Transition from juvenile to adult vegetative phase in maize is associated with pest and disease resistance. However, reports are not consistent on the significance and relative importance of additive or dominance genetic effects and variances. The purpose of the present research was to elucidate the genetic effects and variances and to identify molecular markers associated with phase transition. Three cycles of divergent selection were carried out in a maize synthetic accelerating and delaying phase transition. Three and four inbred lines were released from the third cycles of late phase transition (LPT) and early phase transition (EPT), respectively. Generation mean analyses were performed from two LPT×EPT crosses in order to calculate genetic effects and variances. Markers associated with vegetative phase transition were identified by contrasting simple sequence repeat (SSR) alleles between LPT and EPT inbreds and selection cycles, and by testing whether drift could explain the allelic changes observed in the respective third cycles of selection. Juvenile traits are mainly regulated by additive genetic effects and variances, whereas adult traits have a complex regulation involving dominance and epistatic effects. Based on error variances, EPT improves phenotypic stability. The SSRs phi028, phi112 and umc1725 were associated with selection for phase transition, suggesting that these genome regions are involved in the regulation of vegetative phase transition of maize, although none of the genes previously associated with phase transition has been located in those regions.

Five Suffolk crossbred ram lambs were administered ritodrine, a β2-agonist drug, by continuous intravenous infusion at 0·5 μg/kg per min for 9 days to determine effects of prolonged β-agonist infusion on metabolism and on the responsiveness of the animals to short-term infusions of adrenaline. Consistent with other investigations, this study showed that initially the drug caused rapid increases in heart rate and plasma concentrations of free fatty acids (FFA), lactate and insulin, but decreased plasma growth hormone. There was no effect on plasma glucose or pancreatic glucagon concentrations. After 24 h of ritodrine infusion, these effects were attenuated as tachyphylaxis to the drug developed. On days 2–9 of the infusion, heart rate remained significantly higher than preinfusion values, but plasma glucose concentration was significantly lower than before infusion. Despite the rapid disappearance of these ‘side-effects’ of the drug and the apparent normality of most metabolic parameters, short-term infusion of adrenaline (50 ng/kg per min for 60 min then 500 ng/kg per min for a further 60 min) after 9 days of ritodrine infusion showed that the responses of lactate, FFA and heart rate to adrenaline were significantly attenuated in comparison with the responses determined before β-agonist infusion. This result, together with similar earlier observations on fetal lambs, implies that selective attenuation of β-receptor mediated cardiovascular, metabolic and endocrine responses to the endogenous catecholamines could play an important role in determining how β-agonist drugs act to modify carcass development.

This study was carried out to investigate the effect of crossing the subtropical fat-tailed Ossimi (O) sheep with the Hampshire (H) on ewe and lamb performance. Data used involved 457 ewe records of Ossimi, Hampshire and four crosses, and 404 lamb records of Ossimi and five crosses.

Hampshire ewes performed less well than the local Ossimi ewes in various reproduction traits. They weaned 0·26 lamb/ewe run with the rams compared with 0·82 from the local ewes mated to Hampshire rams. The Hampshire ewes seemed to be anoestrous during the first part of the normal breeding season of the local ewes (May–July). Different Hampshire–Ossimi cross-bred groups showed better ewe reproduction performance than the purebred Hampshire ewes, but were inferior to the Ossimi. The first cross ewes were, generally, the best among all the cross-bred ewes and the reproduction performance declined with increasing percentage of Hampshire genes. When the first cross was interbred, ewe performance declined clearly in the F2. All cross-bred groups of ewes gave significantly heavier annual greasy-fleece weight than Ossimi ewes.

The only lamb performance trait that was improved by up-grading the Ossiroi sheep with the Hampshire breed was the first greasy-fleece weight, while lamb survival and weaning weight were clearly decreased with the advance of up-grading.

The recombined cross-bred groups ( and ⅝ Hampshire) proved to be the best cross-bred and showed considerable improvement in lamb performance traits over the local Ossimi sheep, except for lamb survival.

