Seventy-two Clun Forest ewe lambs were randomly stratified into three groups (I, II and III) of 24 each according to date of birth and body weight at 6 October 1970. The ewe lambs of Groups I and II were shorn on 15 and 30 October, respectively, and Group III acted as unshorn control. The ewe lambs were reared under natural field conditions but supplementary feeding and shelter were provided during the winter months.

A large proportion (94%) of the ewe lambs attained puberty in their first year and differences between the three groups in the number of ewe lambs reaching this stage of development were small and not significant. Autumn shearing of ewe lambs was associated with a very slight but statistically wholly insignificant delay in the mean date of puberty whereas the duration of cyclic activity in these lambs was not affected by such treatments.

A study was made of the effect of increased rectal temperature on digestibility, nitrogen balance and water metabolism in Brahman x British (BX), Africander x British (AX) and Shorthorn x Hereford (SH) steers fed a fixed amount of lucerne hay.

An increase in rectal temperature of c. 1·4 °C caused a decrease in food intake and nitrogen balance and was associated with an increase in dry-matter digestibility in all breeds. Both dry-matter and nitrogen digestibilities were consistently higher in the Zebu crossbreds (BX and AX). Water intakes and ‘water balance’ (water intake – faecal and urinary water) were higher in all breeds when rectal temperatures were elevated. Water intakes were highest in the BX at both normal and elevated temperatures and increased most in the AX with an increase in temperature. ‘Water balances’ were similar in all breeds at normal body temperatures (4–5 1/day) but were lowest in the SH at elevated temperatures. This could partly explain the lower heat tolerance of the SH steers observed under these experimental conditions.

Changes occurring during ripening in dry weight and percentage dry-matter content of grain and rachis (cob) have been studied in Inra 200, and comparable data obtained for a U.S.A. dent hybrid, Minnesota 803, a Canadian flint × dent hybrid, OX 302, and a range of European flint × dent hybrids (Prior, Kelvedon 59A, De Kalb 202, Maris Carmine, Pioneer 131 and Anjou 210).

In Minnesota 803, OX 302 and, to a lesser extent, Prior, loss of water from the grain was more rapid than in Inra 200 during later stages of ripening. OX 302 reached a harvestable stage (40% grain water content) 10–12 weeks after silking, about 7 days earlier than Inra 200 in favourable seasons, and nearly 14 days earlier when conditions for ripening were less satisfactory. The patterns of changes occurring in the cob were quite different from those in ripening grain. Maximum dry weight of cob was reached when the grain was in the milk stage, and then declined throughout the period of rapid grain development; in the ripe ear, cob dry weight was 15–20% below its earlier maximum. At comparable grain water contents, the cob in Inra 200 was wetter than in Prior, Minnesota 803 and, even more markedly, OX 302. In contrast, water content in the cob of Maris Carmine and Anjou 210 was slightly higher than in Inra 200. The possible relationship between the differing varietal trends in ripening grain (and cob) and resistance to stalk rot is discussed.

The dry weight of the cob in ripe ears of Inra 200 was barely half that found in OX 302 and Minnesota 803, and lower than in other European flint × dent hybrids. Shelling percentage in ripe ears of Inra 200 was 88–90; it was 84–86 in other European flint × dent hybrids, about 80 in Minnesota 803 and 75 in OX 302. Mention is made of the relevance of this information to choice of variety for production of ground ear maize.

Analysis of published data relating to the chemical composition of feeds – mostly roughages – before and after grinding and pelleting showed that ash and crude-protein content increased and crude fibre declined. On the assumption that the ash content was unaffected by grinding and pelleting, the crude-protein and crude-lipid content of the original material was shown to be unaffected by the process but the total carbohydrate was depressed. The loss of organic matter on pelleting was 9% and reasons are given for believing that this was due to partial pyrolysis of the carbohydrate.

Calorimetric experiments with a poor quality sainfoin hay and a poor aftermath mixed hay showed that grinding and pelleting increased intake by over 80%, and also increased the metabolizability of the gross energy. The increases were from 37·4 to 40·7% for sainfoin and from 38·2 to 44·4% for the hay. The energy of the pellets was used more efficiently for maintenance in both instances, and with the hay, the efficiency of utilization of its metabolizable energy for production increased from 24·2 to 54·1%. With sainfoin no similar comparison was possible since the sheep given the chopped sainfoin could not achieve positive energy retention. The sainfoin pellets were used for production with an efficiency of 56%. Energy retention in sheep given as much sainfoin as they would consume without refusal increased from – 336 to + 3207 kj/d on pelleting the diet. With hay or hay pellets which were given ad libitumthe corresponding values were + 297 to + 4742 kj/d respectively.

