Pot experiments in which cowpea and hyacinth bean were grown at 15–45% soil moisture showed that nodulation, nitrogen fixation and plant growth were poor at 15%. The weights of nodules and plants were lower in January (winter) than in June (summer). In June cowpea was more tolerant of dry conditions giving good nodulation at 25–35% whereas hyacinth bean required 35–45%.

Under field conditions the number and dry weight of nodules were affected by the irrigation interval whereas plant growth was affected by the amount of water applied. Applying 75 mm depth of water every 7 days gave the best combination of nodulation and plant growth.

The effects of maleic hydrazide (MH) and chlorocholine chloride (CCC) on S. 23 perennial ryegrass grown for seed were investigated in a series of field experiments from 1972 to 1974. MH significantly decreased straw length and lodging, but also decreased all yield components, seed yield and germination percentage. All growth stages and harvest date were delayed and the seed production mechanism impaired. CCC had little effect on length of fertile tillers or lodging but seed yield was increased in 1972 and 1973 when the chemical was applied at spikelet initiation. In 1972 an increase in 1000-grain weight and in 1973 small but insignificant increases in numbers of fertile tillers and seeds per spikelet were responsible. This chemical had no visible effects on the growth and development of the crop or on germination percentage of the seed.

The effect of daily herbage allowance on herbage intakes and growth rates lambs grazing perennial ryegrass and red clover was investigated in two experiments. Herbage allowances defined as g herbage D.M./kg live weight (LW)/day were controlled by varying the areas of plots grazed for 2 days by groups of six lambs.

In the first experiment five herbage allowances in the range 20–120 g D.M./kg LW/day were offered on two areas of a perennial ryegrass (cv. S. 23) sward that received nitrogen fertilizer applications of 39 or 78 kg N/ha/28 days. In the second experiment five herbage allowances in the range 30–160 g D.M./kg LW/day were offered on perennial ryegrass (cv. S. 23) and red clover (cv. Hungaropoly) swards.

Asymptotic curves were fitted to describe the relationship between herbage allowance and daily intake of herbage. In Expt 1 nitrogen fertilizer rates did not affect the yield of herbage or animal performance. In Expt 2 intakes were higher on the clover sward than on the ryegrass sward at the higher herbage allowances.

The asymptotic curves to describe the relationship between herbage allowance and growth rate of lambs differed widely between periods. Growth rate of the lambs increased linearly with increase in digestible organic matter intake. Live-weight gain per unit of digestible organic matter intake was higher on the red clover than on the ryegrass.

The conclusion is drawn that if the herbage present to ground level is not more than three times the daily intake of the animals, intake of herbage of the animals may bo restricted.

The seed-coat of all white-flowered varieties of Vicia faba and segregants tested was free of tannin. In two field trials, the whole grain of white-flowered varieties wassignificantly higher in in vitro digestibility of the dry matter, on average 4·7% higher, than coloured-flowered varieties of similar seed size. In subsequent trials where the testa and cotyledon were examined separately, this difference was shown to be largely due to a mean D value (digestibility of the organic matter) of the testa in tannin-free varieties of 56·4% compared with 17·2% in tannin-containing varieties. Seed size was positively correlated with D value but not because of differing proportions of testa.

Differences between varieties in acid-pepsin solubility and protein content of the testa were much smaller and not associated with presence of tannin. The testa colour of some tannin-free F2 plants was a darker shade of grey than either parental population. An inbred line completely lacking in anthocyanin in flowers and stem but with the normal black wing spot had tannin in its testa.

Grains of peas from the coloured-flowered variety, Minerva, reacted to a tannin test wheieas those from white-flowered varieties, Greenshaft and Flavanda, did not.

The case for breeding further tannin-free varieties of Vicia faba is discussed.

The residues from a continuous millet–maize rotation, grown at two levels of phosphate and two levels of nitrogen fertilization, were either burned and the ash incorporated; chopped and incorporated unburned; or completely removed. After 3 years, differences in soil organic matter were small and largely non-significant, but the ash treatment had minimized the general fall in soil pH, and the ash and the unburned residue treatments had both conserved topsoil exchangeable K and Mg, which, where the residues had been removed, had declined by 44 and 12%, respectively. Fertilizer effects were also significant; single superphosphate had increased exchangeable Ca and lessened the fall in soil pH; calcium ammonium nitrate had depleted exchangeable Mg generally and had lowered pH and exchangeable Ca particularly where unburned residues had been returned.

