A dynamic model is presented in which the problem of predicting P response is broken down into various components, such as:

(a) Weight and P content of emerging seedling.

(b) Normal growth curve of the fully nourished plant.

(c) A ‘deficiency-tolerance’ factor relating depression of relative growth rate to plant P concentration.

(d) An ‘affinity’ term relating sink concentration to P status of plant.

(e) A perirhizal resistance term for diffusive transport to roots.

(f) Capacity and intensity of P supply from the soil. Mass flow supply via the transpiration stream is also included.

By changing parameter values one may attempt to simulate the effect of any of these factors on the shape of the P response curve and any other part of the system throughout crop life. At present the model over-estimates growth at low levels of P supply, but predicted plant P concentrations agree reasonably well with observed data.

The effect of altering the level of protein intake on urea excretion in ewes was assessed in two separate experiments.

In Expt 1, 14 pregnant (during the last 20 days of gestation) and 10 non-pregnant ewes were each offered a different level of digested N intake in the range 5–25 g/day. At all levels of protein intake urea N excretion was lower in pregnant than in nonpregnant ewes.

In Expt 2, 21 pregnant ewe lambs were each offered one of three diets supplying mean intakes of 83 (T1), 113 (T2) or 147 (T3) g crude protein/day. During the last 100 days of gestation the mean levels of urea N excretion were 6·9, 11·0 and 15·2 g/day for T1, T 2 and T 3, respectively. The corresponding values for urinary N excretion were 9·3, 13·8 and 18·2 g/day. At all levels of protein intake urea N excretion was lower just prior to parturition than 95 days prepartum; the difference was correlated with lamb birth weight and maternal body-weight change.

A notable feature of both experiments was the low level of urea N excretion by the pregnant ewes in late gestation, at low protein intakes. It would appear that when energy intake is adequate the decrease in urea N excretion associated with pregnancy is a direct result of an increased N requirement for maternal and/or foetal growth.

Thirteen field experiments were made during 6 years on seed-potato growing farms in south-east Scotland, comparing three rates, 70, 140 and 280 kg K/ha as potassium chloride and four rates of 0–54 kg Mg/ha as kieserite in 3 × 4 factorial experiments.

More than 70 kg/ha of potassium increased total yield only at one site, which had a recent history of low K application and very low available K. Yields were decreased by more than 70 kg/ha of potassium at three sites in a season with abnormally dry conditions just after planting. Applied magnesium had little effect on total yield.

Extra potassium increased ware yield but decreased seed yield, both consistently, probably because the fertilizer damaged some stolons at or before tuber initiation and fewer tubers developed. The ware/seed ratio was generally increased by extra K, but after the dry spring this ratio was unaltered or reduced. Applied magnesium had little effect on the ratio.

Our results suggest that the present rates of K fertilizer, used for commercial seed-potato crops (114–138 kg K/ha) in south-east Scotland are excessive, and a much lower rate of approximately 70 kg K/ha would be adequate except on very low K sites.

The project involved two breeds of Indian goats – Barbari and Jamunapari, three levels of energy and three levels of protein, making a total of 18 treatments. There being no specific recommendations for goats, the high, medium and low levels of energy (T.D.N.) and protein (D.C.P.) represented 125, 100 and 75% of Morrison's standard for sheep, respectively. A total of 97 Barbari and 87 Jamunapari does were allocated to the nine ration treatments and were bred within the breed naturally. The rations comprised a concentrate mixture (linseed cake and/or barley grain), dry roughage (gram bhusa), greens, mineral and trace-element mixtures and common salt. The effect of nutrition on reproductive performance, as revealed by the five and four kiddings completed in the Barbari and Jamunapari was as follows:

While the first kiddings did not indicate a sizeable effect, the subsequent ones showed a significant effect of nutrition. Almost all the does in the low-energy groups, irrespective of the protein levels, did not kid for the last kidding under reference.