Grain yield in wheat, as in other crops, is a complex character, made up of many subcharacters. In the present investigation the study of genotypic and phenotypic correlations and path-coefficient analysis indicated that 250-grain wt. and ear number were two important component characters in wheat. Under these circumstances it would be desirable to select those plants which produce large number of tillers and very large and bold sized grains. The greater the number of tillers on a plant the greater would be the number of grains/plant. Again large and bold type of grain would obviously give higher seed wt.

With the use of discriminant functions it was observed that a maximum genetic gain of 7·44% was obtained when grain yield/plant, 250-grain wt., no. of ears/plant and ear length were included in the function. This would suggest that the discriminant function is superior to straight selection in wheat. However, an expected gain of 4·13% was realized when only 250-grain wt. and grain yield/plant were taken into account. In the present analysis it appeared that relatively more emphasis should be given to grain wt. during selection. To make proper use of such characters in selection, their importance must be considered in the definition of economic worth. Progress measured in terms of yield alone will be less when the economic importance of plant type is ignored.

Potato varieties were grown in the field in soil uniformly infected with Streptomyces scabies. In 1969 tubers were severely and evenly infected but in 1971 infection was slight and not uniform. Agreement of varietal ranking with agricultural experience was good in 1969 but poor in 1971.

In 1971, plots protected from rainfall after planting were dry enough at the start of tubering for severe infection; covering the plots for a further 6 weeks followed by irrigation to field capacity resulted in good yields of evenly and severely scabbed tubers. Irrigation during this period suppressed scabbing. The results were easily interpreted in relation to fluctuations in soil-water content measured by a neutron moisture-meter.

The efficiency of using only one site and the need to reduce variability in scab screening tests are discussed.

The expected merits of the semi-hybrid variety, produced by bulk interpollination of two populations (Foster, 1971a, 6, c), are examined in relation to those of the synthetic variety. With diploid inheritance, the mean expression of both types of variety is seen to be the same. Any postulated difference in productivity must depend not only on the preferential establishment and survival of a small fraction of the total population, but on the existence of a correlation between characters determining productivity and establishment. For two populations producing a heterotic hybrid, a correlation due to loose linkage or gene association without linkage may result in the superiority of the semi-hybrid, but tight linkage or pleiotropy are more likely to favour the synthetic variety. It is concluded that superiority of the semi-hybrid mode of varietal production can only be established by means of a direct comparison with its synthetic counterpart, and not solely by the demonstration of upper-parent heterosis for productivity.

Some aspects of sexual development and the attainment of puberty in Clun Forest ram lambs were studied during the two seasons 1970–1. Strong correlations existed between parameters of penial, scrotal and testicular development. Sexual development in general appeared to be more closely associated with the body growth than the chronological age of the ram lamb.

Nevertheless, marked variation existed in both age and body weight at puberty. Although the majority of the lambs attained this stage of development at 4·5–5 months the age-range extended from 99 to 176 days. The mean body weight at puberty was 32·5 kg, ranging from 24·5 to 38·0 kg. There appeared to be an interaction between chronological age and general body development in relation to the appearance of sperm in the epididymides. Not only did it seem that a certain degree of body growth and testicular size was required before spermatozoa could be released, but also a limit of chronological age below which puberty was not attained. Large differences existed between individual lambs in both testicular and epididymal weights at puberty. There was a high degree of symmetry in growth between the left and the right testes and epididymides.

Time of birth influenced the pattern and rate of body growth and sexual development. This seemed to be largely due to seasonal fluctuations in nutritional conditions during rearing but the results obtained do not preclude the possibility that other seasonal factors, such as the daylight environment experienced by the ram lamb, might have a certain limited influence on sexual development.

A mathematical model has been constructed to simulate pasture contamination by the faeces of grazing cattle and the effects on herbage intake. The model describes the rate of deposition of faeces in relation to herbage intake, the effects of contamination on intake as modified by grazing pressure, and the rate at which the influence of faeces on grazing behaviour declines after deposition.

