceps femoris and semitendinosus were calculated relative to gastrocnemius. Relative growth in weight of the proximal limb muscles was greater than that of the distal muscle, gastrocnemius. The greater relative growth of proximal muscles was not due to greater relative growth of muscle fibre diameters, nor to greater relative growth of muscle cross-sectional areas. In biceps femoris and gluteal muscles, growth in the area of musole cross sections did not keep pace with the radial growth of muscle fibres. The relative longitudinal growth of proximal limb bones exceeded that of distal bones, and the relative longitudinal growth of biceps femoris and semitendinosus exceeded that of any of the limb bones. New sarcomeres were added to muscle length at a faster rate in biceps femoris and semitendinosus than in the peroneus longus located distally in the limb.

Soil-water profiles are often calculated using models based on the application to successive soil layers of an approximate formulation of Darcy's Law. An arbitrary decision is usually made concerning the magnitude of the layer thickness, Δz, and time increment Δt, a decision often based on the intuitive criterion that both should be as small as possible. An unsuitable choice can either give rise to oscillations in the solutions that can be eliminated only by recalculation using different increments, or can culminate in an accuracy unjustified by the precision of the data, both cases resulting in unnecessarily lengthy and wasteful computing. However, mathematicians have shown, for problems which are analogous to particular soil-water models, that oscillations will not occur if τ = D(Δt)/(Δz)2 ≥ 0·50 (where D is the soil-water diffusion coefficient, assumed constant).

This paper considers the development of moisture profiles in soils with a constant rate of loss (e.g. evaporation) or entry (e.g. irrigation) of water imposed at the surface, and demonstrates that the criterion τ ≥ 0·50 can be extended to apply to waterdependent diffusion coefficients by re-interpreting D as the maximum value occurring in the profile. Examples for 10-layer models suggest that it is sufficient for practical purposes to start with Δt values that give τ-values close to 0·50, and to proceed to smaller Δt-values only when necessary. The total gain or loss of water given by integrating the calculated profiles is compared with the known amount entering or leaving at the surface.

The profiles for both evaporation and irrigation are found to advance too rapidly.

The potential yield of the best varieties of winter wheat currently grown in eastern England is estimated to be in the range 12–14 t/ha (15% moisture, 10% protein, freshweight basis).

Increases in the leaf area index at anthesis, in the duration of the grain-filling period and in the light-saturated rate of photosynthesis of the leaves, slower decline in their photosynthetic capacity, and decreases in the respiratory losses of assimilated carbon would increase this potential yield. Such changes might be brought about by breeding or by improved agronomic practices.

The grain growth rates predicted by several published simulation models are shown to be in reasonable agreement with each other.

Soya bean, Bengal gram and lentil plants were grown under field conditions and sprayed with suspensions of different strains of Rhizobium. Irrespective of crossinoculation groups beneficial effects were similar to those observed in nitrogen-free sand culture with respect to dry weight, chlorophyll and N contents. The beneficial effects of spraying Rhizobiumstrains compared favourably with seed treatment by appropriate Rhizobium strains and application of urea. Both an ineffective strain and a mutant strain of R. japonicum showed similar beneficial effects. Acetylene reduction by the Rhizobium-leaf association ranged from 497 to 890 nmol/g leaf/h. The ectosymbiotic association of Rhizobium with foliage of legumes, thus, may meet to a large extent the nitrogen requirement of such plants.

Four sheep were maintained on a pelleted diet based on barley straw, sunflower-seed meal and barley which was offered at 2 h intervals by mechanical feeders. In each of two periods approximately 3 weeks apart, methane production was measured continuously for 6 h in each animal. Despite the frequent feeding regime, methane output varied markedly with time increasing after feeding and then declining. Serial correlation analysis indicated a rhythmical variation of period 2 h which was confirmed by Fourier series analysis for all but one data set. The observations suggest that even with frequent feeding, there is considerable deviation from steady state in the rate of carbohydrate fermentation in the rumen.

Protein synthesis was measured in wether sheep by constant intravenous infusion of [3H]tyrosine. The specific radioactivity of plasma tyrosine at plateau was used to calculate tyrosine flux and the rate of protein synthesis in the whole body was estimated. For wethers fed hay and concentrates tyrosine flux was 2·46 mmol/h and protein synthesized was 5·29 g/kg body weight per day. Corresponding values for wethers fed barley straw were 30–35% lower.

Fractional rates of protein synthesis in individual muscles were between 2 and 3% per day for diaphragm, longissimus dorsi, gastrocnemius, semitendinosus and vastus lateralis muscles from wethers fed hay and concentrates, but the value for vastus intermedius was higher. Corresponding rates for wethers fed barley straw were 18–36% lower.

