Seven Angus steers were reared under controlled conditions, slaughtered and their carcasses dissected. Muscles, fat, bones, connective tissues and samples of the steers' diet were measured by gamma spectrometry and the concentrations of potassium and caesium-137 determined. Significant variations in the concentration of each element were found both within and between tissues. Average potassium concentration was about four times greater in the muscle tissue than in the remainder of the carcass. Caesium/potassium ratios were similar in both Caesium/potassium ratios were similar in both bone.

The main conclusions reached were as follows:

(1) The variations of potassium concentrations in muscle may impose limitations on the potassium-40 technique for estimating muscle content of the living animal for scientific purposes, though not necessarily for estimating commercial value.

(2) Differences between animals in caesium-137 content of muscle were fairly consistent over the different muscle groups, and bore some relationship to caesium intake. This indicates that it may be possible to utilize caesium content of a representative muscle to monitor caesium-137 fallout in remote regions of Australia, where milk is not produced.

The results of more than fifty estimates1 of herbage yield and ninety-seven analyses of chemical composition are presented in the first of several reports on nutritive evaluation studies of Panicum maximum (guinea grass). Effects of stage of maturity and season are discussed.

Herbage yield increased at an increasing rate with maturity, and was depressed by about 40 % in the dry season compared to the wet season. The most significant differences in chemical composition were a decrease in crude protein from 9·8 % to 6·6% and a corresponding increase in crude fibre from 32·1 % to 39·4% as the grass matured from about 2½ weeks to about 2½ months in age. An increased level of nitrogen fertilization resulted in crude protein content being nearly doubled and crude fibre somewhat reduced.

Fifteen digestibility trials were conducted in the wet, early dry, and late dry seasons in the Philippines. Panicum maximum (guinea grass) was fed at growth stages of 1–4 months to Bos taurus (Holstein), Bos indicus (Red Sindhi), and Bos bubalis (water buffalo) bulls.

Significant differences were shown between digestibility coefficients from water buffaloes and those from Holstein cattle, the former having a 5–7 % advantage in most cases. Ratios of volatile fatty acids in rumen fluid from the two species were not different. Separate tables of digestible protein, TDN and digestible energy values for guinea grass were computed for cattle and water buffaloes.

Leaf tensile-strength measurements have been made at Grasslands Division, D.S.I.R., over several years on a number of pasture grasses (Evans, 1964; Wilson, 1965). These measurements were prompted by the work of Beaumont, Stitt & Snell (1933) and Kneebone (1961), who attempted to relate leaf tensile strength to animal production value, and Edmond (1960, 1964), who considered that the toughness of pasture species may be a factor determining their tolerance to animal treading. The following is a description of the apparatus developed for this work and of the techniques employed.

1. Leaf strengths and cellulose contents of eight grasses grown as single spaced plants were compared over a period of 14 months. From some of the samples the proportion of sclerenchyma tissue in the leaves was compared with leaf strength.

2. The leaf strengths of individual plants were measured and the strengths of the six strongest and six weakest plants in each species compared with their cellulose contents.

3. There were significant differences between species, between seasons, and between regrowth ages within seasons in both leaf strength and cellulose content. There were also significant species × regrowth age interactions, particularly in leaf strength.

The effect of subsoiling an old arable clay-loam soil at Broom's Barn Experimental Station, Suffolk, was tested with a sequence of wheat, barley and sugar-beet crops, a lucerne ley and a sugar-beet test crop in the fourth year.

Subsoiling increased the yield of each crop each year, averages over 3 years were: wheat, 0·6 cwt/acre of grain; barley 0·4 cwt/acre; lucerne 0·6 cwt/acre of dry matter. Average increases of sugar beet over 4 years were 0·7 tons/acre of roots or 2·1 cwt/acre of sugar; the increase was greatest (2·9 cwt/acre of sugar) in the first year.

Field experiments with rice were conducted on a flooded soil comparing two standard fertilizers with N fertilizers with various release rates. For each of these fertilizer materials two methods of application were compared: broadcast and incorporated, and placement at 15 cm depth. The .slow release materials resulted in a lower grain yield than did fast or medium release rate or standard fertilizer materials. They released N too slowly during the early growth of rice to permit optimum plant growth and development.

Placement of 80 kg/ha N at 15 cm depth increased the plant N content at all stages of growth and significantly increased the grain yield compared with the broadcast-and-incorporated fertilizer treatment. The highest grain yield in the experiment (7701 kg/ha rough rice) was obtained from a medium release material, which was 88 % more efficient in increasing grain yield per unit of N when placed at 15 cm than when broadcast-and-incorporated.

The recovery of fertilizer N was 68% when deeply placed and 38 % when broadcast-andincorporated.