The information available on these processes is incomplete and imprecise in a number of respects. It appears from the modelling exercise that further data are most urgently needed on the rate at which the inhibitory influence of faeces declines, and on the precise effect of grazing pressure on the amount of herbage rejected.

A secondary effect of contamination is recognized, in which the utilization of herbage initially rejected because of the presence of faeces is modified subsequently because the temporary protection from grazing allows it to become too mature. This effect may be quantitatively larger than the primary contamination effect on untrimmed pastures, but its accurate prediction depends on the establishment of comprehensive relationships between the amount and composition of herbage on offer and intake by the grazing animal. The latter studies deserve at least an equal research priority, in relation to the contamination problem in toto, as the elucidation of the details of the primary effect.

Twenty-three experiments between 1968 and 1971 compared the effect of no magnesium, 50 and 100 kg/ha magnesium as kieserite and 100 and 200 kg/ha magnesium as calcined magnesite, on yield and magnesium uptake by sugar beet. On average, 100 kg/ha magnesium as kieserite increased the mean sugar yield of 7·55 t/ha by 0·17 t/ha whereas 200 kg/ha magnesium as calcined magnesite increased it by only 0·08 t/ha; on fields with less than 15 ppm exchangeable magnesium the magnesium fertilizers increased sugar yield by 0·34 and 0·10 t/ha respectively and there was no response to either fertilizer when the soil contained more than 25 ppm of exchangeable magnesium.

100 kg/ha magnesium as kieserite or calcined magnesite increased magnesium in the dry matter of tops by 0·091 and 0·040% and of roots by 0·013 and 0·004% respectively. Giving 100 kg/ha magnesium as kieserite or calcined magnesite increased uptake of the element in August by 5·1 and 2·6 kg/ha respectively. Differences in soil pH did not influence the uptake of magnesium from kieserite but they greatly affected uptake from calcined magnesite. On the slightly acid soils, the fertilizers were almost equally effective but at pH > 7·6 little magnesium was taken up from calcined magnesite. Glasshouse experiments showed that grinding the calcined magnesite increased the availability of the magnesium.

In Southdown sheep, which grazed and were fed during the day to maintain body weight and were housed at night, there was no clear effect of ambient temperature on hoof growth. In these sheep, equatorial or reversed photoperiods did not influence hoof growth.

In an indoor experiment over 19 months on Merino sheep, with natural light and temperature, fleece accumulated normally between spring shearings. Hoof growth in winter was low at a low level of nutrition but was not reduced in sheep at a higher nutritional level. It fell dramatically at both levels of nutrition in the first month after shearing.

Hoof growth was measured in Merino and Southdown sheep exposed to equatorial daylength in two climate-room experiments in which ambient temperature was varied. Fleece length was kept short and nearly constant by clipping. Hoof growth was greatly reduced by low temperature. At a given ambient temperature it was more rapid when ambient temperature was rising from month to month than when it was falling. The low hoof growth observed in the cold was associated with low hoof temperature and there was some evidence suggestive of reduced blood flow to the skin of the lower legs.

These temperature effects would complicate the use of hoof growth as an index of nutrition.

The biological and useful yield of Phaseolus vulgariscv. ‘Banja’ and cv. ‘Diacol Nima’ were compared when sown at populations, in row spacings, equivalent to 5–4–32–3 plants m~2, at four levels of fertility achieved by the use of zero, five, ten and 20 cwt ae-1 respectively of a fertilizer mixture containing by weight 2:2:1 calcium ammonium nitrate, single superphosphate and muriate of potash. Yield and its components were determined at final harvest. The two cultivars behaved generally similarly. Crop Index, while highest in the plants with no fertilizer, was more or less constant for each cultivar over a wide range of biological yields in those plants receiving fertilizer. Yield is determined to the extent of 85–7% and 86–1% respectively for 'Diacol Nima’ and ‘Banja’ by the product of pods/plant and plants surviving to harvest. High densities, although giving the highest grain yields, are wasteful of seed in that the percentage of plants surviving to contribute to yield is much reduced.

