Two experiments are described in which the potential production of genotypes selected from within S. 321 perennial ryegrass for differing leaf length was assessed (a) in micro-swards composed of populations of similar genotypes and (b) in micro-swards of individual genotypes. In Experiment 1 the long- and short-leaved populations were also compared with the base population of S. 321 and with several other natural populations and bred varieties.

Under infrequent cutting the population of long-leaved genotypes was more productive than the short-leaved and base populations. Under frequent cutting, however, the population of short-leaved genotypes was most productive. Similarly, whilst Ba 6280 ryegrass was highly productive and the natural Ynyslas population unproductive under infrequent cutting the situation was reversed under frequent cutting. The population of long-leaved genotypes and Ba 6280 had a higher leaf area index (L) than other populations and varieties at complete light interception.

Considerable differences in productivity existed between individual genotypes, and there was also an interaction between genotypes and cutting frequencies. The relationships between yield and both leaf length and chlorophyll content are presented and the physiological basis of inter-genotypic and inter-population differences in production are discussed.

Four perennial ryegrass varieties, S.24, S.321, S.23 and Vertas Hardgrazing, were grown in micro plots containing 30 plants each at a spacing of 5 cm apart. Monocultures and four of the possible six binary mixtures between the varieties were grown in a randomized block design with four replicates. The data recorded comprised dry-matter yields and tiller numbers, and the components of the mixtures were harvested separately. The data were based on both whole plots, to give total production of mixtures and monocultures, and half plots, to give the contribution of mixture components to total mixture production. Four harvests were obtained during 1968, and the data from these were analysed separately and summed to provide the annual total data.

Mixtures and monocultures did not differ significantly for annual total dry-matter yield or for dry-matter yield at the separate harvests. However, differences in drymatter yields between monocultures and between mixtures were detected at some harvests. Within mixtures, significant differences between some of the respective components were found at certain harvests, but these were not obtained for the annual total data.

The stability of monocultures and mixtures was investigated by a regression technique and considered in the context of the environments used. This technique revealed that there was a specific mixture effect whereby the mixture (S.24 + S.23) differed significantly from all other treatments.

Significant differences between monocultures for fertile and sterile tiller numbers were detected. Between mixtures there were differences for fertile tiller numbers, and within mixtures certain of the components differed for fertile, sterile and total tiller numbers.

The relationship between dry-matter yield and tiller numbers was investigated by regression analyses over all treatments and for monocultures and mixtures separately. Significant differences between the slopes of the regression lines and zero and between the slopes of the regression lines themselves were obtained.

Possible reasons for the differences recorded both between and within monocultures and mixtures are considered and related to the competitive relations existing in the trial.

Twenty-four sugar-beet plants were cut into quarters, planted and allowed to produce fruit under varying fertilizer and irrigation treatments. Studies on the germination rates of these clusters showed that there were marked genetic differences between the clones. Wetting the seeds continually by overhead irrigation, to simulate heavy rainfalls markedly decreased the rate of germination, apparently by delaying the onset of maturity. Immature clusters from early harvests of plants which were not irrigated also showed a decreased germination capacity. The fertilizer treatments in this experiment were less important as a source of variation than the clonal and irrigation components. The results may be related to the presence of germination inhibitors in the clusters but there may be important changes in the embryos of the seeds themselves.

Evidence was obtained for the presence of germination inhibitors in the aqueous extract from sugar-beet clusters. A positive correlation was shown between the germination of cress seeds moistened with aqueous extracts from clusters of twenty sugarbeet plants and the germination characteristics of other clusters from the same plants. Inhibition was thus greater in extracts from clusters with poor rather than good germination, and also in extracts from immature clusters or those which had received overhead irrigation. The inhibitory effect was found to be located in the perianth and pericarp tissue rather than in the true seed.