It is concluded that crossing Ossimi sheep with the Hampshire improved only fleece weight but not lamb production.

The experiment was designed to compare under Trinidad conditions three varieties of fodder grass and ascertain the correct stage at which each should be cut to give the maximum nutritive value per acre. It consisted of a yield trial in the form of a Latin square in which the treatment series included four cutting rotations on main plots and three varieties of fodder grass on subplots as appended

This paper reviews extensive work at Jealott's Hill and elsewhere in England and Wales on the agronomic effects of including various levels of urea in 2:1:1 NPK fertilizers combine-drilled with spring cereals.

Little evidence of phytotoxicity was found with fertilizers containing up to 12% urea and providing about 0·6 cwt N/acre. The inclusion of 20% urea reduced braird more frequently on soils of high pH than did lower proportions although grain yields were seldom affected adversely. Such soils are not uncommon, especially in the barleygrowing areas of Southern and Eastern England, where perhaps a quarter of the cereal acreage may be located on soils of pH 7·7 and above.

1. A cross-bred sheep was fed successively with supplements of dried skim-milk or lactose. The effect of the supplements on the lactase activity of the rumen liquid was followed.

2. Lactase activity was expressed as mg. lactose hydrolysed per ml. rumen liquid, or per mg. protein nitrogen. The enzymic activity fluctuated considerably after a change in the diet, and did not become constant even when the ration remained the same for 7 weeks.

Two changeover experiments, each on eight buffalo heifers, were conducted in two different years to determine the effect of wilting lucerne herbage (Exps. 1 and 2) and berseem herbage (Exp. 2 only) on voluntary dry-matter intake. The dry-matter content of the herbages increased by field wilting from 27 to 50 and from 26 to 44% for lucerne in Exps. 1 and 2 respectively, and from 21 to 31% for berseem. The drymatter intake, nutrient digestibility coefficients, nutritive value index and retention time of undigested residues were determined for each fresh and wilted herbage.

Wilting increased the dry-matter intake of lucerne from 2·3 to 2·8 and from 2·1 to 3·5 kg per 100 kg body weight in Exps. 1 and 2 respectively. Berseem dry-matter intake was increased from 2·2 to 3·1 kg per 100 kg body weight. Digestibility coefficients of all nutrients of both herbages increased by 6–20%. Retention times were unaffected by wilting. The nutritive value indices for lucerne and berseem in Exp. 2 increased by 160 and 60% respectively. In Exp. 2, the average loss of herbage dry matter due to wilting was 3·8%. The higher consumption of the wilted herbages is ascribed to their lower water content. The practical implications of these results are discussed.

Four of five ‘hairy’ Wiltshire lambs had fibre type arrays (as defined by Dry, 1965) of Plateau (P0 and P1) type, whereas in five ‘woolly’ lambs there was only one Plateau (P3) array, the arrays of the remaining lambs being Ravine or Saddle. In terms of Dry's theory that the severity of pre-natal check determines persistence of wool growth in adults, it appears that the amount of checking in these Saddle and Ravine arrays was insufficient to prevent the casting of the adult coat.

1. Eighty counts of soil bacteria and actinomycetes, made on mannite-asparagine agar and dextrose-casein agar, showed that the latter medium gave significantly higher numbers of bacteria in 76 per cent. of cases, and significantly higher numbers of actinomycetes in 60 per cent. of cases.

2. On mannite-asparagine agar the values of χ2 of the bacterial counts were as a whole in agreement with expectation. The counts of actinomycetes colonies on this medium showed a tendency to subnormal variation.

