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WOS: 000167035700004 PubMed: 11233785 In vitro matured (IVM) and fertilized (IVF) putative Day 1 zygotes (Day 0 = IVF) were allocated randomly to culture in formulations based on Synthetic Oviduct Fluid (SOF) medium and identified on the basis of their contrasting principal supplements, which were 10% v/v steer serum (SS; n = 558) or 4 mg/mL crystalline BSA (SBSA; n = 531) or 3 mg/mL polyvinyl alcohol (SPVA; n = 607) in 9 replicates. SBSA and SPVA also contained 10 mug/mL non-essential amino acids, while the former was further supplemented with 20 muL/mL essential amino acids and the latter with 0.5 mmol/L sodium citrate and 5 ng/mL epidermal growth factor. Zygotes were cultured in 20 muL drops (4 zygotes per drop) until Day 8 in an atmosphere of 5% CO(2), 5% O(2) and 90% N(2) at 39 degreesC and droplets were renewed every 48 hours. The incidence of zygote cleavage was lower (P < 0.05) in SS (mean +/- SEM = 61 +/- 3%) than in SBSA (76 +/- 3%) but not in SPVA (72 +/- 4%) up to Day 3. The SPVA generated a lower yield of blastocysts on Day 7 (12 +/- 2%; P < 0.001) and by Day 8 (21 +/- 4%; P < 0.01) than did SS (33 +/- 3%; 40 +/- 3%) and SBSA (30 +/- 3%; 37 +/- 4%). Cell numbers (n) and diameters (d) of blastocysts on Day 8 were greater (P < 0.001; Replicates 1 to 5) in embryos from SBSA. (n, 156 +/- 9; d, 203 +/- 4 mum) than in those from SS (n, 81 +/- 4; d, 177 +/- 3 mum) and SPVA (n, 76 +/- 5; d, 167 +/- 3 mum). Embryos produced in SS incorporated less (3)H-phenylalanine into PCA-precipitable protein (replicates 6 to 9; log(10) dpm = 3.03 +/- 0.04) than did embryos cultured in SBSA (3.21 +/- 0.03; P < 0.001) or in SPVA (3.14 +/- 0.03; NS). In conclusion, blastocyst yield was poor in SPVA, but the embryos had metabolic activities similar to those of embryos produced in SBSA. Blastocyst yields from SS were not compromised but their capacity for de novo protein synthesis was reduced significantly. (C) 2001 by Elsevier Science Inc.

Through their influence on embryonic and early fetal development dietary nutrients affect the size, vigour and viability of the newborn and, in the case of sheep, adult ovulation rates. Nutritional regimens that impair post-natal growth reduce ovarian follicular development and delay puberty but have little, if any, effect on either N-methyl-D-aspartate stimulated GnRH release or the pituitary content of gonadotrophins. Nutritional effects on ovulation rate in ewes are not always accompanied by shifts in circulating FSH concentrations. Instead they may operate through altered ovarian hormone feedback mechanisms that influence the duration of exposure of the gonadotrophin-dependent follicles to FSH or through threshold-reducing actions of specific nutrients and dietary-induced metabolites on the amount of FSH needed to support the gonadotrophin-dependent follicles. Recent results suggest that the enhanced faecal excretion of oestradiol by well-fed ewes may increase ovulation rate by reducing ovarian oestradiol feedback. In the post-partum period, the key hypothalamic and pituitary secretions for successful ovulation develop normally despite undernutrition but ovulation is prevented by failure of GnRH release with, in the case of suckler beef cows, a delay in oestrus arising from the repeated development and atresia of dominant ovarian follicles. This effect is accentuated in cows that are in poor body condition at calving. Alleviating the energy deficits of high-yielding dairy cows in early lactation by giving supplements of dietary fat can reduce the interval to first oestrus but subsequent fertility can be impaired. Loss of body protein delays oestrous cyclicity; paradoxically attempts to correct this loss in ruminants by feeding diets high in rumen undegradable protein can stimulate body fat mobilization and milk production with detrimental effects on rebreeding. Excess rumen degradable protein and high feeding levels reduce embryo survival, the latter by suppressing circulating progesterone concentrations. In superovulated ewes diet-induced reductions in progesterone concentrations during oocyte maturation can impart a legacy of developmental retardation leading to decreased embryo survival. In late pregnancy, undernutrition decreases uterine blood flow, fetal insulin and IGF-1 concentrations and impairs growth and development. In the newborn, low insulin and a low selenium and iodine status inhibit thermogenesis from brown adipose tissue. Insulin may also be important in conveying information on nutritional status to the GnRH neurones thereby initiating the cascade of events that is required for successful reproduction in both sexes.