An experiment was carried out in which the performance of cattle given diets containing 20 and 40% of coarsely chopped straw (1–3 in lengths) was compared with that of similar cattle given an all-concentrate diet. Each diet was offered ad libitum and twelve Hereford cross steers and twelve Friesian steers were used in the experiment. The live-weight gains and food conversion ratios were significantly better for the Hereford cross animals but there was no significant difference in over-all dry matter intakes. When the combined response of both breed types was considered there was a significantly linear decrease in live-weight gain with increasing straw intake, to the extent of 0.95 kg per week for each 10% increase in straw intake up to 40% in the diet. Similarly there was a significant increase in the conversion ratios of dry matter (P < 0·01) and organic matter (P < 0·01) with increasing straw intake. The effect on the dry matter conversion ratio was an increase of 1·67 units for each 10% increase in straw intake.

Two digestibility trials were carried out, one with coarsely chopped straw and one with coarsely milled straw, the levels of straw in the diets being the same. There was a slight decline in the digestibility of most constituents associated with milling but reductions were not very pronounced. A treatment was included in the second trial in which milled straw was included at 20% of the diet without maintaining the over-all crude protein content of the diet. The apparent digestibility of the organic matter was 5 percentage units lower with this treatment than with that containing the same level of straw in which the level of protein had been maintained.

1. An experiment consisting of two separate trials was carried out to study the utilization by beef cattle of high concentrate diets containing different amounts of milled barley straw and of protein. For each trial twenty-four Friesian steers, initially weighing about 270 kg, were divided into three groups and the animals within each group then allocated at random to eight dietary treatments. The treatments were based on an all-concentrate diet and three others containing 10, 20 and 30% of milled (1 in screen) barley straw. Four of the treatments consisted of giving the same concentrate mixture with each level of straw, and the other four involved giving concentrate mixtures with increasing levels of protein so that the percentage of protein in the diets was maintained. All the diets were fed ad libitum until slaughter.

2. Performance in terms of live-weight gain was considered as the net result of a number of factors, notably the total intake of dry matter, the digestibility of the dry matter, the efficiency of utilization of the end products of fermentation in the rumen and the composition of the live-weight gain. The inclusions of 20 and 30% of straw in the diet were associated with lower rates of gain than on corresponding all-concentrate and 10% straw treatments but the differences obtained did not attain significance. Total intakes of dry matter were greater on treatments containing 10 and 20% of straw than on corresponding all-concentrate treatments, but then declined with further increase in level of straw to 30%. This trend was significantly curvilinear (P < 0·01), the equation for the relationship being

Y = 5·881 + 0·131X - 0·004X2,

with Y being the daily intake of dry matter (kg) and X the percentage of straw in the diet. The maximum intake of dry matter was calculated to occur with a level of 16·4% straw in the diet and represents an increase in total dry matter intake of 18·2% over that on an all-concentrate diet. Food conversion ratio, expressed as total dry matter consumed per kg live-weight gain, tended to increase with increasing proportion of straw in the diet.

3. The mean digestibility of organic matter fell sharply with the inclusion of 10% straw in the ration, the decrease being 8·2% where the protein level was not maintained and 9·1% where it was maintained. Further reductions in digestibility occurred on the 20 and 30% straw diets, but the magnitude of the reductions were considerably less than those brought about by the initial introduction of straw into the ration.

4. The molar percentage of acetic acid in the steam volatile acids of rumen liquor increased markedly, and that of propionic acid decreased sharply from the all-concentrate to the 10% straw treatment with a similar level of dietary protein. Increase in the level of straw to 30% gave rise to a further increase in the proportion of acetic acid and reduction in that of propionic acid. Analysis of samples taken at 3, 6, 9 and 12 h after feeding showed appreciable differences in pattern between treatments.

5. Effects of treatment on killing-out percentage were different for each trial. In trial 1 the inclusion of straw in the diet did not cause any reduction in killing-out percentage, but the maintenance of protein level gave rise to a significantly higher killing-out percentage than was obtained with the lower protein groups. In trial 2 the killing-out percentages showed a significantly linear (P < 0·01) decrease with increasing proportion of straw in the ration, and maintenance of protein level did not give any improvement.

