Thin-layer chromatography and infra-red spectrosoopy were used to identify the components of technical Thanite. A method is developed for qualitative and quantitative determination using a gas liquid chromatograph (GLC) equipped with a flame ionization detector. Two major peaks, having retention times 1 and 5 min, were obtained. This was achieved using a glass column (15 × 0·3 cm), packed with diethylene glycol (1·5%) on chromosorb W, 60–80 mesh, at temperature range 70–170 °C. The results obtained by GLC showed that 33·7–55·8%, and 36·6–68·3% of the initial deposit of Thanite on cotton leaves degraded within 12 h from exposure to sunlight and ultraviolet irradiation respectively. One fifth of the initial deposit of Thanite on cotton leaves was lost after 24 h from spraying, then 70 % of the compound was dissipated after 3 days. Incubation of Thanite with rumen liquor at 39 °C for 24 h under anaerobic conditions resulted in degradation of 45–74% of the initial concentration.

Maize was grown for grain or forage on the same site at Woburn for 7 consecutive years. Yields were satisfactory and there were no serious pest or disease problems, provided the small plots were netted until young plants were established. Different rates of nitrogen fertilizer were tested with and without annual applications of a soil sterilant, dazomet. Average yields of grain (85% dry matter) and forage (dry matter) were respectively 4·5 and 8·8 t/ha with 50 kg N/ha and 5·0 and 9·5 t/ha with 100 kg N/ha. Without dazomet there was a further increase with 150 kg N/ha. Weather influenced the response to nitrogen, and the response to a split dressing of the highest rate was variable. Except for plots receiving the split dressing of N in 1973 and 1974 dazomet always increased yields: grain yields were increased on average by 1 t/ha and forage by 1·6 t/ha. Dazomet-treated plots had taller and heavier plants with more stems, leaves and nodal roots, but fewer seminal roots than untreated plots. Dazomet-treated plots also had fewer migratory nematodes and smaller and less varied root myoofloras. Most of these differences were greatest in the young crop and possible reasons for this ‘early boost’ are discussed.

Different seeding combinations and monocultures of sorghum forage, Abu Sabein, and legume forage, Lubia, were grown under irrigation on saline marginal lands for two seasons. Certain seeding combination treatinents, particularly (¾ Abu Sabein + ¼ Lubia), produced higher total D.M. than the higher yielding component, Abu Sabein, grown as a monoculture. This mixture treatment, together with some others, yielded more total crude protein than Abu Sabein alone. The seeding combination treatments influenced the pattern of D.M. distribution amongst different strata in the crop canopy. As the percentage of Lubia in the mixture increased, the D.M. of Abu Sabein tended to accumulate in greater proportions in the higher strata.

Hereford heifers were fed a diet (7·0 MJ ME/kg D.M.) containing 0·09 % phosphorus but complete with regard to other nutrient constituents. Only after 19 weeks wore the effects of subclinical aphosphorosis evident in the form of reduction in feed intake, cessation of weight gain, increased feed conversion and decreases in tho concentration of inorganic phosphorus in blood and saliva. Heifers supplemented daily with 12 g phosphorus sustained a weight gain of about 0–2 kg/day over 62 weeks as did other supplemented heifers whose feed intake was restricted to that of tho low phosphorus treatment. The effects of phosphorus supplementation were thus demonstrated without being confounded by concomitant increases in feed intake.

Phosphorus supplementation resulted in significantly lowered apparent crude protein digestibility and a slight increaso in cell wall digestibility.

The carcass composition of phosphorus-deficient heifers of lower body weight was similar to ad libitumand restricted-fed controls supplemented daily with an extra 12 g phosphorus. The skeleton of heifers fed a phosphorus deficient diet for 63 weeks contained 18·8% less ash than restricted-fed controls given an extra 12 g phosphorus daily, but not less than ad libitum fed controls. Supplements of phosphorus and energy had different effects on the weights and concentration of bone minerals in skeletal components. A phosphorus supplement increased deposition of phosphorus in head, feet and tail, limbs and vertebrae and increased phosphorus concentration in head, feet and tail, vertebrae, ribs 1–5 and ribs 10–13. Extra energy intake slightly increased phosphorus accretion only in ribs 6–9 but had no effect on its concentration in this and other skeletal components. Only one (40 weeks) of the six biopsy samples taken from the cortex of the 11th and 12th ribs during the course of the experiment reflected the effect of uncomplicated phosphorus deficiency. No treatment differences were found in biopsy samples taken at slaughter in spite of differences in rib 10–13 analyses. The implications of this are discussed as they relate to the use of this method to monitor the phosphorus status of cattle.

