Strong Neutron Pairing in core+4n Nuclei

The emission of neutron pairs from the neutron-rich N=12 isotones ^{18}C and ^{20}O has been studied by high-energy nucleon knockout from ^{19}N and ^{21}O secondary beams, populating unbound states of the two isotones up to 15 MeV above their two-neutron emission thresholds. The analysis of triple fragment-n-n correlations shows that the decay ^{19}N(-1p)^{18}C^{*}→^{16}C+n+n is clearly dominated by direct pair emission. The two-neutron correlation strength, the largest ever observed, suggests the predominance of a ^{14}C core surrounded by four valence neutrons arranged in strongly correlated pairs. On the other hand, a significant competition of a sequential branch is found in the decay ^{21}O(-1n)^{20}O^{*}→^{18}O+n+n, attributed to its formation through the knockout of a deeply bound neutron that breaks the ^{16}O core and reduces the number of pairs.

Quasifree (p, 2p) Reactions on Oxygen Isotopes: Observation of Isospin Independence of the Reduced Single-Particle Strength

Quasifree one-proton knockout reactions have been employed in inverse kinematics for a systematic study of the structure of stable and exotic oxygen isotopes at the R^{3}B/LAND setup with incident beam energies in the range of 300-450  MeV/u. The oxygen isotopic chain offers a large variation of separation energies that allows for a quantitative understanding of single-particle strength with changing isospin asymmetry. Quasifree knockout reactions provide a complementary approach to intermediate-energy one-nucleon removal reactions. Inclusive cross sections for quasifree knockout reactions of the type ^{A}O(p,2p)^{A-1}N have been determined and compared to calculations based on the eikonal reaction theory. The reduction factors for the single-particle strength with respect to the independent-particle model were obtained and compared to state-of-the-art ab initio predictions. The results do not show any significant dependence on proton-neutron asymmetry.

The nutrition of grazing ewes during pregnancy and lactation: relationships between herbage, supplement and milk intakes, and ewe and lamb liveweight and body composition

This paper reports results from a study of ewes in pregnancy and lactation, during which times they grazed at a high versus medium stocking rate and either received or did not receive a pelleted supplement. We measured ewe liveweight, condition score and body composition; intakes by ewes of pasture and supplementary feed; milk production by ewes, and; birthweight, milk intake, liveweight gain and body composition of single and twin lambs. Ewes grazing at the medium stocking rate consumed more pasture in late pregnancy and the intake of supplement significantly reduced pasture intake. Nevertheless, total intakes of organic matter or digestible organic matter were unaffected by supplementation and were significantly higher at the medium stocking rate. Effects of stocking rate on intake persisted into early and mid-lactation, but supplement intake did not affect pasture intake in lactation. Pasture intakes in pregnancy were not markedly different between twin-bearing and single-bearing ewes, nor were pasture intakes in lactation affected by the number of lambs suckled. Ewes suckling twins produced much more milk. There were significant effects of birth type, ewe stocking rate and supplementation on lamb milk intake and liveweight gain. The data were reanalysed by regression, to explore the effects of actual herbage masses and ewe intakes, and the possible effects of non-treatment terms such as ewe age, condition score and dentition score at allocation. These analyses confirmed the above effects of treatment, but also demonstrated that ewes in better condition at the start of the experiment ate less pasture in both pregnancy and lactation, and produced significantly less milk. Ewe organic matter intakes in pregnancy were not related to dentition score at allocation, but in early and mid-lactation were reduced by ~170 g organic matter/day and 280–380 g organic matter/day, respectively, per unit increase in dentition score. There was no significant effect of ewe dentition score on lamb milk intake, but there was a significant penalty of ~19 g lamb liveweight gain/unit increase in ewe dentition score at allocation. Future studies of this kind thus need to include estimates of the condition score and dentition score of ewes when they commence the experiment.

New Measurement of the Direct 3α Decay from the ^{12}C Hoyle State

Excited states in certain atomic nuclei possess an unusual structure, where the dominant degrees of freedom are those of α clusters rather than individual nucleons. It has been proposed that the diffuse 3α system of the ^{12}C Hoyle state may behave like a Bose-Einstein condensate, where the α clusters maintain their bosonic identities. By measuring the decay of the Hoyle state into three α particles, we obtained an upper limit for the rare direct 3α decay branch of 0.047%. This value is now at a level comparable with theoretical predictions and could be a sensitive probe of the structure of this state.

