Different photoperiodic treatments within 2 types of light dark cycles ranging from 24 to 30 h were applied to Peking ducks. The first consisted of constant photoperiods (1, 8L: 16D; 2, 14 L: 10D; 3, 18L:6D; 4, 14L: 13D; 5, 14L: 16D and 6, continuous light) and the second of intermittent cycles (1, 6L:2D:2L:14p; 2, 6L:4D:2L:12D; 3, 6L:6D:2L:10D; 4, 6L:8D:2L:8D and 5, 14L:½D:3½L:6D). The traits studied varied in response according to the photoperiodic regimes used. Rate of lay and eggs laid in the modal 8 h period increased with the duration of the light period in the cycle. Sequence lengths of 1–3 eggs were most frequent under all photoperiodic regimes (constant and intermittent). Length of intra-sequence interval (h) showed an inverse relationship with length of inter-sequence interval. A pause length of 2–4 days was the most frequent for all the different light-dark cycles. Egg weight was heavier in the second season than in the first when the light period of the photoperiodic regime was long. Weights of albumin and yolk showed similar trends to egg weight. The latter differences were significant, while shell weight differences were not significant. Plasma progesterone lvels were lowest in non-laying ducks. The highest values in laying ducks were before ovulation. The highest level of cortisol was shown during the last hours of the dark period. Differences from ovulatory cycle to another were observed.

Two scries of simulation experiments were used to investigate the accuracy of treatment and variance estimation with a neighbour analysis of field trials proposed by Gleeson & Cullis (1987). The first series examined the accuracy of residual maximum likelihood (REML) estimation of seven theoretical error models applicable to field trials. REML estimation provided accurate estimates of the variance parameters, but the Ftest of treatments was slightly biased upward (to +2·4%) for first differences models and slightly biased downwards (to –1·4%) for second differences models. The second series of simulations, based on 19 uniformity data sets, illustrated that treatment effects were consistently estimated more accurately by the REML neighbour (RN) analysis of Gleeson & Cullis (1987) than by incomplete block (IB) analysis with recovery of interblock information. The relative gain in accuracy of RN over IB depends on the amount of systematic variation or ‘trend’ in the trial, and ranged from 6 to 18% with an average of 12% for a range of trend and error variances commonly encountered in field trials. The predicted average standard errors of pairwise treatment differences from the RN analysis were in close agreement with their empirical estimates, indicating that the predicted average S.E.D. is approximately valid.

A study was conducted at Debre Zeit, Ethiopia to examine the differences in mineral composition, root N contents and their rates of transformation in the soil of different species of four genera of forage legumes, Trifolium steudneri (ILCA D/Z), Trifolium steudneri (Shola), Vicia dasycarpa (ILCA 6795), Vicia benghalensis, Lablab purpureus cv. Rongai, Lablab purpureus cv. Highworth, Medicago scutellata cv. Snail and Medicago truncatula cv. Barrel. M. truncatula cv. Barrel had higher N and P values than M. scutellata in both roots and tops. Root N contents of the legumes ranged from 2·43% for Vicia to 0·87% for Lablab. These differences were also reflected in the rates of organic root N transformation in soil as determined in laboratory incubation studies.

The P concentration in the tops of the legumes ranged from 0·32% in Vicia to 0·14% in Medicago spp. The observed P concentration in the Medicago species suggests a low internal P requirement. Potassium concentrations in the Trifolium species were much higher than the average for all legumes.

The results suggest that the Vicia species used in this study could contribute a considerable amount of N to subsequent crops even when the tops are not returned to the soil. Also, the Medicago species are more likely to thrive better under low soil P conditions than the other legumes.

A study has been made of the distribution of 14carbon-labelled assimilates in flowering oilseed rape plants. Up to 10 days after anthesis individual flowers were strong sinks for assimilates for 2 days after opening but thereafter became weak sinks for a period of 24 h. This period coincided with pollination and subsequent fertilization. After fertilization the young pods again became strong sinks. Between 13 and 16 days after anthesis other flower buds, flowers and young pods which had previously been strong sinks failed to attract assimilates and aborted. This fall in sink capacity occurred at about the same time on all branches and appeared to be co-ordinated on a whole-plant basis.

