A mixture of 14C-labelled neo-decanoic acids (NDA) applied to onion foliage was virtually all retained at the site of contact rather than being metabolized or moved within the plant. When [14C]NDA was brought into contact with non-sterile organic (muck) soil, 14CO2 was released, suggestive of oxidation by soil micro-organisms. The volatilized acids of NDA are not toxic to unsprayed plants at temperatures up to 32 °C, nor is residue in organic soil harmful to plants sown 5 or more days after NDA spray application.

Embryo survival was studied in flocks of 500 Saxon Merino and 500 Border Leicester × Merino ewes introduced to rams in either summer or autumn. The ewes were fed 200, 100 or 25% of a maintenance diet from day 2 to day 16 after mating. Embryo survival was greatest in ewes fed the maintenance diet. There was no suggestion that live weight, face cover or condition score were important factors affecting embryo survival. Embryo survival in the twin ovulating cross-breds was higher than in the twin ovulating Merinos, but there was no significant difference in embryo survival in ewes with single ovulations. Embryo survival in ewes with twin ovulations was significantly higher at the autumn mating than in summer.

Fifty-nine full-sib progenies produced in a North Carolina Model I design were assessed fortotal yield (sum of three harvests) under four treatments differing in plot size and density. The treatments were: swards of 0.25 m2, spaced plants at 0.6 x 0.6 m and single and double rowswith 0.3 m betweenrows and 0.15 m between plants, with ten plants per row. Estimates of plot heritabilities ranged from 0.24 for spaced plants to 0.59 for double rows. Heritability in the sward was 0.35. Additive genetic correlations between the sward and the other treatments were surprisingly high: about + 0.86 for the spaced plants and between +0.8 and +0.9 for the row plots. The implications of these estimates for the relative selection efficiencies of the non-sward treatments are discussed.

The influence of ambient weather conditions on the regrowth and morphology of a perennial ryegrass sward, over the period May–October 1972, was assessed by following the performance in the field of a succession of vegetative, single genotype, simulated swards previously grown under standard conditions. Crop growth rates estimated from largely non-destructive measurements of growth components (leaf extension, leaf weight/length ratio, tillering rate and tiller density) agreed with, and were more precise than, rates determined from harvests; the components having the greatest influence on growth rate were leaf extension and leaf weight/length ratio. Leaf extension and appearance were closely dependent on temperature; leaf weight/length was only slightly affected by the weather. The growth rates of total above ground parts, especially of herbage above the cutting height, were largely determined by temperature and initial leaf-area index, and insensitive to insolation. At higher temperatures, a greater proportion of assimilates was partitioned into herbage growth.

A condition known as ‘scorch” with symptoms similar to copper deficiency often occurs in dry weather on cereals grown on a sandy soil (at Woburn) with an unstable structure. Plants with symptoms contained more sulphur than normal and sulphur/ copper interactions were suspected.

Sulphur fertilizers tested in two pot experiments with this soil did not induce copper deficienciesbut increased grain and straw yields of spring wheat especially at higher nitrogen rates. Yields were increased when the mature grain contained less than 0.12% S and the straw less than 0.5% Sin the dry matter. Sulphur concentrations were larger in plants grown in the greenhouse rather than in growth cabinets and in plants grown in oven-dried rather than air-dried soil.

Soil-applied copper sulphate slightly increased grain yields in pots but in one experiment there were no corresponding increases in copper contents of the crop. In a field experiment where ‘scorch’ symptoms occurred in 1972, copper oxychloride sprays increased copper concentrations but not yields of the grain.

These results suggest that copper deficiency is unlikely to be a primary cause of ‘scorch’ symptoms.

The results are presented from a factorial experiment on the effects of genotype (Julia, Inra 200 and Caldera 535), density (4·9, 11·0 and 16·7 plants/m2) and row width (70 and 35 cm) on the quantity and quality of maize produced 136 days after emergence.

The later maturing the variety, the higher was the dry matter yield, but the lower was the dry matter percentage. There was little advantage in favour of the high density when compared with the medium density, while row width did not markedly affect the production character measured. Both density and variety significantly influenced the ripe ear. The dried grain/ear for the low, medium and high densities was 111, 89 and 74 g respectively. However, at the highest density nitrogen content, dry matter digestibility and digestible organic matter in the dry matter were all slightly reduced. With the exception of magnesium, the mineral contents showed similar trends.

Studies were carried out to measure the productivity of selections for extreme expression of the various components of canopy structure from within six Lolium populations of contrasting morphology.

Considerable variation existed for all canopy characters within each base population and this was reflected in the difference between the high and low selections.

In the first harvest year productivity was closely positively correlated with leaf length. Although some significant differences in yield occurred between selections for other characters, no general pattern was evident as with leaf length. Within the base populations differences in yield occurred between selections of similar leaf length, emphasizing the role of other physiological factors in controlling yield.

