Evidence is presented that, in Italian ryegrass, the ability to survive in the sward into a second year after sowing may be assessed on spaced plants or on closely planted rows. There is no indication that selection for the ability to survive into the second year need cause loss of yield in the first year after sowing. In an earlier paper based on the same experiment (England, 1975) incorrect formulae were used for calculating family heritabilities and genetic correlations. In an appendix the correct formulae are derived and the consequent changes in the conclusions of the previous paper are described.

Dry matter and Kjeldahl nitrogen estimations were made on the roots and shoots of the barley varieties Riso 1508, Hiproly and Maris Mink from the seedling stage to maturity under three nitrogen treatments. After heading, the shoots were further separated into ears and stems plus leaves. Total plant nitrogen uptake was greatest in the high lysine variety Riso 1508 and was associated with a greater production of dry matter. However, the proportion of total plant nitrogen and dry matter in the grain was highest in the variety Maris Mink and this effect increased with increasing nitrogen supply. The comparative efficiency of dry-matter production and nitrogen translocation of these varieties is discussed in relation to breeding barley of improved protein yield and quality.

A series of five metabolism trials was made to determine apparent nitrogen digestibility and metabolizable energy (ME) contents of protein rich feedingstuffs. The mean nitrogen digestibilities of fish meal, groundnut, mustard, sesame and cottonseed cakes were 66, 69, 68, 57 and 40%, respectively. Corresponding values for metabolizable energy values were 1820, 2460, 2330, 1870 and 1530 kcal/kg, respectively. The metabolizable energy contents of coconut cake, niger cake and blood meal were 1190, 2360 and 2190 kcal/kg, respectively. The quantity of protein, its digestibility and crude fibre content in the cakes are the prime factors for this trend in MB. Simple and multiple regression equations were derived from biologically assayed metabolizable energy and chemically analysed energy-yielding nutrient contents of the feedingstuffs. The simple regression equation is:

ME kcal/kg = 32·95 (% crude protein + % ether extract × 2·25

+ % available carbohydrate)–29·20.

The multiple regression equation is:

ME kcal/kg = 370·29 + (24·47 × % crude protein)

+ (65·77 × % ether extract)

+ (44·07 × % available carbohydrate)

- (8·15 × % crude fibre).

The correlation coefficients of simple and multiple regression equations were 0·72 and 0·73, respectively, indicating that there is very little advantage for prediction in using the multiple regression equation. The usefulness of the equation for routine checking of poultry feeds for ME is apparent since the nutrients required to predict metabolizable energy can be analysed within a short period of time.

In each of two experiments two potato varieties were grown at a range of plant densities in order to provide mature tubers of different sizes for the study of the relationshipsbetween tuber size and tuber concentration of nitrogen (N), phosphorus (P) and potassium (K). As tuber size increased, the concentrations of tuber nutrients (g/100 g dry matter) declined to a minimum value and then tended to increase with a further increase in tuber size. This suggests that when tuber samples are taken for the determination of tuber nutrient concentration on a dry-weight basis the sampling procedure should ensure that results do not vary because of differences in the tuber size distribution.

Equations to predict the leaching of nitrate either uniformly incorporated to a known depth or uniformly distributed in field soils can be reduced to the approximate form:

where f is the fraction of nitrate leached below h cm in a soil of field capacity Vm (% by volume) after P cm of drainage has passed through the profile. If nitrate is initially incorporated uniformly to a depth of w cm, then x = h – ½w(where h ≥ w); if nitrate is distributed uniformly throughout the whole profile, then x = ½h. For surface-applied nitrate x = h (Burns, 1975).

Observed mean displacements in published experiments have been compared with predictions from the equations and from equations in which the mean movement of nitrate and water are assumed equal. The new equations give better agreement with the observed data.

The results of experiments in which Navy beans (cv. Purley King) were precision drilled at the beginning, middle and end of May in 1972, 1973 and 1974 suggest that the optimum time to sow is mid-May when soil temperatures at 10 cm depth have reached 12–13 °C. Earlier sowing usually led to a reduced plant stand and low yields whilst in 1972 and 1974, two exceptionally cool years, later sowing resulted in lower yields following a reduction in 1000-seed weight.

Despite contrasting weather conditions acceptable yields of seed were obtained in all 3 years from mid-May sowings although cool wet conditions in the autumn of 1974 curtailed drying of the seeds below 30% moisture content. Accumulated temperatures (Ontario units) were successfully used to predict stages in crop development and the data used to demarcate the areas in England most suitable for Navy-bean production.