The device of split-plot confounding for introducing additional factors into a field experiment can only give a balanced design when the number of whole plots per block and the number of replications of each whole-plot treatment are multiples of the number of sub-sets into which the combinations of the additional factors are divided. When this condition is not satisfied it may still be possible to arrange that the design shall be partially or nearly balanced in such a way as to be useful in practice and to require a reasonably simple statistical analysis. Nevertheless, the experimenter should always bear in mind the desirability of balance, and should have recourse to unbalanced designs only when the exigencies of space or material, or an unforeseen necessity of introducing extra factors during the course of an experiment, leave him with no alternative. No attempt has been made to give a comprehensive account of designs of this kind, but the numerical analysis of the yields from a typical experiment has been discussed in detail. Though the lack of balance leads to some non-orthogonality of treatment contrasts, the more important comparisons can usually be satisfactorily estimated. The details of this estimation vary from one experiment to another, but the example given should make the principles clear to those who are familiar with the analysis of variance. I am indebted to Dr E. M. Crowther and to the Agricultural Research Council for permission to use the numerical results discussed in this paper

The nutrition of the carrot in a light gravel soil of known analysis with high available phosphate has been studied by statistical pot-culture methods, and the responses, linear and curvature components, etc., due to nitrogen, phosphate, and potash, have been calculated.

No hard and fast rule can be made as to the adequacy or otherwise of any particular fertilizer in a soil, as the different parts of the plant (top and root) were shown to be capable of responding quite differently to that fertilizer.

Analysis of 21 years' cotton yield data from factorial experiments at three sites in the Sudan Gezira established that yields were significantly increased by nitrogenous fertilizer, that close spacing outyielded wide spacing and that variety X1730A (L type) outyielded variety MSDS (a Sakel type). The effect of nitrogen varied depending on variety and spacing and there were also marked variations from year to year in the effects of nitrogen, spacing, variety and some of the interactions. Year-to-year variations in the overall level of yield were very pronounced and accounted for more than half of the total variance at each site. Causes of year to year variation and the mechanism of the treatmenteffects will be discussed in subsequent papers.

A natural rock phosphate, ‘Kodjari” (RP), sparingly soluble, indigenous to Burkina Faso, and a commercial single superphosphate (SSP) fertilizer were studied at Farako-Bâ in the Northern Guinea Savannah (NGS) and at Oipasse in the Sudan Savannah (SS) regions of Burkina Faso. A 3-year crop sequence either of cowpea, maize and sorghum or of cowpea, sorghum and sorghum was used, respectively, in the NGS and SS regions. The sorghum crop in the third year was not fertilized with any phosphorus (P) source. The objectives of the research were to study the direct and residual effects of the P fertilizers on soil fertility improvement in order to boost agricultural productivity in both regions.

Cowpea daylength-insensitive cultivars, in both regions, and maize and sorghum in the NGS and SS regions, respectively, responded more strongly to SSP than to RP fertilizer treatments. The optimum rate of SSP and RP source was 21·8 kg P/ha and 43·6 kg P/ha, respectively, for cowpea in both regions. The optimum rates of phosphorus fertilizer applied in the second year to maize in the NGS and to sorghum in the SS region, in addition to the optimum rate of P applied to cowpea the previous year, was 10·9 kg P/ha of SSP or 43·6 kg P/ha of RP, and 21·8 kg P/ha of SSP or 43·6 kg P/ha of RP, respectively. Both P sources had significant residual effects for up to 2 years. The agronomic effectiveness of RP relative to SSP, in the year of application of both fertilizers, was greater for cowpea than for maize in the NGS region and similar for cowpea and sorghum in the SS region; it increased markedly for the two subsequent cereal crops in both regions. Cowpea fertilization with both P sources proved, therefore, to be effective in improving the soil fertility and boosting the productivity of cereal crops in the 3-year crop sequence.

A convenient method of introducing into a field experiment additional factors which can be applied to smaller areas than that of the whole plots is to use split plots: each whole plot is split into sections, and the different combinations of the additional factors are randomized over each set of sub-plots. An extension of this idea is the device of split-plot confounding, by which not all the combinations of the additional factors are used in every whole plot; instead, the possible combinations are subdivided into two or more sets which are then assigned to blocks and whole-plot treatments in a balanced manner, in such a way as to confound certain interactions of the additional factors between whole plots and certain higher order interactions between blocks.

