Fifteen British Friesian steers were reared using grain and forages which had been grown on land which has had a long history of use for disposal of sewage sludges. The food consumption was recorded and samples of feedingstuffs analysed for Cd, Cr, Cu, Ni and Zn. The various components used in compounding the feedingstuffs were also analysed. After about 13 months the animals were slaughtered and samples of various organs and tissues obtained for analysis.

The majority of the Cd, Cr, Cu and Zn came from sources other than uptake into plants. The largest single contributor was the high phosphate mineral supplement. No animal health problem due to the feed regime was encountered. Concentrations of cadmium in liver and kidney were slightly higher than average. Muscle cadmium concentrations of Cr, Cu, Pb, Ni and Zn were within the range of published values.

Field experiments were conducted during the rainy seasons (June–October) of 1978 and 1979 in order to determine the effect of fertilizer N rates (0, 40, 80 and 120 kg N/ha) on yield and yield attributes of some new sorghum cultivars in northern India. Sorghum hybrid varieties yielded more than pure line varieties, hybrid CSH 5 outyielding all other cultivars including other hybrid varieties because of its greatest number of grains per panicle. Nitrogen application at 80 or 120 kg N/ha brought about significant improvement in number of grains per panicle and yield per ha.

Cultivar Χ N rate interactions were significant, in affecting the yield per ha and number of grains per panicle in 1978, whereas such differential response of sorghum cultivars to N rates did not occur in 1979. Sorghum hybrid varieties, even at lower N rates, produced identical yields to the pure line varieties supplied with higher N rates.

Sixty-two genotypes of Trifolium repens (white clover) collected from latitudes 52° to 68° N and five selected genotypes of the cultivar S.184 were screened for shoot growth at low temperature and short daylengths in a controlled environment cabinet and in the field, and subjected to cold hardiness treatments ranging from – 2·5 to – 14·0 °C.

Considerable variation was discovered in several of the growth characteristics and in the frost tolerance of the genotypes. Genotypes exhibiting the highest rates of stolon extension were found in the more southerly latitudes. A high proportion of leaves produced during winter on the primary stolons of the selected cultivar plants subsequently died during the late spring at the upland field site, but several of the naturally occurring genotypes were able to retain more leaves per stolon in spring. Some genotypes appeared to maintain either short or long internodes throughout the spring in the field, whilst others produced relatively short internodes in early spring and long internodes later in the season, and vice versa. Only a small percentage of the genotypes possessed relatively long leaflets. A correlation was found between maximum leaflet length of the genotypes in early spring, and maximum leaflet length in late spring.

No relationship was found between frost tolerance and the growth of plants at low temperature. Frost sensitive and tolerant genotypes were found throughout the latitudinal and altitudinal ranges studied. Exposure to prevailing winds and possibly snow cover at the site of origin appeared to be important factors associated with the frost tolerance of T. repens plants.

The roles of leaves, stems and reproductive parts in 14CO2 fixation and its subsequent movement in winter oil-seed rape, cultivar Jet Neuf, were investigated in two field experiments carried out on the Wye College Farm. The relative importance of these organs changed with time. At early flowering the leaves were the most important photosynthetic organs (66·8% 14CO2 activity). Midway between flowering and maturity the stems became the major supplier of photosynthates, a role eventually taken over by the developing siliquae (pods).

These data stress the importance of keeping all photosynthetically active surfaces free from disease if efficient resource utilization and higher yields are to be achieved.

The use of phosphatidyl choline (PC) as a marker of protozoa in duodenal digesta was examined in sheep fed chaffed lucerne hay (Medicago sativa L.; 330–950 g organic matter/day) either once daily or hourly.

PC was present in rumen protozoa (N:PC-P = 185±6·4) but was not detected in rumen bacteria. Dietary intake of PC was less than 5% of the daily passage of PC from the stomach (7·49 mg PC-P/day). A comparison of the SA of PC-P in protozoa and in duodenal digesta of sheep given a continuous intraruminal infusion of 32P-orthophosphate showed that the proportion of dietary PC-P in duodenal digesta was negligible.

The limitations and validity of PC as a marker of protozoa in duodenal digesta are discussed. The daily passage of protozoal N from the stomach (1·38 ± 0·125 g/day) estimated with PC was not affected by frequency of feeding but protozoal N yield (4·96 ± 0·509 g/kg organic matter apparently digested) declined with increasing feed intake.

The SA of DNA-32P, RNA-32P and readily extractable phospholipid-32P (REPL-32P) in rumen protozoa, bacteria and duodenal digesta were similar, showing that the DNA, RNA and REPL-P in duodenal digesta were of microbial origin. A method is described for the estimation of bacterial REPL-P and bacterial N in duodenal digesta using DNA, RNA or DAPA as markers.