The effects of white clover mosaic virus infection on the yield of two red clover varieties grown alone and in mixtures with either perennial or hybrid ryegrasses were examined. The spread of this virus within the pure clover plots was rapid. Clover drymatter yields were reduced and these losses were greater in the grass–clover mixtures than in the pure clover plots. Reductions in yield of about 70% were recorded at the first cut in mixtures of Sabtoron and Sabrina. The response of the clover to different levels of virus infection was best described by a negative linear relationship.

Yields of Sabrina hybrid ryegrass increased as the levels of virus infection in the clover increased. This compensated for the losses in yield of the legume, leaving total sward yields unaffected by the virus.

The nature of the ectosymbiotic association between Rhizobium and such legume leaves as Bengal gram and mung bean was investigated using radioactively labelled compounds. About 8% of the 14CO2 fixed photosynthetically in the 70% ethanol soluble fraction was leached out within 1 h of contact with water. The 14C-compounds leached out include sucrose, serine glycine, glutamic acid, malate, alanine and succinate. A part of the 14C-activity was incorporated by Rhizobium cells sprayed on leaves. Association with rhizobia increased the rate of photosynthesis and leaching by 129–240% and 134–281%, respectively. Bacterial metabolites are translocated along the midribs and veins to different plant parts. The beneficial effects are not restricted to members of the same cross-inoculation group.

This study was carried out at Elminia University farm in two years (1978 and 1980) to evaluate the effect of some growth regulators on the production of sweetmelon and muskmelon. It was found that plants treated with some growth regulators were earlier and yielded better than untreated ones, except that in the first trial (1978), the total yield of plants treated with indole acetic acid (IAA) was less than that of the control. The highest early and total yields of both sweetmelon and muskmelon resulted from spraying ethrel on the foliage. Fruit weight and length and flesh thickness were increased by some growth substances compared with the control for both crops. Also, percentage of total soluble solids and ascorbic acid concentration increased markedly as a result of growth-regulator treatments for sweetmelon and muskmelon. Generally, two sprays of ethrel solution produced the most consistent effects on yield and yield quality in the two trials with both sweetmelon and muskmelon.

Two trials investigating compensatory growth are reported in which lambs and young cattle were placed on either a continuous (C) or a discontinuous (RR) growth path. RR animals were subjected to a phase of restricted feeding and then realimented at an equivalent level of feeding to C animals over the same live-weight range. Eight 4-month-old lambs and 30 9-month-old Swiss Brown steers were used. The restriction (I) and realimentation (II) phase covered the live-weight ranges 23–32 kg and 32–44 kg respectively in tho lamb trial and 236–310 kg and 310–460 kg respectively in the steer trial.

Fifty-six total energy balances were made with lambs using open-circuit respiration calorimetry. Fifty determinations of diet digestibility and N balance were made with steers. Lambs received a pelleted concentrate diet and, except for restrictively fed steers which received hay alone, steers were offered a diet based on maize silage.

The restriction phase of RR lambs and RR steers was longer, and the daily ME intake and daily live-weight gains were significantly lower than those of the C animals.

Compared with C lambs a marked reduction in methane production of RR lambs occurred during feed restriction which persisted throughout realimentation.

During recovery realimented lambs gained non-significantly, but realimented steers significantly, more than C animals from a similar ME intake and required less ME/kg daily live-weight gain. Realimented lambs retained more protein at the start of recovery compared with C lambs but both C and realimented steeis retained similar amounts of nitrogen. Indirect evidence is presented that suggests improved utilization of ME for protein deposition, at least at the start of realimentation.

Although the animals on the discontinuous growth path (RR) took longer to reach slaughter weight, their total intake of gross energy and overall energy conversion ratio (MJ ME/kg live-weight gain) was similar to those of animals on the continuous growth path (C).

The genetic parameters of lifetime production traits and their relationship with milk yield in first, second and third lactations were estimated from information on 753 Tharparkar cows. The heritability estimates for milk yield in first, second and third lactations were 0·22 ± 0·10, 0·33 ± 0·14 and 0·49 ± 0·17 and for number of lactations completed, lifetime milk production, number of days in milk and herd life 0·58 ± 0·23, 0·51 ± 0·22, 0·54 ± 0·22 and 0·34 ± 0·20 respectively. The genetic and phenotypic correlations among the four lifetime production traits were in the range of 0·83–1·0 and 0·84–0·85 respectively. The phenotypic correlations of milk yield in first, second and third lactations with lifetime production traits were significant and ranged between 0·15 and 0·56. The corresponding genetic correlations ranged between 0·26 and 0·83. For the first three lactations, the genetic correlations of lifetime traits with the third lactation were high and that between lifetime milk yield and yield in third lactation the highest (0·83 ± 0·17). The direct and correlated responses from single trait selection were also estimated.

