A physical form of “ropiness” in milk has been described and shown to be due to the formation of thin films of casein and (or) lactalbumin at the milk-air interface.

The “ropes” are a form of the “mechanical surface aggregates” of Ramsden and may occur on appropriate surfaces, such as ordinary farm coolers whenever the rate of flow, the temperature and the acidity conditions are favourable.

A modification of Ramsden’s method demonstrating the formation of mechanical surface aggregates, in an hitherto unobserved form, has been described, viz. horizontal glass tubes in parallel which are especially suitable for opaque fluids.

The condition appears to be identical with that described by Aekma and Brouwer(2) who showed the occurrence of corpuscles in milk after violent agitation. These corpuscles probably consist of thin films of solid protein which as in the cases described by the author have formed at the interfaces of air bubbles and milk.

The phenomenon has been shown to be of importance in handling dilutions of milk in the course of bacterial enumeration.

A technique was developed for the continuous retrograde perfusion of the muscle of the right crus. The hemidiaphragm was perfused for 3 h with a semi-synthetic medium, containing fresh sheep erythrocytes. The metabolic integrity of the perfused muscle was examined. Visual appearance was satisfactory. Perfusion pressure remained constant throughout the perfusion period. An adequate perfusate flow rate (approximately 8 ml/min) was maintained over the perfusion period. Perfusion pressure and flow rate were proportional. Perfusion was complete as indicated by staining with dye and by latex casts of perfused vessels, but there were indications of heterogeneity of perfusion (the dorsal and ventral ends of the organ). Histological changes following perfusion were minor, and the perfused muscle appeared normal under an electron microscope, with the exception of a loss of cytoplasmic granules. Increases in muscle water content (2·3%) and extracellular space were small. Muscle adenosine triphosphate (ATP) and adenosine diphosphate (ADP) concentrations declined significantly following perfusion but ATP/ADP ratio increased significantly. Muscle glycogen content was maintained only when exogenous insulin was added to the medium; significant losses occurred following perfusion in the absence of insulin. Only 2–3% of tissue glutamate-pyruvate transaminase and glutamate-oxaloacetate transaminase were released into the medium over the perfusion period, but approximately 20% of muscle potassium was lost. Lactate was produced by the perfused sheep hemidiaphragm at a rate higher than those that have been reported for the perfused rat hind-limb, but lower than those reported for perfused rat diaphragm. Ratio of lactate/pyruvate produced by the perfused muscle was also higher than values reported for the rat hind-limb. The perfused muscle actively incorporated labelled amino acids into protein, but estimated protein synthetic rate in the absence of exogenous insulin was only approximately 50% of rates reported for diaphragm muscle in vivo. While the isolated, perfused sheep hemidiaphragm shows several deficiencies, it does provide a useful method for the study of ruminant muscle metabolism under carefully controlled conditions in vitro, and overcomes many of the disadvantages of other techniques that are currently available.

Quantifying reasonable crop yield gaps and determining potential regions for yield improvement can facilitate regional plant structure adjustment and promote crop production. The current study attempted to evaluate the yield gap in a region at multi-scales through model simulation and farmer investigation. Taking the winter wheat yield gap in the Huang-Huai-Hai farming region (HFR) for the case study, 241 farmers’ fields in four typical high-yield demonstration areas were surveyed to determine the yield limitation index and attainable yield. In addition, the theoretical and realizable yield gap of winter wheat in 386 counties of the HFR was assessed. Results showed that the average field yield of the demonstration plots was 8282 kg/ha, accounting for 0.72 of the potential yield, which represented the highest production in the region. The HFR consists of seven sub-regions designated 2.1–2.7: the largest attainable yield gap existed in the 2.6 sub-region, in the southwest of the HFR, while the smallest was in the 2.2 sub-region, in the northwest of the HFR. With a high irrigated area rate, the yield gap in the 2.2 sub-region could hardly be reduced by increasing irrigation, while a lack of irrigation remained an important limiting factor for narrowing the yield gap in 2.3 sub-region, in the middle of the HFR. Therefore, a multi-scale yield gap evaluation framework integrated with typical field survey and crop model analysis could provide valuable information for narrowing the yield gap.

Zinc deficiency is a common nutritional problem in calcareous agricultural soils, resulting in reduced crop yield and performance. The effects of zinc sulphate (0 and 40 kg/ha) on seed yield, its components and seed element contents of 21 wheat cultivars were investigated. Zinc sulphate application increased plant height, leaf area index (LAI), flag leaf area, biomass, spike length, number of seeds per spike, seed weight and harvest index (HI). The increase in HI indicates the greater effect of zinc on seed production compared to plant biomass. In most of the cultivars, zinc sulphate application decreased the content of phosphorus and nitrogen in seeds and increased the content of iron and potassium. The cultivars showed significant differences in all the traits measured, indicating the existence of genetic diversity in the cultivars studied. In the second year, which was hotter and drier than the first year, zinc sulphate application reduced the damage caused by drought and heat stress and improved seed yield and quality. The regression fit showed that newer cultivars had lower yields in unfertilized conditions compared to old cultivars and showed their superiority in zinc fertilized conditions. It seems that the newer varieties require more fertilizer because they have been bred on fertile soils.