The calculated total microbial REPL-P (bacterial plus protozoal) in digesta using DNA or RNA as markers was in close agreement with values obtained by direct measurement. It was estimated that protozoa contributed 22 and 14% of microbial REPL-P and microbial N, respectively. Bacterial REPL-P and bacterial N values estimated with DAPA as the marker were higher than values obtained with DNA or RNA. These results are discussed with regard to the use of these markers.

Cell mass (dry matter per cell) and cell composition (concentrations of DNA, RNA, phospholipids, total N, a-dextran, diaminopimelic acid and 18 common amino acids) of rumen bacteria were measured at various times after feeding sheep chaffed lucerne hay (Medicago sativa L.) once daily. Cell composition was measured with sheep fed once hourly. Total DNA and RNA pool sizes in the rumen were also measured.

While cell composition was not affected by level of feed intake (700 g v. 1050 g dry matter/day), total DNA, RNA and D.M. pool sizes in the rumen increased with increasing feed intake. With sheep on the once daily feeding regimen relative rumen pool sizes in rumen digesta at various times after feeding were: RNA, 4 > 14 > 0 h; DNA, 4 and 14 > 0 h; D.M. 4 > 14 > 0 h. With the hourly feeding regimen pool sizes were similar to the averaged daily values for sheep fed once daily.

When sheep were fed once daily bacterial cell mass, DNA and phospholipid concentrations peaked at 12–14 h after feeding and subsequently decreased to the 0 h value. RNA concentration was maximal at about 4 h after feeding and declined to near the 0 h value at about 14 h. RNA concentrations in bacteria were highly correlated with gas production rates by whole rumen digesta. The ratio RNA:DNA was highest shortly after feeding, decreased to below the 0 h value at about 14 h and then increased to the 0 h value. The relative concentrations of a-dextran in bacteria were: 4 > 14 > 0 h. Cell composition witli sheep fed hourly tended to reflect the averaged daily values for sheep fed once daily.

These results are discussed with regard to changes in estimated fermentation rate and pool size of bacteria in the rumen. It is suggested that changes in average composition (DNA, RNA, total N and RNA: DNA ratio) of mixed rumen bacteria reflect changes in the average growth rate of the population.

The paper examines the statistical properties of criteria currently used to determine the distinctness of herbage varieties and suggests alternatives.

The relative importance of some sources of plant-to-plant root-weight variation in a field-grown carrot crop was investigated in two experiments sown in contrasting soil conditions but using the same seed lot and experimental design. In each experiment the following possible causes of root-weight variation were recorded on an individual plant basis: umbel order and size of seed, sowing depth, time taken for seedling emergence, length of cotyledons at emergence, distance to nearest neighbours within a row and row position within the seed bed. The relative importance of these differing sources of root-weight variation was assessed by determining how much of the variation in In (root dry weight) they accounted for at two harvests in each experiment.

In the first experiment, carrot seeds were sown in warm, moist conditions in May. These conditions gave a near-ideal emergence, 82% of seedlings emerging over only 5 days. Thirteen days after sowing, the most important source of root-weight variation, out of the variables measured, was position of the row within the bed. However, approximately two-thirds of the root-weight variation could not be attributed to any of the measured variables.

In the second experiment carrot seeds were sown in hot, drying conditions in July. The subsequent spread of seedling emergence extended over approximately 40 days. The total sum of squares of In (root dry weight) in this experiment was six times greater than the sum of squares in the first experiment. At 105 days, 61% of the rootweight variation in Expt 2 was accounted for by differences in time of seedling emergence. Differences in cotyledon length, measured when fully expanded, accounted for 24% and sowing depth differences accounted for 19% of the root-weight variation. Differences in umbel order, seed size and distance to the nearest neighbouring plants within a row never accounted for more than 8% of the sum of squares of In (root dry weight) in either experiment. Thus these variables were not important sources of rootweight variation. In contrast variables which affected the time of seedling emergence, such as sowing depth and physical conditions around the seed, were major sources of root-weight variation.

A simple technique to evaluate accurately the effect of mechanical stress on root growth has been developed. The roots are allowed to grow against a predetermined pressure in the chamber of a pressure-plate apparatus. The root growth was studied against the applied pressures of 0, 2, 4, 6, 8 and 10 bar. A relationship of the form Y = aXb was observed between the rate of root elongation (Y) and applied pressure (X).

Response of rainfed barley to different methods of nitrogen application was studied on a loamy sand soil in 1974–5 and 1975–6. The nitrogen fertilizer was applied by broadcasting, side drilling, drilling below the seed and in solution. In a year of lower rainfall, applying the fertilizer below the seed or in solution produced significantly more grain yield than broadcasting or side drilling. In a year of higher and well-distributed rainfall, applying the fertilizer below the seed was significantly better than other methods of nitrogen application. The magnitude of the response to applied nitrogen increased with increase of crop season rainfall and its better distribution. Placing N below the seed improved water use. It was followed in order by applying in solution, side drilling and broadcasting in both the years.