This paper briefly looks at the life of Dr. Peter Safar. It provides an overview of his work in resuscitative medicine and his contribution to prehospital emergency care. The main emphasis of the paper centers on the recognition and the theory application of the prehospital resuscitative framework within education systems today.

The aerated static pile (ASP) composting method, when operated using a temperature feedback control system is known to produce rapid drying rates through the mechanism of evaporative cooling. Previous work has shown through rewetting ASP, that the moisture content had been lowered to the point of producing an inhibitive effect. In this study, using mixtures of raw sludge and woodchips, the effect of moisture control on the rate of organic matter breakdown, using ASP was investigated. Results suggest that the duration of the thermophilic phase can be extended, to provide a more stringent treatment. However, the rate of sanitization appeared to be retarded, although numbers of indicator organisms detected at the end of the runs indicated that the level of pathogen destruction was adequate.

During the past decade, the skills required to engineer changes in the genetic make-up of animals have gradually evolved to a level where the use of gene transfer in farmed mammals, birds and fish is now technically feasible. This review examines some of the possibilities for applications of this technology in food production, considers their acceptability, and discusses their relevance to both producers and consumers.

Twenty ewes were used as donors in a 2 x 2 factorial design experiment to investigate the effects of two different insemination times (48 vs 60 h after pessary withdrawal), with or without sedation, on the ovum recovery rate 5 d after insemination, the proportion of transferable embryos recovered, and the subsequent survival rate of embryos transferred to recipients. The ovum recovery rate following intrauterine insemination at 48 h after progestagen pessary withdrawal was 63.8 and 53.4% for sedated and nonsedated control ewes, respectively. Following intrauterine insemination at 60 h the corresponding values for sedated and control ewes were 72.6 and 73.9%, respectively. The proportion of transferable quality embryos recovered was not affected by sedation but was improved by insemination at 48 h rather than 60 h after pessary withdrawal (100 vs 35.4%). Embryo survival following laparoscopic transfer to recipients from donor ewes inseminated at 48 h, with or without sedation was 38.8% (7/18) and 50% (7/14), respectively. Following intrauterine insemination of the donors at 60 h, the survival rate in recipients was reduced for embryos transferred from both the sedated and control ewes to 6.25% (1/16) and 36.3% (4/11). It is concluded that delaying the timing of intrauterine insemination relative to pessary withdrawal and the use of acepromazine maleate as a sedative at the time of insemination are deleterious to embryo development and subsequent viability.

The thoracocardiograph (TCG) displays cardiac oscillations transmitted to the external surface of the thorax through inductive plethysmographic transducers placed transversely around the thorax near or about the xiphoid process. Such signals, with the appearance of ventricular volume curves, were used to compute changes of stroke volume (SV) and cardiac output (CO) in normal subjects. Their values were compared with changes of SV and CO measured with the impedance cardiograph (IC). Increases of SV and CO were produced with subcutaneous terbutaline and there was excellent agreement between TCG and IC values, best from TCG transducers placed at the xiphoid process and 3 cm caudal to it, although TCG locations 6 cm caudad and 3 cm cephalad to the xiphoid were also satisfactory. Since the site 3 cm caudad to the xiphoid process is known to anatomically transect solely a segment of the left ventricle, it was designated the TCG-Reference location. Both TCG and IC derived SV were not altered during postural shifts about a horizontal axis. Neither TCG nor IC showed the expected large decreases of SV from supine posture to head-up tilt. With baseline TCG and IC measurements in 60° head-up tilt, MAST suit application increased CO measured with TCG but not with IC. Neither TCG nor IC revealed alteration of CO with nasal CPAP up to 10 cm H2O despite a rise in functional residual capacity (FRC) level of 870 ml. This investigation indicates that TCG has promise as a near continuous, noninvasive monitor of SV and CO in normal subjects if postural axis is fixed and does not require highly trained personnel or labor-intensiveness for its operation.