Gorse (Ulex europaeus) was harvested in late spring, summer, autumn and winter and fed to six goats kept individually in metabolism cages for 21-day periods. The same gorse was also fed to sheep during the first two periods, but not in autumn and winter, as the hardness and sharpness of the needles caused total rejection by the sheep at these times. Measurements of voluntary intake and apparent digestibility were made over the last 7 days of each period. To minimize effect of diet selection the animals were fed at hourly intervals. Dietary lignin concentration was very high, ranging from 170 to 200g/kg D.M. Voluntary metabolizable energy (ME) intake for goats was respectively 1·60, 0·82, 0·72 and 0·41 times maintenance for the four harvesting times, late spring, summer, autumn and winter. Corresponding values for sheep were 0·90 and 0·33 for gorse harvested in late spring and summer. Thus, in late spring and summer, voluntary ME intake by goats was respectively 1·8 and 2·5 times that of sheep. The reduction in ME intake with time was attributed to increases in the contents of D.M. and of lignin + hemicellulose in depressing voluntary D.M. intake and apparent digestibility respectively. Voluntary intake of both supplementary water and total water per unit D.M. intake were consistently less for goats than sheep. From a comparison with published values, it was concluded that the superiority of. goats over temperate breeds of sheep in digestible dry matter intake (DDMI)/kg W0·75 per day increased as the lignin content of the diet exceeded 120 g/kg D.M., indicating that goats must possess some superior mechanism for breaking down highly lignified diets such as gorse and willow. It is proposed that cashmere fibre production from goats grazing gorse for a 7-month period of each year should be evaluated as an alternative to regulating gorse with chemicals.

Blood samples were collected three times weekly for 21 days before and after calving (day 0) from 29 buffalo cows and 22 buffalo heifers. Plasma concentrations of progesterone and total oestrogens were quantified by validated radioimmunoassays. Ovarian activity and uterine involution were monitored by rectal palpation at the sampling times and extended up to 60 days postpartum. The concentration of plasma progesterone in cows declined from 3·0 ± 0·2 ng/ml (mean ± S.E.) during days 21–17 before calving to 2·1 ± 0·1 ng/ml at day −3, followed by a rapid fall during the last 3 days of gestation, reaching 1·2 ± 0·3 ng/ml at the day of parturition. In heifers, plasma progesterone values increased slightly from 2·9 ± 0·2 ng/ml at days 21–19 before parturition to 3·4 ± 0·3 ng/ml by day −1 and then fell sharply to 2·1 ± 0·1 ng/ml at calving time. During the postpartum period, plasma progesterone decreased gradually and reached baseline values after day 15 postpartum, when the residual corpus luteum of pregnancy had completely regressed in all the animals studied. The plasma concentrations of total oestrogens started to increase at day −15 in cows and day −5 in heifers from below 40 pg/ml to 122·5 ± 51 pg/ml for cows and 100·7 ± 3·4 pg/ml for heifers by day −1. This was followed by a sharp increase to 251·2 ± 17·3 and 240·5 ± 10·1 pg/ml in these animals at the day of calving. Immediately after parturition, total oestrogens dropped abruptly to the lowest values and remained below 30 pg/ml in all cows and heifers until the end of the sampling period. We concluded that female foetuses significantly (P < 0·05) increased the maternal total oestrogens. Moreover, animals having postpartum disorders had significantly higher values for progesterone (P < 0·05) and lower values for total oestrogens (P < 0·01) than those having normal puerperal periods, but the magnitude of this difference varied in samplings between cows and heifers.

Removal of basally positioned pods on the terminal inflorescence at anthesis and 6 days thereafter increased the duration of flowering and resulted in the formation of a larger number of smaller pods.

Removal at 12 days after anthesis did not affect flower production but increased the number of flowers setting pods. Application of benzyladenine to the apices of intact plants from 8 days but not 14 days after anthesis greatly extended flower but not pod production. Liquid scintillation counting showed that the benzyladenine treatment led to more 14C-labelled assimilates moving to the apices.

Sugar cane (Saccharum sp. hybrid cv. Co 1148) was planted in October alone and in association with potato (Solarium tuberosum cv. Kufri Chandramukhi), coriander (Coriandrum sativum cv. Sheetal), mustard (Brassica juncea cv. T59) and wheat (Triticum aestivum cv. K816) to find the optimum N dose in alluvial entisols of Lucknow, India. The yield of sugar cane was least in association with wheat and most with potato. The optimum N doses for sugar cane were 152, 175, 186 and 231 kg/ha when grown in association with potato, coriander, mustard and wheat respectively. The optimum N dose for sugar cane grown alone was 186 kg/ha.

Pulse crops play an important role in Indian agriculture because of their unique ability to fix atmospheric nitrogen. Greengram, blackgram and soya bean are commonly grown during the kharif season (July–October) in Northern India. The availability of pulses is decreasing due to a decrease in area. Average yield of these crops is rather low and subject to great variation due to the vagaries of weather and pest attack.

Data on gestation period of 701 indigenous East African and Galla does and pre- and postweaning growth of 810 pure-bred and cross-bred kids were analysed by least squares statistical analysis. Breeds of kids were East African, Galla, Toggenburg × East African, Toggenburg × Galla, Anglo-Nubian × East African and Anglo-Nubian × Galla. Average gestation length was 149 days and was significantly (P < 0·05) affected by type of birth of the kid, year–month of kidding, and age of dam. Does carrying twins had shorter gestation length than does carrying singles. Sex and breed of kid did not have significant effect on gestation length.