This group, which is concerned with the applications of mathematics to agricultural science, was formed in 1970 and has since met at approximately yearly intervals in London for one-day meetings. The thirtieth meeting of the group, chaired by G. J. S. Ross of the Institute of Arable Crops Research, Rothamsted, was held in the Wellcome Meeting Room at the Royal Society, 6 Carlton House Terrace, London on Friday, 3 April 1998, when the following papers were read.

The objective of this research was to assess the adoption of circular agricultural practices as a tool to improve the recovery use efficiency of phosphorus (P) applied to tropical soils. Two Brazilian farms (1 and 2) that are under long-term no-till and cropped year-round with cover and/or cash crops were used in this study. Soybean, maize and common bean were grown during the summer season (October–February), followed by wheat, common bean and maize during the winter season (February–August). Brachiaria ruziziensis was intercropped with off-season maize. Farm 1 also grew sweet potatoes in rotation with grains. In the integrated crop–livestock system, the leftovers from the silos and crop residues were used to feed beef cattle, while the residues not used in the confinement were turned into compost and applied in the production fields. During the last 3 years, 80 (farm 1) and 71 (farm 2) kg/ha/year of P-fertilizer was applied to meet the demand of the different crops and 56% (farm 1) and 58% (farm 2) of P-fertilizer was exported through the crops and livestock. P-recovery represented more than 50% on both farms. Around 60% of the P consumed by animals was excreted in the form of faeces and urine and the animal manure was used to produce organic compost. Therefore, most of the P consumed by the livestock was returned back to the field to serve as organic fertilizer. This study showed that circular agricultural practices can enhance P-recovery.

Cultivated pastures in southern China are being used to improve forage productivity and animal performance, but studies on grazing behaviour of goats in these cultivated pastures are still rare. In the current study, the grazing behaviour of Yunling black goats under low (5 goats/ha) and high (15 goats/ha) stocking rates (SRs) was evaluated. Data showed that the proportion of time goats spent on activities was: eating (0.59–0.87), ruminating (0.05–0.35), walking (0.03–0.06) and resting (0.01–0.03). Compared with low SR, goats spent more time eating and walking, and less time ruminating and resting under high SR. Goats had similar diet preferences under both SR and preferred to eat grasses (ryegrass and cocksfoot) more than a legume (white clover). The distribution of eating time on each forage species was more uniform under high v. low SR. Bites/step, bite weight and daily intake were greater under low than high SR. Results suggest that the SR affects grazing behaviour of goats on cultivated pasture, and identifying an optimal SR is critical for increasing bite weight and intake.

1. ‘Wet’ soil plants had greater tiller and leaf number, and were also taller than ‘dry’ soil plants.

2. The straw and grain dry weight, and grain weight as percentage of straw weight, were greater in ‘wet’ soil plants than in ‘dry’ soil ones.

3. Wet soil hastened the time of ear emergence.

4. Increasing the phosphate supply, on the whole, tended to increase the tiller and leaf number, weight of straw and grain and also hastened time of ear emergence.

5. Under ‘wet’ soil conditions high phosphate application is not necessary.

6. The yield of grain at high phosphate level of plants grown on ‘dry’ soil is significantly lower than the yield from those grown on ‘wet’ soil with low phosphate application. This suggested that under ‘dry’ soil conditions availability of nitrogen, as well as of phosphorus, is a limiting factor.

In a study of two coarse wool breeds (Awassi and Karadi) and their reciprocal crosses, data were obtained on the mean fibre length, mean fibre diameter, fibre type ratio, medullation and on the effect of some environmental factors on these traits. Reciprocal crosses showed intermediate values, in growth rate of fibres, percentages of fibre types and medullation, between those of the parental breeds. Sex exhibited a significant effect at weaning only, on fibre length. Heterosis in fibre length, at the two ages, was small and negative. Maternal influence on fibre length was small and not significant. Fibre length in Karadi sheep showed the highest frequency of bimodal distribution whereas Awassi showed the lowest. Awassi × Karadi was closer to Karadi and Karadi × Awassi had greater affinity to Awassi in the frequency of samples showing bimodal distribution.

Reciprocal crosses had larger diameter, at weaning, than those of the parental breeds. At 1 year of age they assumed an intermediate position between the pure bred parents.

At weaning, the two reciprocal crosses showed a highly significant heterosis in fibre diameter; its value decreased with advancing age and it showed no significant effect at 1 year of age.

Maternal influence on fibre diameter was very small and not significant.

Karadi × Awassi and Karadi samples had the highest percentage of samples showing bimodal distribution of fibre diameter.

