Thirty-six mature Finnish Landrace × Dorset Horn ewes, each suckling two lambs, were used in a comparative slaughter experiment to measure changes in body tissues during early lactation. Two levels of body fatness at lambing were established by giving ewes a complete diet containing 10 MJ metabolizable energy (ME) and 139 g crude protein (CP)/kg d.m. either close to requirements or ad libitum during the second half of pregnancy. In lactation half the ewes in each group were given a complete diet containing either 90 (diet A) or 60 (diet B) % milled hay ad libitum. These diets contained 7·9 and 9·2 MJ ME and 121 and 132 g CP/kg d.m. respectively.

Ewes fed at the two levels in pregnancy contained 8·4 and 19·6 kg chemically determined fat 5 days after lambing but had similar amounts of body protein, ash and water. Over 6 weeks of lactation ewes given diet A lost 60 and 69% of these weights of fat respectively, while ewes given diet B gained 5% and lost 30% respectively. Up to 26 g of body protein was lost daily from ewes given diet A but none from ewes on diet B. During early lactation the weight of the empty digestive tract increased while the weights of most other body components, particularly the carcass, decreased. The ratio of body energy change to live-weight change varied from 24 to 90 MJ/kg. Thus live-weight change did not accurately reflect relative or absolute changes in body energy.

Voluntary food intake was greater for ewes given the high-energy diet (B) than for those given diet A and was depressed in the fatter ewes. Differences in intake could be explained by the effects of body fatness and diet on the weight of gut contents. Milk yield was not significantly affected by body fat reserves but was higher on diet B than A. Fat content of milk was higher and protein content lower for ewes with the higher fat reserves at lambing.

As the contribution of fat loss to energy available for milk synthesis increased there appeared to be a reduction in the energetic efficiency of milk synthesis. A number of possible reasons for this are discussed.

The efficacy of estimates of gut contents and total body water in increasing the precision with which the chemical composition of the body could be estimated in early lactation was evaluated in 36 Finnish Landrace × Dorset Horn ewes. The ewes were fed at two levels in pregnancy, and, in lactation, given diets of two metabolizable energy concentrations.

The allometric relationships relating weight of chemical fat and protein to emptybody weight were not affected by treatment or stage of lactation. Inclusion of an index of gut contents, based on dry-matter intake, indigestibility and retention time of food residues, together with live weight in a regression equation predicting weight of body fat, only slightly increased the precision of estimate compared with equations using live weight alone.

There was a close negative relationship between the proportions of water and fat in live weight. Inclusion of weight of body water with live weight in a regression equation predicting weight of body fat markedly increased the precision of estimate and the residual error (0·81 kg) was similar at different stages of lactation. However, when deuterium oxide space was used instead of body water there was only a small increase in precision of estimate and the residual error varied from 5·3 kg in early lactation to 2·1 kg in mid-lactation. The relationship between deuterium oxide space and body water was shown to be variable and altered by stage of lactation, and these differences were associated with differences in rate of water turnover in the animal's body.

It is concluded that estimates of body water are unsuitable for estimating weight of body fat in early lactation.

The joint action of several insecticide formulations with a constant concentration of the antifeedant Du-ter that gives 50% starvation with the fourth instar of Spodoptera littoralis (Boisd.) was assessed. The results provided evidence that the toxicity of all the tested insecticides to the cotton leafworm can be markedly increased by using Du-ter in combination with each of the candidate insecticides. Since Du-ter proved to be highly synergistic, its mixtures with insecticides can result in a decrease in the rate of insecticide application.

An analysis is suggested for an experiment investigating plant competition between different genotypes grown in pure culture and in binary mixtures with unequal proportions of genotypes. Worked examples are presented.