In general, dry-matter production was greater in the first harvest year than in the second harvest year. In the second year the long-leaved selections from L. multiflorum and L. multiflorum × L. perenne continued to produce greater yields than their respective short-leaved selections and base populations, but no such differences were evident in L. perenne S. 23 and S. 23 × Ba 6280. Whilst long-leaved selections from the former group were as persistent, or even more persistent than their base populations, the long-leaved selections from L. perenne S. 23 and S. 23 × Ba 6280 showed a lower persistency. Similarly, whilst erect tiller selections from L. multiflorum and L. multiflorum × L. perenne were as or more persistent than their base populations, the three L. perenne erect tiller selections exhibited reduced persistency.

The plant breeding implications of these results are discussed.

Measurements were made on 104 carcasses of Holstein or Holstein cross-bred calves in a commercial slaughterhouse and retail butchers in Monterrey, NL. Measurements were: chilled carcass weight, circumference of side, maximum depth of forequarter (three measurements), length of leg, length of side, and length of forearm. Carcasses were cut and the sum of the weights of round, rump, short loin and rib (all bone in) defined as ‘high-priced cuts’. Multiple regressions were computed for linear, semi-allometric and allometric equations using a CDC 3300 computer.

The linear form of the equation accounted for more of the total variance than either the semi-allometric or allometric forms. In all equations cold carcass weight accounted for the greater part of total variance (98·9, 97·1 and 98·2% respectively for the three equations in the order as mentioned above). The incorporation of circumference of side slightly improved the goodness of fit in all cases as did the inclusion of length of side and length of leg in the semi-allometric form. The particularly high proportion of the total variation attributable to cold carcass weight in the present study was probably due to the sparse fat cover of the calves.

The studies were designed for breeding resistant varieties of rice to bacterial leaf blightcaused by Xanlhomonas oryzae (Uyeda et Ishiyama) Dowson with induced mutations. In 1971, seedlings of irradiated lines (X$) originated from treatments of 60Co γ-and X-radiation and control (C6), which were propagated in bulk up to X6(C6) generations after the treatments, were inoculated with highly virulent isolates.

The results showed that the variability of disease reaction within the irradiated lines increased in both resistant and susceptible directions from the control mean. It was assumed from these results that the irradiation treatments could induce polygenic mutations to give both germ types more resistant and those more susceptible to bacterial leaf blight, suggesting that such treatments might be an effective approach for breeding varieties resistant to the disease.

Fifty-four British Friesian castrated male calves, initially 3, 6 or 9 months of age (107, 180 and 249 kg initial live weight, respectively), were individually fed for 83 days on maize silage (27·9% dry matter (D.M.), 10·7% crude protein in D.M.), offered ad libitum. Silage was offered either alone or supplemented with cobs of dried lucerne (21% of total D.M. intake). Three levels of urea (0, 1 and 2% of silage D.M.) were added to the silage before feeding.

Total D.M. intakes averaged 23·0, 23·4 and 21·6 g/kg live weight (LW) for the 3-, 6- and 9-month-old animals, respectively. Addition of urea increased silage intake by 11% in the 6-month-old group but there was little effect in the 3- and 9-month-old groups. Lucerne supplementation reduced silage D.M. intake from 22·0 to 18·4 g/kg LW (P < 0·001) and increased total D.M. intake by 1·4 g/kg LW (P < 0·001).

Live-weight gain (LWG) of the cattle fed on silage alone increased (P < 0·001) with increasing age of animal. The main effect of urea was to elevate (P < 0·001) LWG from an average of 0·79 (no urea) to 0·94 kg/head/day (2% urea). However, it appeared that most of this effect was confined to the 6-month-old group. The effect of lucerne on LWG decreased with increasing age of animal (P < 0·001). Inclusion of lucerne in the diet significantly reduced the response to urea (P < 0·05).

Feed conversion efficiency (LWG/100 Mcal DE intake) decreased (P < 0·01) with increasing age of animal but increased with urea addition from an average of 4·7 (no urea) to 5·3 kg LWG/100 Meal DE intake (2% urea). The response to lucerne supplementation in terms of efficiency was greatest in the 3-month-old group and thereafter declined markedly with increasing age of animal.

The results of this experiment indicated that cattle older than 6 months of age (180 kg LW) could achieve a rate of growth of 1·0 kg/head/day on maize silage supplemented solely with urea, but that younger animals required supplementary lucerne to support a high rate of live-weight gain.

Food utilization by lactating dairy cows was studied in a randomized experiment covering the first 24 weeks of lactation, with further observations on performance over the remainder of the lactation under farm conditions. Over a 3-year period 90 firstcalf cows each took part in the experiment for one lactation, making six groups of 14–16 animals.

For the experimental period a fixed basal diet was given of hay, concentrates, and wet brewer's grains. One group received only the basal ration. Four groups received in addition a fixed concentrates supplement for 4, 8, 12, 16 weeks from calving onwards respectively. The sixth group also had supplementary concentrates for 16 weeks but for weeks 5–12 inclusive the amount was doubled so that this group's diet simulated broadly ad libitum feeding in early lactation.