The maximum percentage of twins was noted in high-energy-cum-high-protein (47·5%)and high-energy-cum-medium-protein (45·3%) groups of Barbari and Jamunapari respectively. The average twin-birth percentages, irrespective of nutrition, were 14·8, 37·3, 38·0 and 40·2 in Barbari and 9·0, 20·5 and 23·0 in Jamunapari respectively. Triplets, although rare, occurred within the Barbari but only one case occurred within the Jamunapari.

On average Barbari and Jamunapari had 2·0 and 1·5 kids per doe per year in the high-energy-cum-medium-protein group compared with 1·0 and 0·4 in the low-energy ones, respectively. Furthermore, high- and medium-energy groups had shorter intervals between kiddings compared with the low-energy ones.

The relationships between joint and carcass specific gravities and composition are examined and the prediction efficiency of equations relating these parameters tabulated. The problems of assessing carcass composition in large abattoirs are indicated. The use of the tenth rib sample joint in conjunction with a specific gravity estimation technique is recommended.

Experiments were conducted on 12 male growing calves of zebu cattle (Bos indicus) and buffalo (Bos bubalis) to study the effect of feeding wheat straw presoaked with water on the voluntary feed intake, digestibility coefficients of nutrients and volatile fatty acid concentration and production. The feed intake was improved significantly (P < 0·05) in both the species as a result of soaking. The digestibility of crude protein and crude fibre was depressed (P < 0·05), whereas the nitrogen-free extract utilization increased significantly (P < 0·01) on soaking of straw. The availability of digestible energy and metabolizable energy was also more as a result of water treatment of wheat straw. The production rates of total volatile fatty acids and acetic acid were higher in both the species fed on water-soaked wheat straw. It is concluded that pre-soaking of wheat straw for 1–2 h with ordinary tap water may give an overall beneficial effect in both zebu and buffalo calves.

Photosynthetic electron transport, osmotic volume changes and protein loss on osmotic shock were measured in isolated pea chloroplasts after treatment with a range of aldehyde concentrations at various temperatures and times. ADP+Pi-stimulated oxygen production was the most sensitive to inhibition by the aldehyde treatment. With suitable conditions, osmotic volume changes could be prevented and protein losses on osmotic shock reduced to about 1% of the control value, whilst NH3-uncoupled electron transport retained about 40% of its activity. Results showed that basal, ADP + Pi-stimulated and NH3-stimulated O2 production could be used together to indicate the extent of chloroplast fixation thus providing a way of assessing fixation in preparations where osmotic changes are difficult to measure.

Glutaraldehyde (M.W. 100) was found to be 60–80 times as effective as formaldehyde (M.W. 30), on a molar basis, in preventing osmotic volume changes and protein loss on osmotic shock.

The application of this work for the production of large amounts of glutaraldehyde fixed chloroplasts and of fixed herbage for use as a tool in nutritional studies in ruminant animals is discussed.

Grasses of widely differing maturity have been extracted by two chemical and two enzymic methods in order to prepare cell wall materials with low nitrogen contents. These methods involved extraction, with neutral detergent or phenol-acetic acid-water (1:1:1), or digestion with the proteolytic enzymes pepsin or pronase. Wide differences were noted between these methods with grasses at different levels of maturity, both in the nitrogen content of the residue and the actual yield of cell wall preparation. The more efficient of these methods for removing nitrogenous materials, namely neutral detergent extraction and digestion with pepsin and pronase, were also examined for their effect on the structural carbohydrate and lignin content of the cell wall. In all respects, a method involving incubation with the enzyme, pronase, gave the most satisfactory cell wall preparation.

Comparative slaughter was used to assess the effects of body-weight loss on Brahman cross (BX) and Africander cross (AX) steers of the F3generation with respect to gross dissected carcass composition and the distribution of these components over the dressed carcass. Animals were slaughtered at design body weights of 325, 341, 358, 374 and 390 kg, some while during positive body-weight growth (Group A), and others during weight loss from 390 kg at a rate of approximately 0–5 kg/day (Group B).