A balance sheet of soil cations (0–30 cm), drawn up from soil and crop analyses and known fertilizer inputs shows, first, that whereas the calcium added in single superphosphate increased the exchangeable reserves of this nutrient, that added as calcium ammonium nitrate did not and must be presumed lost by leaching; secondly, the decline in exchangeable K where residues were removed was much less than the total crop removal, indicating a probable substantial release from non-exchangeable form.

In the fourth season, treatment-induced soil differences, in particular the ratios between exchangeable cations, significantly affected the chemical composition of the maize test crop but not its final yield.

Although the administration of pregnant mares' serum gonadotrophin (PMSG) to induce superovulation is a well established procedure (see Anderson, Schultz & Melampny, 1963), the unpredictability of the response to this treatment continues to impose a constraint on the commercial application of egg transfer techniques in the large domestic animals. In sheep, the additional use of human chorionic gonadotrophin (HCG) has been mainly centred on attempts to control the time of ovulation (Ortavant, Thibault & Wintenberger, 1949; Braden, Lamond & Radford, 1960; Dziuk et al. 1964; McGovern, Williams & Hancock, 1969). However, Killeen & Moore (1970) found that the proportion of follicles which rupture was increased in PMSG-treated ewes which had been given HCG at the beginning of oestrus. The purpose of the observations recorded here was to examine the possibility that a further gain in ovulation rate in PMSG-treated sheep might be obtained with the use of luteinizing hormone releasing factor (LHRF). No attempt was made to reproduce physiological levels of the releasing factor and dosage was aimed at achieving a superovulatory effect.

Untimely ploughing and rotavation of a silt loam soil was found to increase bulk density, and mechanical resistance to a needle penetrometer probe, and to reduce air porosity. These effects were not found deeper than 8 cm, although measurements with a 13 mm field penetrometer probe indicated some increase in mechanical resistance down to 30 cm. The effect of untimely cultivations on soil conditions was small when compared with the effect of loosening by hand digging. This treatment reduced substantially the bulk density and mechanical resistance; it increased air porosity and moisture content of the subsoil. Although measurements of mechanical resistance with the laboratory penetrometer were 2·4 times those of the field penetrometer, there was nevertheless good correlation between measurements.

Total VFA concentrations, individual VFA proportions and ammonia concentrations in the rumen of cattle grazing tropical pastures for 7 months during the dry season were compared with concentrations of these metabolites in cattle grazing in the wet season and in cattle given two pasture hays in pens.

Neither total VFA nor ammonia concentrations were altered by periods of new pasture growth within the dry season although responses in live weight occurred. Further evidence that concentrations of total VFA were insensitive to differences in feed quality was shown in the pen experiment.

VFA concentrations were 53% higher in the rainy season than in the dry season and ammonia concentrations doubled from 62 mg/1 in the dry to 128 mg/1 in the wet season. Ruminal ammonia was related to ingested bolus N concentration (r = 0·58, P < 0.001) during the dry season.

Individual VFA proportions did not vary greatly. The highest acetic (79·1%) and lowest butyric acid (5.10%) proportions occurred in the same sample. Iso-valeric and valeric acid proportions were related positively to ruminal ammonia (P < 0·001).

In grazing cattle, concentrations of VFA and ammonia in their rumen taken at hourly intervals between 07.00 and 18.00 h did not vary greatly with time. Samples taken before 10.00 h had higher VFA and ammonia levels.

Seven field experiments were made on the effect of two harvesting dates on the nitrogen requirements of sugar beet. All were on Rauceby series soils overlying oolitic limestone in Lincolnshire.

Nitrogen fertilizer increased sugar yield in all experiments, and yield was considerably higher at the mid-December harvest than in early October. On average, the sugar-yield response to nitrogen was greater at the late harvest, and the requirement for nitrogen was about 45 kg/ha higher then than at the early harvest. Sugar content was depressed less at the late harvest than at the early by increasing nitrogen rate.

These results suggest that farmers should apply more nitrogen to fields that they plan to harvest late than to early-harvested fields; they also have implications for the conduct and interpretation of nitrogen response experiments on sugar beet.

The grazing feed intake of four ¾ Brahman and four purebred Hereford steers was measured on four occasions during 12 months while they grazed improved pastures in a cool temperate environment. When pen fed roughage diets, the excretion pattern of chromic oxide and faecal nitrogen–digestibility relationships were also investigated in these animals.