An experiment was carried out in which young beef cattle were given diets containing different levels of coarsely milled (1 in screen) barley straw. The proportions of straw used were 0, 10, 20, 30, 40 and 50 % and the performance of animals on these diets was compared with that of similar animals on an all concentrate diet. Each diet was given ad libitum to six animals. There was a significant linear decline in live-weight gain with increasing straw intake, the rate of decline being 0·62 ± 0·133 kg per week for each 10 % increase in the level of straw in the diet. The dry matter conversion ratio increased linearly with increasing straw intake, the rate of increase being 0·65 ± 0·186 units for each 10 % increase in straw in the diet. Dry matter intake was significantly (P < 0·001) affected by the proportion of straw in the diet. Although dry matter intake increased to a maximum at a level of 18·8% straw in the diet there was no significant increase in the intake of digestible organic matter (DOMI). There was a significant (P < 0·001) linear decline of 0·19 ± 0·04 kg DOMI with each 10% increase in straw in the diet. There was a significant linear decline in chilled carcase weight to the extent of 5·7 ± 0·096 kg for each 10% increase in straw. The killing-out percentage based on unfasted live weight declined significantly as the percentage of straw in the diet rose from 20 to 30%. However, when the killing-out percentage was calculated on the basis of live weight at slaughter less rumen contents there was no significant difference between treatments.

Sixteen field experiments made between 1963 and 1967 on direct-drilled sugar-beet seed crops compared the effects of cultural practices on the yield and quality of seed. Sowing in July gave earlier flowering and ripening than sowing in August and usually increased yields, cluster size and percentage germination. Downy mildew was sometimes more prevalent in late sowings.

Seed yields increased as the crop changed colour from green to yellow and percentage germination increased greatly as more clusters contained ‘mealy’ rather than ‘milky’ perisperm. Because of natural shedding and bird damage, seed yields then decreased and losses of 0·6 cwt/acre/day were recorded for early ripening treatments. Cluster size and percentage germination continued to increase while yield was decreasing. Crops ripened a month earlier in 1967, the ‘earliest’ year, than in 1965, the latest year.

Crops grown in rows 10 in apart lodged less than those sown 20 in apart, ripened earlier and produced, on average, 3 cwt/acre more seed, which was slightly smaller. In one experiment rows 5 in apart gave similar yields but smaller clusters than rows 10 in apart. Row width had little effect on percentage germination. Increasing the distance between plants in the row gave smaller yields with wider spaced rows, but with narrow rows plants 6 in and 12 in apart yielded more than those 2 in apart. Yields from a plant population of 52,200 plants/acre were 4 cwt/acre greater when plants were 12 in apart in narrow (10 in) rows rather than 6 in apart in wide (20 in) rows. Spacing further apart in narrow rows increased seed size. In wide rows many plants 12 in apart lodged, made secondary growth and produced small, late maturing clusters, of which few germinated.

Response to fertilizer nitrogen applied in spring was less, and less was needed for maximum yield on the thin Cotswold soils than on the silty clay loam in Lincolnshire, where it doubled yield in 1966. Phosphate and potash applied in spring had little effect on yield. Usually fertilizers had no effect on cluster size or germination percentages, but 1·6 cwt/acre N given to a late-ripening crop in 1965 decreased seed size and germination.

Ramularia leaf spot, which defoliated crops in the Cotswolds, was worst on early sown and closely spaced plants, and was unaffected by fertilizer.

A series of three large-scale field trials, involving 3500 ewes over a 3-year-period, was conducted to study the effect of restricted nutrition of breeding ewes in early pregnancy. Control or non-restricted ewes were fed at approximately maintenance level and restricted ewes at approximately half-maintenance. The majority of ewes fell into two categories—those 2–3 weeks pregnant at the time restriction was commenced and those 5–7 weeks pregnant. Restriction was applied for from 5 to 8 weeks, live-weight differences of approximately 10 1b were achieved.

Differences in performance in individual trials were invariably very small, and nonsignificant. The main effect of restricted nutrition over all trials was to decrease twinning by 0·5% and decrease the number of barren ewes by 0·8%. These differences are considered to be negligible. Only one statistically significant effect was observed within one of the trials—this was a depression in twinning in ewes 18–24 days pregnant at the time of applying the treatment, but this effect could not be confirmed in the other two trials. However, the fleece grown was affected by treatment—the fleece weight being depressed by approximately ½ lb, and grade reduced slightly.

