The effect of seed protein content on grain yield has been studied in varieties of spring barley, oats and wheat grown under differing cultural conditions. Grain yield was affected by seed protein content in one experiment where very low yields were attained, but the effects were inconsistent. No effect was observed in two other experiments made in a glasshouse and the field. In a growth-room experiment, seed with high protein content produced more vigorous seedlings than low-protein seed; these differences were accentuated by increasing seedling age at very low nutrient levels, but decreased with seedling age at normal nutrient levels. It is concluded from the results that variations in seed protein content are unlikely to have a significant effect on yield under practical conditions.

The effects of several detillering treatments on dry-matter production and grain yield in barley were investigated in a series of pot experiments using two water regimes. When ample water was provided, even quite severe reductions in the number of tillers only slightly reduced grain yield in spite of large effects on total shoot dry weight. When all the plants were grown with the same amount of water, however, the plants with few tillers tended to have greater grain yield, higher water use efficiency (in terms of grain yield) and higher harvest index than the plants permitted to tiller freely. This effect was probably related to the greater transpiration rates from the freely tillering plants which led to their suffering a greater degree of water stress than the plants with few tillers. This led to the freely tillering plants having a greater proportion of sterile ears and a lower harvest index. Water stress apparently had no effect on the grain yield of the main shoot or first tiller. It is concluded that genotypes which produce few large tillers having a high rate of survival should be able to achieve relatively high yields in drought conditions without sacrificing yield potential under optimal conditions.

Nine individually penned Finnish Landrace x Dorset Horn ewes with a mean litter size of 2·33 were offered a diet containing 63% digestible organic matter (DOM) and 13% crude protein in the dry matter at a daily intake of 0·82 kg DOM (1·3 x maternal maintenance) from 95 to 110 days of gestation. On day 111 DOMI was abruptly reduced to either 0·67 kg (T1, 0·54 kg (T2) or 0·36 kg (T3)/day and kept at these levels until a few days pre-partum.

Daily N balance before food restriction was 4·9 ± 0·51 g/day. During the periods 3·9 (S1), 11·17 (S2) and 19·25 (S3) days after food restriction daily N balance was 2·8, 2·8 and 3·6 g for θwes on T1, 1·0,1·0 and 0·8 g for those on T2 and –4·1, -4·0and -4·0 g for those on T3. Total lamb birth weight was 8·0, 7·2 and 6·5 kg for treatments T1, T2 and T3 respectively. Using regression analysis it was calculated that plasma glucose concentration in late pregnancy for ewes with a total lamb birth weight of 8 kg fell below the pre-restriction value of 52 mg/100 ml when daily DOMI was reduced to 747 g. At this intake the plasma FFA concentration was 585/i-equiv./I compared with 288 before food restriction. Corresponding values for daily N balance were 5·1 and 4·9 g. A reduction in daily energy intake below 0·75 kg DOM resulted in a rapid decrease in plasma glucose and N balance, the latter being proportional to the increase in the concentration of plasma FFA. The mean daily loss of N from the maternal body was estimated to be 0·4, 1·6 and 6·1 g for treatments T1 to T3 respectively during the period of food restriction.

The artificial fibre bag technique was evaluated for assessing the proportions of dietary D. M. and N which disappear in the rumen. The most important factor determining the variability in disappearance from bags incubated together was the sample size in relation to bag size. For incubation of 5 g air dry feed, a bag size of 17 ✗ 9 cm was found to be adequate. There were also variations in substrate disappearance between animals and between days of incubation. It was estimated that three sheep and the measurement of substrate disappearance twice were necessary in order to obtain acceptable repeatability.

The technique was found to be satisfactory as a simple and rapid guide for measuring nutrients disappearance in the rumen such as protein degradation and carbohydrate fermentation. It has been used in subsequent work to measure the effect of features of the rumen environment, such as pH and NH3 concentration, on rate of fermentation.

The theory of expected response to selection between families is extended to allow for the effects of field replication and its interactions with number of plants per plot.