The development of spring and winter barley sown in both the spring and autumn has been followed in two seasons. The rates of development were similar in both types for autumn sowings but the spring types developed faster in spring sowings. Differences in the rate of development were related to photoperiod and temperature although soil water stress modified variety response. Yields were higher from autumn and early spring sowings. Sowing in April resulted in a considerable reduction in yield. The significance of these results for barley breeders is discussed.

Two experiments were undertaken with maize silage, which had been sterilized by subjecting it to a 6 Mrad dose of γ radiation, inoculated with micro-organisms implicated in the aerobic deterioration of silage and subsequently exposed to air. The inocula employed comprised mixed strains of yeasts, bacilli and lactic acid bacteria and combinations of these. The changes which accompanied aerobic deterioration were observed. The major losses of fermentation acids, ethanol, ammonia and dry matter, and increases in total nitrogen and temperature were associated with inocula in which yeasts were represented. Similar changes of a lower magnitude were also observed in silage treated with inocula containing bacteria only, although these were not always accompanied by the growth of these organisms or loss of dry matter. However, when employed in mixed inocula with yeasts, the bacteria proliferated and tended in some instances to increase losses further, suggesting an association between the groups of micro-organisms in the aerobic deterioration process. Losses were also sustained in sterile silage which received no inoculum and the possible reasons for this are discussed.

Wool growth rates (WGR) of individual sheep were measured by a patch-sampling technique, during periods of developmental growth, body-weight loss (which ranged from 21 to 34% of original body weight, at rates between 60 and 150g/day) and subsequent compensatory growth under ad libitum feeding.

There was a ‘lag phase’ of about 30 days before WGR appeared to be affected by changes in direction of the animals' growth paths.

During body-weight loss WGR declined about 300% more than the percentage change in body weight, with the duration of nutritional stress exerting a greater influence than the rate of body-weight loss.

During compensatory growth in body weight, the relationship between WGR and rate of body-weight change was initially negative. Sheep required between 11 and 14 weeks to reach the WGR of 21 g/day found during developmental growth. Compensatory growth of wool did not occur.

Duration of the nutritional stress, rather than its severity (as indicated by rate of body-weight loss), was the more important determinant of the time taken for the sheep to regain normal levels of wool growth after the commencement of ad libitum feeding.

The joint action of two pyrethroid insecticides with several foliar fertilizers against the fourth-instar larvae of Spodoptera littoralis was determined. The rate of development of tolerance throughout three successive generations to insecticides alone and their combinations with fertilizers was also assessed. The results indicate that the toxicity of the insecticides tested was greatly enhanced by using fertilizers in admixture with each of them. Moreover, the inclusion of such fertilizers in spray emulsions slows down the development of tolerance to both insecticides. The synergistic action of fertilizers and the decrease in the induction of tolerance to insecticides can be attributed to the presence of inorganic ions and to decreasing the pH of both acidic experimental insecticides resulting in increasing the penetration rate of the internal membranes of the cotton leafworm.

Evaluation of some insecticides against nine strains of S. littoralis, selected with decamethrin and foliar fertilizers separately and their combinations for three successive generations, was conducted to elucidate the effects of fertilizers on the tolerance pattern. The results indicate that the selection with fertilizers induced a low level of tolerance to both cyolane and profenofos. The LC50 of chlorpyrifos for all fertilizers' strains was lower than that of the susceptible strain. The efficiency of cyolane and fenvalerate on strains developed by the selection with decamethrin-fertilizer combinations was remarkably increased. Since the selection with fertilizers has induced a tolerance to some insecticides such as cyolane and profenofos and as the efficiency of these insecticides was enhanced on strains developed by the pressure of decamethrinfertilizer combinations, it is preferable to use decamethrin simultaneously in admixture with foliar fertilizers for pest control.

Computer programs have been developed to evaluate sequential variety selection systems using Monte Carlo and numerical integration methods.

These methods are described in the paper and applied to official U.K. cereal variety testing. The consequences of alternative selection systems are examined.

An experiment was made on a clay loam soil to compare direct drilling, shallow cultivation and ploughing for spring barley over a period of 3 years (1975–7). At a uniform rate of fertilizer application (75 kg N, 40 kg P2O6, 40 K2O/ha) combined drilled with the seed, the mean grain yields over 3 years were 5·89, 6·07 and 6·13 t/ha, respectively, direct drilling producing significantly less grain than shallow cultivation or ploughing in 1975 only.