Twenty-one of the world's prolific sheep breeds and strains were tested for the presence of the FecB mutation of BMPR1B and the FecX(I) mutation of BMP15. The breeds studied were Romanov (2 strains), Finn (2 strains), East Friesian, Teeswater, Blueface Leicester, Hu, Han, D'Man, Chios, Mountain Sheep (three breeds), German Whiteheaded Mutton, Lleyn, Loa, Galician, Barbados Blackbelly (pure and crossbred) and St. Croix. The FecB mutation was found in two breeds, Hu and Han from China, but not in any of the other breeds. The 12 Hu sheep sampled were all homozygous carriers of FecB (FecB(B)/FecB(B)) whereas the sample of 12 Han sheep included all three genotypes (FecB(B)/FecB(B), FecB(B)/FecB+, FecB+/FecB+) at frequencies of 0.33, 0.58 and 0.08, respectively. There was no evidence of FecX(I) in any of the breeds sampled.

Of 111 variable age, pedigree ewes subjected to a range of superovulatory regimens and then submitted to embryo recovery by laparoscopy, nine had adhesions corresponding to a mid-line laparotomy (presumably from a previous attempt to recover embryos) and could not have their embryos recovered by the laparoscopic technique. Of the remainder, 27 ewes (26.5%) had less than three ovulations or had prematurely regressing corpora lutea at the selected time for embryo recovery (Days 5 to 6 following insemination), and no attempt was made to recover embryos from them. For the 75 ewes subjected to laparoscopic ovum recovery following laparoscopic intrauterine insemination, the average number of ovulations (+/- SEM) was 7.9 +/- 0.6; the average ovum recovery (mean of values for each ewe) was 51.7% +/- 3.5; and the percentage of recovered ova that were fertilized was 87.3%. For a further nine 3-yr-old crossbred ewes the mean values for ovulation and ovum recovery were 7.6 +/- 1.2 and 70.1 +/- 7.7, and were not significantly different for the two insemination methods used (laparoscopic intrauterine vs cervical). In general, ovulation rates for ewes given pregnant mare serum gonadotrophin (PMSG) tended to be lower (5.2 +/- 0.7) than for those given porcine follicle stimulating hormone (pFSH, 7.7 +/- 0.8) or human menopausal gonadotrophin (hMG, 7.7 +/- 2.3). Ova recovery rates were similar on Days 5 and 6 (Day 0 = insemination), and were not affected by method of insemination (laparoscopic intrauterine vs cervical).

Serum, which is routinely included in many embryo culture media, can decrease the viability of bovine and ovine embryos produced in cultures employing synthetic oviduct fluid (SOF; Kuran et al., 1999) and represents a possible route for transmission of disease. Alternative approaches include the use of chemically defined culture media but results from studies which avoid sera and its derivatives (e.g., albumin) are generally less favourable due to a lack of knowledge regarding the embryo's response to specific nutrients, most notably fatty acids. As a preliminary step towards investigating fatty acid influences on bovine embryo developmentin vitro, the present study examined the effect of adding palmitic acid (C16:0) to SOF plus bovine serum albumin (BSA) on the performance of this semi-defined culture medium and contrasted it with embryo production in SOF supplemented with serum.

