In Expt 1, 34 individually-penned Finn Dorset ewes of mean live weight 68 kg were synchronized in oestrus and mated to Suffolk rams. From mating until day 28 of pregnancy each received daily 15 MJ of metabolizable energy (ME) and 225 g crude protein (CP). From day 28 to slaughter on days 34, 41, 48 or 55 half of the ewes continued on this feeding regime and half had their daily intake reduced abruptly to 7·5 MJ of ME and 112 g CP. The mean number of ovulations per ewe was 4·03 (range 2–8) and the mean number of viable foetuses at time of slaughter 3·35 (range 2–6). The combined loss of ova (fertilization failure and early embryonic death) was 14·6% and detectable foetal deaths 2·2%. Level of feeding had no significant effect on these measures or on foetal growth. Foetal growth from 34 to 55 days was described by the equation

In w = 0·962–18·613 e-0·0272t–0·00091t(f–3),

where w = foetal weight (kg), t = age (days) and f = litter size. Within-litter variability measured as the S.D. of In w (kg) was 0–081 for twins, 0·108 for triplets and 0·106 for quadruplets and higher multiples.

In a second experiment Suffolk × Finn Dorset embryos were transplanted at the rate of two per uterine horn into 15 recipient Finn Dorset ewes. Embryo survival was 72% and foetal weights at 60 days varied from 67 to 146% of the mean value of 66 g. Withinlitter variation in foetal size was only about 70% of that expected for foetuses developing from the variable distribution in their initial positioning that occurs naturally. The correlation between foetal weight and placental weight at day 60 was 0·72 (P < 0001) indicating that the association between foetal weight and placental weight in prolific ewes is not confined to late pregnancy.

The results of both experiments are consistent with the hypothesis that the greater within-litter variability in birth weight in large litters is controlled by events in early pregnancy.

The effect of altering the level of protein intake on urea excretion in ewes was assessed in two separate experiments.

In Expt 1, 14 pregnant (during the last 20 days of gestation) and 10 non-pregnant ewes were each offered a different level of digested N intake in the range 5–25 g/day. At all levels of protein intake urea N excretion was lower in pregnant than in nonpregnant ewes.

In Expt 2, 21 pregnant ewe lambs were each offered one of three diets supplying mean intakes of 83 (T1), 113 (T2) or 147 (T3) g crude protein/day. During the last 100 days of gestation the mean levels of urea N excretion were 6·9, 11·0 and 15·2 g/day for T1, T 2 and T 3, respectively. The corresponding values for urinary N excretion were 9·3, 13·8 and 18·2 g/day. At all levels of protein intake urea N excretion was lower just prior to parturition than 95 days prepartum; the difference was correlated with lamb birth weight and maternal body-weight change.

A notable feature of both experiments was the low level of urea N excretion by the pregnant ewes in late gestation, at low protein intakes. It would appear that when energy intake is adequate the decrease in urea N excretion associated with pregnancy is a direct result of an increased N requirement for maternal and/or foetal growth.

The composition of yeast communities in the rumen of cattle was investigated using comparative DNA sequence analysis of yeast 26S rDNA genes. 26S rDNA libraries were constructed from rumen fluid (FF), rumen solid (FS) and rumen epithelium (FE). A total of 97 clones, containing a partial 26S rDNA sequence of 0·6 kb length, were sequenced and subjected to an on-line similarity search.

The 41 FF clones could be divided into five classes. The largest class was affiliated with Pezizomycotina class (85·4% of clones), and the remaining classes were related with the Urediniomycotina (2·4%), Hymenomycetes (4·9%), Ustilaginomycetes (4·9%) and Saccharomycotina (2·4%) classes. The 26 FE clones could be divided into three classes and the Saccharomycetes class (92·4% of clones) was the largest group. The remaining classes were related with either Pezizomycotina (3·8%) or Ustilaginomycetes (3·8%). The 30 FS clones were all affiliated with Saccharomycotina. Saccharomycotina were predominant in rumen epithelium and rumen solid while Pezizomycotina were predominant in rumen fluid. Yeast belonging to the Saccharomycotina class was predominant in the rumen as a whole (57%). One clone (FF34) had less than 90% similarity to any sequence in the database and was thus apparently unrelated to any previously described yeast.

An experiment was carried out on a site where the copper content of herbage was relatively low (4·7–6·2 mg/kg d.m.) to examine the value of copper contained in soluble glass rumen boluses as a means of providing supplementary copper to calves.