Four groups of eight lambs, 4 months of age and reared parasite-free from birth, were used to investigate the effect of the intestinal parasite Trichostrongylus colubriformis on the intake and efficiency of utilization of food, using balance trial and comparative slaughter techniques. One group (CI) was killed initially as control. Two further groups (ALC and ALI) were offered ad libitum a complete ruminant diet. The ALI group was dosed orally each day for 14 weeks with 2500 infective larvae. Sheep in a further group (PF) were individually paired to members of the ALI group, and given the same amount of food as their pair. Balances of nitrogen, Ca and P and the digestibility of dry matter and energy were determined for the ALI and PF groups during weeks 6–7 and 12–13 and after 98 days of infection the sheep were killed. The bodies of these and the CI and ALC sheep were analysed for water, fat, nitrogen, Ca and P contents.

Parasitism reduced food intake over the whole experiment by 9%, but had no effect on the digestibility of energy or nitrogen. At the first trial the N balances of the ALI group were inferior to those of the PF group due to increased urinary N excretion, but there was no difference at the second trial. Ca and P balances of the ALI group tended to be inferior to those of the PF group at both trials. The weight gain of the ALI sheep was only 50 % of that of the PF sheep with the same digestible energy and protein intakes. The protein content of the gain in empty body weight of the ALI sheep was 80 g/kg compared with 112 and 124g/kg in the ALC and PF groups, respectively. Possible causes of the poor protein anabolism are discussed.

The gross efficiency of utilization of metabolizable energy for growth was calculated to be 13·3 % in the ALI sheep, compared with 26·2 and 24·2 % respectively, in the ALC and PF groups. It was not possible to determine whether this was due to change in maintenance requirement or in efficiency of fattening.

The Ca and P content of the skeletons of the ALC and PF sheep increased by 55 % during the 98-day period, while no net change occurred in the ALI sheep. It was concluded that this was caused by an induced mineral deficiency resulting from parasitic damage in the small intestine.

Results of a 13-week group feeding study (Expt 1) and a 16-day digestion and mineral, nitrogen and water balance study (Expt 2) in which alkali-treated rice hulls were fed to young Border-Leicester × Merino sheep of 24-kg body weight are reported.

Five pelletized diets comprising a 1:1 mixture of ground lucerne and alkali-treated ground rice hulls (Expt 1) or these five diets supplemented with biuret plus one diet of 100% lucerne pellet (Expt 2) were examined.

Sodium hydroxide at levels of 0, 2·5, 5, 10 and 15% (w/w) was applied to rice hulls for 12 h and neutralized with acid. Sheep fed the 5% NaOH treatment level or greater maintained or increased body weight: those fed the 0 and 2·5% level lost body weight. Daily food organic matter intakes were: 5% alkali, 1025 g, 0% alkali, 765 g; 100% lucerne, 1195 g.

Organic matter digestibility was highest (52%) for the diet containing rice hulls treated at the 15% alkali level and this digestion coefficient was significantly greater (P < 0·05) than for the control diet (nil alkali) (42%) but not significantly greater than for diets with 2·5, 5 and 10% levels of alkali.

It'is indicated that cell wall organic matter of rice hulls treated with 15% alkali was digested to an extent of 62% whereas cell wall organic matter in the control diet (0% alkali) was digested to an extent of 13%.

Cellulose digestion (52%) of the rice hull component of diets was not increased by alkali treatment suggesting the alkali to have freed hemicellulose components of the cell wall for digestive attack. Digestibility of lignin of the rice hull component of diets was not significantly increased by alkali treatment.

Animals tolerated the salt contents of diets containing rice hulls treated at high levels of alkali, were able to clear the excess salt from their bodies without significant alteration of their blood haematocrit ratios, and drank significantly more water. All sheep fed diets containing rice hulls had appreciable amounts of soluble silica in their blood plasma (> 100/μg/l) and urine (> 25 μg/l).

It is concluded that alkali beneficiation of rice hulls offers a means of enhancing their nutrient worth to ruminants and that the process requires further study.

