Calves, fed continuously a P-deficient basal diet, were infused abomasally with a phosphate solution supplying either 0, 3, 6 or 9 g P/day in a 4 × 4 latin-square design experiment. Once steady-state conditions were achieved (after 2 weeks of infusion), 32P kinetic studies were carried out. At the same time, P and Ca balances and rates of flow of P at the reticulum were measured.

The rate of dietary P absorbed increased significantly with increasing P supply as did the serum P concentration. The rate of salivary P secretion was directly related to the serum P concentration and hence to P absorption, but the efficiency of absorption of salivary P remained relatively constant, ranging from 70 to 74% depending on treatment.

Despite the high requirements for P, the rate of endogenous faecal P loss increased directly with increased P supply and absorption, suggesting that some increased loss of P with increased P supply was inevitable. Urinary P secretion was negligible when the P supply was low but increased substantially as the serum P concentration increased from 2 to 4 mmol/1, possibly because the renal threshold was exceeded.

The rates of retention of P and Ca were low on the low-P treatment but increased significantly with increased P supply until this reached about 70 mg/day per kg live weight, beyond which they remained fairly constant, presumably because requirements had been met. Since the growth rate did not reach a maximum until the P supply exceeded 65 mg/day per kg live weight, it is suggested that the Agricultural Research Council (1980) recommendations of P requirements (34 mg/day per kg live weight) for these growing calves must be inadequate.

These results suggest that loss of P in saliva and urine may be determined by the serum P concentration whereas the efficiency of absorption of P from the intestine may be regulated according to P requirements.

Rumen ammonia levels in animals given silage diets are generally high and there appears to be considerable scope for improving the utilization of ammonia for microbial protein synthesis (Thomas & Chamberlain, 1982). Chamberlain et al. (1985) showed that supplements of sucrose were more effective than supplements of starch in reducing the rumen ammonia levels in animals given silage diets. Moreover, the effects of sucrose were increased when it was given together with sodium bicarbonate. The implication was that the sucrose supplements increased the fixation of ammonia in microbial protein through the provision of additional fermentable energy, and that this process was enhanced by the sodium bicarbonate supplements. The experiment reported here was designed to provide quantitative information on these effects and in particular to elucidate more fully the effects of sodium bicarbonate supplements on nitrogen metabolism in the rumen.

Seven plots were laid out for the 1985–6 growing season on the Chalk Downs near Lewes, East Sussex, to study the relationship between cultivation practice, soil conditions and erosion rates. Three plots were sown with cereals in autumn and three in spring. The seventh plot was ploughed and kept bare. In both spring and autumn, one plot was conventionally cultivated by ploughing and harrowing, one was direct drilled through burnt stubble and the third was direct drilled through the debris of the previous year's straw and stubble. Erosion was greatest from the conventionally cultivated plots and least from those direct drilled through unburnt stubble. Monitoring of moisture, infiltration, strength and compaction properties of soils suggests that from late autumn onwards soil conditions on the plots were very similar and the major factor determining the different erosion losses from the plots was the percentage vegetal cover (crop, weeds and residues). The results suggest that direct drilling through unburnt stubble may be a way of obtaining high yields with low erosion risk on the Downs, but the long-term consequences of such a practice remain unknown.

Peking ducklings were classified at 6 weeks of age according to their body weights in two categories: R, below the overall mean of the flock which were considered as retarded growth; and L, those of body weight equal to the overall mean and above which were considered as large. From each group, males and females were chosen to be parents of the next generation in a ratio 1:5 at 6 months of age and four systems of matings were conducted: RR, LL, RL and LR.

At all ages studied the large ducklings were significantly heavier than retarded growth ones and had significantly greater body gain, during the two successive generations.

The RL and LR matings were heavier than the RR and LL groups at the different ages studied, indicating an effect of heterosis and that the retarded growth character is controlled by few pairs of genes. The differences due to mating systems were not significant either in body weight or body gain, except in body weight at 18 and 24 weeks and relative gain at 6 weeks of age in which the differences were significant (P <0·05) in the second generation.

The other environmental factors studied were sex, month of hatch and 6-week body weight.