Mature Merino ewes (n = 320) were fed either maintenance (100% M) or 25% maintenance (25% M) rations from the day after mating until embryos were collected at either day 11 or 21 after mating. On the 4th day after mating 223 ewes were ovariectomized and given 5, 10, 15, 20 or 25 mg progesterone/day (intramuscular) until embryo collection. A further group of sham operated ewes (n = 54) acted as controls. Despite live-weight losses of 10·7 and 15·8% from mating to days 11 and 21 after mating respectively, ewes on 25% M rations showed no evidence that embryonic survival was influenced by undernutrition. The embryos from ewes fed 25 % M rations were significantly (P < 0·05) smaller than those fed 100% M (crown-rump measurements were 5·93 ± 0·139 mm and 6·39 ± 0·116 mm at day 21 after mating in the 25 % M and 100% M groups respectively). Development, assessed by formation of the first pharangeal lobe and the fore- and hind-limb buds, was significantly retarded (P < 0·05) in the 21-day-old embryos from the undernourished ewes. Embryo survival in ovariectomized ewes receiving 5 or 10 mg progesterone/day was significantly (P < 0·05) lower than in ovariectomized ewes receiving 20 and 25 mg progesterone/ day at day 11 after mating. Embryo survival at both days 11 and 21 after mating increased with increasing doses of progesterone. Ewes fed 25% M rations had elevated (P< 0·001) concentrations of peripheral progesterone compared with those fed 100% M. This occurred when the progesterone was derived from either exogenous or endogenous (ovarian) sources, dismissing the possibility that changes in secretion rates could account for these observed differences. Differences in embryo growth and development were not related to these variations in the plasma progesterone concentration. Undernutrition restricted both growth and development to 21 days of pregnancy.

The yield and chemical composition of Sabrina hybrid ryegrass and RvP Italian ryegrass were compared, with special reference to regrowth after defoliation in spring and early summer. Initial cuts were taken on 6, 20 April and 4. and 18 May; subsequently a conservation crop was harvested at either 5 or 7 weeks, and a second regrowth 30 days later. There were four fertilizer treatments. Tiller density, stem development and individual tiller dry weight were recorded in selected treatments.

At the initial cuts and in the conservation crops after the first three initial cuts, varietal differences in yield and dry-matter digestibility (DMD) were relatively small. In all other harvests, RvP was appreciably higher yielding than Sabrina, and it showed greater responses to fertilizer in all second regrowth harvests. The water-soluble carbohydrate (WSC) content of RvP was consistently higher than that of Sabrina in regrowth harvests; the DMD was higher in Sabrina.

In primary growth of the two cultivars, tillering was suppressed at the time of head emergence, but active tillering was resumed earlier in RvP, the later-heading cultivar. In RvP, tillers arising early in the regrowth periods attained head emergence within 5 weeks. In Sabrina there was a marked decline in head production during June, and an increase in the size of individual vegetative tillers.

In regrowth harvests both the yield and the % WSC were markedly reduced when drought conditions were most severe; the most marked varietal differences occurred at this time, both in terms of yield of dry matter and % crude protein responses to fertilizer treatment.

In the two cultivars the DMD of 7-week conservation crops harvested in late May was at least equal to that of 5-week crops harvested later during drought conditions. A distinctly more advanced stage of development was attained in the earlier, heavieryielding crops.

The growth, development and yield of pigeon pea (cv. Cita-1) grown at three population densities of 27 000, 55000 and 83000 plants/ha were evaluated in two field trials during the growing season of 1980.

The results obtained showed that there was a progressive reduction in the developmentv per plant of vegetative characters, dry-matter accumulation and yield characters as population density increased. The calculated growth rates (net assimilation rate, crop growth rate, relative growth rate and leaf area ratio) were more or less the same at all population densities. The yields of seeds were 0·39 and 0·51 t/ha for the lowest population density, 0·43 and 0·65 t/ha for the medium population density and 0·58 and 0·75 t/ha for the highest population density for the two trials respectively.

It would seem, therefore, that under the prevailing lowland humid tropical conditions, a population density of at least 80000 plants/ha would be needed to ensure maximum productivity in the sole cropping of pigeon pea.

In two field trials in 1980, 33, 67 or 100% of the leaves on pigeon pea (cv. Cita-1) plants were removed either at the vegetative stage, the onset of flowering, or at the rapid pod-filling stage, in order to evaluate the effect of reduced assimilatory capacity on the growth and yield characteristics of the crop.

Reduction in the assimilatory capacity of the plant led to significant reduction in the vegetative growth, dry-matter accumulation and seed yield of the defoliated plants compared with the undefoliated control such that 33, 67 or 100% defoliation led to 15–55, 40–60 and 75–80% reduction in seed yield respectively, at both trials. Also, defoliation was more damaging to crop performance if carried out from the onset of flowering than at the vegetative stage. Thus, the seed yields of plants defoliated at the onset of flowering and the rapid pod-filling stage were 30–80 and 40–45 % lower than the yield from plants defoliated at the vegetative stage in both trials.