1. Thirteen experiments were made with spring barley from 1963 to 1965 on soils overlying chalk. They compared yields at ear emergence and of ripe grain from ammonium sulphate and from calcium nitrate, from sodium nitrate or sodium chloride or both, and from potassium nitrate or potassium chloride. Two rates of seedbed N were tested, though they were different each year, and in 1964 and 1965 N top-dressings were also applied. The amounts of N, K, Na and Mg in the green barley, and of N in the grain, were measured.

greatly increased grain yields in all but one experiment, where the barley followed sugar beet. Calcium nitrate gave larger grain yields than ammonium sulphate in three-quarters of the comparisons, but gave much smaller yields than ammonium sulphate on one light soil in 1964 when much rain fell after the fertilizers had been applied. Grain yields from calcium, potassium and sodium nitrates were nearly the same.

3. Na slightly increased grain yields in three and K in two experiments, but combine-drilled P or PK fertilizers increased them in every experiment.

Field experiments of modern design that included carrots were first made at Woburn in 1934, to compare the value of nitrogen in dried poultry manure with ammonium sulphate. The experiments were repeated at several centres and continued until 1939. Most other crops responded well to nitrogen but in only one of the five experiments containing carrots did ammonium sulphate at 3 cwt/acre increase the root yield, and in two it significantly depressed yield. Ammonium sulphate tended to lessen plant numbers, but it increased the yield of tops (Rothamsted Experimental Station, 1934)

1. The object of the experiment was to determine the effects on the diet and production of grazing dairy cows of providing different quantities of herbage over a relatively long period.

2. Three groups of five Ayrshire cows were strip grazed on areas supplying (A) 25, (B) 35 or (C) 45 lb D.M. per cow per day, for a total of 11 weeks. Three swards were used in succession, and measurements of herbage intake, milk production and live-weight changes were made over the last 10 weeks.

3. Mean intakes for treatments A–C, respectively, were 23·9, 25·6 and 26·4 lb organic matter per cow per day, and milk yields were 30·4, 30·8 and 32·8 lb. Differences in digestibility between treatments were small, even when the cows grazed poor herbage in which the organic matter was only 68 % digestible.

4. The treatments had no significant effects on milk composition or live-weight gain, although the latter was less for treatment A.

1. Plants of S.48 timothy were established on a 1 ft square pattern for production of seed. Two series of plots, one irrigated and one not irrigated, were treated with three levels of applied nitrogen: 0 (NO), 87 (Nl) and 261 (N2) lb N per acre (0, 97·5 and 292·5 kg N/ha) per annum, for 3 years. In this, the first of two papers, only vegetative aspects of growth are considered. Since the irrigation treatment started only 2 weeks before most of the data were recorded, effects of irrigation on vegetative growth were generally small.

2. The number of tillers per plant was increased by application of nitrogen; the lower increment was more effective than the additional nitrogen in the higher dose.

3. The weight of tillers per plant was increased by nitrogen at both levels of application. The mean weight of each tiller was increased by nitrogen after the first year, predominantly in the N 2 treatment. In the second year, irrigation also increased the weight per tiller.

4. The weight of roots per plant was significantly affected by application of nitrogen. In the first year, the weight was increased by nitrogen in irrigated plots; in the second year the roots were significantly heavier in the Nl treatment than in N0 and N2 treatments, where weights were similar; the same situation existed in irrigated plots in the third year, but in non-irrigated plots the weights of roots were similar in N1 and N2 treatments and were heavier than in the N0 treatment. Irrigation had positive effects on the weight of roots in the first and second years.

1. Plants of S.48 timothy were established on a 1 ft square (30 cm × 30 cm) pattern for production of seed. Plots at three levels of applied nitrogen, 0 (N0), 87 (Nl) and 261 (N2) lb N/acre (0, 97·5 and 292·5 kg/N ha) per annum were either irrigated to field capacity from 1 week before initiation of spikelets until 2 weeks before harvest, or not irrigated, during each of three years.

2. Application of nitrogen caused earlier initiation and emergence of inflorescences each year, and earlier general anthesis in the first and third years. Irrigation generally had no effect on the date of initiation, but it prolonged the period of reproductive development and delayed the date of harvest by 2–5 days.

3. The number of ears per plant was increased by the N1 treatment above the number produced by plants in the N0 treatment. In the N2 treatment the number of ears per plant was between the number in the N0 and N1 treatments in non-irrigated plots; in irrigated plots, plants in the N2 treatment sometimes had a lower number of ears than plants in the N0 treatment. The length of ears increased with the rate of application of nitrogen.

The plasma lipid concentrations of newborn lambs, kids and calves and of adult ruminants in 0various physiological states have been reported. In newborn ruminants plasma lipid concentrations were 20–40 % of those found in their dams at parturition.

The concentrations of blood lipids have also been estimated in five lambs from birth to weaning at 90 days post partum. The plasma free fatty acid concentrations rose to a maximum at about 45 days post partum and then declined. Possible reasons for this elevation in plasma free fatty acids have been discussed with reference to published data on age changes in lambs of plasma glucose and volatile fatty acid concentrations. The concentration of plasma esterified lipids, mainly phospholipids and cholesterol esters, were very low at birth and rose to reach maximum values at about 20 days post partum before declining to adult values at weaning. These changes have been discussed in relation to diet and rumen development.