There were no breed differences in the relative recovery of Cr2O3 in the faeces when bulking 10.00 and 17.00 h samples nor were there breed differences in the faecal nitrogen–digestibility regression obtained. However, although there were large discrepancies between feed intake and live-weight change when measured in different seasons, the Herefords had the higher feed intake on each occasion while breed differences in live-weight change were non-significant.

Two experiments designed to compare lambs born to Merino ewes subjected to either nutritional deprivation or high ambient temperatures (diurnal: 8 h at 42·2 °C, 16 h at 32·2 °C) during the last two thirds of gestation are described.

In Expt 1, lambs from ewes group-fed to maintain maternal body weight at high ambient temperature were lighter (P < 0·01) and had shorter metacarpal bones (P < 0·01) than those from ewes fed to either lose, maintain or gain weight at prevailing temperatures (– 2·0 °C to + 16·4 °C). The regression of metacarpal length on the cube-root of birth weight (‘linear equivalence’) was linear. Simple maternal under-nutrition was thus not indicated as a cause of foetal stunting in heat-stressed ewes, though the proportions of affected lambs closely resembled those of the nutritional dwarfs.

In Expt 2, in which all ewes were individually fed, heat-stressed ewes fed ad libitum consumed 40% less feed and produced lambs which were markedly lighter than those from controls at prevailing temperatures. Other control ewes pair-fed at the level of intake of heat-stressed ewes gave birth to lambs of similar weight to those fed ad libitum. Thus, although feed intake was substantially reduced at high temperatures, the amounts actually eaten by heat-stressed ewes were sufficient to enable control ewes to produce lambs of normal weight. The relationships between birth weight and the weight of the adrenals, cerebellum, cerebrum, heart, kidneys, liver, spleen and thyroid were linear, irrespective of treatment, and as in Expt 1 metacarpal length was linearly related to the linear equivalence of birth weight. However, not all changes in body components were directly proportional to changes in the body as a whole, and heat-affected lambs were thus neither true miniatures nor achondroplastic dwarfs. Until these relationships are clarified it is suggested that ‘stunting’ is the most appropriate description of the influence of high ambient temperature on the sheep foetus.

The findings are consistent with the suggestion that the adverse effects of high temperature arise from an extreme form of foetal undernutrition.

In three separate experiments, lucerne hay was sprayed with solutions of formaldehyde as it was being baled. Moisture content at baling was respectively 20, 28 and 34% in Expts 1, 2 and 3, the latter being considered higher than normal. Dry matter lost during 4 months of storage averaged 6·7% and was unaffected by formaldehyde treatment.

Increasing rates of formaldehyde application decreased the amount of plant nitrogen digested in the microbial stage of an in vitro system and increased the amount of nitrogen digested in the subsequent acid-pepsin stage (Expt 1 only). When the hays were fed at constant intake to sheep in metabolism cages, formaldehyde treatment depressed the concentration of ammonia and volatile fatty acids (VFA's) in rumen fluid and lowered the molar proportions of iso- and n-valeric acids, but caused either very little or no depression in apparent energy digestibility. It was concluded that formaldehyde treatment of the hays reduced protein degradation by rumen microorganisms and probably increased the amount of protein digested in the post-ruminal region of the digestive system, and that this was achieved without any serious effect on energy digestion.

The hays were also fed for 50 days at restricted and ad libitum intakes to young Komney sheep kept in outdoor pens, followed by a 55-day post-treatment period on spring pasture. Voluntary intake was high in both experiments and was unaffected by formaldehyde treatment in hay baled at normal moisture content. There was a tendency for formaldehyde treatment to cause a small increase in voluntary intake in hay baled at the highest moisture content, but this was counteracted by its effect in depressing digestibility, giving no increase in digestible dry-matter intake. Live-weight gains were low in relation to intake, giving a weight loss in most treatment groups. Formaldehyde treatment significantly reduced weight loss and the effect was still present at the end of the post-treatment period. From regressions of weight change on digestible energy intake, it was considered that formaldehyde treatment had brought about a small improvement in the efficiency with which energy was used below maintenance.