Evidence for triangular D3h symmetry in 12C

We report a measurement of a new high spin Jπ=5- state at 22.4(2) MeV in 12C which fits very well to the predicted (ground state) rotational band of an oblate equilateral triangular spinning top with a D3h symmetry characterized by the sequence 0+, 2+, 3-, 4±, 5- with almost degenerate 4+ and 4- (parity doublet) states. Such a D3h symmetry was observed in triatomic molecules, and it is observed here for the first time in nuclear physics. We discuss a classification of other rotation-vibration bands in 12C such as the (0+) Hoyle band and the (1-) bending mode band and suggest measurements in search of the predicted ("missing") states that may shed new light on clustering in 12C and light nuclei. In particular, the observation (or nonobservation) of the predicted ("missing") states in the Hoyle band will allow us to conclude the geometrical arrangement of the three alpha particles composing the Hoyle state at 7.654 MeV in 12C.

Infusion of noradrenaline through the proximal line of a migrated central venous catheter

A 41-year-old, obese, patient was admitted to Accident and Emergency with a history of leg cellulitis. A central line was inserted. Documented aspiration of blood from all lines, central venous pressure trace obtained and correct position noted on the chest X-ray (CXR). The patient became increasingly septic despite antibiotic therapy. He was subsequently commenced on a noradrenaline infusion; however, the blood pressure was unresponsive. On admission to the intensive care unit (ICU), it was noted he had an area of white skin over the right clavicle. The infusions were stopped and a CXR confirmed proximal migration of the line. The central line was re-sited and his noradrenaline recommenced with an improvement in his blood pressure. Acute renal failure developed which required haemofiltration for 24 hours. The condition improved and the patient was discharged from ICU. It took several weeks for his renal function to return to normal, but he was discharged home with no permanent damage.

Migration of nuclear shell gaps studied in the d(24Ne,pγ)25Ne reaction

The transfer of neutrons onto 24Ne has been measured using a reaccelerated radioactive beam of 24Ne to study the (d,p) reaction in inverse kinematics. The unusual raising of the first 3/2+ level in 25Ne and its significance in terms of the migration of the neutron magic number from N=20 to N=16 is put on a firm footing by confirmation of this state's identity. The raised 3/2+ level is observed simultaneously with the intruder negative parity 7/2- and 3/2- levels, providing evidence for the reduction in the N=20 gap. The coincident gamma-ray decays allowed the assignment of spins as well as the transferred orbital angular momentum. The excitation energy of the 3/2+ state shows that the established USD shell model breaks down well within the sd model space and requires a revised treatment of the proton-neutron monopole interaction.

Signaling through the TRAIL receptor DR5/FADD pathway plays a role in the apoptosis associated with skeletal myoblast differentiation

Apoptosis rather than differentiation is a physiological process during myogenesis and muscle regeneration. When cultured myoblasts were induced to differentiate, we detected an increase in caspase 8 activity. Pharmacological inhibition of caspase 8 activity decreased apoptosis. Expression of a dominant-negative mutant of the adapter protein FADD also abrogated apoptosis, implicating a death ligand pathway. Treatment with TRAIL, but not Fas, induced apoptosis in these myoblasts. Accordingly, treatment with a soluble TRAIL decoy receptor or expression of a dominant-negative mutant of the TRAIL receptor DR5 abrogated apoptosis. While TRAIL expression levels remained unaltered in apoptotic myoblasts, DR5 expression levels increased. Finally, we also detected a reduction in FLIP, a death-receptor effector protein and caspase 8 competitive inhibitor, to undetectable levels in apoptotic myoblasts. Thus, our data demonstrate an important role for the TRAIL/DR5/FADD/caspase 8 pathway in the apoptosis associated with skeletal myoblast differentiation. Identifying the functional apoptotic pathways in skeletal myoblasts may prove useful in minimizing the myoblast apoptosis that contributes pathologically to a variety of diseases and in minimizing the apoptosis of transplanted myoblasts to treat these and other disease states.