Greasy fleece weight (12 months growth) and wool samples from hip and shoulder regions were taken on 15 Dorset, 20 Leicester, 20 Suffolk and 17 DLS ewes (a cross of ½ Dorset, ¼ Leicester, ¼ Suffolk obtained by mating DL rams to DS ewes and DS rams to DL ewes). The purpose of the study was to compare wool production and characteristics of the first generation of DLS with that of the three breeds of origin. Wool production of DLS was 3·58 kg, 8·8 and 14% higher than that of Suffolk and Dorset, but 11% lower than that of Leicester (P< 0·01). The percentage of clean wool was highest in Leicester (78·3%), followed by DLS, Dorset and Suffolk (76·1, 74·3 and 70·5%, respectively). The average fibre diameter of the DLS and Leicester was 38 /m, 4 /m thicker than that for Suffolk and Dorset (P < 0·01). Average fibre length was 15 cm in DLS and Dorset, 6 cm shorter than in Leicester, and 3 cm longer than in Suffolk (P < 0·01). The variability in fibre diameter and length was highest in Leicester, followed closely by DLS.

Two varieties of Lolium perenne, the diploid Hora and the tetraploid Terhoy were sown either as a pure stand or as a binary mixture on to the surface of multipots filled with a standard John Innes compost. Density of sowing was varied over the range of 16, 24, 36, 50 and 100 seeds/pot. There were four replicates. The pattern of germination was followed over a period of 14 days when it was found that (i) the varieties did not differ in their germination when grown alone, but in mixtures the diploid was slower to germinate than the tetraploid, (ii) as the density of sowing per pot was increased, the mean germination time (MGT) was increased, and (iii) the final germination of both verities decreased with increasing density.

In a second experiment the same procedures were followed as before but seed of each variety was sown either as a pure stand or in a mixture of varying proportion as follows: 100:0, 75:25, 50:50, 25:75, 0:100.

The results showed that (i) the diploid had the fastest MGT whilst the mixture values showed no significant variation, and (ii) the final germination percentage of the diploid decreased relative to its pure stand value as its proportion in mixtures decreased, whilst the tetraploid under the same circumstances increased relative to its pure stand value.

It is suggested that differences such as those found could be explained by the presence of germination inhibitors in the seed coats of the two ryegrass varieties.

This paper describes the effect of two paths of weight change on the total feed consumed and on body composition at slaughter of Angus steers. The treatments were: a 15% weight loss from 330 kg live weight, at 0·5 kg/day for 100 days, followed by recovery to 330 kg on ad libitum feed intake (WL/WG group), and constant weight at 330 kg for the same length of time as corresponding paired animals in the WL/WG group took to complete their treatment (constant-weight group). There were six animals in each group and they were slaughtered when the WL/WG steers reached 330 kg. At the beginning of the experiment four animals (preliminary group) were slaughtered at 330 kg.

Intakes of feed were recorded and measurements of apparent dry-matter digestibility were made at intervals. Chemical analyses were carried out on the right side of each carcass and on the other components of the body.

The mean total intake of the WL/WG group was 12% less than that of the constant-weight group. The daily dry-matter intake in the constant weight group decreased from 5·9 kg to 4·4 kg during the experiment.

The time taken for the WL/WG steers to regain the 50 kg weight loss varied from 30 to 68 days. Their intakes at this time and their growth rates were similar to those that they experienced when they grew to 330 kg for the first time.

Apparent digestibility varied between animals but was not influenced by treatment. The constant-weight group were fatter than the WL/WG group at slaughter and had heavier carcasses, both differences being significant (P < 0·05). The difference between groups in empty body weight was not significant. Animals from the final slaughter groups had significantly heavier heads and feet and a higher ash content than the younger steers of the preliminary group. Liver weights were reduced by nutritional restriction and did not fully recover in WL/WG steers.

Two groups of nine in-calf beef cows were given daily for the last 16 weeks of pregnancy and the first 6 weeks of lactation 1·35 increasing to 3·15 kg molassed sugarbeet pulp dry matter containing added urea together with oat straw ad libitum. Additionally, one group of cows received supplementary dicalcium phosphate which increased their total phosphorus intake from about 12 to 28 g P/day.