It is concluded that restricted nutrition at the level and time applied has no effect on reproductive performances of ewes and therefore the practice of restriction in early pregnancy to conserve feed for late pregnancy is a sound policy.

A total of 512 pigs were given from 50 lb live weight one of 16 diets (four lysine levels at each of 12, 14, 16 and 18% protein), at one of four levels of intake. They were killed at 100, 150, 200 or 250 lb live weight and the carcasses jointed in a standard manner and right sides dissected into lean meat, fat, skin and bone.

Mean percentage proportion of shoulder, middle and ham joints in the dressed sides at the four weights was 36·3, 36·4 and 27·3; 35·4, 37·9 and 26·7; 34·5, 39·6 and 25·9; and 33·8, 40·7 and 25·5, respectively. Mean percentage lean meat at the four live weights was 61·5, 59·9, 56·7 and 54·2 and the mean percentage fat was 20·7, 24·4, 29·4 and 32·8.

Carcass quality was influenced significantly by dietary treatment and sex. Increasing the level of protein in the diet up to 16, 16, 14–16 and 14%, respectively, for the four live weight groups gave a significant increase in carcass leanness. Increasing the level of lysine in the diet did not have a very marked effect on carcass composition, while increasing feed intake to the highest level produced fatter carcasses at all weights. Carcasses of males were fatter and with a lower proportion of ham than those of females. Interactions involving dietary treatments and sex were described.

Chemical composition of the m. longissimus dorsi was not altered markedly by dietary treatment or sex but dry matter and intramuscular fat content rose with increasing weight. Protein content of the dry matter remained fairly constant at all weights, while colour and shear value rose with increasing weight but were not significantly influenced by dietary treatment or sex.

The pH values of the m. multifidus dorsi just after slaughter or on the day following were not markedly affected by dietary treatment, sex or weight.

Two greenhouse pot experiments were conducted to evaluate labelled concentrated superphosphate (CSP) and labelled dicalcium phosphate (DCP) alone and in mixtures for maize grown on soils low, high and very high in available P. On the low P soil yield of dry forage, total uptake of P and uptake of fertilizer P increased linearly with 0, 20, 40 and 80 ppm of P applied as the various fine and granular sources varying widely in P water solubility. Hence, all of these criteria were highly correlated and suitable for evaluating effectiveness of the P on the low P soil. On the soil high and very high in P, only uptake of fertilizer P, which also increased linearly with rate of application, was suitable for evaluating the sources. Total uptake of fertilizer P decreased with increase in soil P level, but relative differences among granular sources were similar at the three soil P levels. Effectiveness of the P fertilizers decreased markedly with decreasing water solubility of the granular sources on all soils; the same trend was true for the fine sources at high soil P levels.

Actual uptake of fertilizer P or percentage recovery of labelled P applied was a better basis for source evaluation at high soil P levels than were calculated A values. There was little advantage in this study of labelling with 32P for P source evaluation at the low soil P level over use of multiple rates of the unlabelled fertilizers. However, labelling was essential at the higher soil P levels.

The results of three cotton irrigation experiments in the western Negev region indicate that by increasing the intervals between irrigations and by applying the first irrigation at the beginning of flowering, maximum yields of 1700–2100 kg/ha can be obtained with three irrigations. In all treatments except the one with four irrigations, about 0·31 kg of lint was produced for each 1 m3 of irrigation water. In the three driest treatments, where cotton suffered from moisture stress during various periods of growth, no differences in lint quality could be detected in comparison with wetter treatments. As long as there were clear drought symptoms, such as in the three driest treatments, additional irrigation increased the number of bolls/plant, while the average boll weight remained unaffected. Additional irrigation in treatments where there were no clear water stress symptoms did not increase the number of bolls/plant, but increased the average boll weight.

Eleven forages of known digestible energy/kg dry matter (Naga & el-Shazly, 1963) were used in in vitro fermentation experiments. Direct determinations of digestible energy (D.E./kg D.M.) using the bomb calorimeter were also included, and the values were corrected for gas losses.