Gross composition was similar in the two breeds, irrespective of the body-weight loss treatment. Body-weight loss resulted in muscle and fat approximately reversing the path of development, while bone and fascia and tendon remained approximately constant. No evidence of proportionally early loss of fat and later loss of muscle was found. Of the fat components, kidney and channel fat showed the highest relative loss. The distribution of muscle was different between the breeds, the most statistically significant differences being that AX had heavier muscles around the spinal column and lighter shin muscles, at the same total muscle weight. Bone weight distribution differences also occurred, with AX tending to have lighter leg bones, at the same total bono weight. A breed difference in intermuscular fat distribution meant that the AX animals were earlier developing in the forequarter and later developing in the hind quarter in respect to its intermuscular fat, than the BX animals.

Body-weight loss affected muscle-weight distribution, the most marked effect being that the relative proportion of abdominal muscles fell during body-weight loss. Boneweight distribution was affected to a minor extent, the effects mainly being in the leg bones rather than the axial skeleton. The distribution of neither fascia and tendons nor subcutaneous fat was affected by the body-weight loss treatment, but the distribution of intermuscular fat was affected.

A mixed sward of grasses and clovers, previously established with adequate Ca, N, P and K on deep acid peat, was used for a factorial experiment to determine the amounts of nutrients required to produce herbage for conservation. The treatments consisted of all combinations of 0, 117and 234 kg N, 0, 29 and 58 kg P and 0, 156 and 312 kg K/ha, and their effects on the botanical composition of the sward, the yield and mineral composition of the herbage, and the nutrient status of the peat were measured over a period of five years. Three cuts were taken annually, one third of the N dressings being applied for each cut.

Tall fescue became the dominant grass species while cocksfoot persisted much better than either ryegrass or timothy. The proportion of clover in the sward was reduced to practically zero by applying N, but without N it was maintained at about 20% by applying K.

Yields of dry matter were greatly increased both by N and by K and there was a marked positive interaction between these two nutrients. Due to the marked suppression of clover by applied N there was no response to the first increment of N in 1959, but with this exception, 1 kg N/ha with adequate P and K produced between 15 and 30 kg dry matter/ha. The effect of K increased from 1958 to 1962, the first increment consistently producing most of the response. Applying P had little effect on yield until the fifth year when a significant response was obtained.

The mineral composition of the herbage varied during the season; the percentages of N, Ca, Na and Mg were generally higher in autumn than in early summer whereas the percentage of K showed the opposite effect.

The N, P and K treatments had large effects on the percentages of N, P, K, Na, Ca and Mg in the herbage and on the amounts removed in the crop. Without applied N, but with adequate P and K, percentage of N varied according to the amount of clover in the sward. With applied N there was less variation and the average percentage of N was about 1·7 with 39 kg N and 2·0 with 78 kg N/ha/cut. Percentage of P ranged from 0·14 to 0·54 and percentage of K from 0·5 to 3·5. Apparent recoveries up to 74, 65 and 96 % were obtained from the N, P and K treatments, respectively.

For continuous production by cutting and removing the herbage, a mixed sward containing clovers appears to require, without applied N, about 120 kg K/ha/year. With applied N, an additional 0·3 to 0·5 kg K/kg N appears to be needed. The amount of P required will depend mainly on the concentration desired in the herbage and on the rate of N used. To produce herbage with 0·3 % P in the dry matter about 15 kg P/ha/year, plus approximately 0·1 kg P/kg N applied seems to be needed; for 0·4 %P the corresponding quantities are about 40 kg P/ha plus 0·3 kg P/kg N applied.

The results of a field experiment on winter wheat are presented in which the effects of the soil physical properties produced by different cultivation systems were studied in relation to root development.