Significant (P < 0·05) factors affecting birth weight, weight at 30, 60, 90, 120, 150, 210 and 270 days of age, and preweaning growth rate were breed and sex of kid, type of birth, year–month and age of dam. Male kids grew faster and were heavier than females. Kids born single were heavier and grew faster than twin-born kids. Kids from dams less than 3 years old weighed less than kids from older dams. Cross-bred kids had higher preweaning growth rates than indigenous pure-bred kids. The Anglo-Nubian × Galla cross was heaviest while the East African ranked lowest. The results point to importance of cross-breeding with temperate breeds to increase growth rates of indigenous goats. Comparison of Toggenburg and Anglo-Nubian sires for cross-breeding showed both buck breeds produced kids with roughly equal growth rates. Evaluation of indigenous Galla and East African dams for cross-breeding showed Galla dams produced heavier kids than East African but preweaning growth rates were not significantly different.

In a laboratory incubation study, the effect of natural and artificial soil salinity on the soil N2 fixation, nitrogenase (C2H2 reduction) and N2-fixing populations was evaluated in rice soils under two water regimes. N2 fixation was less pronounced in two saline soils and in a normal non-saline soil amended with salt mixture (salinity level of 4 and 30 dS/m) than in a non-saline soil under flooded and nonflooded conditions. Flooded soils amended with rice straw showed higher N2-fixing activity than the non-flooded soils at all salinity levels used in the study. Leaching the saline soil improved N2 fixation. An increase in the soil salinity led to a decrease in the populations of at least three groups of N2-fixing micro-organisms. The population density of anaerobic N2 fixers and Azospirillum in a saline soil increased considerably after leaching or after addition of rice straw. Azotobacter populations were little affected by the salinity levels used in this study. Results indicate that soil amelioration for salinity with leaching and organic matter addition would improve the implicated microbial populations and N2 fixation in salt-affected rice soils.

Copper has been identified as a deficient micronutrient in many alkaline calcareous soils of Pakistan (Kausar et al. 1979; Anon. 1986b). Copper extracted with DTPA from several soils of Pakistan correlated significantly with organic matter and free CaCO3 content (Kausar et al. 1979). Both soil organic matter and CaCO3 content have been reported by Viets (1962) to be among several other factors that affect Cu solubility and hence the Cu nutrition of plants. Working with temperate acid soils, several investigators (McLaren & Crawford, 1973; Shuman, 1979) have recently used different extractants and indicator plants to characterize the chemical pools which appear to control plant available Cu. Shuman (1979) separated various soil fractions and determined their Zn, Cu and Mn content. However, the distribution of Cu among various fractions in alkaline calcareous soils of arid regions has received little attention. The object of the present study was to investigate the relationship between the Cu content of wheat, and native soil Cu and applied Cu. The contribution of Cu in various soil fractions towards plant uptake and that extracted by different reagents was also ascertained.

Acetic acid bacteria were isolated from maize silages and from samples of maize silage exposed to air. The isolates apparently belonged to the genus Acetobacter. By inoculating maize silage with strains of acetic acid bacteria isolated from silage and by monitoring the development of the microbiota of samples exposed to air it was demonstrated that acetic acid bacteria can be responsible for the onset of aerobic deterioration of maize silage. However, acetic acid bacteria and yeasts often developed simultaneously in uninoculated silage samples exposed to air. In all experiments ethanol was oxidized to acetic acid followed by a rapid oxidation of lactic and acetic acids when ethanol was depleted.

Four systems of harvesting grass for silage were evaluated in terms of in-field losses, in-silo losses and milk output per hectare. The systems were: single-chop flail harvester direct cutting (SCD); doublechop flail harvester direct cutting (DCD); mown with a rotary mower and picked up with a precisionchop harvester either immediately (PCU) or after wilting until the dry-matter concentration had increased by approximately 100 g/kg (PCW). The in-field and in-silo losses were measured at each of three consecutive harvests during 1984 and during the following winter the resulting silages were evaluated through eight British Friesian cows in a balanced change-over design experiment using four periods each of 5 weeks duration.

There was a greater quantity of herbage ensiled with the two direct cutting systems (SCD and DCD) than with the systems involving pre-mowing and picking up with the ensiled yields, being 12·4, 11·8, 10·8 and 10·8t OM/ha for the SCD, DCD, PCU and PCW systems respectively. These differences were only partly reflected in greater mechanical in-field losses with the pre-mown systems.

