The mixed buffer salts of artificial saliva were incorporated at three rates: 0 (diet 1), 5·7 (diet 2) and 11·4% (diet 3) (w/w) in pelleted diets prepared from60% ground flaked maize and 40% dried ground grass. The control and mineral-supplemented diets were fed to sheep hourly (Expt 1) or twice daily (Expt 2).

When the sheep were fed hourly or twice daily the pattern of fermentation in the rumen was altered from a predominantly propionate to mainly acetate fermentation. Dilution rate in the rumen increased from 0·036 to 0·053 to 0·064 when diets 1, 2 and 3 were fed hourly, and dilution rate was negatively related to the molar proportion of propionic acid (P < 0·05) and positively related (P < 0·05) to the molar proportion of acetic acid in rumen fluid, but these relationships were not apparent in Expt 2.

Nitrogen retention was higher for lambs fed diet 2 than for those fed diets 1 and 3 (P < 0·05) in Expt 1.

In sheep fed hourly, selenomonads and bacteroides were the predominant rumen bacteria associated with the control diet but the inclusion of mineral salts resulted in the bacteroides being replaced by large number of chain-forming cocci. Numbers of protozoa were variable. The relationship of these changes to the fermentation pattern is discussed. In sheep fed twice daily there was much variation between animals.

The joint scaling test of Cavalli (1952) and the six-parameter procedure of Jinks & Jones (1958) were applied to test the adequacy of the additive-dominance model and to estimate various main and interaction gene effects for five characters, namely, final plant height, ear length, number of spikelets per spike, number of grains per spike and yield per plant, in three wheat crosses (Kalyan Sona × Norteno 67, Norteno 67 × WL 212 and K. Sona × Moti). Goodness of fit of the model varied from cross to cross for the same character except for number of grains per spike and yield per plant for which the model was inadequate for all three crosses. The two methods were in complete agreement regarding the presence of epistasis in the material. Among the interaction parameters, the component [1] showed the greatest effect for most of the characters in all three crosses where there was evidence of epistasis.

A total of 225 herbage samples were taken from two areas with a history of bovine hypocupraemia and examined for their Cu, Mo, total S, Zn, Fe and Cd content.

In general, the concentrations of Cu and Mo (mean values 10·4 and 1·6 mg/kgD.M. respectively) were normal, as were those of Zn, Fe and Cd (mean values 43, 255 and 0–59 mg/kg D.M. respectively). The total S concentrations (mean value 3·5 g/kg D.M.) were, however, higher than found by some other workers.

The concentrations of available herbage Cu were calculated using the following relationship of Suttle & McLauchlan (1976):

logTA Cu = –0·0019 Mo–0·0755 S–0·0131 Mo × S–1·153,

where TA Cu is the true availability of Cu, and Mo and total sulphur (S) are dietary concentrations as mg/kg D.M. and g/kg D.M. respectively. Animal requirements for available Cu were derived from estimates of the factorial Cu requirements of various classes of livestock, and when these were compared with the calculated concentrations of available Cu in the herbage they provided a possible explanation for the widespread hypocupraemia experienced in these areas.

Investigations of the reasons for the instability of emulsifiable concentrates (ECs) during storage and a study of reprocessing insecticide ECMs whose emulsification propertieshad deteriorated during storage is reported. Bioassay showed that very stable emulsions, although physically perfect, leave inadequate residues on the treated leaves. When a deteriorated EC was reprocessed, its emulsification properties were restored, resulting in better adherence of the insecticides on the leaves' surfaces; the residual toxicity was increased.

In three experiments, ryegrass and lucerne were ensiled for 100 days in test-tube silos containing about 100 g of crop either without additive or after the addition of paraformaldehyde or formalin to provide 0·1–0.4% of the fresh crop weight as formaldehyde (HCHO). When applied as prills containing 82% HCHO, paraformaldehyde was as effective as formalin in restricting fermentation and preventing extensive protein breakdown at comparable HCHO application rates. The lower solubility of paraformaldehyde containing 98 % HCHO as powder or prills made these forms less effective than formalin in restricting fermentation. Paraformaldehydecontaining 98% HCHO was, however, effective even at the lowest rate of application, in preventing clostridial-type fermentations when these were present in silages made from untreated crops.This was in contrast to formalin which promoted such fermentation at low rates of application.