During a period without rainfall the upper layers of the soil may become dry whilst the lower layers provide sufficient moisture for the plant to continue growing. In experimental conditions simulating such a soil environment, new main root axes ceased to be produced by plants of perennial ryegrass. Shoot growth and leaf elongation rate were little affected during the first 2 weeks of the treatment. The subsequent introduction of moisture round the base of the plant resulted in the rapid production of new root axes and increase in the leaf elongation rate. Although there was considerable intra-varietal genetic variation in the rate of development of new root axes and leaf elongation after wetting it is concluded that this would be of doubtful value as a selection criterion.

Radiological examinations were carried out on ten sheep to see what changes in intestinal motility and flow of digesta were caused by intestinal cannulation. Barium sulphate was injected or infused into the abomasum via an implanted catheter; its passage through the intestine and associated muscular contractions were observed using X-ray image intensification. Once the normal pattern had been established for each individual, single or re-entrant cannulae were inserted into one of four positions in the small intestine.

All the cannulations caused some disruption of the normal flow of digesta, causing retention of digesta and distension of the intestine around and proximal to the intraluminal flanges of the cannulae. The duodenum was affected the most, particularly by one type of re-entrant cannula which reduced the degree of jejunal filling; peristaltic contractions often failed to propagate beyond these cannulae and also caused some retrograde movement of digesta between the cannulation site and the duodenal bulb during the irregular contraction phase (ICP) of the migrating myoelectric complex (MMC). These re-entrant cannulae also impaired the clearing effect of regular contraction phase (RCP).

Eating behaviour and the diet selected by cattle progressively defoliating a crop of Lablab purpureus cv. Rongai were measured in three periods each of 12 days. Crop composition during defoliation was recorded.

At the beginning of grazing the crop contained 2230 kg green leaf/ha but after 12 days' grazing the crop contained only 300 kg/ha. In the first 6 days cattle selected a diet which contained 85% green leaf but after 12 days' grazing the selected diet contained only 17% green leaf. As available leaf declined, grazing time increased from 465 min on day 1 to 685 on day 6 before declining to 490 min on day 12. Maximum grazing time occurred with a green leaf yield of 1185 kg/ha. The number of eating bites increased from 26000 to 44500 between days 1 and 6 and then declined to 30000 after 12 days' grazing. Grazing time and the number of eating bites were significantly correlated (r = 0·99).

Bite size declined from 410 mg organic matter (OM)/bite on day 1 to 90 mg OM/bite on day 12. This decrease in bite size caused a linear decline (927 g/day) in estimated organic-matter intake. The rapid decline in bite size and intake was caused by the reduction in the quantity of leaf per unit area and the lack of desire of cattle to eat stem.

It was concluded that the desire of cattle to select leaf is so strong that stem yield should be largely disregarded when considering Rongai as a grazing crop.

In Expt 1, lactating dairy cows grazing kikuyu grass (Pennisetum clandestinum) were given no supplement (C), supplements of rolled barley grain at 4 (4R) and 6 (6R) kg/day and supplements of NaOH-treated whole barley grain at 4 (4A) and 6 (6A) kg/day. Daily production of milk (kg/day), fat and protein (g/day) and live-weight changes (g/day) respectively were C 7·82, 303, 276, 450; 4R 9·26, 338, 315, 865; 4A 10·23, 366, 349, 529; 6R 10·09, 352, 343, 672; 6A 10·61, 363, 348, 361.

Milk production was significantly higher (P < 0·05) and live-weight gain significantly lower (P < 0·05) on NaOH-treated grain than on rolled grain.

In Expt 2, yearling steers in pens were fed pasture hay ad libitum with no supplement (C) and 3 kg/day of barley grain which was either rolled (3R) or NaOH-treated whole grain (3A). Mean intakes of hay (g/day) and DOMD in vivo (%) respectively were C 7684, 60; 3R 5224, 65; 3A 6209, 60.

Hay intake was significantly higher (P < 0·05) on NaOH-treated grain than on rolled grain.

Fractional disappearance rates of rolled and NaOH-treated grain from nylon bags suspended in the rumen were, respectively, 0·15 and 0–07/h for the period 0–4 h, and 0·07 and 0·02/h for the period 4–12 h incubation. In Expt 2, rumen pH was higher and the digestion rate of hay in nylon bags in vivo was higher on C than on 3R and 3A. Volatile fatty acid (VFA) concentrations in the rumen did not differ significantly between diets.

