Passive lability of body core temperature during brief exposures to thermal stress is an efficient means of thermoregulation which few species of domestic animals appear to utilize. The body temperature changes of 30 shorn sheep and 10 shorn goats have been measured during standard heat and cold exposures lasting 7 h. During exposures to heat, air temperature was increased from 20 °C to 45 °C then reduced again to 20 °C. Rectal temperatures of goats and Soay, Welsh Mountain, Merino and Clun Forest sheep rose by an average of 1·96 °C, 1·22 °C, 1·04 °C, 0·85 °C and 0·80 °C respectively. All animals had similar increases in respiratory rate. During exposures to cold, air temperature was reduced from 20 °C to about 6 °C then increased again to 20 °C. Rectal temperatures rose by 0·18–0·20 °C in goats and in all sheep except Soays in which they fell by 0·28 °C. All animals showed moderate to vigorous shivering. None of the animals exhibited passive body temperature lability as an adaptation to thermal stress.

The effects of crop density and fertilizer application on three varieties of marrowstem kale were investigated. The yield of stem, yield of leaf, components of leaf yield and plant height were studied separately. Varietal differences and effects of density and fertilizer application were significant for all characters, except for the effect of crop density on leaf and stem yield per ha.

Significant variety x treatment interactions occurred for a number of the characters measured. The possible importance of these is discussed.

Merino lambs had higher serum protein concentrations at birth than Blackface lambs. In both breeds single lambs had higher concentrations than twins. The maximum mean immunoglobulin concentrations in Merino singles, Blackface singles and Blackface twins were 2·50±0·12, 2·50±0·19 and l·96±0·15 g/100 ml serum respectively, and were recorded 18 or 21 h after birth.

Relative growth rates in swards of vernalized plants of perennial ryegrass were one and a half times as great as those found in swards of comparable non-vernalized material. This difference was associated with changes in the distribution of the products of photosynthesis and differences in the scale of losses of dead matter. Changes in sward geometry appeared to be of less importance.

1. In a series of experiments with cannulated lambs the amounts of 2, 6-diaminopimelic acid (DAPA) and a-amino nitrogen passing daily through the abomasum, terminal ileum and rectum were measured. While there was a very significant net absorption of α-amino nitrogen between the abomasum and terminal ileum, there was no net absorption of DAPA between these points. Indeed, there was a tendency for more DAPA to leave the terminal ileum than entered the abomasum, though this was only significant at the 10% level. In all cases significantly less DAPA passed out of the rectum than passed through the terminal ileum, indicating extensive degradation of this amino acid in the hind-gut, probably as a result of microbial activity.

2. In adult sheep given control rations no DAPA could be detected in the blood, even when 643 ml plasma were analysed. These sheep usually excreted less than 5 mg DAPA daily in the urine.

3. When synthetic DAPA was introduced into the peritoneum, blood, abomasum, rumen or caecum of cannulated adult sheep in physiological amounts, approximately 80, 83, 53, 5 and 0 % of the administered dose was recovered in the urine. Furthermore, when introduced into the abomasum, DAPA could be measured in plasma from the anterior mesenteric and jugular veins.

4. It was concluded that in the normal sheep the DAPA-containing fraction of the bacterial cell-wall material synthesized in the rumen is not digested in the small intestine. In the caecum and colon, however, this fraction is extensively degraded by hindgut bacteria.

A feeding and balance trial was conducted for 15 weeks on 25 lambs (aged 3–5 months) divided into five groups of 5 animals each on a basal ration consisting of oats, groundnut cake, barley, common salt, green grass and wheat straw. The five groups were fed a mineral supplement as follows:

Group I. Basal ration plus ‘Supermindiff’ mineral mixture (control group).

Group II. Basal ration plus calcined superphosphate.

Group III. Basal ration plus superphosphate.

Group IV. Basal ration plus superphosphate plus oral cobalt chloride (3 mg Co/10 kg body weight).

Group V. Basal ration plus superphosphate plus parenteral vitamin B12 (50 μg/week/ animal).

Calcination of fertilizer-grade superphosphate at 600°C for 2 h reduced the fluorine content from 23350ppm to 1600 ppm. The results show that high fluorine or superphosphate significantly reduced growth rate and retention of calcium and phosphorus and significantly increased blood inorganic phosphorus. Calcination of superphosphate in Group II gave comparable results to the control group (Group I). The oral Co or parenteral vitamin B12 supplementation (Groups IV and V) did not ameliorate the adverse effects of high fluorine in superphosphate.

It is concluded that calcination of superphosphate at 600°C for 2 h yields a suitable defluorinated product which can be used as a phosphorus supplement in the feeding of animals. Fertilizer-grade superphosphate is unsuitable due to its high fluorine content, the adverse effects of which are not mitigated by oral Co or parenteral vitamin B12 supplementation.