For 1975 and 1976 the mean uptake of nitrogen by shoots of barley at anthesis was 25 kg N/ha less after direct drilling than after ploughing but in 1977 there was no difference. The smaller uptake of nitrogen by direct-drilled barley in 1976 was more likely caused by less available nitrogen in the soil than by smaller root systems. Soil strength (cone resistance) and soil bulk density of the direct-drilled treatments were greater than those of the ploughed and shallow cultivated. Although concentration gradients of extractable phosphorus and potassium formed in direct-drilled and shallow-cultivated soils, the quantities of these nutrients in the top soil differed little between the treatments. After 3 years there were more deep burrowing earthworms (particularly Lumbricus terrestris) in tilled than in untilled soil.

The effect on phosphorus and calcium metabolism of a high rate of Ca infused directly into the blood of 10-month-old sheep, already receiving an adequate Ca and P intake, has been studied by a combination of balance and radioisotope techniques. Ca retention was significantly increased during the infusion and most of the extra Ca was retained in bone. Urinary Ca excretion also showed a small but significant increase and the efficiency of Ca absorption a small but significant decrease. Because of the close association of Ca and P in bone, the increased skeletal retention of Ca resulted in an increased skeletal P retention and hence an increased demand for P. This increased P demand was met partly by a decrease in the rate of endogenous faecal loss of P and partly by an increase in the rate and efficiency of P absorption. Because the increase in P demand was relatively small, it was not possible to decide whether the endogenous faecal loss of P can be reduced in response to increased demands to the level found at zero P intake as suggested by the Agricultural Research Council (1980) or whether higher losses at normal P intakes are inevitable.

The effects of coat colours on thermal balance, behaviour and weight gain were studied. Measurements of thermal balance were made over 36 days in strong sunshine on highly contrasting coat colours of three white and three dark steers in each of two breeds, Brahman (B) and Shorthorn (S), and three light- and three medium-red steers in Brahman Hereford-Shorthorn cross breed (BX) where there was less contrast in coat colour. Each steer was measured for 30 min on six occasions randomly distributed among 6 h between 08.00 and 13.00 h, and on six occasions between 11.00 and 16.00 h, all on different days. For B, the difference between colours in mean rate of environmental heat gain at the skin was 64 ± 22·5 W/m2 and for S, 44 ± 20·5 W/m2, while the difference in mean rate of evaporative heat loss, between colours for B and S respectively was 44 ± 15·1 and 42 ± 14·3 W/m2. However, only within S was rectal temperature significantly higher in steers which were dark red and the reasons for this are discussed. Within BX the range of colour shades diminished during the experiment so thermal effects of colour were small. Colour had significant effects on growth; these effects were greatest in S where white steers gained 0·13 kg more per day than dark red ones. There were also differential effects within colour groups on activities at pasture; light steers spent more time in the sun and grazing than dark ones. In addition to colour, deep or woolly type coats negatively affected growth (P < 0·05), time spent in the sun (P < 0·05), and grazing time (P < 0·05); however, between animals within breeds the magnitude of the adverse effect of coat type on growth and behaviour was greater in dark- than light-coloured steers. These results provide evidence that coat colour is a trait which, interacting with coat type, exerts an influence on performance of cattle under heat stress.

Three groups of red deer hinds of 9–10 years of age were grazed upon an indigenous hill pasture (A), an improved species grass sward (predominantly perennial ryegrass) maintained at < 1500 kg D.M./ha (B), and one maintained at 2000 kg D.M./ha (C) from immediately after calving on 29 May until weaning on 22 September. Numbers of hinds in each treatment were 8, 6 and 9 respectively. Milk yields of hinds were estimated on swards A and C by the calf-suckling technique and hind and calf live-weight changes and hind grazing behaviour were recorded on all three swards during lactation.

Hinds on award C yielded on average 60% more milk over the lactation period than hinds on sward A, day 40 yields being 2·2 and 1·5 kg/day respectively. Calf growth rates (treatment A, 257 ± 9·5, B, 324 ± 12·1 and C, 369 ± 14·5 g/day) were higher on the improved species sward than on the hill sward and higher on the improved sward with the greater herbage mass. On treatments A and C calf growth rates were significantly (P < 0·05, r = 0·69) correlated with milk yield throughout lactation. At weaning, calves on sward C were 7·5 and 4·5 kg heavier than those on swards A and B respectively. Biting rates were lower (33 v. 56 bites/min) and grazing times higher (11.7 v. 6.0 h) on sward A than swards B and C. The poorer performance of hinds and their calves on sward A was considered to be due to a lower quality of diet ingested, and to behavioural limitations on intake occurring when hinds graze indigenous swards of relatively high species diversity. These results are discussed in relation to the grazing behaviour of cattle and sheep on similar swards.

The significance of the results to red deer farming in the U.K. is briefly discussed.