Alpha:2n:alpha molecular band in 10Be

The 10.15 MeV resonance in 10Be has been probed via resonant 6He+4He elastic scattering. It is demonstrated that it is the Jpi=4+ member of a rotational band built on the 6.18 MeV 0+ state. A Gammaalpha of 0.10-0.13 MeV and Gammaalpha/Gamma=0.35-0.46 were deduced. The corresponding reduced alpha width, gamma2alpha, indicates one of the largest alpha-cluster spectroscopic factors known. The deformation of the band, including the 7.54 MeV, 2+ member, is large (h2/2I=200 keV). Such a deformation and the significant degree of clusterization signals a well-developed alpha:2n:alpha molecular structure.

Structure of 12Be: intruder d-wave strength at N=8

The breaking of the N=8 shell-model magic number in the 12Be ground state has been determined to include significant occupancy of the intruder d-wave orbital. This is in marked contrast with all other N=8 isotones, both more and less exotic than 12Be. The occupancies of the [FORMULA: SEE TEXT]orbital and the [FORMULA: SEE TEXT], intruder orbital were deduced from a measurement of neutron removal from a high-energy 12Be beam leading to bound and unbound states in 11Be.

Predicted methane emissions and metabolizable energy intakes of steers grazing a grass/alfalfa pasture and finished in a feedlot or at pasture using the GrassGro decision support tool

Dry matter intakes (DMI) and methane (CH4) emissions from steers grazing alfalfa/(Medicago sativa L)/meadow bromegrass (Bromus biebersteinii Roem & Schult.)/Russian wild ryegrass [Psathyrostachys juncea (Fisch.) Nevski] at 1.1 and 2.2 steers ha-1 in continuous and rotational grazing systems at Brandon, Manitoba, during the 1994 grazing season were predicted using the GrassGro decision support tool and compared with those reported from a field experiment. Observed DMI (13.82 ± 0.39 kg d-1) did not differ significantly (P = 0.052) from predicted DMI (12.10 ± 0.19 kg d-1). Mean predicted CH4 (278.5 ± 2.2 g d-1) was greater (P < 0.002) than field observations (195.8 ± 9.7 g d-1). This difference may reflect the difficulty of ensuring total collection of all CH4 emitted in a field experiment. GrassGro predicted that feeding a barley supplement to the steers while at pasture would cause a small though significant increase (P < 0.001) in mean daily emissions of CH4 (287.8 ± 1.9 g d-1) compared with unsupplemented steers (274.1 ± 2.9 g d-1). However, when CH4 emissions were compared as g kg-1 liveweight gain (LWG), they were less (P < 0.0001) for supplemented (133.2 ± 6.4 g kg-1 LWG) than unsupplemented steers (199.1 ± 5.9 g kg-1 LWG). In addition, supplementing barley at pasture would reduce (P < 0.0001) the total emissions of CH4 (38.7 ± 2.1 kg) compared with backgrounding at pasture and finishing in a feedlot (54.4 ± 1.1 kg). This would also reduce (P < 0.001) the metabolizable energy intake (MEI) required for liveweight gain (68.3 ± 1.94 vs. 87.2 ± 1.20 MJ MEI kg-1 liveweight gain). We conclude that finishing cattle at pasture will reduce the total emissions of CH4 and increase the efficiency of conversion of feed energy to liveweight gain when compared with backgrounding at pasture and finishing in a feedlot. Key words: Methane, steers, grass, alfalfa, pasture, barley, feedlot, metabolizable energy intake

Reevaluation of the 22Na(p,gamma) reaction rate: implications for the detection of 22Na gamma rays from novae

Understanding the processes which create and destroy 22Na is important for diagnosing classical nova outbursts. Conventional 22Na(p,gamma) studies are complicated by the need to employ radioactive targets. In contrast, we have formed the particle-unbound states of interest through the heavy-ion fusion reaction, 12C(12C,n)23Mg and used the Gammasphere array to investigate their radiative decay branches. Detailed spectroscopy was possible and the 22Na(p,gamma) reaction rate has been reevaluated. New hydrodynamical calculations incorporating the upper and lower limits on the new rate suggest a reduction in the yield of 22Na with respect to previous estimates, implying a reduction in the maximum detectability distance for 22Na gamma rays from novae.

