Experiments were devised to establish suitable techniques of screening seedling material of Lolium perenne for cold tolerance under controlled conditions: these techniques were then used to distinguish between varieties and ecotypes from contrasting climatic regions. For the wide range of material used, greatest discrimination was achieved by 14 days hardening at 2 °C and 8 h photoperiod, followed by 2–4 days freezing at -8 °C in the dark. There were indications that the light intensity and/or temperature before and during hardening could considerably modify the cold tolerance.

The most useful criterion of cold tolerance was the percentage of tillers surviving 14 days after thawing. In some instances, death of tillers and whole plants continued after this time, and this tendency appeared to be related to growth habit; southern ecotypes were particularly susceptible.

Varieties from north Europe were generally more cold tolerant than ecotypes from the Mediterranean region, but tolerance depended also on the altitude of the original habitat. The cold tolerance of a population could, in part, be related to the average lowest temperature in the coldest month and in part to environmental conditions of solar radiation and/or temperature during the autumn in its place of origin.

Along with the experiments under controlled conditions, spaced plants of the same populations were grown in the field in order to evaluate winter hardiness under local conditions. The overall correlation between winter hardiness in the field and cold tolerance as assessed in the growth rooms was not high. Results from one year's field testing showed that indigenous varieties such as S. 23 and S. 24 were more winter hardy than foreign ecotypes and varieties, even if these came from colder climates and showed greater cold tolerance in the growth room.

A 2·year grazing trial was carried out on an equatorial Themeda triandra range grassland in the Rift Valley of Kenya, at 1890 m altitude with a bimodal rainfall of 700 mm p.a., to characterize seasonal changes in the pasture and to determine the influence of climatic and management factors on forage availability and composition, grazing selection and live-weight gains on Boran steers (Bos indicus).

Fourteen categories of sampling and measurement techniques used in this work are described and some methodology problems in rangeland evaluation discussed.

For precise estimation of herbage yields in large paddocks unacceptably large plotsizes and numbers were required so an arbitrary sample of twelve 10 yd x 1 yd plots per paddock was adopted giving c.v.s of 16–50%. Subsequent sampling was limited to three contrasting treatments in the most uniform block. A ‘forceps point’ method was developed for botanical estimation of oesophageal fistula samples and provisional weight correction factors calculated. In a parallel feeding trial regressions were calculated for relating the chemical composition of oesophageal fistula samples to that of the herbage ingested.

Stylosanthes humilis was grown at Brisbane at densities of 10, 50, 250, 850 and 3800 plants/m2 in boxes of sand which received basal nutrients, applications of 0, 10 and 50 kg P/ha as calcium dihydrogen phosphate, and frequent irrigation.

Maximum seed yield was 69 g/m2 at a density of 850 plants/m2. Seed yield was linearly related to the logarithm of density up to 250 plants/m2, and was comparatively stable over the upper density range, declining slightly at supra-optimal density. Inflorescence density exerted the primary control over seed yield, but seed set per floret and floret number per inflorescence were also influential.

The application of 50 kg P/ha increased yield of plant tops by 54% and seed yield by 20%.

Fibres of anomalous length or diameter are undesirable in the Merino, a breed noted for uniformity of fleece characters. Previous studies which have aimed at estimating adult fleece quality have been based on visual appraisal of the birthcoat. This study was undertaken to test the prediction of uniformity of fibre length at 10½ months and fibre diameter at 15 months from the objective measurement of birthcoat fleece and skin follicle characters.

The results indicated that fibre length uniformity at 10½ months cannot be predicted from measurement of fleece or skin characters at birth. It was found that fibre diameter uniformity at 15 months can be predicted from objective measurement of mean fibre diameter of the birthcoat but not by visual appraisal.

The environment, design and methods of this 2-year Kedong grazing trial in the Rift Valley of Kenya were described in Part I.