Nine 5-year field experiments between 1964 and 1971 tested the effect of kainit, kieserite, magnesium and calcium limestone, and farmyard manure on yield and magnesium uptake by sugar beet and on exchangeable soil magnesium. The experiments were in the main sugar beet growing areas on soils that contained little (12–24 ppm) exchangeable magnesium. The fertilizers were applied in the year before the first sugar-beet crop and fresh dressings of some were given to other plots each time sugar beet was grown. Kieserite increased sugar yield equally when applied in the sugarbeet seed bed or three years before the sugar beet. Magnesium limestone was effective only when the soil pH was less than 7·0. FYM greatly increased yield but the increase could not be explained entirely by the magnesium it supplied.

On average, applying 100 kg/ha magnesium (as kieserite) to the seed bed increased the magnesium concentration in dried tops and roots by about 0·135 and 0·020% respectively and the total uptake by the crop in August by 9·0 kg/ha. The same treatment applied in the sugar-beet seed bed or 3 or 4 years previously increased exchangeable magnesium in the surface 25 cm of soil by 29·0, 7·6 and 1·8 ppm respectively. Thus much of the fertilizer given to the first sugar-beet crop was lost from the plough layer for the second sugar-beet crop but the yields indicated that some of it was available from depth.

On alkaline soils, when exchangeable soil magnesium in the plough layer is 0–25, 26–50 or > 51 ppm, an initial application of 100, 50 or 0 kg/ha respectively of water-soluble magnesium is needed, applied either in the previous autumn or to the sugarbeet seed bed. If the exchangeable soil magnesium before the following or subsequent sugar-beet crop is 0–15, 16–25 or > 26 ppm, a further application of 100, 50 or 0 kg/ha respectively of magnesium should be given.

Dorset Horn × Merino and Corriedale wether lambs grazed one of four tropical legume species or the grass Panicum maximum for up to 4 months in the immediate pre-slaughter period. A laboratory taste panel compared the flavour of the meat from legume-fed lambs with that from corresponding grass-fed lambs.

Lamb meat from animals grazed for up to 15 weeks on Siratro (Phaseolus atropurpureus) was not significantly different from the control meat in any flavour property, while showing a slight but insignificantly greater degree of acceptability of flavour.

The meat from lambs grazed for up to 6 weeks on Silverleaf desmodium (Desmodium uncinatum) showed no significant difference from the control meat in flavour properties except for a slightly greater intensity (P < 0·05) of an uncharacterized aroma.

The meat from lambs grazed on Dolichos axillaris for up to 4 months occasionally exhibited a characteristic and sometimes objectionable odour and flavour. However, this characteristic flavour had no significant influence on the acceptability of the meat.

The meat from lambs grazed on Glycine wightii for up to 6 weeks exhibited a characteristic and objectionable odour and flavour (P < 0·001). After 4 months of grazing the intensity of this flavour was considerably reduced. A low intensity of this flavour was also found in a group grazed for 4 weeks in the previous year, indicating a variability in the tainting properties of this legume.

Fifty Clun Forest ewe lambs with uniform birth dates were randomly stratified into two groups (A and B) of 25 each according to date of birth and body weight at 23 August 1971. On 26 August Group A (control) was joined with rams whilst Group B remained completely isolated from any contact with rams until 18 October.

The sudden introduction of rams to ewe lambs in the transition from non-breeding to breeding activity resulted in a high degree of synchronization of first matings in Group B. However, it did not affect the mean date of onset of oestrous activity.

A 6 x 6 Latin Square balance experiment was carried out using six Friesian steers, each of which initially weighed about 304 kg. The six treatments studied were an all-hay diet and five other diets containing 20,40,60,80 and 100 % of rolled barley fortified with mineral and vitamin supplements, accompanied by correspondingly reduced proportions of hay. Each diet was fed at an estimated maintenance level of feeding.

The progressive increase in the proportion of concentrate gave a significantly linear increase (P < 0·001) in both digestible and calculated metabolizable energy. The actual increase in digestible energy was from 2·62Mcal/kg dry matter (59·3% of the gross energy) on the all-hay treatment to 3·42 Mcal/kg dry matter (79·5% of the gross energy) on the all-concentrate treatment. Use of the determined digestible energy values for the all-hay and fortified barley diets to calculate the digestible energy of the four mixed diets gave results in reasonably good agreement with the determined values, the maximum difference being 0·12 Mcal/kg dry matter, which represented 3·83 % of the determined value. The losses of energy in the urine expressed as percentages of the gross energy of the diets showed a small but significantly linear decrease (P < 0·01) with increase in proportion of barley in the diet. The molar proportions of steamvolatile acids in samples of rumen fluid taken from two animals on each treatment indicated that increase in the proportion of concentrate was associated with tendencies for increase in acetic acid, decrease in propionic acid and little change in butyric acid. The mean digestibility of the organic matter was 62·6 % on the all-hay treatment and 81·8 % on the all concentrate treatment. The progressive increase in the proportion of concentrate gave a significantly linear increase (P < 0·001) in digestibility of the organic matter. Although intakes of nitrogen decreased with increase in the proportion of concentrate due to a decrease in the amount of dry matter fed, the weights of nitrogen retained were well maintained and when expressed as percentages of intake showed a significantly linear increase (P < 0·01).