1. In experiments with four lambs cannulated in the abomasum and terminal ileum the amounts of muramic acid, diaminopimelic acid and α-amino nitrogen passing through the abomasum, terminal ileum and rectum were compared. While the concentration of muramic acid and diaminopimelic acid was higher in the ileal than in the duodenal dry matter, the ratio of muramic acid to diaminopimelic acid remained fairly constant at about 1·00:0·86 on a molar basis.

2. There was a very significant net absorption of α-amino nitrogen between the abomasum and terminal ileum, but no net absorption of muramic acid between these points. However, less muramic acid passed out of the rectum than passed through the terminal ileum.

3. It was concluded that in the normal sheep bacterial mucopeptide synthesized in the rumen is not digested in the small intestine, but is extensively degraded by bacteria in the caecum and colon.

Productivity and percentage conversion of light energy were measured in (a)clonallypropagated swards of populations of genotypes selected from the variety S. 321 forcontrasting combinations of leaf rigidity and tiller angle, and (b) families from assortativecrosses between genotypes of this variety of differing canopy structure. A further experiment was carried out to examine the canopy structure and pattern of light interception of populations, families and genotypes of contrasting productivity.

Under infrequent cutting (28–34 days) the tiller population selected for erect tillers and rigid leaves was more productive than those selected for prostrate tillers and rigid leaves, and prostrate tillers and lax leaves. Under frequent cutting (14–17 days), however, the populations with prostrate tillers were most productive.

Considerable differences existed in the productivity of the S. 321 families, and their relative performance differed under the two cutting frequencies. Under infrequent cutting the highest yielding family was 17% more productive than the base population, whilst under frequent cutting the yield of the most productive family was 19% greater than that of the base population.

The heritability of sward yield was 0·64 under infrequent cutting and 0·86 under frequent cutting.

The most productive genotypes, populations and families under infrequent cutting had the highest leaf-area index (LAI) at complete light interception and the lowest extinction coefficients for visible radiation (Kvis). By contrast, under frequent cutting the most productive types had high extinction coefficients and large LAI in the basal layers of the canopy.

The physiological basis of differences in productivity is discussed in relation to canopy characters whioh may be used as selection criteria for increasing the efficiency of light utilization in herbage grasses.

Treatment effects on levels of soil carbon and nitrogen in four long-term experiments at Samaru are reviewed in relation to an expected change in the future away from a bush-fallowing agricultural system towards an intensive mechanized system of permanent agriculture.

Where different rates of farmyard manure were applied to the soil annually for nearly 20 years marked differences in soil organic matter contents developed. The mean soil carbon (0·82 per cent) of plots that received 12·5 tonnes ha-1 annum-1 is now almost four times as great as the mean content (0·22 per cent) of control-plot soils. Phosphate applications tended to encourage higher levels of soil organic matter, but where mineral fertilizers (N, P and K) were applied with farmyard manure lower soil organic matter levels and C:N ratios than those of manure-only plots resulted. Apparent retention in the soil of carbon and nitrogen applied as farmyard manure was of the order of 12–15 and 30% respectively. A groundnut shell mulch, applied for 9 years, produced significantly higher levels of soil organic matter than control plots.

In a rotation experiment in which three years of cropping alternated with either 2, 3 or 6 years of planted Gamba grass (Andropogon gayanus) fallow, large differences in soil organic-matter status and rate of turnover existed between the three rotations. In particular the 3-year fallow showed an annual rate of soil organic-matter increase over twice that of the 2-year fallow. Soil nitrogen build-up exceeded 50 kg ha-1annum-1 in the 3-year fallow.

Shortage of farmyard manure and the relatively poor return from systems that include unproductive fallows suggest that in future soil organic matter must be maintained by the return to the soil of all crop residues.

When incoming radiation was reduced artificially to 50% daylight during the postflowering period in peas, the rate of abscission of flowers and pods increased in the same way as when the density of planting is raised. Shading from flowering onwards reduced yield almost to the level of peas that were shaded throughout the growing season, even though peas that received full daylight until flowering had many fertile tillers and a greater reproductive potential in terms of the total number of flowers produced. Conversely, when shades were removed at flowering time the crop was able to compensate and yields approached those of peas grown entirely in full daylight, this was mainly due to a reduction in absoission losses of flowers and pods so that the majority of pods formed on the main stem contributed to final yield.

It is suggested from these results that the major source of dry matter for pea yield is the photosynthate produced during the post-flowering period rather than that translocated from roots or stems following storage during the vegetative period.

The effect of temperature on the heat production, of temperature-acclimatized feathered and defeathered cockerels was examined at 15, 22, 25, 29, 34 and 38 °C. The maintenance ME requirements and the net availability of ME (NAME) were determined for each temperature.