The extension rate of the seminal root axes was slower in undisturbed or shallow (5 cm) cultivated soil than in ploughed or deep (20 cm) cultivated soil leading to earlier lateral branching and the production of an effectively shallower seminal root system which persisted throughout the season. During the first four weeks after drilling the soil in the ploughed and the deeper cultivated plots was of lower bulk density and there were more pores of a diameter suitable for unimpeded root extension. It is suggested that seminal root development in uncultivated soils, which are less readily deformed than cultivated ones, is related to the probability of the extending seminal axes contacting pores of suitable dimensions.

The implications of shallower rooting are discussed and related to field experience with cereal crops drilled directly into uncultivated soils where success has consistently been achieved on free-draining, open-textured soils.

The weight of the ruminal mucosa of breeding Blackface ewes and its total DNA and RNA content rose after parturition to reach a peak at 45 days post partum. There were no constant significant changes with time in the concentration of the nucleic acids.

It was found that there was a positive correlation between the amount of food eaten during the final week of life and the weight of the ruminal mucosa and the length of ruminal papillae. The mitotic index of the ruminal epithelial cells was very variable but most of the higher values occurred between 7 and 80 days post partum. The mitotic index could not be correlated with the amount of food eaten in the week before slaughter, but high values were not recorded when the food intake of lactating ewes was restricted to that of non-breeding controls. It is suggested that the most likely explanation for these findings is that in the ruminal epithelium of lactating ewes fed to appetite, oell division occurred in waves or bursts.

Hyperkeratosis of the ruminal epithelium occurred in pregnant and control animals but regressed during lactation and reappeared in the post-weaning period. The inverse relationship between the hyperkeratosis and the rate of cell division is of great interest when considering the aetiology of ruminal disease.

Radiographs were taken, of the medially sectioned half heads and flesh-free mandibles of 32 pigs serially slaughtered between birth and 120 kg live weight. From these radiographs, measurements were taken of the length of the skull, the depth of the cranium, the length and depth of the brain cavity, and five separate measurements of the mandible. Observations were made of the changes in configuration of the skull as a whole including sinuses. The patterns of development and eruption of the deciduous and permanent teeth were examined. It is suggested that the elongation of the mandible and the maxilla necessary to accommodate the full permanent dentition, together with the increasing size of the frontal sinuses, has an important influence on the shape of the skull as a whole. The results are discussed in relation to other published descriptions of the chronological development of the teeth.

Fifteen intervarietal F1hybrids and their parents were evaluated in two field sward trials, representing three levels of management intensity each maintained over a 2-year harvest period. The trials were sown in different years and at different sites. Several hybrids exhibited significant levels of heterosis for total annual dry-matter yield – up to 5–5 % mid-parent and up to 3–6 % higher-parent heterosis. Within individual trials mid-parent heterosis up to 8% was found, while at particular harvests over 25% heterosis was not uncommon. Comparisons made of performance in swards, simulated swards and spaced-plant conditions showed that genetic differences found maximum expression in non-competitive conditions. This was greatly reduced in simulated swards and further suppressed in sown swards in the field. Expression of heterosis was highly specific to the conditions in which it was tested, although the two hybrids most heterotic as spaced plants were also significantly heterotic in field swards.

Pot-culture experiments were made with the rice variety IR-8 on a sandy clay loam soil to study the relative efficiency of urea, urea treated with nitrification inhibitors N-Serve and AM, AM-fertilizer, and slow-release nitrogen fertilizers IBDTJ, oxamide and N-enriched coal. N-enriched coal supplied very little nitrogen to rice and gave no more yield than the control. All other materials were superior to urea. Largest yield of rough rice and nitrogen uptake by rice was obtained with IBDU and AM-fertilizer. Compared with untreated urea IBDU, oxamide, AM-fertilizer and urea treated with N-Serve or AM left larger amounts of mineral-nitrogen in the soil after the harvest. In the case of nitrification inhibitors residual ammoniacal-nitrogen was more at the higher rates of inhibitors.