The number of cells in bovine and ovine embryos is reduced when steer serum which can generate high concentrations of ammonia in vitro is included in the culture system (Kuran et al., 1998). Moreover, production of embryos in synthetic oviduct fluid (SOF) medium supplemented with this serum causes fetal oversize (Sinclair et al., 1998). The present study investigated the effect of the same high ammonia-producing steer serum in a two-phase culture system on bovine embryo development and blastocyst cell numbers.The experimental design was a 2 x 2 factorial with 5 replicates and involved a total of 928 bovine oocytes that were matured and fertilized in vitro (IVF = Day 0). Presumptive zygotes were cultured in SOF supplemented with 10% v/v steer serum (SOF+SS; n=461) or with amino acids plus 0.4% w/v crystalline BSA (SOFaaBSA; n=467) for an initial period of 48 h following IVF.

In a review of the effects of protein nutrition on reproduction in dairy cattle, Ferguson and Chalupa (1989) expressed concern at the low conception rates to first insemination in high-producing dairy cows and suggested that a contributory factor may be an excess of rumen-degradable protein leading to toxic effects of ammonia and its metabolites on gametes and/or the embryo. More recently Elrod and Butler (1993) have provided data suggesting that degradable protein intakes which were 50% above the requirements for maximum microbial protein synthesis reduced embryo survival in dairy heifers. The objective of the present study was to investigate the effect in ewes of varying the amount of rumen degradable protein during the pre-ovulatory progesterone priming phase and the first four days thereafter on ovulation, fertilization, early in vivo and subsequent in vitro ovum development.

Superovulatory treatments for ewes are normally preceded by a period of priming. In a recent study involving two contrasting levels of feeding (0.6 versus 2.4 x maintenance), McEvoy et al (1993) observed that the higher level of feeding suppressed pre-ovulatory plasma progesterone concentrations and the subsequent early development and viability of fertilized ova. This finding suggests that there is a need to reconsider the recommendation, based on data for spontaneously-ovulating ewes, that ‘superovulated embryo donor ewes’ should be maintained on a high level of feeding during the period of oocyte maturation. It also raises questions regarding the form of the relationship between food intake and plasma progesterone concentrations over the wide range of feeding levels that occur in practice. The aims of the present study were therefore two-fold; firstly, to investigate the relationship between level of feeding and plasma progesterone for feed intakes that ranged from 0.6 x maintenance (M) to 2.4 M and secondly to assess the effect of pre-ovulatory feeding levels on the number, quality and viability of ova produced following superovulation.

An increasing proportion of Agricultural Research funding is being directed to biotechnology and to cell and molecular biology. This shift in funding has two effects on animal production research. First it provides a certain amount of novel information and technology with which to improve current production systems. Second, it leaves less of the research budget for whole animal experiments. It behoves us therefore to keep abreast of the achievements and aspirations of the molecular and cellular biologists. The diverse interests and expertise of the BSAP membership in research, development, advisory work and teaching make the Society a unique forum for conducting the open and on-going debate that is needed to ensure that the results of modern biotechnology are examined critically and applied to the animal production industries in an efficient and acceptable manner.

Several studies have shown that the level of peri- and post-ovulatory progesterone in ewes can critically influence embryo survival (Ashworth, Sales & Wilmut, 1989; Parr, 1992). However, the effect of altering pre-ovulatory progesterone concentrations in superovulated sheep has not been fully investigated. In view of the inverse relationship between the plasma concentration of progesterone and food intake (McKelvey & Robinson, 1986; Parr, 1992), the present study was carried out to determine the effect of altering feed intake on progesterone concentrations during the pre-ovulatory priming phase and on the subsequent viability of ova collected from superovulated ewes.

New systems for estimating the requirements of ruminants for dietary protein involve separate estimates of the extent to which microbial and undegraded dietary protein meet the animal's net requirements for amino acids. The paper provides a brief review of the factors influencing both the synthesis of microbial protein and the amounts of dietary protein that escape the rumen undegraded. Although quantitative data on many of these factors are now emerging, the extensive nature of most sheep-production systems makes their application in a precise quantitative manner difficult. It is suggested that considerable improvements in production could be achieved by using the principles in a qualitative sense. For low-producing animals such as dry ewes, pregnant ewes up to a few weeks before lambing, and ‘store’ lambs, microbial protein will meet the animal's net requirements for amino-acid nitrogen provided that the animals have not been previously subjected to a specific protein deficiency. In contrast, the maximal yield of microbial protein will not meet the net requirements of high-producing animals, such as young, fast-growing lambs, and ewes in the final few weeks of pregnancy and during early lactation. These animals require protein supplements which at least in part escape degradation in the rumen.