Crude protein of grasses varied seasonally, usually between 3 and 6 %, while most shrubs and herbs, leguminous and non-leguminous, were in the 10–20 % range, although contributing only about 3 % by weight of the total sward, excluding large bushes and trees. Steers selected herbage of 2–3 % units higher C. P., more Themeda leaf and more herbs than the sward average. Treatment effects on sward and diet C. P., and their relationships, were generally small and inconsistent. Higher C. P. in post-burning ro-growth declined to average levels after 2–3 months, except when grazed at one steer to 4–4 acres, rotational (i.e. 1–5 acres available). At this pressure available herbage fell below 1000 lb D.M./acre (1120 kg/ha). In all other treatments 2500–4500 lb D.M./acre wore available at all times. Estimated herbage production varied from almost nil to 320 lb D. M./acre/month. Burning removed 3000 lb D.M./acre. Relationships between herbage C. P., diet c. p. (oesophageal fistula samples) and faeces N were determined.

The nitrogenous composition of the water soluble, non-protein nitrogen fractions of three samples of high-pH-spoilt silage and one sample of overheated silage were examined in detail. The amino acid nitrogen content of the high-pH-spoilt silages declined with increasing extent of spoilage, due to a selective degradation of the amino acids. Losses of amino acids were associated with proportionate increases in the amount of volatile basic nitrogen. Lower aliphatic amines were not present and it was therefore concluded that the ultimate end product of nitrogen metabolism in high-pH-spoilt silages was ammonia. Only low concentrations of putrefaction products, such as putroscine, cadaverine and histamine were present.

The composition of the non-protein nitrogen fraction of the overheated silage was unusual in that the ammonia nitrogen content was high and associated with the complete destruction of certain amino acids. The free amino acid nitrogen content was low but this was partially compensated for by a very high ‘peptide’ nitrogen content. There was no evidence of putrefaction products in this silage.

An analysis of germination characteristics of progeny from a diallel cross between five sugar-beet plants showed that the genotype of the maternal parent controlled to a marked extent the behaviour of the progeny. This may be related to the presence in the fruits of inhibitory substances.

Some evidence was found for genie and maternal interactions but these were always of less importance than the maternal effects. Heritability estimates from parent, off spring regression and analysis of half-sib family variances demonstrated that genetic variation for germination characteristics had not been eliminated during the improvement of sugar beet from the wild form.

The oestrous response and subsequent lambing performance of 264 sheep was studied after treatment with intravaginal sponges and PMS during July (period of late anoestrus). Four progestagen treatments were employed, each in combination with one or other of four dose levels of PMS (0, 250, 500 and 750 i.u.) given at pessary withdrawal; the sixteen resultant treatments were applied in each of seventeen flocks. Modification of standard ‘Cronolone’ (9α-fluoro-11β-hydroxy-17α-acetoxy-progesterono; G. D. Searle) pessaries to ensure thorough dispersion of the compound resulted in a significantly higher mating response and lambing outcome. The highest lambing outcome followed the use of 500 i.u. PMS. The onset of heat, relative to progestagen withdrawal, was affected both by progestagen treatment and PMS dose level. The conception percentage was highest in sheep which were bred on the second day after treatment. The implications of the data, in explaining some previous results with standard ‘Cronolone’ sponges, are briefly discussed.

The metabolizable energy (ME) values and net absorption of tallows containing 20, 40, 60, 80 or 98% free fatty acids were determined using mature laying hens. By restricting food intake, the intake of the tallows was controlled to 3, 5, 10 or 20 g per bird d. The tallows were added to a diet of known ME content and the ME's of the tallows were calculated from the data collected from 6- or 7-day energy balances.

ME and net absorption values of the tallows were significantly (P < 0·001) lowered when the level of intake was increased from 3 to 20 g/bird d. The values were also significantly (P < 0·001) lowered when the free fatty acid content was increased from 20 to 98%. The effects of free fatty acid level (F) and level of intake (L) on the ME and net absorption values were considered in terms of curved surfaces represented by equations embracing the factors and their product. The equations obtained were:

ME(kcal/g) = 8·745 – 0·004F – 0–361 log10L–0·011 F log10L,

Net absorption (%) = 95·82 + 0·02F – 4·65 log10L – 0.13F log10L.