In the absence of phosphorus supplementation, there was a marked and significant reduction in the concentration of phosphorus in the blood, and by the 4th week of lactation this was reflected in a decrease in radiographic density of the tail bones but not in a depletion of rib bone ash.

During pregnancy a severely reduced phosphorus intake did not reduce either calf birth weight or the digestibility and voluntary intake of straw. An inadequate phosphorus intake during lactation resulted in a significant decline in voluntary straw consumption and digestibility. There was an accompanying decrease in metabolizable energy intake from about 78 to 55 MJ/day, an increased weight loss in the cows and a depression in their milk yield such as to significantly reduce calf live-weight gain.

The long period of phosphorus inadequacy did not affect the subsequent satisfactory reproductive performance of the cows when both groups were transferred to grass and mated with a bull.

Seed extracts prepared by soaking ryegrass seed in water were tested for their ability to suppress germination. The tests were carried out by sowing seed on to sand-filled basins moistened with seed extract.

Extracts prepared from the two diploid varieties, S. 24 and Hora and the tetraploid variety Terhoy were able to reduce both the rate of germination and the final percentage germination when applied to the sown seed. The details were as follows, (i) When S. 24 perennial ryegrass seed was used to obtain the extract inhibition was found to be related to the concentration of the extract, (ii) The final germination of diploid seed was reduced by 16% in the presence of its own seed extract and by 27% when tetraploid seed extract was applied, (iii) The final germination percentage of the tetraploid seed was reduced by 14% in the presence of either its own extract or that prepared from the diploid seed, (iv) Simple chemical tests carried out on the seed extract, although not conclusive, gave some indication that the inhibitory substance may have been a member of the alkaloid group.

Forty (20 barrows and 20 gilts) Large White and Landrace pigs allocated on the basis of litter origin, sex and initial weight to four treatment groups with mean initial weights of 50 kg were individually and semi-restrictedly fed to about 93 kg one of four diets containing 18·8, 28·5, 38·2 and 46·5% palm kernel meal (PKM) and 11·3, 8·4, 5·5 and 4·6% blood meal respectively such that the ratio of protein contribution to the diet from blood and palm kernel meals were 2·7:1, 1: 1·3, 1: 1·6 and 1: 2·30 for diets 1, 2, 3 and 4 respectively. Growth performance was measured over the liveweight range of 50·93 kg at which latter weight the pigs were slaughtered for carcass evaluation. Live-weight gain and feed efficiency were highly significantly influenced by varying the levels of palm kernel meal and blood meal, the lowest level of palm kernel giving significantly the best rate and efficiency of gain. There was a tendency for carcass leanness to improve as the proportion of dietary protein supplied by palm kernel meal was increased, only the differences for lean meat percentage were however significant. Carcass cuts as percentage of total carcass did not appear to be influenced by the level of palm kernel meal in diets except for percentage fat cuts which decreased significantly (P < 0·05) as the dietary levels of palm kernel meal were increased.

One hundred Large White x Landrace barrows and gilts were used in two experiments involving 50 pigs (25 barrows and 25 gilts) allocated on t h e basis of sex, litter origin and initial weight to five treatment groups of t en pigs each and individually and semi-restrictedly fed one of five diets. Diet one, t h e control, was a conventionally used fattener's diet based on groundnut, blood meal and maize mixtures, and containing 16 to 17% crude protein on dry-matter basis. The remaining four diets were approximately 17% crude protein diets based on palm kernel, blood meal and maize mixtures. The maize fraction was however replaced by 0, 10, 20 and 30% cane molasses in diets 2, 3, 4 and 5 respectively. Growth performance, feed efficiency, nutrient utilization and carcass quality were studied.

I n both trials, the groundnut meal (GNM) based diet (treatment 1) supported significantly faster rates of gain t h a n all other diets except 3. I t also tended to produce fatter pigs than those on t h e palm kernel meal (PKM) based diets. Addition of 10% cane molasses (CM) to t h e basal PKM diet (treatment 3) significantly improved feed and dry-matter intake, r a t e and efficiency of gain, crude fibre digestibility and nitrogen retention. Higher levels depressed performance as well as d ry matter, protein and ether extract digestibility. Addition of cane molasses did not significantly influence carcass characteristics.