The effects of light illuminance and wavelength on the growth of male and female broiler chickens from day-old to 8 weeks of age were studied.

Different coloured lights, at equal illuminance and peak wavelengths of 425, 525 and 610 nm and a broad-spectrum white light of median wavelength 560 nm had no significant effect on the growth rate or cumulative food intake of birds of either sex.

The performance of male broilers was unaffected by light of different illuminances, equal to 0·7, 3·0, 15·0 and 46·5 lux. The weight gain of female broilers, adjusted for food intake, was progressively depressed at illuminances above 3 lux.

There is probably no commercial advantage in using broad-spectrum white light at intensities above 3 lux.

A new and detailed model, involving meteorological, crop and soil variables, is proposed to provide daily estimates of moisture deficits in soils under cereal cropping in Britain. The model incorporates developments in the calculation of potential evapotranspiration specifically for cereal crops. Four processes of loss of water are considered, namely drainage, evaporation of free water from the crop canopy, evaporation from the soil surface and transpiration by the crop. Thus the model is applicable at all stages of the cropping cycle. Above-ground and root system development of the crop are modelled and available and extractable water capacities of a wide range of soils are estimated. Thus the demand for water and its availability are varied with crop species, stage of development and soil type as well as with meteorological variables.

The calculation of water losses is not dependent on arbitrary assumptions about the division of losses between the four processes considered or between different horizons of the soil.

Extreme simplicity of input data requirement has been maintained. The model has been programmed in FORTRAN, and is compatible with Meteorological Office data archives.

Wheat production in Australia relies heavily on superphosphate to maintain maximum grain yields. The current rock-phosphate supplies for superphosphate manufacture are derived from Nauru and Christmas Island in the Pacific Ocean; these supplies are anticipated to last only for the next 10–20 years. The supplies of ‘A’ grade ore (apatite) which can be used directly for superphosphate production are greatly overshadowed by large amounts of lower grade rock phosphate which is high in total phosphate but low in apatite. This material is termed ‘C’ grade rock and, to date, it has found little use in Australian agriculture.

One of the major limitations of white clover in Britain is the delay in commencement of spring growth compared with companion grasses (Williams, 1970) and the delay is further increased. by the resulting competitive disadvantage (Davies & Young, 1967; Spedding & Diekmahns, 1972). Thus there is a need to increase growth of white clover at low temperatures particularly in the uplands where the season is short (Ollerenshaw & Baker, 1981). However, the work of Cooper (1964) suggests that increased spring growth rate will be detrimental to survival. Small-leaved cultivars, e.g. S.184, have been favoured for upland use because they are well able to survive. This paper presents a study of the survival and early spring growth of 13 commercial varieties of white clover. Early spring growth was described by the increase in numbers of leaves per growing point and lamina length. The density of growing points was not recorded as previous field studies (Haycock, 1980, 1981; Davies & Evans, 1982) showed this variable to be of minor importance in spring yield increase.

The new model, described in a previous paper (Francis & Pidgeon, 1982), for estimating soil moisture deficits under cereal crops in Britain, was evaluated against experimental neutron probe data for eight test crops. The test crops covered a wide range within Britain of growing-season weather and soil types for both winter and spring cereals. Comparisons were also made with estimates of three other models, those of Ritchie, Rhoades & Richardson (1976), Jensen, Wright & Pratt (1971) and Smith & Douglas (1975).

The new model gives the best fit for six of the eight test crops, with root-mean-square errors (RMSE), taken over the whole season, of less than 10 mm of deficit and having small random bias. RMSE seldom exceeds 10 mm for any section of any season. By contrast, the other three models have whole season RMSE values in the range 10–40 mm. The model of Ritchie et al. (1976) generally overpredicted deficits early in the season and thereafter performed erratically; those of Jensen et al. (1971) and Smith & Douglas (1975) generally underestimated deficits. For two test crops where the new model performed poorly, serious inadequacies in crop growth and/or meteorological input data were identified as the reasons.

A sensitivity analysis for the new model emphasized the importance of the soil variables that were incorporated and the need for rudimentary crop growth information to supplement default assumptions.

It is concluded that the new model, having average RMSE values similar to expected neutron probe measurement errors, offers significant advantages over other models in estimation of soil moisture deficits. The new model could further provide a basis for extension to other crops or to description of the distribution with depth of soil moisture deficit.