Apoptosis coincident with the differentiation of skeletal myoblasts is delayed by caspase 3 inhibition and abrogated by MEK-independent constitutive Ras signaling

We demonstrate that during 23A2 skeletal myoblast differentiation, between 30-35% of the population apoptose. Both differentiation and apoptosis are controlled by the variables of cell density and time and these variables are inversely related. In response to conditions that permit both differentiation and apoptosis of parental 23A2 myoblasts, myoblasts rendered differentiation-defective by constitutive Ras signaling (A2:H-Ras myoblasts) do not apoptose. This is not merely a consequence of their differentiation-defective phenotype since myoblasts rendered differentiation-defective by expression of E1A (A2:E1A myoblasts) still apoptose. Although signaling through MEK is important to the survival of proliferating parental 23A2 myoblasts, constitutive signaling through MEK is not responsible for the survival of A2:H-Ras myoblasts. Finally, we demonstrate that caspase 3 is activated and that pharmacological inhibition of caspase 3 activity delays apoptosis without affecting differentiation. Abrogating apoptosis without affecting differentiation could be a useful approach to improve the efficacy of myoblast transfer in the treatment of muscular dystrophies.

Prenatal detection of facial clefts

OBJECTIVES

To determine (1) the antenatal detection rate for isolated cleft lip and/or cleft palate during the routine anomaly scan; (2) the correlation between prenatal diagnosis and postnatal findings, and (3) the association of apparently isolated cleft lip and/or cleft palate with other anomalies, in particular chromosomal abnormalities.

METHOD

A population-based retrospective analysis of all cases of isolated cleft lip and/or cleft during an 8-year period in an academic teaching hospital in the UK.

RESULTS

Thirty-nine cases of isolated cleft lip and/or cleft palate were identified among deliveries at the hospital. Twenty-eight cases had a routine anomaly scan. Fourteen cases were detected prenatally (sensitivity 50%). None of the isolated cleft palates was detected, while 14 of 20 cases of cleft lip (70%) were detected. One of the isolated cases of cleft lip was associated with trisomy 21, while 3 of the isolated cleft palate cases were associated with the Pierre Robin syndrome. In all cases, an antenatal diagnosis of cleft was confirmed following delivery or post-mortem examination (specificity 100%).

CONCLUSIONS

Ultrasound is a useful tool in screening for cleft lip with or without cleft palate, but not for cleft palate alone. Even with an isolated cleft lip, there is an increased risk of chromosomal abnormality. The role of prenatal education and support is extremely important in the preparation of prospective parents and can help alleviate the shock which occurs when there is an unexpected cleft at birth.

Halo structure of (14)Be

The two-neutron halo nucleus (14)Be has been investigated in a kinematically complete measurement of the fragments ((12)Be and neutrons) produced in dissociation at 35 MeV/nucleon on C and Pb targets. Two-neutron removal cross sections, neutron angular distributions, and invariant mass spectra were measured, and the contributions from electromagnetic dissociation (EMD) were deduced. Comparison with three-body model calculations suggests that the halo wave function contains a large nu(2s(1/2))(2) admixture. The EMD invariant mass spectrum exhibited enhanced strength near threshold consistent with a nonresonant soft-dipole excitation.

The nutrition of grazing ewes during pregnancy and lactation: a comparison of alkane-based and chromium/in vitro-based estimates of herbage intake

The n-alkane and chromium/in vitro procedures for estimating herbage intake were compared in grazing ewes during late pregnancy, early lactation, and mid-lactation. To ensure differences in herbage intake, the ewes were grazed in 4 plots of phalaris-dominant pasture at 2 levels of stocking: 17.1 ewes/ha and 30.8 ewes/ha. To investigate whether either procedure for estimating herbage intake was influenced by supplement consumption, half of the ewes at each stocking level received 500 g/day air-dry of a pelletted supplement (1 : 1 milled oat grain : sunflower meal). Supplement intakes were estimated using tritiated gypsum as a marker. During intake measurement periods, ewes were dosed twice daily with both alkane capsules and capsules containing chromium sesquioxide. For the last 6 days of the 12-day dosing period, rectal faecal samples were taken twice daily, immediately before the dosing. Over these same periods, wether sheep fitted with faecal collection harnesses were similarly dosed and sampled, and their total faecal output collected to establish the faecal recovery of chromium and the alkanes. Herbage intakes were estimated using the C27/C28, C29/C28, C31/C32, and C33/C32 alkane pairs. Estimates of intake based on the shorter alkane pairs were lower than those estimated with the C33/C32 alkane pair, by amounts which differed between the periods. Evidence is presented that estimates based on the last pair of alkanes (C33/C32) are the most accurate and are also more accurate than those based on the chromium/in vitro procedure. The relationship between these 2 methods for estimating intake was different in mid-pregnancy compared with either stage of lactation. The consumption of supplement did not interfere with any of the methods for estimating herbage intake. Estimates of faecal output based on the use of chromium, C28 alkane, or C32 as an external marker were statistically identical, indicating that the difference between the 2 methods for estimating herbage intake was not related to a failure to accommodate the incomplete recovery of any of the markers used or to the failure of rectal grab samples to be representative of total faeces. Our results indicate that herbage collected by oesophageally fistulated (OF) sheep was representative of that grazed by the ewes and could thus be used to provide the herbage alkane data needed to estimate herbage intake by the alkane method. However, the in vitro digestibility values obtained from the OF samples did not represent the digestibilities actually occurring in vivo. This was the main cause of the observed difference between the 2 methods for estimating intake. Possible reasons for the differences between the in vitro and in vivo estimates of digestibility are discussed.