Milk yield was increased by extra concentrates. The greater part of the effect was apparent in the first 2 weeks of different levels of intake, with a further build-up over the next 6–8 weeks. The size of the response fell as time from calving to initiation of different intakes increased. Additional food increased and delayed peak yield level. Persistency of milk yield was not affected by fixed differences in intake. Rate of liveweight change was improved by extra concentrates, less so in the third compared with the first month on treatment.

A higher level of feeding in early lactation led to a greater partition of nutrients in mid-lactation to milk at the expense of gains in body reserves. This advantage to milk production extended to the end of lactation. In it the greatest response per unit concentrates was obtained from supplementation in the first 4 weeks of lactation but the total effect was increased by giving a double allowance of concentrates, and by extending the period of extra feeding to 8 weeks after calving.

Solids-not-fat content and yield, and fat yield but not fat content, showed a similar response pattern to milk yield.

Animal-to-animal variation in output on constant diets was characterized by negative regressions of live-weight change on milk yield. The regression coefficients were greater in early than in mid-lactation but they were constant in size at any one time for the various groups. A change in ration induced a change in output of the individual in which that production pathway favoured naturally by the animal was the more affected.

Maize was cut at 22·6, 27·0 and 41·6% dry matter and ensiled in 4 kg quantities in polythene bags without additive or after the addition of urea at 0·5, 1·0, 1·5 and 2·0% of the crop dry-matter content. Silos were opened at intervals up to 96 days. Maize of 23·4% dry-matter content was ensiled in 10 t butyl rubber silos without additive or after the addition of urea at 1·0% or fishmeal at 4·0% of the crop dry-matter content.

Silages from the polythene bag silos were all well preserved. pH values increased and total acid content fell with increasing maturity of the crop. Addition of urea had little effect on these values. Only with the most mature crop did ammonia content increase markedly with increasing level of urea addition. All silages from the butyl rubber silos were well preserved with low pH values and similar total acid contents.

Silages from the butyl rubber silos were used to measure voluntary, intake live-weight gain and efficiency of utilization of young beef cattle. The diets fed were silage without nitrogen supplement or supplemented with urea or fishmeal, added at ensiling, at feeding or included in a concentrate feed. One third of the total dry-matter intake of all cattle was provided by a pelleted concentrate feed consisting of equal quantities of dried grass and rolled barley.

The increase in nitrogen content brought about by the addition of urea or fishmeal did not affect total dry-matter or organic-matter intake but was associated with 25% increase in nitrogen consumed. Live-weight gain on all treatments with added nitrogen was 20% higher than for the unsupplemented silage. This improvement in growth rate was accompanied by significant increases in efficiency of utilization of dietary dry matter and organic matter but efficiency of nitrogen utilization was reduced. The results indicate that neither the source nor site of addition of supplementary nitrogen significantly affect live-weight gain, dry-matter intake, organic-matter intake or utilization of dry matter or organic matter. They also demonstrate that urea can be used effectively to provide supplementary nitrogen to young cattle fed a maize silage-based ration.

The rate of change in the test weight of four winter wheat varieties, with changing grain moisture content, was greater when the grain was wetted than when it was dried. The test weight of grain which had been dried and returned to its original moisture content was lower than that of the original sample.

The digestibility and intake by sheep of a neutral mixture of alkali-treated straw and grass silage was compared with an all-silage diet, mixtures of treated straw and silage adjusted to pH of 4 and 10 and with mixtures of untreated straw and silage. Treatment of the straw with alkali increased the digestibility of the organic matter from 46% to 68%. The daily intake of dry matter and digestible organic matter of the neutral, treated-straw/silage mixture was 24·1 and 15·0 compared with 14·7 and 8·8 g/kg live weight for the untreated straw/silage mixture. The sheep when fed ad libitum ate more of the neutral mixture than they did of the mixtures made acid (pH 4·0) and alkaline (pH 10·0) or of the grass silage although the differences were not significant. Calves were fed similar diets of grass silage, a neutral mixture of treated straw and silage and treated straw and grass silage offered without premixing. The calves offered the neutral mixture ate 16·0% more dry matter and 14·5% more organic matter than did the calves offered either silage alone or the unmixed diet and gained live weight at the rate of 0·42 kg/head/day compared with 0·44 for the silage alone and 0·37 for the unmixed diet.

A significant proportion of the sulphur (S) ingested by animals grazing Sorghum spp. may be utilized to detoxify hydrogen cyanide liberated after the forage has been ingested. In 1973 young sheep grazing a sorghum x sudangrass hybrid were given access to salt licks containing < 0.1 % (control) or 18 % S; in two experiments the live-weight responses to S were 32% (P < 0.05) and 18% (P > 0.05). In 1974 sheep grazing forage fertilized with 84 kg N/ha and given access to licks containing 8.5% S gained 32 % more live weight than controls with 0.1 % licks. Those with S on forage fertilized with 168 kg N/ha gained 88 % more (P < 0.01). Gypsum applied as a fertilizer (0 or 21 kg S/ha) did not affect the response.