The fasting heat production of defeathered cockerels measured at 22, 29, 34 and 38 °C, decreased continually with increasing temperature. The feathered cockerels also showed a general decrease in fasting heat production with increasing temperature between 15 and 34 °C, but there were relative increases in fasting heat production between 22 and 29 °C.

The ME requirement for maintenance and the NAME were determined from measurements of heat production at different levels of ME intake. In general, the maintenance ME requirement decreased with increasing temperature for both feathered and defeathered cockerels. The NAME for the defeathered birds varied between 75 and 77% at 29, 34 and 38 °C. There was evidence for the feathered birds of an increasing NAME with increasing temperature, one feathered bird having a NAME of 56% at 15°C, increasing to 81% at 34 °C.

The importance of feathering and environmental temperature on the heat production and the possible effect of feather cover and activity on the NAME are discussed.

Two attempts were made to increase the number of lamb crops in intensively managed dairy sheep flocks. Rams were introduced into the flocks for the first 100 days after lambing. The ewes were milked twice daily from parturition. In the first flock of 188 ewes, the lambs were weaned at birth. Half the ewes received a course of progesterone and PMS in the third week post partum. 49% of the treated ewes conceived at average of 49 days post partum, and 59% of the non-treated ewes at an average of 53 days post partum. The hormone treatment reduced milk yield by 17% in the ewes which conceived and by 26% in those which did not conceive. Milk yield was 7% lower in those ewes which conceived a second time. Yield in the subsequent lactation was very low. In the second flock, the lambs of 83 ewes were weaned 40 days after lambing. 89% of the sheep conceived at an average of 64 days after lambing. The pregnant ewes yielded 6% less milk than those ewes which did not conceive. Yield in the following lactation was satisfactory. The practical implications of the results in terms of the possibilities of future production in dairy flocks are discussed.

Experiments were carried out to assess the effect of the following diets: unwilted and wilted silage, barn-dried hay and wilted silage and ensiled mixtures of grass and barley on the ruminal VFA patterns in sheep.

There was a tendency for the unwilted silage to result in a slightly higher level of rumen acetate and a lower level of propionate than grass, wilted silage or barn-dried hay. In two of the experiments (Exps. 2 and 4) significant direct relationships were found between rumen acetate and the crude-fibre content of the diets and significant inverse relationships were found between the rumen propionate and the crude-fibre content of the diets.

Significant relationships were also found between the rumen acids and the metabolizable energy content of the diets and in Exp. 2 there was a significant relationship between the rumen acetate and the water-soluble carbohydrate content of the diet.

The addition of barley meal to grass produced different ruminal VFA patterns in sheep fed the ensiled material and the resulting silage.

A partial castration technique is proposed for use in cattle husbandry where bulls are used for slaughter beef, whioh renders the animals sterile apparently without otherwise impairing the expression of their male characteristics.

Fifty such infertile bulls were compared with an equal number of steers in six growth trials under a range of nutritional conditions. In all cases the bulls grew faster than the steers. The results showed that the higher the rate of gain achieved, the greater was the advantage in favour of the bulls from about 1% at under ½ kg/day to over 25% at 1 kg/day). Accordingly, it is suggested that under conditions of good growth rate (in excess of about ¾ kg/day) complete castration is contra-indicated for efficient beef production, and that partial castration might be adopted as a routine management procedure.

Results of two groups of experiments testing phosphate fertilizer for sugar beet were re-examined; there were 53 experiments made between 1957 and 1960 in group 1 and 25 experiments between 1957 and 1959 in group 2. The mean response of total sugar to 126 kg/ha P2O5 was only 160 kg/ha but on a few fields response exceeded 1000 kg/ha. Response seemed to be greater in 1958 than in the other years, but between-site variance accounted for most of the difference from year to year.

Stored soil samples were analysed for phosphorus by four methods; the results were compared and related to the yield response to phosphate fertilizer. After allowing for experimental error, the percentages of the between-sites variance of the responses accounted for by log (soil P) were (group 1 first): sodium bicarbonate, 60 and 62%; anion resin, 52 and 30%; ammonium acetate/acetic acid, 52 and 0%; and calcium chloride, 42 and 2%. When soil pH was included in the regression equation, prediction of response by anion resin much improved and equalled that of sodium bicarbonate. Ammonium acetate/acetic acid was ineffective on soils with much free calcium carbonate.

