The methods used for the determination of — log [] fall naturally into two groups:

(a) Electrometric, and

(b) Colorimetrie methods.

Electrometric methods were first introduced into analytical practice in 1897 by Böttger(l) who determined the neutral point in titrating acids with alkalis by using a gas chain; subsequent improvements were made by Hildebrand (16), Gumming and Gilchrist(10); Hasselbalch(15), W. M. Clark(6), Michaelis(19), Walpole(28, 29) and others. The method has been applied to the measurement of [] of biological fluids with considerable success*. It was first applied to the measurement of [] of soil suspensions by G. Fischer (12) in Germany in 1914 and subsequently in America by Sharp and Hoagland(23), and by Gillespie(13, 14) and his co-workers.

In the preceding paper, attention is drawn to the fact that wide differences occur between individual animals in their capacity for converting food into fat. It is shown, for instance, that an individual ox on a fattening diet may increase in live weight as much as 3 lb. a day or as little as 1 lb. a day. The former would give out 17,000 Cals., and the latter 22,000 Cals. per day, a difference in heat evolution of about 25 per cent.

Eighteen trials were carried out to test factorial combinations of N, P, K and Na fertilizers on sugar beet over 3 years on deep light peat soils in the area surrounding the Wash. The average yield responses to all fertilizers were very small, and only rarely profitable, except to sodium. Nitrogen increased yield on a few sites, but there was no obvious way of distinguishing these, and on average there was no justification for using this fertilizer, which depressed sugar percentage. The difference from earlier work, which showed good responses to P and K, is ascribed to repeated heavy dressing of fertilizer given to these soils during the last two decades.

The rate at which organic matter added to soils decomposes under temperate conditions seems to have been little studied. It depends, as Russell (1950) remarks, on the soil aeration, the calcium supply, and the temperature, and tends, in an arable soil, to an equilibrium value depending on the crop rotation practised for a given soil under given climatic conditions. And while this equilibrium value is lowest for a rotation containing a high proportion of wide-spaced intertilled crops or cultivated fallows, it increases with crops of small grains or grass. The results at Rothamsted, Broadbalk Field, as judged by the nitrogen content, show that this equilibrium value with no organic additions has remained almost constant from 1865 to 1945 and similarly, at a higher level, where 14 tons of farmyard manure are applied annually, has remained constant from 1914 to 1945.

Nine individually penned Finnish Landrace x Dorset Horn ewes with a mean litter size of 2·33 were offered a diet containing 63% digestible organic matter (DOM) and 13% crude protein in the dry matter at a daily intake of 0·82 kg DOM (1·3 x maternal maintenance) from 95 to 110 days of gestation. On day 111 DOMI was abruptly reduced to either 0·67 kg (T1, 0·54 kg (T2) or 0·36 kg (T3)/day and kept at these levels until a few days pre-partum.

Daily N balance before food restriction was 4·9 ± 0·51 g/day. During the periods 3·9 (S1), 11·17 (S2) and 19·25 (S3) days after food restriction daily N balance was 2·8, 2·8 and 3·6 g for θwes on T1, 1·0,1·0 and 0·8 g for those on T2 and –4·1, -4·0and -4·0 g for those on T3. Total lamb birth weight was 8·0, 7·2 and 6·5 kg for treatments T1, T2 and T3 respectively. Using regression analysis it was calculated that plasma glucose concentration in late pregnancy for ewes with a total lamb birth weight of 8 kg fell below the pre-restriction value of 52 mg/100 ml when daily DOMI was reduced to 747 g. At this intake the plasma FFA concentration was 585/i-equiv./I compared with 288 before food restriction. Corresponding values for daily N balance were 5·1 and 4·9 g. A reduction in daily energy intake below 0·75 kg DOM resulted in a rapid decrease in plasma glucose and N balance, the latter being proportional to the increase in the concentration of plasma FFA. The mean daily loss of N from the maternal body was estimated to be 0·4, 1·6 and 6·1 g for treatments T1 to T3 respectively during the period of food restriction.

The cause of variation in the live-weight increase of animals on experiment has been further investigated. It had been shown previously that varying food intakes and initial weights-inherent drawbacks of the group-feeding method-accounted for much of this variation. When these two factors are rigidly controlled small differences in live-weight gains are still obtained. Evidence is presented to show that the basal metabolism and the digestive capacity of animals are for all purposes the same, and cannot account for any great part of the residual variation.