Heritability estimates were 0·489, 0·509, 0·576, 0·346, 0·713, 0·809, 0·651 and 0·386 for body weight at hatch 4, 6, 8, 12, 16, 18 and 24 weeks of age, respectively, using the data which were adjusted for the effects of sex, month of hatch, 6-week body weight and mating system. The same estimates were 0·482, 0·554, 0·578, 0·352, 0·713, 0·808, 0·650 and 0·386, respectively, using the same data but adjusted for month of hatch and sex only.

Phenotypic and genetic correlations between body weights at different ages for the two sets of data were estimated. The phenotypic correlations were negative between body weight at hatch and each of the body weights at 16 and 18 weeks of age for the two corrected sets of data. The genetic correlations were negative between hatch weight and each of the other body weights for the two adjusted sets of data and between body weight at 4 weeks of age and each of the body weights at 16, 18 and 24 weeks only for the first set of data. Phenotypic and genetic correlations between the body weights in older birds were highly positive.

Calves were fed continuously at 4 h intervals an adequate-P diet and were infused intravenously with a solution of phosphate supplying either 0, 3, 6 or 9 g P/day in a 4 x 4 latin-square design experiment. Once steady-state conditions were achieved, rates of flow of P at the reticulum, serum P and Ca concentrations, and urinary excretion rates of P and Ca were measured.

The concentration of serum P increased significantly with increased intravenous infusion of P as also did the salivary P secretion. Results suggest that it is the serum P concentration that regulates the secretion of P through saliva. Urinary P excretion, which was low in the control group, increased significantly with increased intravenous loading of P. Substantial urinary P excretion occurred, however, only when the serum P concentration exceeded 2·30 mmol/1, which is probably the renal threshold for P. The serum Ca concentration was unaffected by the intravenous infusion of P and urinary Ca excretion remained negligible on all treatments.

Sugar beet has never been grown commercially in Cyprus. Sugarcane was grown in the Middle Ages but its cultivation has since gradually declined, and none has been grown in the last 200 years (Aristidou, 1986). Recently a research programme was undertaken to assess the feasibility of growing sugar beet so that imports of sugar may be reduced. Sugar yields of up to 20 t/ha (165 t fresh roots/ha) were obtained in a coastal area (Akhelia) when the crop was sown in November and harvested in July–September (Hadjichristodoulou, 1984, 1987). Because the period April–October is practically rainless, the crop has to be irrigated, but with November sowing full advantage is also taken of the winter rainfall.

Previous attempts to study the effect of virus infection on nitrogen-fixing ability of some legumes (Tu, Ford & Grau, 1970; Singh & Mall, 1974; Gupta & Joshi, 1976; Tu & Holmes, 1980) concentrated mainly on the effect of virus infection on the extent of nodulation or on the amount of nitrogen fixed by diseased plants or both. The effect of virus infection on the bacterial population and the physiological status of virus-infected nodules has received little attention.

Data on 841 purebred Bauscat, White Flander, Giza White and Baladi Red litters provided estimates of genetic, phenotypic and environmental parameters for gestation length, litter size at birth and at weaning, mortality and sex ratio at weaning. A total of 170 daughters (paternal half-sisters) of 76 sires were available for the analysis. No important differences were detected among breeds for litter traits studied except litter size at weaning (P < 0·001). Year of kindling affected (P < 0·001) gestation length, litter size at birth and mortality percentage. No clear patterns of the effect of parity and month of kindling on litter traits were observed. The sire of the doe and doe within sire affected most of the traits studied. Estimates of heritability indicated that the sire's genetic contribution to litter traits are much higher during the pre-natal period than for the suckling period. Estimates of repeatability for litter traits studied were relatively low. Genetic and phenotypic correlations between gestation length and other litter traits were relatively low. Litter size traits were positively correlated both genetically and phenotypically. Estimates of genetic and phenotypic correlation between litter size traits and preweaning mortality were generally negative. Phenotypic and environmental correlations were generally very similar in size and sign. Predicted direct selection was shown to give greater improvement in litter size at birth than indirect selection through litter size at weaning.

The left half carcasses of 64 female, 64 castrated male and 64 intact male indigenous Nigerian pigs were dissected in order to study the bone growth between birth and 672 days of age. Total bone weight as well as the weights and lengths of femur, tibia–fibula, humerus and radius–ulna were studied at 16 ages. While bone weights increased between 34 and 45 times from birth to the terminal age range, bone lengths on the average only quadrupled within the same period. Maximum growth in bone weight occurred at 112 days of age whereas bone length attained maximum growth rate at 56 days of age when the body weights had averaged 15·8 and 6·2 kg respectively.