Results of a co-ordinated trial carried out at twenty-one centres indicated that the performance of growing pigs (20–90 kg) can be improved by supplementation of their diet with copper sulphate.

Three levels of copper supplementation were tested, 150, 200 and 250 mg Cu/kg diet. Though significant improvements were recorded on all three levels, the best performance and the highest increase in profitability were obtained with 250 mg Cu/kg diet. With increasing dietary intake of copper, the copper content of the pigs' livers increased markedly.

The melting-point of subcutaneous fat was lower in carcasses of pigs that were given supplementary copper sulphate in their diet.

Two clones of perennial ryegrass were planted along the radii of a fan in such a way that any group of four adjacent plants was approximately square, with spacings ranging from 3 to 30 cm. During the first year the amount of regrowth per vegetative plant was found to be related to the area available at the high densities, whereas at low densities there was little change in weight per plant with change in density. At high densities the number of tillers declined following defoliation, but at low densities it increased consistently. In the second year, the ratio of fertile to barren tillers was lower and ear emergence was later at high densities. Results indicated that the performance of the clones differed in each of three stages of regrowth. It appeared that early regrowth was better in the erect clone, but after the first week, and where the canopy remained open, the RGR of the prostrate clone was greater. In a dense sward the crop growth was greater in the erect clone indicating that better use was made of the available light.

Eighteen foetal sheep were used to study the relationship between suboptimal growth and linear size of skeletal units, dry weights of representative muscles and muscle histology. Foetuses with suboptimal growth caused by inadequate maternal nutrition and competition with other foetuses showed a decrease in skeletomuscular growth although allometric growth was not affected. A slight correlation (r =0·14, P < 0·005) existed between dry weight of the longissimus dorsi and mean minimum myofibre diameter. On morphological evidence, myofibre hyperplasia was thought to be complete by approximately 80 days gestation in all foetuses. Increases in the number of myofibres crossing mid-length transverse sections of the sartorius occurred after this time but were thought to be due to intrafascicularly terminating myofibres growing in length. Suboptimal muscle growth of foetuses in the latter third of gestation was thought to be associated with an inhibition of growth in length of intrafascicularly terminating myofibres.

Five selected clones of Lolium perenne were selfed and diallel crossed without reciprocals to produce 15 families. These families were grown in a replicated field trial for 2 years at four rates of applied nitrogen – 0, 225, 450 and 675 kg N/ha – per annum. The data recorded included dry-matter yield, number of fertile and sterile tillers per plant, mean dry weight per fertile and sterile tiller and total dry weights of fertile and sterile tillers. Conventional analyses of variance and diallel analyses were applied to the data as well as path analyses, used to examine the interrelationships between yield and the tiller characters.

The main effect of years was significant only for mean dry weights per tiller and dry-matter yield. Increasing the rate of applied nitrogen increased the number of tillers and yields but decreased mean tiller dry weights. Differences between progenies were due to both general and specific combining ability for most characters. Relatively high narrow-sense heritabilities were obtained for the tiller characters although there were differences between the two years.

The progenies achieved their yield through different combinations of tiller characters, some having large numbers of fertile tillers with medium dry weights and others having numerous sterile tillers with high dry weights. Although there was inconsistency in the interrelationships between characters, number of tillers was always more important in determining yield than mean dry weight per tiller.

The results are discussed in relation to the predictive value of tiller characters on yields and the implications for breeding programmes.

Swayback disease of lambs occurs widely in Britain, its incidence varying from year to year, but is usually most severe in lambs born in March and April after a mild winter. It is known to be related to a copper deficiency in both the ewe and the lamb, but not all copper-deficient owes give birth to swayback lambs. The disease can be effectively prevented by administering copper compounds to ewes in susceptible flocks at mid-pregnancy (Allcroft, Clegg & Uvarov, 1959).