Grain production potential is mainly influenced by agroclimate and land use. In the present study, substantial regional differences associated with the impact of climate change were found (i.e. the degree of climate-related impacts varied among regions). Currently, there is an urgent need for effective responses and adaptations to different agricultural districts and agricultural production modes. Therefore, the aim was to examine ecotones and explore trends and influential factors associated with grain production potential change. Using the Global Agro-ecological Zone model, the grain production potential of West Jilin, China under different conditions during various years were estimated, considering meteorological, soil, topographic, land use and other data. The results showed that total grain production potential (TGrPP) of West Jilin increased continuously from 1976 to 2013. The average annual increase in TGrPP was higher in period 1 (1976–2000) than period 2 (2000–2013). In period 1, grain production potential was influenced mainly by irrigation percentage changes, followed by land use change. The conversion of grassland to farmland was the most important land use change factor that was associated with increased grain production potential. Climate change affected grain production potential in period 1 negatively. In period 2, climate change had the largest impact and land use imparted the smallest effect on grain production potential. Finally, the decrease in irrigation percentage resulted in reduced grain production potential.

The differential effect of subclinical helminthosis on digestion and nitrogen metabolism in 1-year-old Brahman x Hereford/Shorthorn cross and British (Hereford/Shorthorn cross) steers was investigated.

When helminths were present, the British steers had lower digestibilities of dry matter and nitrogen, lower nitrogen balances, and higher dialysable faecal nitrogen, than had the Brahman cross steers. There were no breed differences in plasma gastrointestinal leakage (estimated by Cr labelling of plasma proteins), plasma content, total plasma protein, plasma protein half-life or plasma urea.

When helminths were eliminated, plasma gastrointestinal leakage was reduced, and plasma content and total plasma protein were increased. These changes were relatively larger in the British steers. The Brahman crosses had lower plasma protein concentrations and higher plasma urea concentrations than the British steers. Plasma protein half-life was unaffected by parasites.

The breed difference in the haematocrit was not affected by the presence or absence of helminths.

Concentrate diets supplemented with 5, 20 and 40% high- and low-quality hay were given ad libitum to British Friesian steers from 9 weeks of age to slaughter.

The performance of the animals was studied over 91 kg weight ranges from 91 to 363 kg live weight and from 9 weeks of age to slaughter. In the whole experimental period the daily live-weight gain was significantly greater on diets containing high-quality hay. There was also an increase in the daily live-weight gain in each of the weight ranges studied on diets supplemented with high-quality hay but this increase was not significant at the stage of growth from 272 to 363 kg live weight. As the level of concentrate in the diet increased there was a significant increase in the daily live-weight gain at each stage of growth studied and over the complete experimental period.

The mean feed conversion ratio was greater for diets containing low-quality hay. Except during the stage of growth from 272 to 363 kg live weight the proportion of hay in the diet significantly affected the mean concentrate conversion ratio. With increasing levels of hay in the diet there was a significant increase in the total dry-matter conversion ratio.

The conversion ratio of metabolizable energy was also increased on diets containing low-quality hay. The proportion of concentrate in the diet significantly affected the conversion ratio of metabolizable energy at all stages of growth studied.

There were significant differences in the killing-out percentages, weight and contents of the reticulo-rumen and the omasum plus abomasum expressed as a percentage of empty body weight, with increasing levels of hay in the diet. These measurements were not significantly affected by the quality of hay in the diet.

Indirect measurements of carcass composition indicated that the level of hay in the diet tended to affect the amount of fat in the carcass but the amount of lean was similar at the different ratios of concentrate to hay. The ratios of the weight of separable lean to the weight of separable bone in the 9–10–11th rib cut were similar at different levels of hay supplementation. The organoleptic appraisal of sample joints indicated that carcass quality was satisfactory.

The yield of crops in the low rainfall areas of eastern Kenya has been shown to vary within each season according to the crops grown in preceding seasons. This phenomenon of crop sequence was associated more especially with the amount of soil nitrates remaining at all depths in the soil than with the amount of water that may be left. The quantity of nitrates left by a crop was generally related to its vegetative bulk, its rooting habit and duration on the ground, and increased as the crops were ranked in the order: local maize, short-term maize, silage maize, beans and fallow. The beneficial effect of a bean crop or a fallow was reflected in a third crop when the intermediate crop had a low nitrogen requirement.

The persistence of the relative differences in the nitrate levels in the soil would seem to be due to their low mobility under leaching.

The increase in yield of a crop was shown to be due to the more rapid development of the crop when nitrate supplies were more plentiful. When the duration of the rains was short the earlier, more abundant flowering resulting from the rapid growth gave better grain set, and hence greater and more reliable yields. When crops matured in dry weather the availability of soil nitrates at depths of up to 4 ft had a positive influence on yield.

Although rainfall was the main determinant of yield within each season, the use of fallowing to store water from one season to the next was inefficient. Similar amounts could be held in cropped land if late rains occurred. If early rains were plentiful the benefit of stored water could be lost by the thorough wetting of the soil profile.