It was concluded that greater milk production and hay intakes when cattle were fed NaOH-treated whole barley than when they were fed rolled barley were attributable to the slower rate of digestion of the former. The NaOH treatment (30 g NaOH/kg grain) was probably too low and further study is necessary to determine optimum levels of treatment, which are likely to vary with the ratio of grain: forage in the diet.

DNA and protein concentrations were measured in selected muscles from foetal and neonatal pigs; the protein: DNA ratios of hind-limb muscles were similar to those of the forelimb from 83 days gestation to 27 days after birth. The ratios increased during the perinatal period, providing evidence that maturation of muscle began in the last few days of pregnancy. RNA concentration, cathepsin D activity and tritiated thymidine incorporation were measured in muscles from the neonatal animals and the results indicated a surge of biosynthetic activity in the first days of life. Values obtained from the hind- and forelimb muscles were similar throughout the period of study with RNA: DNA ratio, cathepsin D activity and thymidine incorporation reaching maximum values at 4 days of age. A considerable proportion of thymidine incorporation was attributed to the mitotic activity of satellite cells.

The effects of N, P and K fertilizers on the yield and N, P and K contents of grass cut for conservation, measured during 1958–63, were again measured during 1964–7. Grass given 38 kg N/ha per cut needed 31 kg K/ha per cut for full yield, grass given 75 or 113 kg N/ha per cut needed twice as much K. With sufficient K, at least 75 kg N/ha per cut was justified. The grass responded little to P.

Percentage N in the grass, though greatly increased by N fertilizer, was little altered by K fertilizer. Percentage K, whilst greatly increased by K fertilizer, was decreased by N unless 62 kg K/ha per cut also was given. Percentage P in the grass was little increased by P fertilizer.

Exchangeable K in the surface soil (0–20 cm) was maintained with time where the grass was given either 38 kg N plus 31 kg K or 75 kg N plus 62 kg K/ha per cut, corresponding to an N:K ratio of 1:0·82. Percentage K in the grass decreased with time throughout. Whereas a N:K ratio of 1:1·66 best maintained % K in grass during 1958–63 it was no better than an N:K ratio of 1:0·82 during 1964–7.

Although exchangeable Mg in the surface soil decreased markedly between 1958 and 1967 (Mg fertilizer was not applied), % Mg in the grass did not. Mg in the grass was increased by N, but decreased by K fertilizer, and exceeded 0·2% (in dry matter) only in 1967 and then only where 75 or 113 kg N/ha per cut was applied.

An experiment at Rothamsted during 1958–67 measured effects on yield, on K uptake and on soil K of applying all combinations of 38, 75 and 113 kg N and 0, 31 and 62 kg K/ha per cut to grass leys, which were cut and removed. Soil K was depleted most where most N and least K were given. Annual applications of 0, 33 and 66 kg P/ha were also tested; soil P was not depleted. The grass was then ploughed.

In 1968, residual effects were measured by spring wheat. In 1969 and in 1970 104 kg/ha of fresh K was applied on half of each plot; potatoes (1969) and spring wheat (1970) valued residual and fresh effects of K.

In 1971 potatoes tested 0, 104 and 208 kg/ha of fresh K, cumulatively with the three amounts given to the grass and also extra K (104 kg/ha) on half-plots, cumulatively with that given in 1969 and 1970. In 1972 winter wheat, and in 1974 and 1975 spring barley, measured residues of all treatments previously applied (the site was fallowed in 1973).

Finally, in 1976, potatoes tested 0, 156 and 312 kg/ha of fresh K on whole plots, cumulatively with the previous dressings of K, and also 156 kg/ha of extra K on half-plots, again cumulatively. All these test crops were given basal N.