Forty-five spring-born suckled calves (mean live weight 91 kg) were divided into three groups on the basis of body weight. Animals in group GB were given two boluses initially, those in group CI each received copper injections at approximately monthly intervals and those in group C remained as controls throughout. Group C calves became progressively hypocupraemic (minimum mean plasma copper 8·5 μmol/1) compared with those in groups GB and CI which showed an increase in plasma copper concentration. In addition measurements of plasma caeruloplasmin activity, blood haemoglobin concentration and erythrocyte superoxide dismutase activity all showed significant increases due to treatment. No response in live-weight gain was observed but overall live-weight gain was approximately 1·05 kg/day. Although the initial response in plasma copper was quicker with copper injections, measurements of erythrocyte superoxide dismutase activity and haemoglobin showed advantages of glass boluses not shared by copper injections. This possibly resulted from the slow release nature of copper in the glass. Under the conditions of the experiment where herbage molybdenum values were relatively low (1·2–1·9 mg/kg d.m.), copper contained in soluble glass boluses appeared to prevent hypocupraemia in calves as effectively as regular copper injections.

In an experiment to determine the effect of photoperiods of 11, 13 and 15 h on the floral development of five determinate varieties of Phaseolus vulgaris it has been shown that long photoperiods bring about the abscission of flower buds on the main axis and secondary branches of three varieties native to South America. On the basis of these results it is concluded that under field conditions it is the long photoperiods of the British summer which are largely responsible for the poor development and eventual abscission of flower buds in these varieties for most of the growing season.

It is shown that the theory of diffusion of water through soil accomplishes three things:

(a) It accounts qualitatively for the water movement from wet to dry soil observed by the American workers quoted.

(b) It fits the best experiments numerically.

(c) It is at present alone in doing this.

A series of stocking rate trials running for differing periods between 1961 and 1972 are summarized. Weight gains of steers grazed at 2·4, 1·2, 0·8 and 0·6 ha/300 kg animal on Cymbopogon/Hyparrhenia/Themeda pasture are detailed. Subtreatments included continuous and rotational grazing and the removal of the unpalatable Cymbopogon afronardus.

Weight gains at 0·6 ha/animal were higher than a linear relationship between stocking rate expressed as animals/ha and weight gain would predict. This was ascribed to the dominance of the high quality grass Brachiaria decumbens at this grazing pressure.

Rotational grazing was less productive than continuous grazing, because C. afronardus increased more rapidly under this management, but there was less soil erosion. Removal of C. afronardus increased cattle growth rates and gains/ha by over 40% at 0·6 ha/animal. The cost of clearing this weed should be recovered in 2 years from a commercial cattle ranch. A grazing pressure of ca. 0·8 ha/animal is expected to maximize long-term profits on C. afronardus-free Ankole rangeland and in 3 years in this trial average gains of 0·29 kg/day/animal were achieved. This was an annual production level of 131 kg/ha/annum, which compared with 53 kg/ha at 2·4 ha/animal and 143 kg/ha at 0·6 ha/animal.

The fungicidal and phytocidal properties of manufactured hydrocarbons and their simpler hydroxyl-derivatives and esters have been examined by application in spray-form to young leaves of hops bearing powdery patches of the hop powdery mildew (Sphaerotheca humuli (D.C.) Burr.). The sprays were prepared by agitation with 0·25 per cent. Agral I solutions. For ease of description the term fungicidal is applied only to sprays which are lethal to the fungus, whilst a spray is termed phytocidal when injury to the leaf results at areas not invaded by the fungus.

1. Benzene was fungicidal and phytocidal at concentrations of 2 per cent., whereas the hydrogenation products, cyclohexane, methyl cyclohexane and dekalin, were inactive at this concentration. Fungicidal and phytocidal properties were shown at 7 per cent, of the two former, and 3–4 per cent. of the latter.

The neutron method of estimating soil moisture content in the field has the advantage that once access tubes are installed no further disturbance to the site is necessary and readings can be taken repeatedly throughout the soil profile at a fraction of the time necessary for the gravitational method. However, measurement of moisture content in the surface layer of soil, the top 10 cm, has proved difficult since the source and detector must be at a depth less than the sphere of influence allowing some neutrons to escape to the atmosphere. This air-soil interface effect can lead to an underestimation of moisture content which is greatest in wet soil (Van Bavel, Hood & Underwood, 1954).