Effects of species, plant part, and plant age on the n-alkane concentrations in the cuticular wax of pasture plants

Plants of the pasture species Phalaris aquatica cv. Sirosa, Lolium perenne cv. Victorian, Trifolium repens cv. Irrigation White, T. subterraneum ssp. subterraneum cv. Mt Barker, T. subterraneum ssp. yanninicum cv. Trikkala, and Medicago sativa cv. Siriver were grown under controlled glasshouse conditions. At weekly intervals, 6 plants of each species were harvested and dissected into their component plant parts. The concentrations of n-alkanes in plant parts from all species were then estimated using gas chromatography. Results confirmed earlier studies that alkanes with odd-numbered carbon chains were predominant in cuticular wax, especially C27, C29, C31, and C33 alkanes. For the individual alkanes (225433, differences between species accounted for 85% of the total variance in alkane concentration. Calculation of similarity coefficients indicated that the greatest similarities in the pattern of alkane concentrations occurred either between plant parts within a species or between the same plant part in closely related species. Multivariate statistical analysis using canonical variates analyses indicated that despite these similarities, it would still be possible to distinguish both plant species and plant parts in mixtures of these components. In particular, an examination of hypothetical perennial ryegrass-white clover or phalaris-subterranean clover pastures demonstrated that all fractions of all species would be likely to be distinguishable. The results are discussed in relation to the use of herbage and faecal alkane concentrations in least-squares estimates of the composition of the diet of the grazing animal.

Prime lamb production in relation to time of mating

Over 3 years, we examined the possible benefits of moving the joining date from mid March to early February for the productivity of a prime lamb system based on Border Leicester x Merino ewes on the southern tablelands of New South Wales. The proportion of ewes with >1 lamb (fertility) was affected more by year and by age of ewe than by joining date. The mean proportion of fertile ewes with >1 lamb (fecundity) was reduced from 0.28 to 0.15 at the earlier date, while immunisation against androstenedione increased fecundity at both mating times to 0.42 but significantly reduced fertility in the earlier group. Over the 3 years, the earlier joining produced 12 fewer lambs per 100 ewes mated and immunisation increased lamb number by 17, but flushing (for 3 weeks with sunflower meal) had no significant effect. Immunisation did not have a consistently greater effect at the earlier joining. Groups of these ewes, balanced for fetus number, grazed at 6.5, 10, or 13 per ha on pastures based on phalaris and subterranean clover. Ewe liveweight after lambing, lamb birth weight, and perinatal mortality were not affected by joining date, but mean daily weight gain by later born lambs over the first 90 days of life was 44 g greater than for earlier born lambs. However, earlier joining enabled 17 more lambs per 100 ewes to reach a marketable weight of 31 kg within the pasture season. Twins grew more slowly and relatively few reached sale weight. With a mean 1.4 lambs per ewe, the optimum stocking rate on these pastures appeared to be 6.5-10 ewes/ha. Superphosphate application to half of the experimental area, after 17 years without treatment, increased pasture weight, lamb growth rate, and numbers sold. The increase was such that a treated pasture could have carried an extra 3 ewes/ha without depression in individual productivity, relative to an untreated pasture. Supplementation of ewes in late pregnancy and early lactation benefited only twin lambs at the higher stocking rates. The results suggest that a prime lamb system in this environment is more likely to succeed with the earlier joining date. The lower lambing percentage, resulting from a decrease in fecundity, is likely to be of benefit, rather than detriment, to the efficiency of a system in which single- and twin-bearing ewes and their lambs are given equivalent treatment.