Beyond these body weights, the growth rates declined. Although sex differences for total bone weight were not significant, the individual long bones studied exhibited significant sex differences. Highly significant age and sex influences were obtained for the relative bone weights.

The growth coefficients b determined for the individual bones and total bone using the logarithmically transformed allometric equation Y = oXb, ranged from an average of 0·76 for radius–ulna to O·80 for femur. Pooled values for total carcass bone was 0·84. The values agreed with those reported in literature with side weight as independent variable, and confirm bone to be early developing. Bone lengths were related more to body weight than to chronological age as judged by the R2 values. In all the bone traits studied, intact male pigs showed larger values than the castrated male and female pigs.

Incubation of feed samples in nylon bags in the rumen has been used extensively to evaluate the rate and extent of dry matter, protein, starch and cellulose degradation (Mehrez & Ø0rskov, 1977; Mehrez, Ørskov & McDonald, 1977; Ganev, Ørskov & Smart, 1979; Weakley, Stern & Satler, 1983) and to predict the energy values of ruminant feeding-stuffs (Cottyn et al. 1984).

Green manuring in situ with sunnhemp (Crotalaria juncea) and dhaincha (Sesbania aculeata) significantly improved growth and yield of transplanted rice. Giving the green manure crops 15 kg N/ha or 15 kg N and 30 kg P2O5/ha further increased yield. Interaction between green manuring and N fertilizer revealed that a considerable quantity of fertilizer N (45–60 kg N/ha) applied to rice could be replaced by incorporation of green manure crops to which a small amount of fertilizer had been applied. Residual fertility in terms of organic carbon and available N, P and K increased under green manuring, whereas N fertilizer made no impact on fertility build up. Grain yield of wheat and gram increased when grown after rice in plots which had grown green manure.

An experiment was carried out on a site where the copper content of herbage was relatively low (4·7–6·2 mg/kg d.m.) to examine the value of copper contained in soluble glass rumen boluses as a means of providing supplementary copper to calves.

Forty-five spring-born suckled calves (mean live weight 91 kg) were divided into three groups on the basis of body weight. Animals in group GB were given two boluses initially, those in group CI each received copper injections at approximately monthly intervals and those in group C remained as controls throughout. Group C calves became progressively hypocupraemic (minimum mean plasma copper 8·5 μmol/1) compared with those in groups GB and CI which showed an increase in plasma copper concentration. In addition measurements of plasma caeruloplasmin activity, blood haemoglobin concentration and erythrocyte superoxide dismutase activity all showed significant increases due to treatment. No response in live-weight gain was observed but overall live-weight gain was approximately 1·05 kg/day. Although the initial response in plasma copper was quicker with copper injections, measurements of erythrocyte superoxide dismutase activity and haemoglobin showed advantages of glass boluses not shared by copper injections. This possibly resulted from the slow release nature of copper in the glass. Under the conditions of the experiment where herbage molybdenum values were relatively low (1·2–1·9 mg/kg d.m.), copper contained in soluble glass boluses appeared to prevent hypocupraemia in calves as effectively as regular copper injections.

Two ecotypes and three varieties of white clover (Trifolium repens) of contrasting morphology were established in monoculture field plots in Truro, Nova Scotia (45° N) in July 1985. Destructive measurements were taken at monthly intervals from August to November 1985 and April to August 1986. The seasonal distribution of number of active stolons/m2, number of leaves, number of leaves per stolon, and lamina weight together with dry weights of leaves-I-petioles, stolons and flowers + peduncles were recorded. Number of leaves was inversely proportional to leaf weight, smaller-leaved varieties and ecotypes having higher leaf densities than large-leaved white clovers. Leaf and petiole dry-matter yields were related to leaf and number of active stolons in 1985 and to leaf weight increments in 1986. The two naturalized ecotypes exhibited considerably less leaf loss than the three varieties in a winter where mean minimum air temperatures drop to as low as – 13°C. There were considerable differences between ecotypes and between varieties in the seasonal distribution of leaves and petioles, stolon and flower dry weights over the limited time period of this study.