Reproduction in Finnish Landrace × Polled Dorset Horn ewes was accompanied by thickening of the wall of the gall bladder. The thickening was caused by hypertrophy of the epithelium, the presence of cysts, proliferation of blood vessels, glands and fibrous tissue in the lamina propria and hypertrophy of smooth muscle. The changes appeared to be initiated during pregnancy but to persist in a modified and chronic form in post-parturient animals.

Twelve bulls of approximately 140 kg bodyweight were each fitted with simple cannulae in the rumen and abomasum and a re-entrant cannula in the terminal ileum. They were kept in individual pens and given daily 1.8 kg of a basal diet containing dried maize meal (whole plant), dried sugarbeet pulp and a urea/mineral preparation in the proportions 0.80, 0.18 and 0.02. Four animals received this diet alone, four received in addition 198 g daily (11 g N) of rapeseed meal by infusion into the abomasum and the remaining four the basal diet plus the same amount of formaldehyde-treated rapeseed also by infusion. The concentration of ammonia-N in the rumen fluid of animals given the untreated rapeseed meal was higher (P < 0.05) than for those on the other two treatments. The pH of the rumen and abomasal fluid was similar on all treatments. Coefficients for the apparent disappearance in the small intestine of the dry matter and nitrogen of untreated rapeseed meal infused into the abomasum were 0.76 and 0.75, respectively. In contrast formaldehyde-treated rapeseed meal was poorly digested. It is suggested that procedures for the treatment of rapeseed meal that will minimise the degradability of its protein in the rumen, yet prevent depression of its digestion and absorption in the abomasum and small intestine have still to be defined.

Attention is drawn to the recent finding that early foetal loss which occurs in prolific ewes can depress the subsequent growth and development of the remaining foetuses. Reference is made to the causes and nature of other forms of growth retardation in late pregnancy and it is concluded that the separate effects of age and size on development of the foetus are relevant to the viability of the newborn lamb. For example, while the skeletons (a measure of functional competence) of small lambs at birth are larger than those of younger foetuses of the same weight, the same is not true for their total lipid content which is their main energy source in the period before suckling. The reduction in neonatal viability as birthweight decreases is unlikely therefore to be due to a failure of small lambs to reach targets in skeletal development that are critical for functional competence but rather to their low lipid content in relation to body size. A simple procedure for boosting the energy supply of the small lamb is the administration of colostrum directly into the stomach, using a catheter and syringe.

Summary Music appreciation deals with the development and application of that general factor in aesthetic judgments described in the main by Burt and Eysenck. This has little to do with appreciation in terms of the assessments of Wing et al. For purposes of identification one might describe seven basic approaches in teaching method. Though each method has its place in success, two methods seem to promise the better result. These methods, the ‘Activity’ and the ‘General discriminative’ might be profitably supplemented by the other five. The effect of a student's appreciation of music is likely to be reflected in his personality and might be termed a measure. It is therefore likely that by studying a student's musical preferences the teacher might better understand his personality which in turn might facilitate sound appreciation of music.

Reduced instrument responses are presented for Thermal-Hydraulic Test Facility (THTF) Test 3.03.6AR. This test was conducted by members of the ORNL Pressurized-Water-Reactor (PWR) Blowdown Heat Transfer (BDHT) Separate-Effects Program on May 21, 1980. Objective was to investigate heat transfer phenomena believed to occur in PWRs during accidents, including small and large break loss-of-coolant accidents. Test 3.03.6AR was conducted to obtain transient film boiling data in rod bundle geometry under reactor accident-type conditions. The primary purpose of this report is to make the reduced instrument responses for THTF Test 3.03.6AR available. Included in the report are uncertainties in the instrument responses, calculated mass flows, and calculated rod powers.