As two-thirds of the soils had sodium bicarbonate-soluble phosphorus concentrations between 15 and 45 ppm P with mean response 65 kg/ha sugar, there is only limited scope for increasing the profitability of the crop by improving P manuring. However, more P fertilizer can be recommended for the few soils with ≤ 10 ppm P and P fertilizer can be withheld from fields with more than 45 ppm. The dressings we recommend are 180, 120, 60, 30 and 0 kg/ha P2O5 (approximately 1·5, 1·0, 0·5, 0·25 and 0 cwt/acr P2O5) on soils with ≤ 10, 11·15, 16·25, 26·45 and ≥45 ppm sodium bicarbonatesoluble P respectively.

The graphical and statistical analyses of competition diallels devised by Durrant were applied to an experiment investigating competition between four spring-wheat varieties. The results indicated that at low seed rates mixtures between varieties having a wide phenotypic difference between them in competitive characters, such as height and early maturity, could significantly outyield pure-stands of the component varieties. However, the results of a second experiment, in which these mixtures were grown at a range of seed rates, indicated that the yield advantage of mixtures over pure-stands was unlikely to occur at normal seed rates.

It is suggested that, at the low seed rates likely to be used in growing F1 hybrid wheat crops, mixtures of F1 hybrids and male parental lines might achieve very nearly the same yield as the pure F1 hybrid variety with a seed bulk that was cheaper to produce.

The feed conversion efficiency of four intensively fed, partially castrated male cattle, measured over an 11-week period from approximately 9-months of age, was found to be significantly higher (P <0·05) than that of four steers.

The effect of adding 5% beef tallow to the diet during this period was also studied. Although no statistically significant result of this on feed conversion was obtained, there was an indication that fat in the diet improved the bulls' efficiency, but not that of the steers. Added dietary fat had an effect on carcass composition, increasing signifioantly (P < 0·05) the deposition of carcass fat by steers but having no such effect in bulls. It appears, therefore, that the two sex types metabolized the added dietary fat differently, the steers converting much of it to depot fat; the bulls using it (with some evidenoe of greater efficiency) for growth of non-adipose carcass components.

The carcass characteristics of a total of 43 infertile bulls were oompared with those of 42 steers from five independent trials. In most cases there was no significant difference between the bulls and the steers for dressing percentage, or fleshing index. Bulls were generally found to have greater hide percentages than steers, the difference being very highly significant (P < 0·001) in one of the trials and significant (P < 0·05) in another. Eye musole area expressed relative to caroass weight was greater in the bulls, the difference being significant (P < 0·05) in three of the trials. The depth of fat over the eye musole and the hind to fore-quarter weight ratio were greater in the steer carcasses. Head weights were found to be significantly greater (P < 0·05) and caul and kidney fat weights less (P < 0·05) in bulls than in steers in the one trial where these parameters could be measured.

Carcass composition was estimated by the three-rib sample joint teohnique in four of the trials, and in these the bulls had a greater percentage of bone and muscle, but a lower peroentage of fat than the steers, the differences being significant in most oases. In the fifth trial composition was estimated by half carcass dissection. This, too, showed bulls to have a greater percentage of bone and muscle and a lower percentage of fat, the differences being highly significant (P < 0·01) and very highly significant (P < 0·001) respectively. On a fat-corrected basis the estimated retail value of the carcasses favoured the bulls by about $20.00 each.

The studies, conducted over a range of nutritional conditions, showed that non-castration favoured muscle growth while suppressing fat deposition, and that this advantage was more pronounced when growth rates were high.

The nitrogen requirements for maximum production of perennial ryegrass swards in August/September were shown to be of the order of 4 kg N/ha/day. Further increases above this level had no appreciable effect on dry-matter production, leaf area or light intercepted, but maximum tiller numbers were considerably enhanced. Shortage of nitrogenous fertilizer had comparatively little effect on crop growth rate in the early stages of regrowth, but thereafter caused the rate to fall increasingly short of potential. At high fertilizer levels crop growth rate based on total above-ground parts was linearly related to percentage light intercepted in the first month after defoliation, but values subsequently became erratic and at times negative. This change in crop growth rate and the resulting halt in effective net dry-matter production could be associated with the overall pattern of leaf and tiller formation and death, maximum net yield being achieved at the point in time when three new leaves had been produced on each tiller since cutting. It is concluded that in August and September worth-while increases in harvestable net dry matter are unlikely to occur after this stage has been reached, and that managements based on the maintenance of a complete crop cover are not likely to be successful at this time of year.

The growth and development of the spring wheat varieties Kolibri, Sirius and TB 435 ranging in height from relatively tall to semi-dwarf were compared when sown at 50, 200 and 800 plants m−2, with and without a spray application of CCC at the six-leaf stage. Growth analysis measurements were made throughout the season. Yield and yield components were determined at final harvest.

A number of varieties x density and variety x CCC interactions were found which support the hypothesis that genotypic variation and environmentally induced differences in GA metabolism affect the agronomic performance of the crop.