Eight amounts of nitrogen ranging from 0 to 210 kg N/ha were applied to two tall and one semi-dwarf variety of winter wheat in the spring of 1975 and 1976. The tall varieties were Cappelle-Desprez and Maris Huntsman; the semi-dwarf variety was Maris Fundin in 1975 and Hobbit in 1976. Interactions between varieties and nitrogen were few and small compared with the main effects. All varieties produced their maximum grain yields with 180 kg N/ha. The yield of the semi-dwarf varieties, but not the others, decreased slightly with more nitrogen.

Cappelle-Desprez yielded less grain than the other varieties in both years. In 1975 the yields of Maris Fundin and Maris Huntsman were similar and in 1976 Hobbit yielded more than Maris Huntsman. The varieties had similar numbers of ears at maturity and similar patterns of tillering. The semi-dwarf varieties had most grains per spikelet, and hence grains per ear, and Cappelle-Desprez had least. The semi-dwarf varieties had the smallest grains. The semi-dwarf varieties had less straw than the other varieties and hence the largest ratios of grain to total above-ground dry weight. The decrease in dry weight of stem and leaves between anthesis and maturity was similar for all varieties. In 1975 the efficiency of the top two leaves plus top internode in producing grain was the same for all varieties, but in 1976 Hobbit was more efficient than the other two. There were some small differences between varieties in nutrient uptake that were not related to differences in growth. Maris Fundin tended to have a greater phosphorus and potassium content than the tall varieties. Hobbit contained slightly less nitrogen than the tall varieties at maturity, and had a smaller concentration of nitrogen in the grain.

Applying 210 kg N/ha doubled grain yield in 1975. Applying nitrogen resulted in a largeincrease in number of ears and a small increase in number of grains per ear due to the development of more fertile spikelets per ear. Nitrogen decreased dry weight per grain, especially of the semi-dwarf varieties. With extra nitrogen, straw dry weight at maturity, shoot dry weight atanthesis and leaf area were all increased relatively more than grain yield, and stems lost moredry weight between anthesis and maturity than without nitrogen. The year 1976 was exceptionallydry and nitrogen had only small effects in that it affected neither straw dry weight nor numberof ears but slightly increased grain yield by increasing the number of spikelets and number of grains per spikelet. It also increased leaf area proportionately to grain yield. In 1975 nitrogen increased evaporation of water from the crop before anthesis but decreased it after anthesis, even though it continued to increase the extraction of water from below 90 cm.

Analysis of measurements of absorbed radiation and leaf area indices of wheat and barley crops showed that throughout most of growth the fraction of absorbed solar radiation could be described by a simple exponential equation.

For several of these crops grown under a wide range of weather and husbandry at Sutton Bonington and Rothamsted, 2-weekly values of crop growth rate (C) were closely related to radiation absorbed until ear emergence and about 3·0 g of dry matter (D.M.) were produced by each MJ of photosynthetically active radiation (PAR) absorbed. Final crop weight was closelyrelated to total PAR absorbed during growth (SA); on average about 2·2 g D.M. were produced per MJ absorbed, equivalent to a growth efficiency (Eg) of approximately 3·9%. Unfertilized and drought-stressed crops had a smaller Eg.

The fraction of total crop D.M. harvested as grain (harvest index) varied more for wheat than for barley. Calculations of a maximum realizable grain yield made using the largest values of Eg and SA for the crops measured and assuming a harvestindex of 0.53 (achieved in an experimental crop) showed a grain D.M. yield of 10·3 t D.M./ha to be possible. To achieve such a yield would require full crop cover from the beginning of April until the end of July in a typical English growing season.

A standard method is proposed for establishing the seasonal pattern of production for grasses. The procedure consists in recording the yield from grass swards cut every 4 weeks and from which limitations to growth from the supply of water or nutrients have been removed. Four series of plots are harvested in rotation, spaced a week apart so that there is a routine of harvesting a constant number of plots on the same day each week. A statistical analysis is also described enabling comparisons to be made between the grasses under test. An example is given to illustrate the method and the results obtained.

The management of an experimental flock of dairy sheep was changed from a onceyearly to a frequent-lambing regime. Results are reported on the performance of the flock under the new regime in the course of 3 years. There were 53 and 160, 46 and 242, and 70 and 237 Awassi and Assaf (East-Friesian x Awassi) ewes, respectively, in the flock at the beginning of the 3 consecutive years. A breeding calendar was adopted to produce four mating seasons each year, namely June–July; September–October; December–January; March–April.