In seven experiments involving a total of 300 Large White pigs, moist maize preserved with propionic acid was compared, at dietary inclusion levels of approximately 85%, in whole (W) or rolled (R) forms with maize taken from the same samples, dried and then ground (DrG). Propionic acid lost in drying was returned to give identical levels in all three forms. In the first two experiments the moist maize contained 37·4% moisture, was included in diets to which no synthetic tocopherol was added and had been in storage for approximately 1 year when drying was effected and experiments on acceptability (using 54 pigs offered diets based on the three forms simultaneously in Expt 1) and digestibility and nitrogen retention (using 12 pigs on two occasions in Expt 2) were started. The moist maize used in Expts 3, 4, 5, 6 and 7 contained 45·8% moisture and was dried 2 months after harvesting. Between this time and 12 months post-harvesting experiments were made, with all diets supplemented with 10 g/t δ-α-tocopherol, on digestibility and nitrogen retention (using 18 pigs on two occasions in Expt 3) and performance between approximately 20 and 72 kg live weight (using three sets of 48 ad libitum group-fed pigs per set in Expts 5, 6 and 7). A further performance study (Expt 4) of factorial design and conducted over a similar live-weight range, between 2 and 5 months post-harvesting, investigated, using 72 individually but restrictedly fed pigs, responses from R, W and DrG based diets with or without the addition of 10 g/t δ-α-toeopherol.

Four months post-harvesting the δ-α-tocopherol levels of the moist and dried maize used in Expts 3–7 were 0·5 and 7·2mg/kg D.M. respectively. Five-six months post-harvesting the peroxide values of the other extractable fat of the moist maize markedly increased. In Expt 1 the diet based on the DrG form was eaten to the virtual exclusion of the diets based on the other two forms but performance responses were poor and symptoms (partially confirmed) of a tocopherol deficiency apparent. However, in Expt 4 there were no significant differences in response to the zero and 10 g/t δ-α-tocopherol supplementation. Overall, the DrG and R forms of maize gave similar utilization and growth (up to 8 months post-harvesting) responses. Compared with these responses those from the W form were inferior (in most cases significantly). When the moist cereal in R and W forms was fed after 8 months of storage (Expts 1, 6 and 7) the daily intakes of D.M. and induced growth responses obtained were lower than those obtained from the DrG form.

The experiment described was carried out to compare the effects of some combinations of dietary ingredients which were within the bounds of current commercial use but which differed in their lipid characteristics.

The four dietary treatments used were either low or high in lipid content with a high or low proportion of unsaturated fatty acids in that lipid. Fourteen pigs (seven gilts and seven barrows) were assigned at random to each dietary treatment. The major dietary constituents were barley × wheat × dried skim milk (treatment 1), barley × wheat × soyabean meal (treatment 2), barley + wheat + dried skim milk × tallow (treatment 3) and barley × wheat × maize × fish meal (treatment 4).

Production performances were satisfactory on treatments 1, 3 and 4. The pigs on treatment 2 ate less food, grew more slowly, had poorer feed conversion ratios and fatter carcasses than the animals on the other treatments; the reason for the poor performance on this diet is not clear.

Comparison of the fatty acid compositions of the backfat triglycerides and the dietary lipid shows that the dietary lipid had little effect on the backfat lipid characteristics; only in the case of linoleic acid was there a dietary-induced effect on the amount of this fatty acid in the backfat triglycerides of pigs on treatment 4.

Treatment 4 which produced the backfat with the greatest linoleic acid content also produced the softest backfat. The subjective fat scores of the carcasses of pigs fed the other diets were not related to the fatty acid compositions of the backfat triglycerides or the monoene/saturated fatty acid ratio.

These results are discussed in relation to the effects of diet and triglyceride structure on pig backfat lipid characteristics.

In laboratory tests tri-n-butyl phosphate applied by spraying as an emulsion at a rate equivalent to 0·25% of leaf fresh weight doubled the drying rate of individual S.24 perennial ryegrass leaves measured at 28 °C, relative humidity 22% and air speed 40 cm/sec. Increasing the rate of application produced no further increase in drying rate. In other experiments the same rate of application stopped respiration of leaves and no resumption of respiration was found in the subsequent 4 days. Comparisons of the dry-matter contents of leaves when removed from the plant and after being allowed to dry for 1 week at 27 °C and relative humidity 80%, indicated that inhibition of respiration resulted in large reductions in dry-matter losses. The potential value of a chemical spray which will both increase drying rate and reduce respiration as an aidto the field drying of grass crops is discussed. While it would be incautious to extrapolate from laboratory tests on single leaves to the field situation, evaluation under more practical conditions is clearly warranted.

For the purposes of compounded feed formulation an important assumption with regard to the digestible energy (DE) content of ingredients is made. It is assumed that the energy contents of individual ingredients in a feed are additive and therefore that, irrespective of the combinations in which the various ingredients occur, the energy contributed per unit of a particular ingredient remains constant. This implies that the DE content per unit of that ingredient is the same at all concentrations of the ingredient in the feed mixture. In other words, as one ingredient is substituted in increasing amounts for another in a dietary mixture, there is a linear change in the DE content of the whole feed. The purpose of this experiment was to determine whether this assumption is valid.