In a pot experiment and two field trials, the apical portionof the main stem of a dwarf variety of pigeon pea (ev. Cita-1) was removed at 3 or 7 weeks after sowing in order to evaluate the effect of apical bud removal, during the vegetative stage of growth, on the subsequent growth, development and yield of the crop.

The early loss of apical dominance led, in all cases, to increased vegetative development, reduced plant height (except in one of the field trials), higher dry-matter accumulation and more pods per plant, with the treatment effect on number of pods being related to the number of branches developed. The yield of seeds was significantly increased by the early loss of apical dominance in the pot experiment and second field trial.

The results therefore show that an early loss of apical dominance, as could happen with insect and pest attack, may not be damaging to the vegetative growth and seed yield of pigeon pea under the prevailing lowland humid tropical conditions.

Eight Morino lambs equipped with simple cannulac in the duodenum and terminal ileum were divided into two equal groups and used to study the net absorption of calcium, phosphorus and magnesium from concentrate diets supplemented by soyabean meal or by ensiled poultry litter. Mean net absorption of Ca, P and Mg for the soya-bean meal and poultry-litter treatments, respectively, was 31·6, 10·1; 34·7, 35·4; and 51·5, 41·6.

Irrespective of the diet, the small intestino was the major site for Ca and P absorption and the stomachs for the absorption of Mg. A large secretion of P in the stomachs was found with both diets; 8·50 and 9·32 g/day for the soya-bean meal and poultry-litter treatments, respectively.

The results of the present study support the view that poultry litter is a good source of P and Mg for sheep and can be used with deficient diets. Owing to the low rate of Ca absorption from the poultry-litter diet, it appears that at limited levels of inclusion, the extra added Ca would not be a detrimental factor.

The digestible energy (DE) and metabolizable energy (ME) content of eight samples of barley, eight of wheat, four of maize and two each of oats and rye were determined using growing gilts. The DE content of barley ranged from 15·35 to 15·89 MJ/kg D.M., from 15·15 to 16·42 MJ/kg D.M. for wheat and from 16·05 to 16·47 MJ/kg D.M. for maize. DE values for the two oat samples were 12·48 and 12·74 MJ/kg D.M. and 15–04 and 15–47 MJ/kg D.M. for the two rye samples. There was a significant correlation between DE and ME:

ME (MJ/kg D.M.) = 0·050 + 0·965 DE: r = 0·99; P < 0·001.

The ratio ME/DE was significantly influenced by crude-protein content:

ME/DE = 100–0·254 CP%: r = –0·77; P < 0·001.

ME values were also corrected to zero nitrogen retention (MEno) and to 30% nitrogen retention (MEN30). The effect of such corrections was expressed as MEN0/ME and MEN30/ME. Values thus obtained were 0·98 and 1·00 respectively for the pooled values for all cereals.

The data indicated that there was unlikely to be significant variation in the DE content of samples of the same cereal species, selected from commercial sources within the U.K. when evaluated under standardized experimental conditions.

Cell walls of three bloat-causing legumes, lucerne, red clover and white clover tended to be thinner and disintegrated significantly (P < 0·05) faster during cellulase digestion than those of two non-bloat-causing legumes, sainfoin (reported to contain tannins) and cicer milkvetch (reported not to contain tannins). Response to one generation of selection for speed of mesophyll cell-wall disintegration was marked in a diploid red clover (h2 = 0·66, 1·13) but slight in a tetraploid (h2 = 0·10, 0·13).

Field experiments consisting of three mulch treatments (no mulch, straw mulch and dust mulch) and six transpiration suppressants (no suppressant, kaolin, phenyl mercuric acetate, atrazine, mobileaf or alachlor and 2-chloro ethyl trimethyl ammonium chloride) were conducted under dryland conditions during the summer rainy seasons (July–November) of 1976, 1977 and 1978. Compared with no mulch, straw mulch increased yield in all 3 years, water use efficiency in 1977 and 1978, and uptake of N and of P in 1977 and 1978. Dust mulch had only a marginal advantage. Amongst transpiration suppressants, only kaolin and atrazine had a marked effect. Both these chemicals increased grain yield, water use efficiency and uptake of N and P, compared with no suppressant.

Results of visual and radiographic development of the mandibular caudal teeth were obtained from 135 cattle between 1 and 2 years old. Age ranges for each stage of tooth development were obtained. Using visual assessment of second molar intra-oral eruption the maximum age range before animals could be differentiated was 8 months (1 year 3 months from 1 year 11 months). Animals showed different stages of development in all six teeth using criteria based on resorption of the temporary premolar teeth and crown and root formation in the permanent premolar and molar teeth. The maximum age range before animals could be distinguished was 5 months (1 year 6 months from 1 year 11 months) and at all other ages the age difference before differentiation was less.