Losses during the in-silo period tended to be greater with the wilted than the unwilted silages being 98, 76, 83 and 132 g/kg OM with the SCD, DCD, PCU, and PCW systems, respectively.

Animals offered the PCW silage tended to have a higher silage organic-matter intake and had a significantly higher milk yield than those offered the other silages with fat corrected milk yields being 25·1, 24·5, 24·5 and 25·9 kg/day for the SCD, DCD, PCU and PCW systems, respectively. Milk outputs per hectare, at 30·3, 27·8, 25·7 and 240 for the SCD, PCD, PCU and PCW systems respectively, was lowest for the PCW treatment.

In a long-term cultivation experiment comparing mouldboard ploughing, shallow cultivation and direct drilling, soil compaction was identified as a problem. Root growth was restricted and this possibly caused a decline in grain yield of spring barley. The residual effects of a slant-legged subsoiler (Trade name, ‘Paraplow’) on the growth and yield of spring barley up to 34 months after its use were measured.

In 1982, soil not loosened with the ‘Paraplow’ had a grain yield of 5·16 t/ha and cultivation with the ‘Paraplow’ either 22 or II months previously had a negligible effect. Although the implement improved mean plant establishment by up to 12 plants/m2, compensatory tillering occurred in the treatments that initially had fewer plants, thus reducing differences in dry-matter production and grain yield at harvest. The long-term system of cultivation had a larger effect on grain yield than the ‘Paraplow’ did. Grain production on direct-drilled and shallow cultivated soils exceeded that after mouldboard ploughing by up to 0·55 t/ha (P < 0·05). The ‘Paraplow’ used 22 months previously increased grain yield by 0·47 t/ha on a direct-drilled soil that had become compacted.

In 1983, the emergence of seedlings was low (54%) due to waterlogging of the seed bed between germination and emergence. The ‘Paraplow’ used 8 months previously increased the mean number of plants that emerged by 20 plants/m2. More seedlings survived on the soil loosened by the ‘Paraplow’ because it drained more freely than the undisturbed soil. Cultivating with the ‘Paraplow’ 11, 23 and 34 months previously increased grain yield by 0·27, 0·29 and 0·13 t/ha respectively, but the mean grain yield was only 2·70 t/ha. This improvement was caused by a greater number of grains per m2 on the soils loosened with the ‘Paraplow’. Grain weight was unaffected by cultivation system or by ‘Paraplow’ treatment.

We describe a computer algorithm to generate efficient incomplete-block designs for any number of varieties, any number of replicates, and any number of plots per block. It considerably extends an earlier catalogue published in this Journal by Patterson, Williams & Hunter (1978). We describe also some uses of the algorithm for which no efficient designs are available from existing sources.

The effects of winter shearing on ewe live weight, body condition score (BCS) and the concentrations of glucose, non-esterified fatty acids (NEFA), 3-hydroxybutyrate, growth hormone (GH), cortisol, insulin and the thyroid hormones in plasma plus that of oxygen and carbon dioxide in jugular vein blood and packed cell volume (PCV) were measured at weekly intervals over the final 7 weeks of pregnancy in two groups of multiple-bearing shorn and unshorn pregnant ewes.

Shorn ewes lost 47% more live weight than unshorn controls over the period from the day of being shorn to immediately after lambing. There was a significant decrease in BCS in both groups between 45 and 9 days before lambing. Three days after shearing the plasma NEFA concentration was higher in the shorn group but there were no other significant differences between shorn and unshorn groups in the plasma concentrations of NEFA, cortisol or insulin over the remaining 7 weeks of pregnancy. Both the PCV and concentration of carbon dioxide in blood were higher in shorn sheep throughout the final 6 weeks of pregnancy indicating they were making metabolic adaptations to long-term cold exposure. This response may have been mediated via an increase in thyroid hormone concentrations which were higher throughout the 7-week sampling period in shorn animals compared with unshorn controls. A decrease in ambient temperature was associated with a significant increase in the plasma concentration of GH and glucose in shorn animals. At 2 weeks before lambing there was a decrease in the plasma glucose concentration and an increase in 3-hydroxybutyrate concentration in the unshorn ewes, but these changes were not observed in the shorn animals. It is concluded that winter shearing of the pregnant ewe results in an increased loss of maternal body tissues and metabolic adaptations to long-term cold exposure without any of the changes associated with an increase in energy expenditure during the final third of pregnancy.

Tetrapleura tetraptera (Schum & Thonn) is a member of the Family Mimosaceae. It is a perennial, wild West African tropical forest tree (Hutchinson & Dalziel, 1973) and is extensively used in many traditional medicines. The fruit is used in Nigeria as a spice added to soup for nursing mothers from the day of delivery to about 1 month postnatally, to prevent post-partum contractions.