Wool growth rates appeared normal for the levels of intake achieved and were increased 14·5% by formaldehyde treatment at ad libitumintake and 5·5% at restricted intake. Residual responses to formaldehyde treatment in the post-treatment period averaged 8%. The total amount of extra clean wool produced from formaldehyde treatment over both periods was 46and94g respectively at the restricted and ad libitum intakes, representing only 1·5 and 3·0% of the annual fleece production. Wool growth on diets treated with formaldehyde in sheep feed at the maintenance level of energy intake is discussed in relation to the concentration of protein-bound sulphur-containing amino acids (SAA's) in the diet dry matter. It was concluded that large responses in wool growth from protein protection of forage diets are unlikely unless the concentration of SAA's in the dry matter can be considerably increased from their present low levels. It is suggested that the possibility of achieving this through plant breeding techniques be investigated.

MCPA and 2,4-D sprays at up to 1/20 the dosage normally vised for weed control in cereals severely distorted sugar beet, which subsequently grew at near normal rate but remained distorted. The severity of symptoms and yield depression depended on the stage of growth of the beet when sprayed. Sugar-yield loss was greatest when plants were sprayed at the 6–8 leaf stage.

Hotroom treatment of ewes during the last two-thirds of gestation resulted in the birth of lambs which were significantly lighter than lambs born to nutritionallydeprived ewes. Neither high temperature nor undernutrition had significant effect on the density of either primary or immature secondary wool follicles, but the total number of mature secondary follicles tended to decline in the lambs from unheated ewes as the level of nutrition declined, and was significantly reduced by a further 30 % in the hotroom group.

In a second experiment, heated and unheated ewes fed to appetite were compared with unheated ewes pair-fed to the hotroom level of feed intake. High temperature had no apparent effect on maternal wool growth, but did reduce total wool follicle number in new-born lambs by approximately 50%. This effect was most marked with respect to mature secondary follicles (only 18% of unheated mean), less so in immature secondaries (56% of unheated mean), and barely discernible amongst primary follicles (93% of unheated mean). None of the differences in follicle numbers between the two unheated groups was significant.

The results suggest that the effects of high temperature on wool follicle development in the sheep foetus are akin to those of extreme undernutrition.

Thirty-eight mature Scottish Blackface sheep were mated at pasture and 32 brought indoors when 3–4 weeks pregnant. Eight were killed at this stage as controls (CI). The remaining 24 were offered a basal hay ration (200 g/head/day) supplemented with a semi-purified diet containing 84 g crude protein/kg and either 1·5 (P1), 2·8 (P2) or 9·3 (P3) g P/kg dry matter. The rate of feeding of the supplement allowed a mean daily P intake (g/day) in groups P1, P2 and P3 of 1·1, 1·6 and 4·7 and 1·6, 2·5 and 7·9 during weeks 4–15 and 16–21 of pregnancy, respectively. Six well-nourished sheep, fed conventionally, provided control ewes and lambs.

Balance trials were conducted on four sheep from each of groups P1 P2 and P3 during weeks 9–10, 14–15 and 19–20 of pregnancy. All sheep were slaughtered at parturition and selected bones of ewes and lambs removed for histological and chemical examinations. Whole body fat, nitrogen, Ca and P contents of the ewes and mineral content of the lambs were determined.

The faecal P excretion of the P1 sheep ranged from 10·8 to 19·1 mg/kg body weight/ day; urinary P excretion ranged from 0·7 to 2·9 mg/kg body weight/day in early and mid-pregnancy and from 1·0 to 8·1 mg/kg body weight/day in late pregnancy. It is suggested that on this evidence the minimum net faecal and urinary endogenous P loss can be no greater than about 13·5 mg/kg body weight/day. Carcass analysis and bone histology and chemical composition confirmed that the P requirement of pregnant ewes is much smaller than has been generally assumed.

It is suggested that for a 50-kg ewe carrying twins the P requirement increases from an average of 1·1 g/day during the first to about 2·5 g/day during the last month of pregnancy.

Penned Romney wether sheep were fed ad libitum diets of untreated silage and hay made from the same pasture (Expt 1), untreated silage (Expt 2), and high quality fresh pasture (Expt 3). Voluntary intake and wool growth were measured. In each experiment half of the sheep were given intraperitoneal injections three times per week which supplied the equivalent of 1·03 g DL-methionine/day.

Relative to silage in Expt 1, hay increased voluntary dry matter intake, depressed apparent nitrogen digestibility and increased wool growth. Methionine supplementation increased voluntary intake and wool growth with animals fed on hay or silage in Expt 1 and with those fed on silage in Expt 2, but had no effect on either variate with the diet of fresh pasture.