Yields and K contents of wheat at ear emergence and yields of wheat grain were largest after grass given 38 kg N and 62 kg K/ha per cut, because here soil K depletion was least. Wheat grain yields benefited consistently from fresh K. K content of the wheat at ear emergence was a good indicator of the need for K, but K content of grain was not, because it was unaltered by K fertilizer. Barley was a poor test crop for K, because yields of grain were little affected by previous treatments.

Percentage K in potato leaves (in July in 1969 and 1971, in August in 1976) and yield of tubers were well correlated. Largest yields in 1969, 1971 and 1976 came where the leaves contained 3·43, 3·76 and 2·82% K, respectively, i.e. from soil containing most exchangeable K, plus most fresh K. There was no indication that maximum yields had been obtained, so the largest amounts (kg/ha) of fresh K tested (104 in 1969, 312 in 1971 and 468 in 1976) were insufficient to counteract depletion of soil K by the grass. Because the grass did not deplete soil P, the test crops benefited only little from either residual or fresh P.

The effects of temperature, light intensity and nitrogen supply on the amount and fatty acid composition of the seed oil in Lupinus albus has been investigated. The percentage seed oil was reduced and its degree of saturation increased at higher temperatures. High temperatures during the dark period caused a reduction in percentage oil only when combined with day temperature of 20 °C, indicating a highly specific interaction between day and night temperatures. Shading reduced oil content, an effect which may determine response to population density and the optimal phenotype for high-oil cultivars.

Aqueous glutaraldehyde, in the presence of wetting agents Tween-20 or Haemosol, reacted with fresh cut lucerne (Medicago sativa L.), complete reaction being obtained with about 7·2 g (72 mmol)/kg herbage, or 18g/100g crude protein. Reaction with 25% w/v aqueous glutaraldehyde sprayed on to fresh lucerne was rapid, and at the rate of 66 mmol/kg lucerne, all aldehyde had reacted in 3 h and about 60% of the soluble leaf protein became insoluble. Formaldehyde at twice the molar concentration of glutaraldehyde was absorbed rapidly, but a longer time, up to 24 h, was required for the protein to become insoluble. Treatments with 22, 44 and 66 mmol glutaraldehyde/kg lucerne, and 44, 88 and 132 mmol formaldehyde/kg showed that reaction with leaf protein was approximately proportional to the amount of aldehyde. A major effect on the leaf cells was the fixation of chloroplasts, and intact fixed chloroplasts were isolated from treated lucerne with high protein: chlorophyll ratios of 5·8:1 to 9·5:1.

Two varieties of lucerne, Kabul and Europe, pot-grown in a controlled environment cabinet, reacted rapidly when sprayed with glutaraldehyde and in 3 h soluble leaf protein was reduced from 30 to 16–17% of the total N. The plants rapidly lost water and the dry matter of the leaves rose to 42% for Kabul and 45% for Europe in 24 h. Stems showed little effect. Field spraying of lucerne with glutaraldehyde similarly fixed soluble leaf protein and caused desiccation of the leaves, rising to 47–50% D. M. in 3 days. The stems were little affected and subsequent regrowth of the plants was not inhibited.

Feeding glutaraldehyde- and formaldehyde-sprayed lucerne to rumen-fistulated cattle showed that release of soluble leaf protein into the rumen fluid was greatly reduced, mean values being 40 and 43% respectively of the values obtained when control lucerne was fed. Mean ammonia concentrations were similarly reduced to 49 and 33% of the control values. Formaldehyde-treated lucerne, even after reaction for several days, frequently showed toxic effects on rumen micro-organisms, particularly protozoa. Glutaraldehyde reacted more rapidly with herbage and no toxic effects were observed. Both glutaraldehyde- and formaldehyde-treated lucerne were highly palatable to cattle.