Lead was determined in soil and grass from transects across three main roads and one minor road in Birmingham, England. The pattern of enhancement of lead contents was consistent with aerial contamination by lead compounds from motor vehicle exhausts. Data from grass sampled during wet and dry weather suggested that approximately half the lead was present as a removable surface film on the grass blade. Generally, the lead content of the grass was not high enough to affect grazing cattle adversely but the growing of vegetables for human consumption might need regulation. The lead values for contaminated soil, although locally high, were within the normal range for British and American soils and, for comparable traffic volumes, were less than those reported in the U.S.A. Attention is drawn to inter-laboratory differences when reporting analyses of reference rocks and the implications for environmental research.

Nine different capacitance probe methods were used to estimate the herbage yields of 32 small pasture plots; ten meter readings were used in conjunction with the yield data from a variable number (n) of quadrats in each plot. Expected yields were determined by cutting ten quadrats per plot. Estimated yields were compared with expected yields for both the differing methods and the differing values of n. At each level of n the yield estimates from the different probe methods were compared with those obtained simply by cutting n quadrats.

Using calibration data from only one quadrat per plot (n = 1), all probe methods except one gave greater accuracy than that obtained from the single quadrat yields only. For n = 2, the advantage of the probe methods was less pronounced and where n = 3 only one probe method (one which involved no regression computations) gave superior accuracy to that obtained merely by using the yield data from the three cut quadrats. At n > 3, only the one probe method gave increased precision; all other probe methods were markedly less accurate than the equivalent raw quadrat results.

Only one probe technique (which combined data from markedly dissimilar swards) gave yield estimates which were noticeably biased.

Results from an earlier study are presented to demonstrate the influence of season, species and irrigation on probe calibration.

Recommendations are made on the various probe methods which may prove effective in some experimental situations.

The characteristics of ion active transport by excised roots of hybrid and inbred maize were evaluated in short-term uptake experiments with 35S-labelled sulphate. Hybrids showed a higher transport rate per unit of both dry matter and protein, in comparison with inbred lines.Vmax and Km were quite different for inbreds and hybrids, demonstrating an effect of crossing on the characteristics of the transport system. An effect on the transport system was also shown by better adaptation of the hybrids to low temperatures: the hybrid to inbred transport-rate ratio increased with the temperature decrease.

A field experiment was made during the rainy seasons of 1968 and 1969 on a sandy loam soil to study the response of Sorghum hybrid CSH–1 to phosphorus in relation to content of water-soluble phosphate in fertilizers. Triple superphosphate, dicalcium phosphate, rock phosphate (200-mesh), nitrophosphate and mixtures of triple superphosphate with dicalcium phosphate and rock phosphate in 3:1, 2:2 and 1:3 ratios were studied. The amounts of phosphorus applied were 30 and 60 kg P2O5/ha. Phosphorus application significantly affected dry matterproduced, plant height, days to 50% bloom, number of grains per ear, thousand-grain weight, stover and grain yield. Triple superphosphate and 3:1 triple superphosphate/dicalcium phosphate mixture were the most effective while rock phosphate and 1:3 triple superphosphate/rock phosphate mixture the least. Differences among sources were more marked in 1968 and at the higher amount i.e. 60 kg P2O5/ha. The response of sorghum to phosphorus was considerably lowered when the water solubility waa below 50% in triple superphosphate/dicalcium phosphate mixtures and below 75% in triple superphosphate/rock phosphate mixtures. Relative effectiveness was assessed by calculating ‘superphosphate equivalents’ and ‘multiple regressions’. Using superphosphate equivalents dicalcium phosphate, nitrophosphate and rock phosphates were 47–53%, 35–56% and 3–25%, respectively, as effective as triple superphosphate.