In vitro fermentations were interrupted every 12, 8 and 6 h, the medium was renewed and volatile fatty acid (VFA) production and cellulose digestion were estimated. Volatile fatty acid production from legumes was high early in the fermentation periods and became lower in later periods. Non-legumes behaved in an opposite manner.

Significant negative correlation coefficients between VFA production and D.E./kg D.M. were found for legumes at later intervals of fermentation, while correlation coefficients for non-legumes lost their significance at later periods of fermentation.

Digestible energy/kg dry matter could best be predicted for legumes from the volatile fatty acids produced in the second 12 h fermentation period or from the sum of the VFA produced in second, third and fourth 6 h periods of fermentation.

A comparison was made of six different methods of inoculation with Cercosporella herpotrichoidesFron on field plots of the spring barley variety Impala. All inoculation treatments produced significant differences in terms of disease incidence and grain yield compared with the uninoculated controls. Significant differences were found between treatments in terms of disease incidence, disease severity, mean yield/head and 1000 grain weights. The time of inoculation was also found to be significant. The earlier inoculation caused a reduction in yield of approximately 66 % compared with 50 % at the later inoculation. The application of these methods is discussed.

Statistical analyses were carried out on the data obtained under strictly controlled conditions in metabolism stalls with 41 different rations fed to 127 adult non-pregnant dry cows, and with 14 other different rations fed to 35 adult non-pregnant lactating cows that had calved 2–6 months earlier and whose daily milk production ranged from 11 to 20 kg.

The authors have calculated and studied the correlations between faecal and urinary potassium losses, potassium excretion in the milk, digestible potassium and potassium balance, and the 75 other nutritive factors which were analysed for each of the 55 above mentioned experimental diets.

The results show that three nutritional factors, potassium, dry-matter and nitrogen intakes, influence the fate of dietary potassium. The apparent digestibility of potassium is hyperbolically related to potassium content of the diet since the true digestibility of potassium is very high, unrelated to potassium intake and rather constant and since about 2·2 g of endogenous potassium are excreted in the faeces per kg of ingested dry matter.

The quantities of digestible potassium strongly influence both the potassium urinary outputs and potassium balance. An increase in digestible dry matter enhances too the urinary potassium excretion as well as faecal output and lower potassium balance twice as much.

But the most interesting feature in the potassium metabolism is that at any level, ingestion, digestion, excretion, there is a very close correlation between potassium and nitrogen.

Statistical analyses were carried out on the data obtained under strictly controlled conditions in metabolism stalls with 41 different rations fed to 127 adult non-pregnant dry cows, and with 14 other different rations fed to 35 adult non-pregnant lactating cows that had calved 2–6 months earlier and whose daily milk production ranged from 11 to 20 kg.

The authors have calculated and studied the correlations between faecal and urinary sodium losses, sodium excretion in the milk, digestible sodium and sodium balance and the 75 other nutritive factors which were analysedfor each of the 55 above mentioned experimental diets.

The most important factor in the fate of sodium is the amount of dietary sodium. Sodium digestibility is neither total nor constant: faecal losses and digestible amounts are enhanced when sodium intake is increased and faecal losses are also positively correlated with dry matter and nitrogen intakes. An increase in digestible sodium benefits both urinary excretion and balance, the latter being reduced by an increase in dry matter and nitrogen intake.

Sodium balance is always negative when sodium content of the diet is lower than 0.1% in the dry cows and 0.2% in the lactating cows. In our experimental conditions, the sodium requirements for milk production do not influence sodium digestibility, but are met above all to the detriment of urinary losses.

Three dry cows, each fitted with a permanent rumen fistula, were fed hay and flaked maize or hay and rolled barley in widely different proportions. All rations were offered at 7 kg dry matter daily for 3 weeks following hay alone. The cows refused all cereal 3 or 4 days after introduction of rations including 80 and 100% flaked maize; recovery of intake occurred in most instances within a further 3–10 days. On the 100% flaked maize ration, the refusals were associated with very low pH and high concentrations of lactic acid in the rumen.Refusalsof rolled barley were small and showed no clear pattern.