A high level of resistance to the bean common mosaic virus strains NL3 and NL4 when inoculated separately or together was confirmed in the cultivars Turkish Brown, Valja and 1750–73. Following crosses between the susceptible cv. The Prince and all three resistant cultivars, inoculation of F2 and F3 populations revealed that the cvs Turkish Brown and Valja each differed from The Prince in being homozygous for a major recessive gene conferring resistance to both NL3 and NL4. Homology tests indicated that the same gene was present in both Turkish Brown and Valja. Polygenes in Turkish Brown and Valja also appeared to confer some resistance to NL3, or environmental variation led to continuous distribution patterns in the F2's of resistant parents crossed with The Prince. Although a major recessive gene controlled resistance to NL3 in cv. 1750–73, it differed from that in the two other resistant cultivars. In addition, cv. 1750–73 carried a dominant gene determining reaction to the virus; probably the I gene originally found in Corbett Refugee. An attempt is made to relate these results to Drijfhout's (1978) gene-for-gene model. Using Drijfhout's gene nomenclature all the cultivars tested appear to carry the strain nonspecific gene bc-u. Further genetical tests will be necessary to determine with certainty which, if any, of Drijfhout's strain-specific resistant bc-genes are present in the three resistant cultivars studied here.

Ewes in body condition scores of 2·4 (thin) or 3·2 (fat) on a 5-point scale and suckling twin lambs were grazed at two stocking rates for the first 16 weeks of lactation. Paddocks were grazed for periods of 2 weeks at densities of 80 and 160 ewes/ha in weeks 1–8 and then 70 and 140 ewes/ha in weeks 9/16 of lactation.

Intakes of herbage by ewes were not significantly affected by body condition. Estimation of milk yield by weekly measurement of secretion rates over 4 h failed to demonstrate significant differences due to body condition except in weeks 9, 11 and 12, although there was a tendency throughout for fat ewes to produce more milk. However, the daily growth rates of the lambs during the first 8 weeks and the overall live-weight gains were significantly higher for lambs suckled by fat ewes than for those suckled by thin ewes. Intake of herbage by lambs was not affected by the body condition of the ewes.

Herbage intakes, milk yields and lamb growth rates were all significantly higher at the low stocking density than at the high stocking density.

Experiments were made over a 3-year period in order to evolve a production package for yam that would eliminate the laborious operations of hand weeding and staking. First, nine herbicides were applied to yam plots before or after yam emergence. On the basis of weed control effectiveness and low phytotoxicity to yam plants, ametryne (2-(ethylamino)-4-(isopropylamino)-6-(methylthio)-S-triazine) was chosen for subsequent experimentation. Next, ametryne at 2, 4 or 6 kg/ha was applied to yam plots either immediately after planting, or with 1 kg/ha paraqviat (l, 1'-dimethyl-4,4'- bipyridinium ion) 3 weeks after planting. The delayed applications gave more effective weed control and higher yields than the early applications. For the delayed application, 4 and 6 kg ametryne/ha did not give significantly different yields, but yielded significantly more than 2 kg/ha. When a combination of ametryne at 4 kg/ha and paraquat at 1 kg/ha was applied 3, 6 or 9 weeks after planting, the weed control effectiveness was greatest at 6 weeks after planting while the 3- and 6-week applications did not give significantly different yields. Herbicide applied 9 weeks after planting gave the poorest weed control and the lowest yields.

Finally comparisons were made between the conventional staked, hand-weeded yam production, and a new production package in which the yams were not staked and weeds were controlled with ametryne (4 kg/ha) + paraquat (1kg/ha) applied at or just before emergence. When small (150g) setts were used, yields from the new package were not significantly lower than those from the conventional system, even though the new package was considerably less laborious. Cultivation with large setts, however, resulted in a decrease in yield when the plants were not staked. Strategies that could further enhance the attractiveness of the new production

In St Vincent, West Indies, the yellow passionfruit (known as Passiflora edulisf. flavicarpa Degener, but probably specifically distinct from P. edulis Sims) is grown commercially and is pollinated by the indigenous bee Xylocopa mordax Smith. The diel patterns of anthesis and nectar availability are described and related to the timing of bee visits and pollination. Flower-bagging experiments confirmed that the setting of fruit depended on cross-pollination, was prevented by exclusion of flower visitors, and was sometimes limited in the field by inadequate pollination.