The mating response and lambing outcome was studied in 584 sheep in twentyeight farm flocks after treatment with progestagen impregnated intravaginal sponges and PMS during June/July (period of late anoestrus). Each pessary carried a dose of 30 mg ‘Cronolone’ (9α-fluoro-11β-hydroxy-17α-acetoxy-progesterone; SC-9880, G. D. Searle) in finely dispersed form; half the number of pessaries carried an additional dose of 400 mg progesterone. Intravaginal treatment was for 12 days; a single intramuscular injection of 500 i.u. PMS (Burrough's Wellcome) was made at pessary withdrawal. Breeding was by natural service, using 10% rams. The response was 98·8% bred in the 4 days after treatment, 61·2% conceptions in those served and an average of 1·65 lambs/conception. This resulted in the birth, within the period of about 1 week, of 100 ‘early’ lambs for every 100 ewes exposed to rams. The addition of 400 mg progesterone to pessaries or the injection of a dose of 5 mg progesterone at sponge withdrawal did not improve response beyond that found with ‘Cronolone’ alone.

In a pot experiment, the growth of sugar beet on one soil with three levels of exchangeable Na ceased when the intensity of K measured as the activity ratio aK/√[a(Ca + Mg)] in the equilibrium soil solution had fallen to 6 × 10–4 (mole per litre)½;, the intensity of Na, aNa/√[a(CaH-Mg)], to between 1·7 and 4 × 10–3 (mole per litre)½;and exchangeable Mg to 0·14 m-equiv per 100 g soil. It was concluded that both the Na and the K intensities were exhaustion values but that K supply was preventing further growth. The additions of Na did not affect either yield or the uptake of K, Mg and Ca, but more Na was taken up from soils with higher Na levels.

The two experiments described here were the 3rd and 4th in a series of experiments investigating the effect of time of application of nitrogen and potassium on the growth and yield of potatoes.

The effect of applying all the fertilizer nitrogen in the seed bed was compared with applying all the nitrogen at the time of tuber initiation or dividing the dressing between these times. Similar times of application were tested for potassium. CCC was applied after a leaf area index of 3 had been reached (on all but the no N treatments) in order to offset the tendency for late nitrogen to increase stem growth, but to avoid any tendency for CCC to depress yield by reducing leaf area indices (L) below an assumed optimum value of 3. These treatments were applied in separate experiments to a second early variety (Craig's Royal) and a maincrop variety (Pentland Dell), planted a month later.

In both crops the response to nitrogen was large and delaying or splitting the application of nitrogen increased tuber yield compared with nitrogen applied in the seed bed. Responses to potassium were small, but there was a tendency for split applications to be superior to late or early applications.

The beneficial effect of delayed or split applications of nitrogen was associated with an improvement in the recovery of nitrogen in the crop which was largely ascribed to a reduction in loss due to leaching. Total and tuber dry-matter yields were linearly related to leaf area duration (D) in both crops, although the earlier variety was more efficient per unit of D. High values of L (6) were recorded for both crops, but there was no indication of an optimal value of L; consequently CCC which reduced L also reduced yield. D was closely related to the maximum quantity of nitrogen accumulated in the leaves per unit area of ground.

Seventy-nine pregnant Merino ewes grazing pasture at two intensities were slaughtered in groups at intervals from 60 days after conception to post-partum. Sixty-one nonpregnant ewes were also slaughtered. The weights of various organs including uteri and their contents were recorded and the energy content of each ewe was determined.

The weight of uterine contents (conceptus) increased rectilinearly with increasing foetal age to 100 days: differences between singles and twins were not significant. From 100 days to term, the relationship was also rectilinear but the slope was greater: a more rapid increase occurred with twins than with singles (P < 0·05). The nutritional difference imposed did not affect the relationship.

A regression of total energy reserve on live weight (less fleece and conceptus) was established. Differences between this relationship and those established separately for non-pregnant, pregnant and post-partum ewes were not significant.

The contribution of changes in conceptus weight to live-weight changes in gravid ewes is discussed.

In four series of experiments Merino ewes were exposed to ambient temperatures of about 44 °C and water vapour pressure of 33 mmHg for 9 h daily, and to 32 °C and 18 mmHg for the remaining 15 h daily, during the middle third, the final third or the final two-thirds of pregnancy. Birth weight and the weight of the placenta were considerably reduced by the treatments and the reductions were considerably more than could be accounted for by the partial loss of appetite produced by heating.

