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.

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.

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.

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.

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 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.

Defluorination of rock phosphate by heat treatment is an important method of producing phosphates suitable for animal feed. A variety of such products have been evaluated as phosphorus sources for ruminants, e.g. Beeson et al. (1945) recorded that a material produced at a low temperature (600°C) was unsatisfactory for steers, but Ammerman et al. (1957) indicated that a calcined calcium phosphate acidified with either sulphuric or phosphoric acids was fully as satisfactory as dicalcium phosphate for steers, but not for growing sheep. Wise, Wentworth & Smith (1961) and O'Donovan et al. (1965) recorded that defluorinated rock phosphates (produced by unspecified methods) were as useful as dicalcium phosphate for growing cattle. Arrington et al. (1963) have reported that 32P contained in reagent grade dicalcium phosphate was better retained by growing cattle than when present as a defluorinated rock phosphate.