Further exploitation of the increasingly popular oil-seed rape crop, Brassica napus L., as a valuable break in cereal production in the U.K., is threatened by the susceptibility of the crop to a number of diseases of which the most serious is likely to be stem canker caused by Phoma lingam (Tode ex Fr. Desm.), perfect stage Leptosphaeria maculans (Desm.) Ces et de Not. (Gladders, 1977; Hewitt, 1977). This pathogen has already severely restricted the cultivation of oil-seed rape in France (Lacoste et al. 1969) and in Australia (Bokor et al. 1975; McGee & Emmett, 1977).

Plot trials measured the effect of fertilizers and defoliation on Hyparrhenia veld.

N was the only nutrient limiting growth, and N fertilizer markedly increased the herbage yield and crude protein %. The herbage response was linear up to the highest rate used, 189 lb. N/acre, with a calculated N recovery of approximately 35%. Split fertilizer applications were only advantageous in one year out of three. The effect of N fertilizer steadily decreased at successive harvests after application, and the residual effect in a following season was transient. N fertilizers did not alter the botanical composition of the veld.

Forty-two Awassi lambs, 21 males and 21 females, were used to investigate the effect of early shearing, before the hottest months, on their performance and heat tolerance as indicated by rectal temperature and respiration rate.

Within each sex, half the number of lambs were sheared and the rest were left unshorn. All lambs were fed for 132 days, covering the hottest period of the year, on a concentrate mixture at the daily rate of 2% of their average live weight plus green roughage offered ad libitum. Rectal temperatures and respiration rates were recorded 1 day of each week on three occasions each day.

Shorn lambs of both sexes had significantly (P < 0·01) higher values for body gain and final body weight than the unshorn ones. Average total digestible nutrients intake was slightly higher for shorn lambs. However, average dry-matter intake as a percentage of body weight was almost the same for shorn and unshorn lambs. Shorn lambs of both sexes were more efficient than the unshorn ones in converting food to body gain.

Shorn lambs were more heat-tolerant than the unshorn ones as indicated by their significantly (P < 0·01) lower rectal temperature and respiration rate.

In each of the crops studied, weeding increased grain yield, weeding 2 weeks after sowing being better than weeding either four or eight weeks after sowing and weeding two and four weeks after sowing being better than weeding either two and eight weeks or four and eight weeks aftersowing. Weeding thrice (two, four and eight weeks after sowing) was significantly superior to all the other weeding treatments. Weeding increased leaf area index, dry weight of side and mainstem and number of mature pods at harvest in green gram and cowpeas. In sorghum, apart from increasing leaf area index, it also increased the length of ears and grain weight per unit lengthof ear. The weeding treatments affected grain yield in cowpeas and green gram due totheir influence on leaf area development, development of the main and side stems and on the number of mature pods produced at harvest. The effect of the weeding treatments on grain yield of sorghum was due to their influence on leaf area development, length of ear and grain weight perunit length of ear.

1. A diluter for semen containing egg yolk, glycine, sodium citrate, fructose and glycerol is described.

2. 2005 inseminations gave an over-all conception rate of 65·7% (90–120 days non-returns) after periods of storage varying from 24 to 196 hr.

3. 401 inseminations after storage for 24–48 hr. gave a conception rate of 75·3%, compared with a conception rate of 60·0% on 398 inseminations after 96–144 hr. storage, using semen from the samecollections.

4. A possible use for modified glycine diluters for nominated service at A.I. centres is suggested.

The yields of seed from a hybrid, one of its parents and different mixtures of the hybrid and parent were compared in the case of two different hybrids. Open-pollinated controls were included in the trial, which was sown at about the normal rate for beans. With both hybrids a mixture of 11 of hybrid to 1 of parent yielded as well as the hybrid itself and mixtures of 2 of hybrid to 1 of parent yielded in both cases about 7 cwt./acro more than the mean of the open-pollinated controls. With the higher-yielding hybrid, which had less contrast in vegetative vigour between hybrid and parent, mixtures in the proportions 5:1 and 2:1 showed declining yields, but with the other hybrid they yielded as well as the pure hybrid.