To investigate the effects of soybean isoflavone (SI) on immunity in infectious bursal disease virus (IBDV)-infected broilers, chicks were fed the same basal diet supplemented with 0 (non-infected control), 0 (infected control), 10, 20 or 40 mg/kg SI for 44 days. At 21 days old, chickens were inoculated with bursal infectious dose causing 50% morbidity of the IBDV BC 6/85 strain by the eye-drop and nasal route (except for non-infected controls). Results showed that, over 1–23 days post-infection (dpi), there was a significant interaction between SI supplementation level and time: high-level SI supplementation increased peripheral T lymphocyte proliferation, percentages of CD3+, CD4+ and CD8+ T lymphocytes, CD4+ to CD8+ ratio, serum concentrations of IgA, IgM and IgG, and IBDV antibody titres. Except for serum IgA and IgM, these variables increased over time with far higher values at 23 dpi than earlier. Compared with non-infected controls, IBDV inoculation decreased peripheral T lymphocyte proliferation at 3 dpi, percentages of CD3+, CD4+ and CD8+ T lymphocytes, and serum IgG, IgM concentration at 23 dpi, and increased IBDV antibody titres at 7, 15 and 23 dpi. Supplemental SI quadratically increased peripheral T lymphocyte proliferation, CD4+ to CD8+ ratio and serum IgA concentration at 3 dpi, percentages of CD3+, CD4+ and CD8+ T lymphocytes at 3 and 23 dpi, and serum IgM concentration and IBDV antibody titres at 23 dpi. These results indicate that dietary SI improved cellular and humoral immunity of IBDV-infected birds and may enhance resistance of Yellow-feathered broilers to infectious diseases.

When this investigation was begun in 1929, the conception of intensive grassland management, involving rotational grazing and the liberal use of manures, including artificial nitrogenous fertilizers, was just coming into prominence in this country. It had become necessary to secure information about the improvement of yield and composition of herbage that could be brought about by such a system of management, since somewhat extravagant claims were being made for the magnitude of the effect of sulphate of ammonia and other soluble nitrogenous manures on the yield and composition of pastures.

Forty-two Persian Blackhead ewes were used to investigate the effect of three prenatal planes of nutrition 6 weeks before lambing on birth weights and weights at 4 and 12 weeks after birth of their progeny. Nutritional regimes were: good grazing with concentrate supplement (high), good grazing without supplement (medium) and poor grazing without supplement (low). Pastures used were rotationally grazed Pangola grass. High-plane ewes gained significantly more weight during the last 6 weeks of gestation than ewes of the other two groups. Ewes nursing twin lambs lost significantly more weight than ewes nursing singles during the first 4 weeks of lactation. Birth weights of male single lambs and lambs from mature ewes were significantly affected by the prenatal plane of nutrition of the ewe. Lambs from mature ewes weighed significantly more than lambs from maiden ewes and male lambs weighed significantly more than females. Live-weight gains to 4 weeks were significantly affected by prenatal plane of nutrition in all cases. Type of birth was an important factor affecting growth rate and maturity of the ewe less so. Male lambs gained more weight than females during this period. Similar tendencies were apparent during the growth period of 4–12 weeks after birth although rate of gain was lower.

The results of a number of experiments carried out at Hillsborough on the growth of chickens, covering two seasons and involving 45 groups of 30 to 100 chickens, are discussed with particular reference to the variability of the live weights. It is concluded that the weights of cockerels or pullets taken separately should not show a standard deviation very much greater than 15 per cent. of the mean weight for the group, unless the experimental treatment or other conditions have seriously interfered with the rate of growth. It is pointed out that comparisons of mean weights and of standard deviations may be misleading unless cockerels and pullets are considered separately. Smallest significant differences between the mean weights of groups are tabulated for standard deviations of 15 per cent., 17·5 per cent, and 20 per cent., and for groups of 10 to 100 birds.

Growth and digestibility trials were conducted to investigate responses of young cross-bred sheep to alkali-treated straws and supplements. Oat and wheat straws were coarsely milled, sprayed with NaOH solution and then sprayed with a solution containing N, S, P, Cu and Co, and mixed with powdered limestone. The treated straws were fed ad libitum with no supplement (0) or with 150 g/day of either cotton-seed meal (CSM) or whole barley grain (B). In a preliminary trial to study the effect of frequency of ort collection on intake of treated straw, consumption decreased (P < 0·05) when frequency of ort collection was reduced from once daily to once weekly. This was associated with an increase in the neutral detergent fibre content of the orts. During the growth trial, which lasted 105 days, intake of treated straw increased by 34%.

When no supplement was fed, digestibility of treated oat straw was higher (P < 0·05) and dry-matter intake lower (P < 0·05) than that of treated wheat straw. However, calculated intakes of metabolizable energy (ME) and measurements of growth and wool production were similar on the two straws (P > 0·05).