Average annual production was 1·16 ± 0·24 lambs and 209±9 kg milk for Awassi ewes, and 2·07 ± 0·20 lambs and 287 ± 19 kg milk for Assaf ewes. Hoggets of the same breeds produced 0·61 ± 0·14 and 1·23 ± 0·10 lambs and 99 ± 37 and 220 ± 21 kg of milk, respectively.

Following the February-March lambing, conception rates of hormone-treated ewes weaned 2 or 70 days post-partum were 57·1 and 48·8% respectively (P < 0·10). There were no differences in the length of the post-partum interval to conception between low and high milk-yielding ewes. Fertility was highest in the September–October and December–January mating periods, intermediate in June–July and lowest in March–April.

Twenty-seven per cent of the original 126 mature Assaf ewes and 15% of the original 46 mature Awassis remained in the flock at the end of 3 years for further breeding. Thirty-one per cent of the mature Assaf population (mixed ages) and 21% of the hoggets were culled in the course of 3 years due to failure to conceive within 6 months post-partum. With Awassi ewes the rate of failure was much higher.

Ewes which had lambed twice and completed, on average, 1·5 lactations in a year, produced 30% more milk per year than those which lambed only once during the same period. The more frequent lambing resulted in shorter lactations (156 days) and lower average daily milk yields (1·27 kg) compared with the 182 days and 1·41 kg in the less frequently lambing groups. Pregnancy during early stages of lactation had a small but significant (P < 0·05) effect on the concurrent lactation. Shortening the breeding interval had a much more marked effect on the subsequent lactation. Ewes that conceived, on average, 120 days post-partum, in the subsequent lactations produced 17% more milk than those conceiving 60 days post-partum (P <0·02).

Ewes gaining weight at a rate of 5–7 kg during the first 2 months of pregnancy produced, on average, 0·27 kg less milk per day than those which either lost or maintained their weight in that period (P < 0·01).

The herbage production and response to nitrogen fertilizer by kikuyu grass were measured in a field experiment conducted over a 12-month period. The experiment was designed to measure the growth of kikuyu grass at different rates of application of nitrogen fertilizer but without limitation due to mineral nutrient supply other than nitrogen, soil pH effects of nitrogen fertilizer, defoliation and pests and diseases.

Growth rate and response to nitrogen were closely related to mean temperature and moisture supply. Relations were established between growth rate, nitrogen response and apparent nitrogen recovery and the climatic variables, mean temperature and mean available soil moisture in 14-day periods. With nitrogen applications of 224 kg N/ha the predicted growth rate at 13 and 23 °C mean temperature were 38 and 196 kg D.M./ha/day, respectively; with 112 kg N/ha growth rate at the higher temperature was 106 kg D.M./ha/day. Growth and response to nitrogen ceased at mean temperatures around 10 °C.

Apparent recovery of nitrogen in harvested herbage over a 16-week growth period after nitrogen application was 51%; recovery in the first 4 weeks of growth varied from 1 to 56 % depending on temperature and moisture supply.

Relations between growth rate and mean temperature were used to predict the seasonal growth pattern for a range of environments in which yield data for the species are available. The results indicate the potential for high annual dry-matter production from kikuyu grass when adequately supplied with nitrogen and moisture is nonlimiting. The grass is also adapted for growth and survival in areas ranging from moist sub-tropical to cool-temperate.

The production of root axes and the growth of the root system are reported for a commercially grown crop of Maris Huntsman winter wheat. Soil cores were extracted on 17 occasions during the growing season permitting a detailed study of root length and root dry weight with depth and time.

Production of seminal root axes was complete by the beginning of March when all plants possessed six (occasionally seven) axes which persisted throughout the life of the crop. Nodal axes were produced continuously from mid-February until late May and finally numbered approximately 20 stem nodal axes per main stem. Total root dry weight increased exponentially until the beginning of April and then almost linearly to reach a maximum of 105 g root/m2 field in mid-June (anthesis). After anthesis, total root dry weight decreased but root growth continued below 80 cm. From April onwards, approximately 65% of the total root dry weight was in the 0–30 cm layer.

Volumetric soil water content and soil water potential were measured beneath a winter wheat crop during the 1975 growing season. Almost no rain fell between mid-May and mid-July and the soil dried continuously until the potential was less than – 20 bars to a depth of 80 cm. Evaporation was separated from drainage by denning an ‘effective rooting depth’ at which the hydraulic gradient was zero.