The most harmful of gaseous air pollutants include ozone (03), sulphur dioxide (SO2) and nitrogen dioxide (N02). These three pollutants are responsible for up to 90% of the total crop losses due to air pollution (Heck et al. 1981). Reduction in crop yield is one of the most common consequences of pollutant-crop interaction (Koziol & Whatley, 1984; Treshow, 1984). Mean yields of four soya-bean cultivars, York, Dare, Cutler and Clark, grown in open-top chambers with non-filtered air, were reduced by 20% compared with those grown in carbon-filtered air (Kohut et al. 1982). The major components affected were number of pods, number of seeds per filled pod and weight of seeds; a linear reduction in seed weight per plant was reported with increasing concentration of O3.

Periwinkle (Catharanthus roseus (L.) G. Don) is an important medicinal plant grown in different parts of India. Its leaves contain vincristine and vinblastin, alkaloids which are used in the treatment of various leukaemias and limphomas, and its roots contain ajmalcine, another alkaloid, used in the manufacture of antihypertensive drugs. Cultivation of periwinkle has recently gained importance in India. The yield of periwinkle can be increased with the use of mineral fertilizers (Pareek et al. 1981, 1982; Rajasekharan et al. 1982; Reghunath & Sethumadhavan, 1982a, b; Hegde, 1986). The effect of fertilizer application on the alkaloid concentration is not clearly established though there are a few reports which suggest that application of N increases alkaloid concentration in roots (Rajasekharan et al. 1982; Reghunath & Sethumadhavan, 1982a) and leaves (Pareek et al. 1982). Therefore, the present experiment was designed to study the effect of application of nitrogen and phosphatic fertilizers and farmyard manure on the root and leaf yields, and total alkaloid concentrations in roots and leaves in Catharanthus roseus (L.) G. Don.

Tasmanian Merino sheep show a bimodal distribution in the concentration of reduced glutathione (GSH) in their red cells, 40% of sheep having GSH values of around 27 mg GSH/100 ml red cells and 60% with values of about 92 mg GSH/100 ml red cells (Tucker & Kilgour, 1972). The GSH deficiency was shown to be due to an impaired activity of γ-glutamyl cysteine synthetase (γ-GC-S), the enzyme catalysing the first step of GSH biosynthesis (Tucker, Kilgour & Young, 1976). Family data indicated that the deficiency in this strain of Merinos was under the control of a dominant gene, designated GSHL (Tucker et al. 1976). In contrast, Board, Roberts & Evans (1974) reported that a similar type of GSH deficiency in Australian Merino sheep was under the control of a recessive gene. The reasons for this apparent discrepancy remain unresolved.

Muscle growth was studied for 64 female, 64 castrated male and 64 intact male indigenous Nigerian pigs at 16 ages between birth and 672 days of age. Highly significant (P < 0·001) age differences were obtained for the proportion of total muscle, each muscle group and the 13 individually dissected (seven hind limb, two spinal column and four fore limb) muscles. Sex differences were significant (P < 0·05) for the proportion of total muscle and some of the individually dissected muscles.

A highly significant (P < 0·01) increase in the rate of muscle deposition for each muscle group occurred between 56 and 112 days. Muscle deposition continued at the same rate up till 224 days of age before the peak was attained between 280 and 392 days when the average body weight was between 40·8 and 61·2 kg. A continuously significant (P < 0·05) decline in the rate of muscle deposition was obtained beyond 392 days of age. Growth coefficients b calculated from the linearly transformed allometric equation Y = aXb were generally higher in the early phase of growth (0–168 days) than in later phases considered. However, growth coefficients obtained for the whole period revealed that apart from M. gastrocnemius, the other hind limb and spinal column muscles exhibited either ‘high’ or ‘average’ growth impetus. The fore limb muscles had growth coefficients significantly (P < 0·05) less than 1·00 and were therefore classified as having ‘low’ growth impetus. Generally, the intact male pigs showed superiority to the female and castrated male pigs in muscle growth and development.

A simple and rapid test is described which can be used to determine tolerance to metoxuron and chlortoluron herbicides in winter wheat (Triticum aestivum L.) cultivars. Seedlings 5 days old were treated by root application of herbicide for 24 h and tolerant and susceptible cultivars were identified by comparing the chlorophyll fluorescence induction curves for both herbicide-treated and control plants after 7 days. The method was thus capable of detecting cultivar tolerance or susceptibility to the herbicides within 12 days of sowing the seed, providing a rapid and effective screening method. Possible uses for this new test are discussed.