The sowing of improved tropical forages in tree plantations can increase animal productivity considerably, but planted grasses often fail to persist under grazing, resulting in unstable pastures. An experiment was conducted in Brisbane, Australia during the summer of 1989/90 to investigate whether the failure of tropical grasses to persist in shade when regularly defoliated is related to their growth habit. Two shade-tolerant grasses of contrasting growth habit (prostrate Paspalum wettsteiniiv. erect Paspalum malacophyllum)were grown in simulated swards at light levels of 100, 50 and 20% of full sunlight and defoliated every 2 or 4 weeks. Shading and frequent cutting reduced total dry matter yield equally in the two grasses. Shading also reduced tiller density. Paspalum wettsteinii persisted poorly under frequent (2-weekly) defoliation in shade. Plant survival rate of this grass was 66% in the 2-weekly defoliation-20% light transmission treatment, compared with 94% in P. malacophyllum. The poor survival of P. wettsteinii was related to its high allocation of total yield to roots, low tiller density and low total nonstructural carbohydrate yield in residual biomass after defoliation. The inability of P. wettsteinii to adjust in shade to frequent defoliation led to a continual decline in photosynthetic area and light interception, resulting in the depletion of energy reserves, increased susceptibility to Rhizoctonia fungal infection and ultimately to death. It was concluded that growth habit per se cannot be used as a simple indicator for selecting tropical grasses for shaded environments. Instead, morphophysiological adaptation to defoliation in shade was critical for plant persistence.

The relationships of normalized water index three (NWI-3) and canopy temperature (CT) with grain yield in north-west Mexico were determined in a set of wheat lines planted in multi-location yield trials. Advanced wheat lines developed by The International Maize and Wheat Improvement Centre (CIMMYT) were included and tested internationally in the trials including the 24th Elite Spring Wheat Yield Trial (ESWYT), the 11th Semi-Arid Wheat Yield Trial (SAWYT) and the 11th High Temperature Wheat Yield Trial (HTWYT). In north-west Mexico, NWI-3, CT and grain yield were determined in three growing seasons (2006, 2007 and 2008) and three environments (well irrigated, water-stressed and high-temperature), while grain yield was measured at international locations in the same advanced lines of the 24th ESWYT, the 11th SAWYT and the 11th HTWYT . The CIMMYT database was used to obtain grain yield from worldwide nurseries. The mean grain yield ranged from 0·8 to 12·7 t/ha for the 24th ESWYT (59 international sites), from 0·6 to 8·2 t/ha for the 11th SAWYT (28 international sites) and from 0·4 to 7·5 t/ha for the 11th HTWYT (26 international sites). NWI-3 and CT for the advanced lines in the three yield trials measured in north-west Mexico in distinct environments showed significant associations with the grain yield from a few international locations (0·12–0·23 of sites). Locations from Central Asia and North Africa had the best associations with NWI-3 and CT. The lack of more associations may be due to either an interaction of other factors (low rainfall and limited irrigations), which affected yield performance, or few of the advanced lines were well adapted to local growing conditions at each testing site, or a combination of these factors. The present results indicate that NWI-3 and CT have limited potential to predict yield performance at international sites.

Determination of the phosphorus partition in blood is described, combining dry combustion with the ceruleo-molybdate procedure of Deniges. Advantages in speed and convenience are claimed over the conventional Briggs methods.

In dealing with the Inheritance of Glume-Length [Engledow(1)] there were encountered certain problems relating to metrical characters. As it appeared that these problems must attach to all genetic work upon a metrical basis, they were made the subject of a separate investigation. A simple account of some of the difficulties experienced in connection with Glume-Length Inheritance will serve to formulate the problems.

Effects of temperature, hydrogen ion and substrate concentrations on conjugation of l-chloro-2,4-dinitrochlorobenzene by glutathione S-transferase from susceptible and dichlorvos-resistant strains of cotton aphid (Aphis gossypii Glover (Homoptera: Aphididae)) were evaluated. Enzymes from both strains had common optimum temperature and substrate concentration values of 30 °C and 10 mM respectively. Also, while enzyme activity of the susceptible strain peaked at pH 7·2, that of the resistant strain showed complete linear dependency up to pH 8·0. Of four subcellular fractions, the 100 000 g supernatant (soluble fraction) gave the highest enzyme activity in both phosphate and Tris/HCl buffers. There was no linear relationship between insecticide application frequency and production of enzyme activity in the susceptible strain but there was a very high positive correlation between these two parameters in the resistant strain.