Bees collected Passiflora nectar, and evaporated it on their tongues from 45–50 % to 62–63 % sugar before storing it. But the Passiflora pollen deposited on the bee's dorsum was groomed off and rejected; only Gliriddia pollen was used for bee bread. Thus the bees treated ‘acceptable’ (Gliriddia) pollen and ‘unacceptable’ (Passiflora) pollen differently, and since pollen unacceptability improves the pollen's chance of reaching a stigma, it may be a widespread adaptation.

The yellow passionfruit flower shows many features characteristic of tropical Xylocopa flowers. Here, as elsewhere, this introduced crop depends for its pollination on indigenous bees which, though suitable morphologically and behaviourally, are not abundant enough to cause a high proportion of flowers to set fruit. The setting of fruit might be improved by increasing bee populations through provision of more timber for nestsites, and suitable flowers to supply pollen and nectar throughout the year.

In a field experiment in the north-west region of Tasmania, poppies (Papaver somniferum L.) were harvested at weekly intervals beginning 10 days after full bloom and continuing until 4 weeks after the dry commercial harvest stage. At each harvest the plants were cut off at ground level and partitioned into terminal capsules, lateral capsules, seed and the combined stem plus leaf component.

The dry-matter yield of total plant and of all the components except seed achieved maximum values 2–3 weeks after full bloom and then progressively declined. For the total plant this decrease between maximum dry weight and that at the time of commercial harvest (8 weeks after full bloom) amounted to 26% while for terminal capsules it was 37% for lateral capsules 15% and for stem plus leaves 39%. In contrast, the dry-matter yield of total seed rose to a maximum by 4 weeks after full bloom and then remained constant for the duration of the experiment.

The morphine concentration of both terminal and lateral capsules reached a maximum value of 1·1% 6 weeks after full bloom and then decreased by about 10% at the dry harvest stage. The morphine concentration of stem and leaves also reached a maximum of 0·1% about the same time as capsules but decreased rapidly and had halved by dry commercial harvest. The mutually compensating factors of decreasing dry-matter yield and increasing morphine concentration gave similar total plant morphine yields at any time of harvest from 2 to 7 weeks after full bloom. The morphine extracted from the whole plant at these times of harvest was about 50% greater than that derived from capsules alone at the time of dry commercial harvest.

Three experiments, each consisting of a feeding trial plus a digestibility and nitrogen retention study, compared long barley straw with rolled barley as basal diets and oat hulls with maize starch as energy supplements for yearling dairy cattle. The protein ontent of the diets was varied by the addition of flshmeal.

Growth rates were reduced by the dietary combination of high fibre and low protein, so that diets rich in straw, or containing a supplement of oat hulls, gave a large response to a supplement of fishmeal compared with low straw or maize starch supplemented diets. The data suggest a crude protein concentration of 115 g/kg dry matter as a requirement for high fibre diets supplemented with fishmeal, when fed to yearling cattle. Retention of nitrogen reflected the pattern of live-weight gain. Molar proportions of VFA were affected by changes in the roughage: concentrates ratio, except where energy and protein intakes were both low.

Barley straw was of a higher nutritive value than oat hulls.

Fishmeal, soya-bean meal and urea were compared as nitrogen sources in diets rich in fibre for yearling cattle, using feeding trials and digestibility and nitrogen retention studies. All animals were individually fed. Diets supplemented with fishmeal supported the highest rates of daily live-weight gain and nitrogen retention. There was no response in dry-matter intake and digestibility from extra nitrogen, either from fishmeal or urea, when the crude protein of the diet was 8·5% or over, and a small response in digestibility when soya-bean meal was used.

Molar proportions of VFA, rumen NH3-N concentrations and blood urea nitrogen concentrations were all affected by both amount and source of nitrogen supplementation. Multiple regression analysis showed the undegradable protein supply to be more critical with high than with low fibre diets.