There was a close inverse relationship between birth weight and the elevated rectal temperature of heated ewes in several series; but the absence of foetal dwarfing in ewes with elevated rectal temperatures due to daily heating for only 9 h at 44 °C indicates that the elevated rectal temperature of the ewe is not the main cause of dwarfing.

Contrary to previous suggestions, the dwarfed lambs were not proportional miniatures, for the head components, the body lengths, the kidneys and adrenal glands were disproportionately large in heated lambs, while the liver, thyroid and thymus glands and the biceps femoris muscle were disproportionately small, and the ratio of secondary to primary wool fibres was very much reduced. There were cavities in the white matter of the cerebral hemispheres of heat-dwarfed lambs.

The hypothesis that foetal dwarfing is due to stunting of the placenta was examined, but conflicting evidence was obtained in the different series. However, it appears that under some circumstances a heat-stunted placenta is capable of considerable growth in the absence of heating during the final third of pregnancy, when the placenta is normally shrinking, and that placental shrinkage in late pregnancy may be greatly accelerated by the application of heat.

Neither thyroxine nor a preparation of ovine growth hormone, injected into heated ewes, prevented foetal dwarfing; the injections of growth hormone appeared to increase foetal mortality.

A Lolium perenne L. population derived from a very productive 6-year-old S.23 ley was compared with that obtained from breeders' seed of S.23. The ryegrasses wqre grown in boxes sown separately, together, and also with Poa trivialis L. Three rates of nitrogen were applied equivalent to 28, 336 and 672 kg N/ha.

The results obtained when the two ryegrasses were sown separately differed from those obtained in mixtures. When sown alone, the difference between the two ryegrass populations was small, but the ‘survivor’ ryegrass had a slightly higher yield of dry matter and nitrogen at some sampling dates and fertilizer nitrogen rates. In the mixture of the two ryegrasses, S.23 was higher yielding than the ‘survivor’ population when the equivalent of 672 kg N/ha was applied, but not at lower nitrogen rates.

When grown as pure swards, P. trivialis did not yield as much dry matter and nitrogen as L. perenne at the highest N application. In the intergeneric mixtures, the total yield of ryegrass × P. trivialis was not very different from that of ryegrass sown alone. P. trivialis depressed the yield of ryegrass in May and June, particularly when fertilizer N was applied; the reverse effect was recorded later in the year. Total drymatter yield of ryegrass and P. trivialis grown together was similar at the highest fertilizer N rate, but the yield of N was much higher in ryegrass than in P. trivialis.

The relationship between digestibility (% DOMD in-vitro)and voluntary drymatter intake of a range of grasses conserved as artificially dried grass, has been studied in two experiments with reference to growth stage, percentage of leaf, stem and dead material, number of days to harvest and dry-matter yield.

In the first experiment digestibility accounted for 69% of the variation in intake during first growth and differences were established between varieties of the same and of different species in (a) intake at similar levels of digestibility and (6) the rate of change of intake per unit change of digestibility. In the second experiment differences in intake were established between varieties, within and between first growth and regrowth, when compared at a similar level of digestibility.

The variation in intake between varieties at a similar level of digestibility was not correlated with stage of growth or percentage leaf, stem and dead material in either first growth or regrowth. However, number of days to harvest and to a lesser extent, dry-matter yield, were associated with this variation, but only in first growth.

regrowths of grasses generally resulted in higher intakes than first growths, but the varietal variation in intake was not correlated between growths.

An experiment, involving 68 female pigs, was undertaken to measure the effects of two diets differing in protein content, and of two patterns of feeding. The animals were housed in an enclosed building. The experiment extended through several parities; culled sows were replaced by gilts during the experiment, the whole course of which lasted 5 years.

The diets were given at the rate of 1–8 or 2–3 kg per day throughout gestation, but the rate was reversed during the 5-week lactation so that, for litters of eight to nine pigs sows in each treatment group received the same quantity of food per parity. As a result of unsatisfactory performance, dietary composition was changed after 2 years so that for the last 3 years the digestible energy contents were higher.

Treatments significantly influenced gestation live-weight gain, lactation weight loss and gestation backfat gain. The lower rate of gestation feeding was associated with low or negative gestation weight increases after the third to fourth litters, and a greater apparent rate of decline with increasing age in birth and 3-week weight per piglet. The high gestation, low lactation, rates of feeding led to slightly greater litter size and lower weaning weights per pig. A daily intake of 208 g crude protein and 8'3 g lysine appeared to meet the sow's requirements throughout gestation.