Rates of water uptake per unit length of root (inflow) were calculated for the whole soil profile and for individual soil layers. Generally, inflow decreased throughout the period of measurement from a maximum of 2·5 × 10–3 to a minimum of 0·66 × 10–3 ml water/cm root/day. Values in individual layers were frequently higher than the mean inflow and the importance of a few deep roots in taking up water during a dry season is emphasized. A similar correlation between inflow and soil water potential was found to apply for the 0–30 cm and 30–60 cm layers during the period of continual soil drying. This relationship represents the maximum inflow measured at a given soil water potential; actual inflow at any particular time depends upon the interrelationship of atmospheric demand, soil water potential and the distribution of root length in the soil.

Features of the gross morphology of primary growth of Dactylis glomerata and Lolium perenne, and associated changes in digestibility are described.

Species differences were noted with regard to the relationships between head emergence and the time when stem apices were raised to defoliation height, vegetative/ reproductive tiller ratios, and tiller size.

Also there were differences in the sequence of extension growth of leaf sheaths, internodes and inflorescence leading to emergence of the head. Associated changes in the vertical distribution of leaf blades were examined.

In perennial ryegrass extension growth of the inflorescence continued after emergence had begun, but not in cocksfoot. Weight increments in the inflorescence, from emergence onward, followed the same pattern in the two species, however.

Differences in the developmental patterns of the two grasses did not appear to influence their relative digestibility.

Upper internodes of reproductive tillers of S. 24 ryegrass declined rapidly in digestibility Species differences, and the pattern of changes in the digestibility of lower and upper parts of reproductive tillers are discussed in relation to mechanical aspects of sward development and micro-environmental effects.

Simple mathematical models to predict leaching fractions and mean displacement depths of salts either uniformly distributed in the soil profile or surface applied have been derived from the solution of Peck's differential equation of salt balance. Predictions from these models are comparable with those obtained from Burns' equation and fit published data well.

supplements of protected soya-bean–tallow were incorporated at 0, 1·7, 3·0 or 5·0 kg/day into a hay–concentrate diet and fed ad libitum to Friesian cows during the first 13 weeks of lactation.

Intakes of supplement during weeks 1–6 were 0,1·34, 2·25 and 3·18 kg/day and during weeks 7–13, 0, 1·64, 3·10 and 4·24 kg/day on each of the respective treatments.

As the lipid supplement increased there was a reduced intake of hay and concentrates, giving rise to reduced intakes of total, protein, and particularly ‘carbohydrate’ (non-protein, non-fatty-acid) energy. Apparent digestibilities, particularly of fibre, decreased as fatty-acid intake increased. After correcting for endogenous losses, true digestibilities of organic matter, carbohydrate, protein, non-fatty-acid lipid, total energy, calcium, magnesium and phosphorus were unaffected by the amount of supplement given, whereas fibre digestibility was reduced by increasing the supplement. Fatty acid digestibility was little affected up to an intake of 1·4 kg/day but above this there was a sharp reduction.

Yields of milk, milk energy, protein, fat and lactose were increased at low lipid supplementation but reduced at the highest supplementation when amounts of protein and carbohydrate digested were lowest.

Lipid supplementation reduced concentrations of rumen total volatile fatty acids in association with reduced, proportions of butyrate and. increased proportions of propionat. Plasma β-hydroxybutyrate and magnesium were reduced and plasma free fatty acids increased in cows given lipid supplemented diets.

There were no differences between treatments in plasma glucose, lactate or calcium nor in live-weight changes.

During the first 13 weeks of lactation, four groups of seven cows were given hay and a basal concentrate mix containing 0, 1·7, 3·3 or 5·0 kg/day of a protected lipid supplement (320 g long-chain fatty acid/kg D.M.). The proportion of hay to total concentrate was maintained at 25:75 and cows were fed to appetite.

The total amount of energy digested corrected for endogenous loss (DEc) was partitioned into crude protein energy (CPEc), fatty-acid energy (FAEc), ‘carbohydrate’ (non-protein non-fatty acid) energy (CEC) and non-fatty-acid energy (NFAEc = CPEc + CEc).

Partial efficiency of milk production and live-weight gain was curvilinearly related to FAEc, maximum efficiency occurring at about 30 MJ/day of FAEc.

Net energy utilized was significantly related to DE0c for both of the periods considered, Weeks 2–6 and weeks 7–13. In addition, a curvilinear effect of the ratio of fatty acid energy to non-fatty-acid energy was established. At fixed intakes of digestibl energy, net energy utilized was maximal for ratios of FAEc/NFAEc of 0·14 and 0·18 for weeks 2–6 and 7–13 respectively.