This group, which is concerned with the applications of mathematics to agricultural science, is sponsored by the Agricultural and Food Research Council. It was formed in 1970, and has since met at approximately yearly intervals in London for one-day meetings. The twenty-third meeting of the group, chaired by P. H. Nye of the Department of Plant Sciences at the University of Oxford, was held in the Wellcome Meeting Room at the Royal Society, 6 Carlton House Terrace, London on Friday, 7 May 1993, when the following papers were read.

The intensive finishing of steers on simple rations of 10% sorghum stubble and 90% sorghum grain plus urea was investigated. Fine grinding of the grain resulted in a lower mean daily intake, but a significantly greater efficiency of conversion of feed to carcass weight gain (P < 0·01) than coarse grinding the grain. Coarse chaffing of the stubble significantly reduced the intake of the stubble in comparison with hammer milling, but had no significant effect on rate of body weight gain, total feed intake or efficiency of feed conversion.

The addition to the ration of either 1 mg of selenium, or 200 mg vitamin E, 200 mg vitamin E and 100 mg vitamin K per day had no significant effect on rate or efficiency of body or carcass weight gain. Seven out of 32 steers which were not injected with 3 million i.u. of vitamin A at the start of the experiment exhibited nyctalopia. None of the 32 steers which received the vitamin A injection had hepatic vitamin A concentrations less than 33 μg/g. Vitamin A injection did not have a significant effect on the rate of body weight gain (mean ±S.E. 1·3 ± 0·03 kg per day), efficiency of feed conversion (10·4 ± 0·16 kg D.M. per kg carcass weight gain), or time to attain slaughter weight (133 ± 3 days). Drenching twice with thiabendazole had no significant effect on rate of body weight gain.

With the great increase in the use of palm kernel cake, which has taken place in this country in the last few years, attention has been drawn to the rancidity which the cake is liable to develop under certain conditions. R. B. Calder (see this Journal, April, 1916, VII, 470) has shown that the cake develops rancidity under sterile conditions and concludes that the action is due to the presence of a lipase. Calder has taken as his criteria of rancidity a sour smell in some cases and an acid reaction with litmus in others. There is some confusion in the use of the terms “rancidity” and “ acidity.” Although rancidity stands in close relationship to acidity and invariably accompanies a high acidity in oils and oil cakes, the terms are not synonymous.

A central issue in the husbandry of seed crops of perennial tropical grasses is the disposal of residues from previous crops. Flowering of these grasses is usually poorly synchronized, and the sudden removal of all shoot material by burning, mechanical removal or stock concentration is necessary to create a population of tillers of similar age (Humphreys & Riveros, 1986). There has been little critical study of alternative systems of residue disposal and their effects on the ways in which seed yield is realized. Questions requiring attention are whether cutting differs from burning in its effects, and whether the fuel load, determined by the size of the previous crop, influences the potentially damaging effect of fire on crown buds.

The tubers of Dioscorea composita Hemsl. contain a high level of diosgenin, and hence there is economic interest in this plant. Levels of diosgenin vary greatly in different clones of the species. Vegetative propagation was studied with a view to obtaining plants with high levels of diosgenin. In this study cuttings from 1-year-old vegetative plants were used for propagation. The cuttings were treated with a single application of indole-3-butyric acid (IBA) and several applications of 6 benzyladenine (6-BA). Rooting was never observed in untreated cuttings. Cuttings treated with IBA produced callus and roots. Early application of 6-BA delayed senescence but inhibited callus and root formation. New plants were obtained with one application of IBA followed by applications of 6-BA at 48 h intervals initiated 2 weeks after IBA application. In some experiments, all cuttings treated this way produced new plants.

Eighteen bulls were used to investigate the influence of feeding frequency on feed consumption, nutrient utilization and nitrogen metabolism in growing zebu cattle.

Results indicated higher feed intake, nutrient utilization and average daily live-weight gains for animals fed two or three times daily compared with those fed once daily. Feed efficiency and feed cost per kg gain as well as nitrogen metabolism also increased as the frequency of feeding increased from once to three times daily.

More frequent feeding could evidently be of practical advantage in intensive beef cattle production where zebu cattle are raised on tropical hay diets.