In the pregnant sow feeding area, winter air temperatures were on average 16 °C below those in the summer, but were rarely below freezing point. Winter backfat gain was lower than, and gestation gain only half that in the summer. Litter size was also greater following summer pregnancies and 3-week weight per pig was greater following winter pregnancies. Independent of litter size, birth and 3-week weight per pig were positively correlated with gestation gain within treatment and season. The apparent positive correlation of litter size at 3 weeks with gestation backfat and weight gain was not found at birth. Litter size at birth was negatively correlated with gestation gain within season. The percentage of fertile matingswas less for matings between 1 September and 31 January. This coincided approximately with the reduced litter size (alive) which occurred following winter gestations.

Lactation weight loss and 3-week weight per pig declined with increasing age of sow and the degree of weight loss was unrelated to subsequent litter size.

The apparent effect of seasons and treatments on litter size at birth appeared not to be an obvious function of changes in live weight, which were also marked between seasons and treatments, but level of food intake in early gestation may have affected litter size independently. It was concluded that birth weight especially in the older sows, was associated with the rate of food intake in gestation, and possibly also in lactation, and with gestation empty weight gain.

Six hundred and sixty-two sheep in twenty-two farm flocks were treated in June/July (period of late anoestrus) with intravaginal sponges impregnated with 30 mg ‘Cronolone’ (9α-fluoro-11β-hydroxy-17α-acetoxy-progesterone; G. D. Searle) or ‘Cronolone’ plus 400 mg progesterone and incorporating doses of 0-800 μg oestradiol-17β. Treatment was for 12 days; a single dose of 500 i.u. PMS (Burrough's Wellcome) was injected at pessary withdrawal. Seventy rams were joined to breed the ewes at first and second heats.

Oestradiol treatment resulted in a significantly higher incidence of sponge loss, a lower mating response, a lower conception rate and a lower number of lambs/conception. There was also a tendency for onset of oestrus to be delayed. Such effects were confined to first services and were much less evident in sheep receiving doses of 50 μg oestradiol or below. Data indicate that an intravaginal treatment for the induction of early breeding should consist of progestagen alone rather than progestagen in combination with oestradiol. The addition of 400 mg progesterone to the ‘Cronolone’ sponges appeared to reduce the adverse oestrogenic effects. Sheep treated with ‘Cronolone’/progesterone pessaries in the absence of oestradiol showed a mating response of 97%, a conception rate of 64% and 1·7 lambs/conception at the controlled oestrus.

The effect of seedling disturbance on the yield and growth habit of swedes was studied in ten experiments during the period 1960–3. Seedling disturbance consisted of the removal of soil from around the seedlings during singling, thus exposing the hypocotyl and leaving the seedlings prostrate.

Plant numbers were reduced slightly by seedling disturbance in half the experiments but not sufficiently to be a source of yield loss at the populations attained.

Seedling disturbance greatly increased the incidence of prostrate growth in swede varieties of intermediate shape, such as Victory. Two globe-shaped varieties, Bangholm and Pentland Harvester, grew erect irrespective of singling technique.

Disturbance of seedlings reduced yield when it increased the number of prostrategrowing plants. The yield depression ranged from 0·2 to 5·2 cwt D.M./acre.

The phosphorus requirement of the buffalo (Bos bubalis) for maintenance has been determined from the data of two feeding and balance experiments each with twelve animals in randomized block designs and one with six animals using 3x3 latin square designs in duplicate. The level of phosphorus intake was varied by adding appropriate quantities of sodium dihydrogen phosphate in Exp. 1, by adding wheat bran in Exp. 2 and by adding dicalcium phosphate in Exp. 3.

Regressions of phosphorus outgo (7) on P intake (X) gave values of 14–7 g/day in Exps. 1 and 2 and 17–2 g/day in Exp. 3. These values can be taken to be estimates of the P requirement of the adult buffalo for maintenance.

The initial and final serum inorganic phosphorus in Exp. 1 also indicated that the phosphorus requirement was between 12 and 17 g/day.