1. Seven experiments with main-crop potatoes on heavy soils from 1962–5 measured yields from 0, 5, 10 or 15 cwt/acre of 13–13–20 fertilizer; (1) broadcast and worked into the soil by seed bed preparations; (2) broadcast on the final seed bed; (3) placed in bands 3 in. from the seed centre. Wheat followed the potatoes and was manured with 0, 5, or 10 cwt/acre (of the equivalent) of 13–13–20 fertilizer, in all combinations with the four amounts of, and the three ways of applying, the fertilizer given for the potatoes.

2. Fertilizer greatly increased potato yields and 15 cwt/acre of 13–13–20 was justified, provided it was broadcast. Both methods of broadcasting gave similar yields with 5 or 10 cwt/acre, but working the fertilizer into the seed bed was usually the better method with 15 cwt/acre of the fertilizer. Placing in bands beside the seed was the best method in four experiments with 5 cwt, in two with 10 cwt, but never with 15 cwt/acre of fertilizer.

3. Yields of green wheat, and of grain and of straw, were increased by residues of fertilizer applied for the potatoes, but were increased much more by freshly applied fertilizer. The residues increased wheat yields by the same amount as one quarter as much freshly applied fertilizer. The residues had smallest effects when the winter rainfall was largest, and were the same however the fertilizer had been applied.

Introductions of red clover indigenous to the Atlas mountains of North Africa were shown to have a high degree of resistance to Sclerotinia trifoliorum when a natural attack occurred in field trials at Cambridge. Differences between the two classes of clover varieties: (1) North African populations, and (2) the British varieties Essex broad red and S. 123, were highly significant for the proportion of row affected, the number of affected areas and the average length of affected area. The North African material is expected to be a useful source of resistance to Sclerotinia trifoliorum, in breeding programmes.

We are indebted to Mr H. H. Rogers for his guidance and for collecting the red clover plants during the 1962 North African expedition which was supported by the Agricultural Research Council. We also acknowledge valuable criticism of the manuscript and provision of a computer programme by Mr J. L. Fyfe and help with field records by Mr M. Pope and Mrs H. E. Pape.

1. Data from eleven forages fed in digestibility trials were used to obtain statistical relations between organic matter intake (I), faecal dry matter output (F) and the concentration of nitrogen (N), copper (Cu), magnesium (Mg) and silicon (Si) in faecal dry matter.

2. Exploration of multiple regressions using all variables, and their products, gave a prediction relationship with four variables that was slightly better than that for nitrogen alone, as obtained by Arnold & Dudzinski (1963). FN and the products of(FN × FCu) and (FN × FSi) were the contributing variables. The eleven forages could not be brought into a single expression.

(1) In a 3×2 factorial experiment sixty Large White type weaner pigs (30 hogs and 30 gilts) were individually and restrictedly fed to 200 lb live weight, six diets (as wet mashes) containing 70 % of either maize, sorghum or barley, each cereal having been processed by either crimping or grinding prior to inclusion in its respective diet. A further two groups of six litter-mate hog pigs per group were used to measured the digestibility of and the nitrogen retention from these six diets at approximately 50, 110 and 190 lb live weight.

2. Grinding gave significantly better digestibility than crimping, the ground diets having significantly higher digestible energy contents than the crimped. Between cereals the order of significant decreasing digestible energy content was from maize to sorghum to barley dietary treatments.

3. There were no significant differences between cereals in nitrogen retention. Between processing treatments grinding, in terms of g. retained per kg live weight per day, gave a significantly higher value than crimping, at 107 lb live weight.

1. In experiments on potatoes and sugar beet, interplant competition for light was varied by altering the spacing distance between plants grown in containers, while competition for water and nutrients was eliminated.

2. In both experiments the relative growth rate was 10 % less in closely spaced plants because net assimilation rate was greatly decreased; leaf area ratio was increased. Increasing competition for light decreased mineral nutrient uptake.

3. It was considered that differences between the treatments in the intensity of competition for light was greater in these experiments than it normally in the field because differences in leaf area index were greater. The leaf area of widely spaced plants was smaller in these experiments than in the field; this was thought to be due to a more limited supply mineral nutrients in the former.

4. In both species, the greatest crop growth rates were observed at leaf-area indices well below the maxima attained. The likelihood that observed crop growth rates were near maximal under the prevailing environmental conditions is discussed.

In crosses segregating 1:1 for normal: variegated inflorescences there was a consistent and statistically significant tendency for individuals with variegated inflorescences to be less erect than those with normal.

A mean of 27·137( ± 2·634) × 109 sperm were found in ten epididymides from six Suffolk rams. This is substantially fewer than has been reported previously because fewer spermatozoa were found in the cauda. However, the total number is similar to that calculated on the basis of daily sperm production and testis weight.