Lettuce obeys the Shinozaki–Kira relationship in which the reciprocal of plant weight is linearly related to plant density. The intercept (a) represents the reciprocal of the weight of an isolated plant and the slope (b) represents the reciprocal of yield/unit area at high densities (the ‘ceiling yield’). This work examines the time course of (a) and (b) in an ‘ideal environment’ in which water and nutrients are non-limiting, and the light/temperature regime is constant.

Two pot experiments are described: the first showed that the growth of isolated lettuces follows a logistic expression, which can therefore be substituted for a–1 in the Shinozaki-Kira equation. It was then hypothesized that b–1, the ‘ceiling yield’ would be constant over time. This was confirmed by the second experiment, giving the equation

w–1t = w–10 e1–kt × w–1max × bd,

in which wt is mean plant weight at time t, w0 and wmax are the initial and final weights of isolated plants, k is the early relative growth rate of such plants, b–1 is the constant ceiling yield, and d is the plant density.

Two examples of the use of the equation are given: one shows how it predicts the interaction between seed size and plant density within a species (subterranean clover): the other illustrates how it can be used to explain why lettuce growth appears to be log-linear against time whereas cereal growth is more nearly just linear.

The inheritance of the units of the character complex which differentiates Avena nuda from Avena sativa was studied in F1 hybrids and in the F2 generation derived from inter-crossing five cultivars of A. saliva with four cultivars of A. nuda. The 14 derived F1 hybrids could be classified into four types depending on the level of dominance of the sativa or nuda character expression. Type-I hybrids involving the cultivar Milford as parent showed a high level of dominance of the sativa-type expression, whereas the F1 hybrid from the cross, Condor × China, type IV, had the character expression typical of the A. nuda parent. Segregation in the F2 generation indicated that the entire character complex was under the control of a major gene, and supported the suggestion from previous work that modifying genes interact with the major gene to alter the expression of the homozygous nuda genotype towards the heterozygous phenotype

Homozygous nuda and heterozygous genotypes were shown to exhibit a gradient in the expression of the nuda character complex from the apex to the base of the panicle, the nuda-type characters being most pronounced in the apical spikelets. It is suggested that the variation of character expression within single panicles of homozygous nuda and heterozygous genotypes indicates the operation of an inhibitor-type gene action rather than a mutation to loss of function.

The F1 and F2 generations of a diallel cross of six-row barley involving the parents, Beecher, Athenais, Atlas 46, 3130-4564-3, and 3130-864-4 were studied and heterosis, inbreeding depression, and combining abilities were measured for grain yield, number of tillers per plant, number of kernels per plant, kernel weight, and plant height. Significant heterosis was detected for grain yield in two of the ten crosses, for number of tillers per plant in one cross, for number of kernels per plant in two crosses, for plant height in three crosses, and for kernel weight in none of the crosses. The inbreeding depression of the F2 generation was present in most cases but significantly so in a few. Atlas 46 x 3130-4564-3 exhibited inbreeding depression for grain yield, number of kernels per plant, and plant height.

The general combining ability (GCA) mean squares of both generations were significant for all characters studied except number of kernels per plant in the F1 generation. The specific combining ability (SCA) mean squares were significant for only plant height in the F1 generation and all characters studied except number of tillers per plant in the F2 generation.

The GCA effects indicated that Beecher and Athenais are good general combiners for grain yield and its components. The latter parent produced good yielding hybrids with slightly shorter plants than the remaining hybrids.

The SCA effects revealed that Athenais × 3130-4564-3, Athenais × 3130-864-4, and Beecher × Atlas 46 seem good specific combinations for high grain yield. Also, the former two crosses tend to produce shorter plants.

Soils from 55 maize fields in southern and eastern England were tested for available zinc, copper, magnesium and potassium by routine extraction procedures. A high proportion (64%) of the samples contained less than the recommended 50 mg/kg available magnesium, and 24% were within the deficiency range (< 25 mg/kg) for this element. Fewer sites were deficient in copper (7%) and zinc (5%) and these were mainly sandy soils or loams developed on Clay-with-Flints over Chalk. Zinc deficiency in maize does not appear to be a serious potential problem in Britain even though it occurs frequently in other countries, including parts of France.

A field of maize with growth problems of varying severity was studied in detail and the available magnesium concentrations found to correlate most closely with the degree of stunting. Soils with healthy plants differed from those in stunted patches of the crop by having higher extractable magnesium, copper and potassium contents. In general the composition of the maize leaves tended to reflect the supply status of the soil, except in the case of chlorotic plants.