The growth, development and yield of three soya-bean varieties, Hampton, Kent and CNS, were compared in two field experiments during 1974 and 1975 in Nigeria. The results, which were similar for both years, showed that the varieties differed significantly in the order Hampton > Kent > CNS for the development per plant of leaf area, number of branches, number of nodes, number of mature pods, number of seeds, pod and seed yields, husk dry weight and seed to husk ratio as well as seed yield per hectare. The differences between the varieties in seed yield could be genetic but leaf area development seems important as well. Hampton therefore appears to have the potential for high seed yield under the prevailing local conditions.

Three soya-bean (Glycine max L.) genotypes (Bragg, Type I and Hark) were grown in Mollisol supplemented with 0, 2·5, 5·0 mg Zn/kg in pot-culture experiments. The genotypes showed significant differences in their capacity to absorb Zn. Maximum Zn accumulation was found in the genotype Bragg and minimum in Hark. The pattern of Zn distribution in plant parts was also different in the three genotypes and was differently affected by Zn application. The uptake and percentage distribution of 66Zn followed more or less the same trend as that of total Zn. The genotypes differed significantly in R(recovery), A(availability of native Zn) and L(labile soil Zn) value indicating that these three genotypes differed in their capacity for recovering applied and native Zn. The genotype Bragg had maximum R, A and L values. These results correspond well with the reported tolerance of these genotypes to Zn deficiency (Bragg > Type I > Hark).

In a field experiment with 47 wheat genotypes, plant samples were taken at anthesis and maturity and analysed for nitrogen. Taking means over all genotypes, the plants contained at anthesis 83 % of the total present at maturity, while at maturity 68 % of the plant nitrogen was present in the grain.

There was significant genetic variation in most of the component attributes determining nitrogen uptake. At anthesis, the heaviest plants contained most nitrogen. Because the nitrogen concentration in the leaves (average 2·8%) was much greater than in the stems and ears (average O8 %) and the leaves comprised, on average, 37 % of the plant weight at anthesis, variation in leanness was the main cause of variation in the nitrogen content of plants of a given weight. During grain filling, plants which lost the most dry weight from their stems and leaves took up the least nitrogen.

It is suggested that the strong positive correlation between the accumulation of dry matter and of nitrogen, both until anthesis and during grain filling, occurred because both carbon assimilation and nitrate reduction depend on energy made available from chloroplasts. In addition, assimilate is required to sustain the growth of roots which is necessary for continued nitrate uptake.

The results show that it should be easier for breeders to select for high nitrogen uptake from among heavy than from among light genotypes. However, although dwarf genotypes tended to be light, none of the correlations found was strong enough to render it impossible to produce dwarf genotypes capable of giving high yields of high-protein grain.

Four groups of eight sheep, 4 months of age and reared parasite-free from birth, were used to investigate the effect of the abomasal parasite Ostertagia circumcincta on the intake and efficiency of utilization of food. 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 daily for 14 weeks with 4000 infective larvae. Sheep in a further group (PF) were individually paired to members of the ALI group and offered the same amount of food as was consumed by their pair. Balances of N, Ca and P, and the digestibility of energy and N were determined for the ALI and PF groups during weeks 2–3, 7–8 and 12–13. After 14 weeks of dosing the sheep were killed and the bodies of these and the CI sheep analysed for water, fat, N, Ca and P contents.

Parasitism caused a 20% reduction of food intake by week 2 which was maintained throughout the experiment. Apparent digestibility of nitrogen was reduced from 60 to 44% at weeks 2—3 but subsequently showed a gradual recovery. Nitrogen balances of infected sheep were inferior to those of controls which, with the exception of the first trial during which urinary N excretion of infected sheep was increased, was entirely related to the reduced digestibility. Energy digestibility was reduced by 2 percentage units during all trials.

Weight gain of ALI sheep was only 80% of that of PF sheep. Nitrogen anabolism was reduced by parasitism, but pair-feeding showed that reduced food intake rather than a specific effect on protein metabolism was responsible. Fat deposition was markedly reduced. It was calculated that the gross efficiency of utilization of metabolizable energy for growth was reduced by 30% compared with either ALC or PF controls.