Samples with bimodal distribution of both length and diameter, indicating two coats, had the highest frequency in Karadi followed by Karadi × Awassi; Awassi showed the lowest value.

Percentages of fine, coarse and kemp fibres were significantly affected by breed and age of dam. Type of birth showed a significant effect only on percentage of coarse fibres.

Karadi wool might be more suitable for carpet manufacturing. It excelled the other groups in the bimodal distribution of both length and diameter as well as in medullation. Cross-breeding increased the bimodality of fibre distribution.

Eight cultivars of peas (Pisum sativum L.) were evaluated for six traits in a diallel experiment using regression coefficients, correlations and combining ability estimates. Regression coefficient was high, indicating large additive effects for 100-grain weight. Yield was significantly and positively correlated with plant height, number of pods per plant and 100-grain weight, indicating that selection for either of these would result in higher yield. The best index of yield among the traits studied was number of pods per plant. Significant general combining ability (GCA) variances and specific combining ability (SCA) variances were observed. GCA variances were larger than SCA variances except for yield, suggesting predominance of additive gene effects.

1. Individual birds have a characteristic date for the termination of the egg laying cycle.

2. The date of cessation of production at the end of the pullet year is not a reliable indication of the bird's potentiality in this respect.

3. The longer the birds are retained the greater is the chance of distinguishing the true date.

4. Individual dates for the termination of the cycle occur at so many points throughout the total range (from July to December) that this must either indicate a multiple factor situation or that the genes involved show a considerable range of expression.

As part of an ongoing investigation of ovine neuroendocrine mechanisms relating to photoperiod and eventually to wool growth, the diurnal variation of depilation force (an index of the strength of attachment of wool fibres to the skin of sheep) was investigated in Merino wethers and Border Leicester Merino ewes. Circadian rhythms were demonstrated in depilation force in both ewes and wethers. Further experiments were performed to investigate circadian endocrine rhythms which may have some bearing on the observed rhythm in depilation force. Circadian rhythms 180° out of phase with the depilation force rhythm were observed in plasma cortisol concentrations and in pineal serotonin N-acetyltransferase activities in Merino wethers.

The relationship between rate, spray interval and number of applications of Decis for pest control in cow pea was investigated. In 1978 and 1979, neither the rates nor the interaction effects were significant in grain yield when 12·5 and 25·0g a.i./ha of Decis were applied three times weekly or twice at intervals of 10 or 14 days.

Further trials in 1980 showed that for the contro l of thrips (M. sjostedti), rate, interval and number of applications were significant for samples at 49 days after planting and beyond, suggesting that the residual life of Decis is about 10 days. Three applications were significantly better than two for lowering the population of C. tomentosicollis and the number × interval interaction was also significant. The number, rate and interval were significant without interaction effects for shrivelled pods caused by all hemipteran pests. In all the trials in 1980 and 1981, damage by the pod borer M. testulalis was low. Rate and number × interval interaction were generally significant but no differences were observed in grain yield. However, in 1980 the higher rate and three applications gave better quality crop, resulting from less hemipteran damage.

An analysis of cost–benefit of the trial showed that 12·5 g a.i./ha gave higher returns than 25 g, as did two applications than three, but the trend in the spray interval was less consistent.

The response of three spring cultivars of oilseed rape to five levels of nitrogen fertilizer (0 to 200 kg/ha) was studied during 1978–9 (Scarisbrick, Daniels & Alcock, 1981). Sampling problems, practical difficulties of measuring yield components, and the high co-efficients of variation for these data were discussed. During the course of further investigations on the winter cultivar Jet Neuf (established on approximately 75000 ha in the U. K. during 1980–1) within-plot variability for plant weight was assessed in order to indicate the size of sample necessary to compare treatment means.

It has been found from controlled environment studies that high temperatures lead todepressions in milk production (Johnson, 1965; Hafez, 1968; McDowell, 1972). Under outdoor situations where all climatic variables may act simultaneously on the animal, responses may vary from the classical chamber studies.

Manufacturing properties and quality of Cheddar, Wensleydale and Cheshire cheeses made either with milk from cows treated with Sometribove, methionyl bovine somatotropin (BST), or with milk from untreated control cows were compared.

The source of milk did not affect manufacturing properties in terms of processing time. Renneting times for Cheddar cheese made from control milk and that made from milk produced by cows treated with BST were 57 and 55 min, respectively. Corresponding values for Wensleydale and Cheshire cheeses were 50 and 53 min and 49 and 46 min, respectively. The source of milk did not influence cheese composition in terms of moisture, fat, protein and salt. When cheeses were submitted to the National Grading Service, those made from milk produced by BST-treated cows were indistinguishable from those made from control milk. The total points scored (maximum 100) for Cheddar, Wensleydale and Cheshire cheeses made with milk from control and BST-treated cows were 89 and 88, 85 and 85, and 86 and 86, respectively.