Monitoring the fate of dietary proteins in rumen fluid using gel electrophoresis

1. When fractionated by sodium dodecylsulphate-polyacrylamide gel electrophoresis (SDS-PAGE), strained rumen fluid from sheep fed on pelleted lucerne (Medicago sativa) hay showed no major protein components that stain with Coomassie Blue. This feature made it possible to monitor the fate of individual polypeptides within a protein mixture incubated in rumen fluid in vitro. 2. Extracts from a number of seed meals (sunflower (Helianthus annuus), lupin (Lupinus angustifolius), rape (Brassica napus) and pea (Pisum sativum L.)), as well as casein and bovine serum albumin, were examined in this system. The protein components of each seed type showed a wide range of resistances to degradation. One protein in pea seeds (pea albumin 1), which is particularly rich in cysteine, was almost as resistant to rumen degradation as bovine serum albumin. 3. Analysis of synthetic-fibre-bag experiments by SDS-PAGE showed that the rate of loss of total protein from solid meal residues does not provide an index of the resistance of individual protein components of the meal to rumen degradation. While there was no qualitative change in the protein profile of residual pea-seed meal inside a synthetic-fibre bag, there was considerable variation in the rate at which individual, solubilized protein components were degraded in the surrounding rumen fluid.

Responses to supplements by weaned lambs grazing mature pasture or eating hay in yards

Weaned crossbred lambs grazing mature pasture in summer at stocking rates of 14, 28 or 42 lambs/ha were supplemented for 60 days with 0, 400, 600 or 800 g/day of either sunflower meal or a 1:1 mixture of sunflower meal and oats. Mean daily gains in fasted weight without and with supplement were - 51 and 62 g, respectively, with no significant difference between the three feeding levels. Greasy wool production increased from 4.7 g/day without supplement to 9.9 g/day at the 600 or 800 g level but the composition of the supplement had no effect. Stocking rate had no effect on animal performance. It was estimated that pasture intake increased slightly with the first 400 g of supplement but fell sharply as the level increased further, with a substitution rate of 1.3. In two experiments, yarded lambs were offered oaten or lucerne hay ad libitum and mixtures of sunflower meal and oats at levels from 400 g/day to ad libitum. Mean daily gain in fasted weight increased from about 140 to about 190 g/day over this range of supplementation and greasy wool production from about 9 to about 10 g/day. In one experiment weight gain and wool production were significantly lower with a 1:6 mixture of sunflower meal and oats than with a 1:2 mixture and the same trend was shown in the other experiment. Measurements of intake showed that the substitution rate for both types of hay was only about 0.5. Comparisons of the animals' estimated requirements and intake in all three experiments indicated that the relatively poor performance of grazing animals was due to the very high substitution rate for grazed pasture at levels of supplement intake above 400 g/day.

Feeding value of subterranean clover, lucerne, phalaris and Wimmera ryegrass for lambs

The feeding values of subterranean clover, lucerne, phalaris and Wimmera ryegrass were measured in three experiments using weaned lambs. With dried herbage, the voluntary intake of each species increased linearly with organic matter digestibility over the range tested (57-83%). Regressions for the two grasses did not differ from each other, nor did those for the two legumes; a common regression for the legumes had the same slope as that for the grasses but dry matter intake was about 190 g/d greater on legume diets. Digestibility accounted for 50 and 68% of variation in intake of legumes and grasses, respectively, but when cellulose concentration in the diet was used as the predictor, a single regression satisfied all the data and accounted for 76% of variation in intake. Energy retention by weaned lambs offered diets of dried subterranean clover or lucerne was 53% greater than that by lambs receiving the same intake of metabolizable energy from phalaris. When the intake of the two legume diets was unrestricted, this difference increased to 128%. Despite the 30% higher voluntary intake of the legume diets, the weight of digesta in the reticula-rumen at the end of a meal was the same as it was for the phalaris diet. When all four species were compared in the field, with herbage amply available, lambs grazing the two legumes retained 57% more energy than those on the grasses during the main spring period when the species were of comparable digestibility. As there was little or no difference, under the conditions of this experiment, in the intake of food from the four swards, it is concluded that the difference in feeding value resulted from more efficient use of metabolizable energy. Overall, subterranean clover had as high a feeding value for lambs as lucerne, and phalaris was not inferior to Wimmera ryegrass.