When supplements were fed, there was no effect on intake of the treated straws. Mean live-weight gains were 51·4, 80·2 and 77·3 g/day on treatments 0, CSM and B respectively (P < 0·01). This was associated with higher intakes of ME (P < 0·01) which accounted for 73% of the variation in live-weight gains. Mean clean wool growth was 7·6, 10·5 and 9·3 g/day on treatments 0, CSM and B respectively (P < 0·01). This effect was associated more with nitrogen (N) absorption than with ME intake (80 and 48% of the variation in wool growth respectively).

It was concluded that the treated straws provided sufficient nutrients for modest growth in young sheep, that the supplements had no effect on intake of the treated straws and that additional live-weight gain and wool growth obtained by feeding CSM and B were associated with energy intake and nitrogen absorbed respectively.

The results of digestion trials carried out some years ago in this Institute have led to the belief that at least 6–7 lb. of young, leafy grass is needed to replace 1 lb. of ordinary pig meal in the rations of bacon pigs. More recent farm-scale feeding trials at the Harper Adams Agricultural College have given rise to the conclusion that no more than 1¼ lb. of young grass is required for this purpose when the pigs are receiving, in addition to the grass, a basal allowance of 2½ lb. of balanced meal per head per day.

The in vivo digestibility of soyabean integuments, rape integuments and dehydrated beet pulp was determined in sheep in the Centre de Recherches de Clermont-Ferrand-Theix, in 1985. Organic matter digestibility was 83·5, 59·6 and 85·0%, respectively, for the three feeds. The nylon bag method was used to determine the disappearance of dry matter (DM) in the rumen. After 72 h, 89 and 96% DM had disappeared for soyabean integuments and beet pulp, respectively, but only 61% for rape integuments. The DM disappearance rate was slowest (P < 0·05) for soyabean integuments. Microscopic examination showed that the different layers of the soyabean integument could be ranked in increasing order of resistance to microbial degradation as follows: parenchyma, aleurone layer, column cell layer, palisade layer and epidermis. The hilum area was the most resistant and the only one lignified. The cell layers of the rape integument could be ranked in increasing order of resistance as follows: epidermis, aleurone layer and palisade layer. The last was highly lignified and not degradable. Degradation of beet pulp was fast, occurring first in the parenchyma. The vessels resisted degradation but were only a small part of the feed. This study shows why beet pulp has a low fill value and allows high intake. The soyabean integument is very digestible and is degraded slowly, whereas almost half of the rape integument is made up of a cell layer that is not degradable.

An electrical method is suggested for reducing the friction between a metal surface and soil, or other moist substances; and its possible application to soil cultivation is considered.

Large reductions in friction were obtained in laboratory tests with a metallic slider moving over moist soil.

Preliminary tests in the field demonstrated that the draught of a plough was reduced by applying a current between the coulter and the mouldboard. The magnitude of the reduction obtained with this arrangement was too small to have immediate practical value, but the possibility of increasing the effect is discussed.

It appears that in ruminant animals one of the important effects of rumination is to decrease the particle size of the diet (Pearce & Moir, 1964; Gordon, 1968; Welch & Smith, 1969). This thesis is borne out by Gordon (1958) who showed that grinding a dried-grass diet markedly reduced rumination. Therefore, it is fair to assume that rumination behaviour is, at least in part, concerned with changing the physical properties of food, especially roughage, so that digestion and utilization are improved. Fujihara (1980) observed more efficient rumination in fresh-grass feeding than with hay in sheep given either fresh grass or hay alone, diets clearly differing in physical properties.

Wheat straw (WS), paddy straw (PS), farmyard manure (FYM) and water hyacinth (Eichhornia crassipes) compost (WHC) were applied at four rates and on four dates before transplanting to the rice cultivar Ratna, in a pot experiment at Kharagpur, India in the wet (first crop) and dry (second crop) seasons of 1985/86. Grain yield of the first crop increased significantly with increasing rates of FYM and WHC up to the equivalent of 15 t/ha but, with the application of WS and PS, the yield was greatest at 10 t/ha and decreased at 15 t/ha. On the other hand, yield increased appreciably when WS and PS were applied up to 30 days before transplanting (DBT) but, with FYM and WHC, such increases were less pronounced. The effect of higher rates (10 and 15 t/ha) was more pronounced with early application of organic materials (20 and 30 DBT). Residual soil fertility estimated by organic carbon and available N, P and K increased under all the organic materials, which favourably influenced growth and yield of the second crop grown without supplementary fertilization. The residual effect of increasing rates of WS and PS in increasing grain yield was significantly higher than with FYM and WHC.