Milk yield was significantly related to DEc for weeks 1–6 and 7–13; milk energy yield was significantly related to DEc for weeks 7–13. The multiple regression relationships between milk yield or milk energy yield and CPEc, FAEc and CEc gave a negative effect of crude protein, possibly indicating that the proportion of total energy supplied as crude protein (18–26% of DEc) was above the optimum requirement.

At fixed intakes of digestible energy, outputs of milk and milk energy were maximal at ratios of FAEc/NFAEc of 0·16 and 0·15 for weeks 1–6 and 7–13 respectively. The inclusion of a curvilinear effect of total energy (DEc2) gave some indication that utilization of energy for milk production for weeks 7–13 diminished at the highest digestible energy intakes whilst energy utilized for live-weight gain increased.

Three field experiments in 2 years were made in S.E. Scotland to investigate the effect of water (normal rainfall or irrigation to maintain soil moisture tension between pF 2·0 and 2·5) on the response of the potato crop to nitrogen fertilizer (0, 100, 200 or 300 kg N/ha).

Final tuber yield was closely related to leaf area duration. Addition of water reduced the delay in early haulm growth resulting from fertilizer nitrogen application. The beneficial effect of reducing moisture tension could not be related to water per se, nitrate, ammonium or conductivity levels in the fertilizer band or nitrogen uptake. Accumulation of nitrate in the roots and stems + petioles early in the season indicated that the rate of protein synthesis was reduced at high soil moisture tension in the presence of fertilizer nitrogen.

In a long growing season (1971, 153 days) there was a significant response of tuber yield to nitrogen, with an increase in yield even at the highest rate tested (300 kg N/ha) and irrigation enhanced this response.

In a normal season (1970, ca.130 days) there was a significant irrigation x nitrogen interaction on tuber yield. Irrigation increased the optimum rate of nitrogen from 100 to 200 kg N/ha in one experiment and from nil to 200 kg N/ha in another.

Addition of water increased the number of tubers at harvest but the effect of nitrogen was less consistent. Yield increases resulting from application of nitrogen or reduction in soil moisture tension were mainly due to increases in the proportion of large tubers.

Data are presented from 104 sheep from three separate sources (batches) in which variation in the degree of maternal body protein loss was induced by nutritional means. The change in body protein content during pregnancy was calculated as the difference between body protein content in early pregnancy, predicted from the relationship with body weight in control sheep killed in early pregnancy, and actual content on slaughter at parturition. Serum albumin and globulin concentrations and body weight were measured at intervals during pregnancy and examined for relationships with body protein change.

Highly significant linear relationships were found between the change (%) in albumin concentration during pregnancy or albumin concentration in late pregnancy and the calculated change (%) in maternal body protein content (P < 0·001 in both cases) though fitting separate intercepts for each batoh of sheep led to improvements in fit.

Equations for prediction of loss (%) of body protein from change in body weight or maternal body weight during pregnancy though significant, were also improved by fitting separate intercepts for batches. The relative value of the relationships for predicting body protein loss is discussed.

Serum globulin concentration was not affected by protein status of the animal.

The least-squares means for first lactation milk yield, yield per 100 kg of body weight at first calving, yield per day of first lactation length, yield per day of first calving interval and yield per day of age at second calving were 1692 ± 28·2, 339·8 ± 7·30, 5·51 ± 0·97, 3·37 ± 0·81 and 1·07 ± 0·03 kg and the heritabilities of those traits were 0·192 ± 0·086, 0·078 ± 0·078, 0·287 ± 0·096, 0·192 ± 0·086 and 0·305 ± 0·097 respectively. The genetic correlations of first lactation milk yield with various measures of efficiency of milk production (except with yield per 100 kg of body weight) were positive and high (> 0·80). These results indicate that milk yield per day of age at second calving may be used for the selection of buffaloes.

Tri-w-butyl phosphate has previously been shown to increase the drying rate of cut grass leaves. It also markedly inhibited respiration and thus reduced loss of dry matter during drying. In the work reported here, some other commercially available phosphate esters were tested for the same effects, except for the inhibition of respiration. Four mixtures of ethoxylated phosphate esters increased the drying rate of excised S. 24 perennial ryegrass leaves, and three of these also reduced the loss of dry matter during drying.

The results suggest the possibility of devising single chemical treatments for both increasing the drying rate and reducing the respiration rate of forage crops conserved by drying in the field. The potential advantages of such treatments, together with the difficulties of realizing these advantages in practice, are briefly discussed.