The accuracy of tritiated water turnover rate as an estimate of milk intake in lambs

The accuracy of water turnover measurement as an estimate of milk intake was evaluated, with special reference to the validity of the assumptions underlying the technique. Even when milk was the only source of water for penned lambs, water turnover measurement significantly underestimated known milk intake. The underestimates were greater over longer measurement periods. It is suggested that these underestimates occurred because changes in body water pool size were not considered in the calculation of water turnover, since estimates were improved by the incorporation of a pool size correction. In a second pen trial, it was demonstrated that the inhalation of vapour from tritiated water excreted by other lambs was not a source of error in the estimation of water turnover. .In a field trial, the turnover technique was successfully employed to estimate milk intake in the first 3–4 weeks of life. A method for accommodating changes in pool size is presented, and it is suggested that the effects of pool size changes on the accuracy of the estimate of milk intake are too large to be ignored. In later weeks of the experiment, it was obvious that lambs were consuming water in forms other than milk, so that milk intake estimates were inaccurate. .It is concluded that in animals consuming only milk, measurement of tritiated water turnover provides an accurate estimate of milk intake, but only if changes in body water pool size are taken into account.

An evaluation of cereal stubbles for sheep production

The production of young crossbred wethers grazing oat, barley and wheat stubbles was measured in each of three years at stocking rates ranging from 15 to 30/ha. In one year, production on 'weedy' stubbles was compared with that of 'clean' (weed-free) stubbles, and also the effect of a wheat–urea–mineral supplement on the production of sheep was measured on oat stubble. Liveweight change and wool production were significantly influenced by the availability of green plant material and by stocking rate, but not by supplementation. The maximum liveweight loss in any year was 7.5 kg and the maximum gain 6.0 kg, both recorded over 11 weeks' grazing. Mean daily clean wool production was 9.9 g/sheep at the lower stocking rate and 6.6 g/sheep at the higher rate, but production per hectare was 10–60% higher at the heavier stocking rate. The ranking of the crop stubbles with respect to animal production was not consistent from year to year. Intense selection for green plant material by sheep resulted in the proportion of green in the diet being nearly always greater than 80%, when the weight of this material on the plots was more than 40 kg dry matter/ha. It appeared that a low intake of nitrogen was not the main limitation to animal production. A maximum of only 36% of the crop residue which disappeared during the experiment could be accounted for as animal intake. Thus it is unlikely that the potential of cereal residues as a source of food for animal production will be realized with grazing sheep.

Efficiency of lamb production in relation to the weight of the ewe at mating and during pregnancy

The intake of pasture by nine groups of 40 Border Leicester x Merino ewes was controlled to achieve three levels of liveweight at mating and three levels at the end of the 15th week of pregnancy. Over the last 6 weeks of gestation all groups gained about 7 kg per head, and after lambing the intake of pasture was unrestricted. Ewes that weighed 58 kg at mating produced 152 lambs per 100 ewes compared with a lambing percentage of 107 by ewes that weighed 44 kg. However, when the lambs reached 10 weeks of age there was little difference in their numbers. This was partly because of the higher death rate of young lambs when the liveweight of the ewe fell during mid-pregnancy, and partly because of the loss of single lambs following dystocia in ewes maintained at a high weight throughout pregnancy. The percentage of lambs reaching marketable weight (32 kg) before the end of the pasture season was related directly to the liveweight gain of the ewe during mid-pregnancy, and inversely to the proportion of lambs reared as twins. The weight of lamb marketed per unit weight of food eaten by the ewes over the autumn and winter was much greater from the ewes that increased from 51 to 58 kg during mid-pregnancy than from those that followed the reverse pattern. In general, a fall in ewe weight over this period led to inefficient use of food and a reduction in the weight and soundness of the fleece. These results suggest that in areas that are marginal for prime lamb production because of a short pasture season, it may be better to ensure a rising plane of nutrition throughout pregnancy than to aim for a high weight at mating.