Simple series of trigonometric terms (Fourier series) give good representations of response curves including sigmoid curves and intersecting straight lines.

Three experiments were carried out to investigate factors which might affect the voluntary intake of effluents.

Effluent was introduced into the diet of pigs at rates of 25, 50 and 100 g D.M./day, replacing dry meal to maintain a constant amount of dry matter offered. The mean maximum daily intakes of effluent on the three treatments were similar indicating that, within this range, the rate of introduction of effluent had no effect on its potential maximum intake.

When solutions with differing concentrations of effluent dry matter were offered it was found that the intakes at the 20 and 10 g/kg concentrations were progressively lower than when tho concentration was 30 g/kg or higher. This suggested a physical limitation to the intake of effluent at low concentrations. A physiological limit may operate at concentrations of 30 g D.M./kg or higher.

In the third experiment daily air-dry meal allowances of 80, 90, 100 and 110 g/kg W0.75 were offered in addition to an ad libitum supply of effluent. The voluntary intake of effluent dry matter was not significantly affected by tho amount of meal offered and the total amount of dry matter consumed remained virtually constant.

A mathematical plant competition model developed by Currah (1975), and subsequently modified by the author, is briefly described. The model has two useful properties: (a) it can cope with complex irregular row spacing systems such as occur in commercial practice and (b) it can be ‘calibrated’ to the yield values at any site by using data from previous crops.

Parameter values of the modified model are calculated for both carrot and red beet crops. At least 70% of the variation in these data could be accounted for by fitting the model, a performance which was similar to, but never as good as, fitting analysis of ariance models. There were no systematic deviations between the fitted and observed values.

Previously estimated parameter values were used to predict mean root weights of carrot and red beet storage roots. Overall agreement between predicted and observed data was good, although some systematic deviations occurred.

The practical value of the modified version of the model and its strengths and weaknesses are discussed.

In an experiment on permanent grass at Rothamsted during 1975–9 fertilizer-N was applied each year either by injecting an aqueous solution of urea (supplying 250, 375 or 500 kg N/ha) in spring, or by broadcasting ‘Nitro-Chalk’ granules (supplying 100, 200, 300, 400 or 500 kg N/ha) in six equal dressings for each of six cuts.

Dry-matter production was largest on plots injected with urea through knives 30 cm apart, and more N was recovered from the injected than from the broadcast applications. Aqueous urea injected at the 60 cm knife spacing nitrified more slowly and persisted in the soil longer than urea injected at 30 cm spacing; this persistence caused grass to grow more uniformly throughout the season, but yields were less. Injecting the nitrification inhibitor sodium trithiocarbonate (STC) with the aqueous urea postponed N uptake much less than doubling knife spacing, but the inhibitor substantially diminished percentage N03-N in harvested grass.

In spring 1977 individual plots were split to measure N residues. Half-plots thus received N at the specified rates, either in 4 successive years (1975–8) or in two pairs of successive years (1975 and 1976; 1978 and 1979). In 1977 urea injected in the 2 previous years gave large residual effects, which were increased by STC and also by injecting in bands 60 instead of 30 cm apart. Broadcast ‘Nitro-Chalk’ had much smaller residual effects. In 1979 residual effects of N applied in the 4 previous years were apparently small, regardless of the method of application, because clover became abundant on plots not given N.

In 1978 dry-matter production was smaller where N had been given each year during 1975–8 than where N was withheld in 1977. Analysis showed this was caused by a shortage of potassium. This effect was most pronounced where 375 or 500 kg N/ha had been injected in bands 60 cm apart.

The results showed that a single, injected application of aqueous urea increased yields of dry grass as effectively as equivalent repeated dressings of ‘Nitro-Chalk’.

Proximal colons taken from lambs up to 3 weeks after birth were shown to transport both sodium and chloride from lumen to blood when incubated in vitro.

Sodium transport fell into three phases during postnatal development. The first covered the period from birth to 3 days of age when sodium transport was high and equal to that calculated from measurement of short-circuit current. The second was seen in 5- and 7-day-old lambs where the short-circuit current was low and the net transport of sodium was negligible. The third was seen in 2-3-week-old lambs where sodium transport was high, but the short-circuit current was low.

Chloride absorption by colons taken from 1-day-old lambs appeared to be in exchange for an anion, possibly bicarbonate. Chloride absorption by colons taken from 3-week-old lambs appeared to be electrogenie or coupled directly to the transport of sodium.

A possible explanation for the failure of electrolyte absorption by colons taken from 5- and 7-day-old lambs is discussed.