Wool sulphur content, measured in Expts 2 and 3, was increased by methionine supplementation, and it was calculated that 34 and 15% respectively of the sulphur administered as methionine was recovered in the wool.

The effects produced by methionine supplementation in this work are compared with those produced from different forms of post-ruminal amino acid supplementation in sheep fed a variety of diets. Factorial estimates of the requirements for sulphur of sheep and cattle in different physiological states have been calculated, and are discussed in relation to results of trials involving supplementation with sulphur-containing amino acids.

The effect of six intervals between harvests and three levels of N application on digestibility, digestible yield and nitrogen content and yield was studied in four ryegrass(Lolium) varieties during a 30-week period in the first harvest year in a field experiment.

Digestibility was higher with a 3-week than with a longer interval between harvests. Yield of digestible organic matter was increased by extending the interval from 3 to 6 weeks, but was slightly reduced by extending from 6 to 10 weeks.

Increase in the level of applied N increased the degree of curvature downwards in the response to extending the interval in both yield of digestible organic matter and yield of N, supporting the view that N use should be accompanied by shortened intervals between harvests.

Digestibility varied by up to 15 units D-value from one time of the year to another with a constant interval between harvests. The highest values were in the spring. Autumn values were low in spite of a relatively high proportion of green leaf.

During the period immediately following the main period of stem development, doubling the interval from 4 to 8 or from 5 to 10 weeks reduced digestibility by 10 units and reduced digestible yield by 22%.

In the absence of applied N, the N yield of S. 321 was 31% greater than the average of S. 22, S. 23 and S. 24. However, the apparent recovery of applied N in S. 321 was much lower than in the other varieties.

Gas liquid chromatography was used to investigate the influence of several T, S and unclassified cytoplasms on the fatty acid composition of oil from A632 and CrS4HLA maize seeds. The fatty acid compositions of the A632 and CrS4HLA seeds differed markedly from each other with respect to oleic and linoleic acids but were stable within each seed line with respect to all sixteen of the cytoplasms tested.

The results of field experiments on the influence of nitrogen fertilization on the yield components, starch and prussic acid content of two of the cassava cultivars recommended for cultivation in Nigeria are presented. The two cultivars 53101 (local) and 60506 (improved) were harvested at 9, 12 and 15 months. In general, the improved cultivars appeared to respond better to N fertilization, but high rates of N (150 kg N/ha) tended to reduce the yield performance of the two cultivars. The local cultivar produced maximum yields of 31·5, 37·5 and 55·7 fresh tuber t/ha with 60 kg N/ha at 9, 12 and 15 months, respectively, while the improved cultivar gave maximum yields of 31·5 and 48·4 t/ha with 120 kg N/ha at 9 and 12 months, respectively, and 64·1 t/ha with 90 kg N/ha at 15 months. By allowing the crop to grow up to 15 months, the starch yield was more than doubled and about three times the yield obtained at 9 months. The 53101 strain seemed to produce maximum starch yields with 60 kg N/ha while the 60506 type tended to give maximum starch yields with 90 kg N/ha. Influence of N treatments was significant up to 12 months of age but not at 15 months.

The HCN content of both cultivars diminished considerably with the age of the plant, dropping at 15 months to about half the level at 9 months. While the HCN concentration of the local cultivar tended to increase with higher N-fertilization, that of the improved cultivar diminished, particularly at 12 months after planting. At 15 months however, the HCN content of both cultivars rose with increasing N. fertilization.

Twenty-two beef cows, producing on average 5·5 kg 4% fat corrected milk per day, were offered diets of rolled barley and silage such that eight animals were consuming 70%, seven 95% and seven 120% of their estimated energy requirements. Blood samples were taken at intervals during the day and the plasma concentrations of glucose, free fatty acids (FFA), ketone bodies, total protein, albumin, globulin, urea nitrogen, calcium, inorganic phosphate, magnesium and copper determined.

Diurnal variation was found in the plasma concentration of glucose, FFA, ketone bodies, urea nitrogen, albumin, calcium and magnesium; it was particularly marked for the first four constituents and appeared to be related to feeding.

There were no overall significant differences between groups in the mean daily concentrations of the measures of energy status (glucose, FFA, ketone bodies), but significant (P < 0·001) prefeeding group differences were found in glucose and ketone body concentrations. No significant differences between groups were found for the remaining constituents.

There was a postprandial depression in plasma glucose concentration, which was positively correlated with FFA concentration.