Rumen fermentation was reasonably stable during the last week of each period except with the 100% barley rations. On the rations containing flaked maize, molar proportions of volatile fatty acids (VFA) varied widely but on only one occasion did the proportion of acetic acid fall below 55% and in two cows that consumed flaked maize alone, the proportion of acetic acid in the rumen exceeded 60%. On the rations containing rolled barley, increasing proportions of barley were associated with large decreases in the proportion of acetic acid and increases in the proportion of propionic acid. The maximum proportion of n-butyric acid was found on the rations containing 50% cereal.

It is suggested that, when large proportions of cereals are fed, the proportions of VFA bear no clear relationship to the crude fibre content of the ration but that an association with rumen pH may exist.

Three experiments were conducted to investigate the influence on nitrogen retention of feeding protein supplements to early weaned lambs direct to the abomasum via the oesophageal groove. In Exp. 1 the lambs received a basal diet of barley and a protein mixture consisting of soyabean meal, sunflower meal and fish meal which was given either in a liquid suspension from a bottle or as dry feed incorporated with the barley. The results showed that the regression coefficients of nitrogen retention on intake were 0.48 and 0.33 with liquid and dry feeding respectively. The regressions of urinary nitrogen on intake were with liquid and dry feeding respectively 0.26 and 0.44.

In Exp. 2, various sources of protein were compared isonitrogenously as substitute for part of a barley concentrate ration. The nitrogen intakes and retentions were 14·28 and 5·09, 20·16 and 9·39, 20·53 and 8·19, 19·00 and 7·80, and 18·87 and 7·86 g/day for the control diet and fish meal, yeast, soyabean meal and sunflower meal supplemented diets respectively.

In Exp. 3 the fish meal supplement was compared with a high lysine, bloodmeal and with casein as liquid supplements to a basal diet of barley concentrate. The intake and retention of nitrogen were for bloodmeal, casein and fish meal respectively 23·41 and 7·48, 22·56 and 9·11, and 21·88 and 8·31 g/day. It appeared that the protein sources high in methionine resulted in the highest nitrogen retention. The implications of these findings in relation to the nutrition of young ruminants is discussed together with an evaluation of the experimental method as a technique to study postruminal digestion.

Results are presented from freezing tests on five varieties of winter oats from diverse origins, on their crosses in the F1 and F2 generations and on selected F3 lines from six of the crosses.

Analysis of the F1 results indicated that frost resistance was mainly determined by recessive genes, additive in their effect, but in the F2 experiment there was evidence of non-allelic gene interaction. Significant general combining ability (GCA) effects were obtained in both the F1 and F2 experiments but specific combining ability (SCA) effects were significant only in the F2 crosses. The variety Novosadsky II displayed consistently high general combining ability.

Tests on F3 lines derived from selected F2 plants revealed considerable transgression for frost resistance in all six crosses studied. The results are discussed in relation to breeding for improved frost resistance in oats.

An experiment was conducted with 32 spring-born Friesian heifer calves, purchased at an average age of 10 days and fed on cold reconstituted milk substitute at pasture.

The milk feeding treatments were 4, 4½, 6½ and 9½ weeks in length, during which time calves consumed an average of 17, 23, 43 and 70 kg dry matter/head of milk substitute respectively. The differences between treatment mean live-weight gains for 10½ weeks of the experiment were highly significant (P < O·OOl): the gains were 0·49, 0·43, 0·64 and 0·78 kg/head/day. There was no significant difference between mean rates of live-weight gain after the tenth week so that the overall treatment—mean live-weight gains for the first 23 weeks, which were 0·65, 0·61, 0·72 and 0·74 kg/head/day, strongly reflected the length of the milk-feeding period and demonstrated no significant compensatory growth by the calves.

Twenty of these animals were housed for the subsequent winter period and were returned to pasture for a second grazing season. These were artificially inseminated as their individual live weights reached approximately 320 kg. Animals weaned after only 4 weeks of milk feeding took an average of 9½ weeks longer to reach live weights of 320 kg than these receiving milk for 9½ weeks. There were no marked indications of compensatory growth during this extended period of observations.