The influence of factors affecting the availability of the elements investigated and the significance of marginal deficiencies of magnesium and micronutrients in maize are discussed.

In this paper the method proposed by Jones & Sandland (1974) for testing the linearity of the animal gain–stocking rate relationship is examined. It is shown that the method cannot be used to establish such linearity. An examination of the biases in estimation of optimum stocking rate and gain per animal and per unit area at the optimum stocking rate arising out of assuming linearity where the true relationship was quadratic led to the following conclusions. Quite large biases can arise. Selection of stocking rates straddling the true optimum reduces these biases. If experimental stocking rates are lower than the true optimum stocking rate the optimum stocking rate is overestimated and the animal gain at optimum is underestimated and vice versa if the experimental stocking rates exceed the true optimum rate.

The effect of season of harvest and previous seasonal applications of fertilizer N on the response of perennial ryegrass/white clover swards to pre-cut applications of fertilizer N was studied in three consecutive years on different sites. Herbage D.M. yield responded in a curvilinear manner to increased pre-cut N application rates. There was a tendency in all experiments for the marginal response of herbage D.M. to increased pre-cut N application rates to decrease as previous seasonal fertilizer N application rates increased. Although the effect of season of harvest on the response of herbage D.M. to pre-cut N application rates varied with site/years, it was concluded that the marginal response of herbage D.M. to pre-cut N application rate varies little throughout the greater part of the growing season. The exceptions to this are the very early and late harvests and swards that receive low supplies of N from the sward/soil complex. The results are discussed in relation to other published data and to their possible use in the control of the seasonal pattern and total seasonal supply of herbage D.M. for rotational grazing management systems.

A laboratory and glasshouse study investigated whether it was possible to improve the availability of magnesium from calcined magnesite (MgO). Samples varying from largely unchanged magnesite (MgCO3) to overburnt MgO were made by calcining small quantities of magnesite ore for up to 6 h at several temperatures between 500 and 1000 °C in the laboratory. The effect of calcining conditions on weight loss on ignition, particle size distribution, total, water-soluble and NH4+ -exchangeable Mg was determined and results compared with the current commercial oxide and kieserite (MgSO4. H2O).

The results indicated that an oxide could be produced containing nearly double the amount of readily-exchangeable Mg of the oxide used at present. The analysis showed that the most reactive oxide was produced either by burning for 3 h at 700 °C or about half-an-hour at 800 °C, i.e. the minimum time at each temperature for complete conversion of the carbonate to the oxide. Either of these two oxides increased the Mg in plants of the three crops grown in the glasshouse by 0·3% on average, whereas plants given the commercial oxide increased it by only 0·2%. The three crops removed about 70% of the applied Mg from the most reactive oxides but only 50% of the Mg from the commercial oxide. The results of an incubation experiment suggested that burning at 700 °C for 3 h gave a marginally more reactive oxide than the short burn at 800 °C. However, the most reactive oxide produced supplied magnesium at a slower rate than kieserite. This may not necessarily be a disadvantage since most of the soils where Mg deficiency of sugar beet and similar crops is a potential problem need a Mg fertilizer which maintains or gradually increases soil Mg. Thus the improved oxide may bo suitable and a comparison in field experiments of the effects of kieserite and oxides produced under different calcining conditions is needed.

Twelve Finnish Landrace × Dorset Horn ewes with a mean litter size of 1·92 and a mean body weight of 75±3 kg were individually penned from 80 days of gestation to parturition and offered a diet with a metabolizable energy (ME) and crude protein content in the dry matter of 9·7 MJ/kg and 11·4% respectively. At 120 days of gestation daily ME intake was abruptly reduced from a mean of 0·48 to 0·25 MJ/kg W0·75 for a period of 10 days.

The observed increase in the plasma concentration of urea due to the reduction in food intake was better correlated with lamb birth weight (r = 0·87) than was the increase in plasma free fatty acid concentration (r = 0·53) or the decrease in plasma glucose concentration (r = 0·76). Mean daily nitrogen balance decreased from a mean of 5·6 g before food restriction to – 1·8 g after food restriction. Although the effect was not significant, single bearing ewes excreted more total and urea nitrogen in the urine than multiple bearing ewes before food restriction. During food restriction the trend was reversed. The change in urea nitrogen excretion (Y, g/day) that resulted from the reduction in food intake was correlated (r = 0·73, P < 0·01) with lamb birth weight (X, kg); the relationship was Y = 0·54(±0·16)X – 3·48. It was estimated that the daily loss of nitrogen from the maternal body during the period of food restriction was approximately 80% of published values for the urinary nitrogen excretion of fasting non-pregnant sheep.