Mineral deposition (Ca or P) in the skeleton of the ALI sheep was reduced to about 35 and 50% of that in ALC and PF groups, respectively.

Growth and tuber yield of local sweet potato cultivars were compared during the 1974 and 1975 growing seasons. Three cultivars significantly outyielded the others. The cultivar effect was associated with differences in individual tuber weight, rate of bulking and percentage of total dry matter diverted into the vine or stem. Mean crop growth rate (C) and percentage of total dry matter diverted into the tubers were greater in the higher yielding cultivars and there was positive and significant correlation between Cand final total dry weight. Leaf area duration (D) was greater in 1975 than in 1974 but the differences between cultivars in D was not consistent. Higher yielding cultivars had significantly greater tuber/leaf ratio than the other cultivars.

Bulking rate and tuber weight were positively correlated with tuber yield, while the percentage of total dry matter diverted into the vine was negatively correlated with tuber yield.

Experiments were carried out over two growing seasons to find out the effects of fertilizer application and age at harvest on the yield, available carbohydrates and hydrocyanic acid content of Manihot palmata.Fertilizers were applied at the following rates: 0–0–0; 45–45–0; 45–45–45; 45–45–67, and 45–45–90 kg/ha of nitrogen, phosphorus and potassium respectively. Harvests were at 9 and 15 months after planting. Application of nitrogen and phosphorus resulted in significant yield increases. Fertilizer application had no significant effect on the hydrocyanic acid content of the tubers. Harvesting at 15 months gave more than double the tuber yields and a higher percentage of hydrocyanic acid than harvesting at 9 months. It is, therefore, desirable to use efficient methods of processing the tubers harvested at 15 months to obtain safe products for industrial and nutritional uses.

Soil responses to deep (30–35 cm) and normal (15–20 cm) mouldboard ploughing, chisel ploughing and zero-tillage have been compared for 7 years in a field experiment growing continuous spring barley near Edinburgh. The soil was of variable texture, from moderately well-drained sandy loam overlying loam to imperfectly to poorly drained sandy clay loam overlying clay loam, classified as stagnogleyic brown earth to cambio stagnogley soil. Soils of this type derived from Carboniferous till are widely used for cereal production in south-east Scotland. Measurements of soil physical properties were made at crop emergence, midseason and at harvest to characterize seasonal and long-term responses to tillage and traffic. After the first 3 years bulk density responses varied little within or between seasons, showing a compacted horizon from 0–15 cm under zero-tillage and a looser horizon from 21–33 cm under deep ploughing compared with normal ploughing. Immediately below the depth of normal ploughing there was no difference in bulk density between this treatment and zero-tillage while in some years the chisel-ploughing treatment was denser. Moisture content responses on a weight basis, together with air-filled porosity responses, showed large differences between treatments particularly at the time of crop emergency, indicating substantial alterations in the soil profile hydrology. Expressed on a volume basis the increased moisture content near the surface under zero-tillage became more pronounced and the other effects disappeared. Cone resistance responses were proportionately larger than those for bulk density and showed one major difference in that below the depth of ploughing cone resistance was greater for zero-tillage than normal ploughing in the sixth and seventh seasons, but not previously. For bulk density, but probably not for cone resistance, there were no increases after the third season of zero-tillage, the soil reaching an equilibrium density for the current management practices and machinery usage.

Twenty-one stocks of spring and •winter types of field bean were sown in April 1975 and 59 stocks of spring bean cv. Maris Bead were sown in March 1976, to investigate the relationship between seed germination and seedling emergence in the field. Laboratory germination percentage proved to be a very poor indicator of emergence in the field whereas the seed leachate conductivity test was a more useful guide. Even at recommended sowing rates low plant stands are shown to be a likely cause of yield loss and it is suggested that the conductivity test should be used to identify seed stocks of low vigour so that sowing rates of such stocks can be increased. It is recommended that the conductivity test be carried out as a useful adjunct to the standard laboratory germination test.