Sixteen former military personnel who were present at the "Smoky" atmospheric nuclear weapon test have been investigated for internal deposits of radioactivity. Whole-body and thorax gamma-ray measurements, thorax and skeletal actinide measurements, and urinalyses for plutonium-239 and strontium-90 indicated no evidence of radioactivity in excess of that found in the general population.

Summary The use of sheep as convenient small ruminants for fundamental studies on digestive physiology and substrate utilization together with direct observations on their nutrient requirements for maintenance, pregnancy and lactation, has provided us with a comprehensive framework for the formulation of optimal feeding strategies for the breeding ewe. What this chapter demonstrates is that rarely do these feeding strategies involve meeting the exact nutrient requirements of the ewe at each stage of her reproductive cycle. Instead, for practical, economic and indeed sound physiological reasons they involve periods in which nutrient intakes exceed requirements and others where they are below requirements, the overall aim being to achieve balance in the composition of the body over the breeding cycle as a whole. Failure to achieve the correct body condition at mating leads to suboptimal ovulation rates. Equally damaging to overall reproductive performance are extremes of nutrition in the first month of pregnancy in that they are detrimental to embryo survival. During the second and third months of pregnancy, a period when the nutrient requirements for conceptus growth are minimal, there is now evidence that a mild degree of undernutrition is beneficial to placental growth and lamb birthweight in ewes that are in good body condition at mating. Recent advances in our understanding of the interrelationships between energy and protein and their effects on fetal growth and milk production have allowed greater flexibility in diet formulation and have provided us with a means of efficiently using body fat reserves at a time when energy requirements invariably exceed intake. Due to the fact that for most sheep production systems, housing is intermittent rather than continuous, few attempts have been made to develop an overall feeding strategy for continuously housed ewes. This chapter contains a description of the diets, feeding regimes and levels of reproductive performance achieved by a continuously housed flock of highly prolific ewes maintained on a 7 month lambing interval.

Thermal-Hydraulic Test Facility (THTF) Test 3.05.5B was conducted by members of the ORNL PWR Blowdown Heat Transfer Separate-Effects Program on July 3, 1980. The objective of the program is to investigate heat transfer phenomena believed to occur in PWRs during accidents, including small and large break loss-of-coolant accidents. Test 3.05.5B was designed to provide transient thermal-hydraulics data in rod bundle geometry under reactor accident-type conditions. Reduced instrument responses are presented. Also included are uncertainties in the instrument responses, calculated mass flows, and calculated rod powers.

Two separate approaches were used to develop a prototype for entering data into a remote host computer in an automated manner. In the first approach, revisions were implemented in the IBM PC's terminal emulator VTEK 4.2. These revisions allowed pre-written script files to be processed to the host-based operating system and applications software as if the script file information had been entered on the keyboard. The script processing capability was implemented taking advantage of existing using-defined key capability and the DEC VT100 asynchronous terminal emulation of VTEK communications software. At present the script command and data files must be manually created at the PC using an editor or word processor. The script processing capability works with any host-based operating system or application software that interacts with a DEC VT100 terminal. An example is provided where VTEK script processing is used to automatically interact with a VAX-based Database Management System (DBMS), INGRES, appending PC-resident data records to an INGRES table, creating a default report, aborting to VMS, and disposing of the report /hor ellipsis/ all without touching a key. An appendix is provided which discusses the second approach of developing a prototype VT100 emulator specifically designed for data entry to amore » remote host computer system. This software loads data automatically into a Vax Datatrieve database. It provides an alternative method of prototype development. The challenges for future development are identified and discussed. The use of the programmable terminal emulator for data control in the case of distributed database applications is also discussed. 7 refs.« less

An unusual instance of a large aneurysm of the posterior leaflet of the mitral valve associated with a bicuspid aortic valve and bacterial endocarditis is reported, along with a review of the pertinent literature. The possible relationship of this lesion to the treatment of bacterial endocarditis with antibiotics is discussed.

Within a few days of fertilization, the sea urchin embryo develops into a small differentiated organism consisting of about 1800 cells and capable of feeding, swimming, and the further ontogenic transformations required in the succeeding weeks of larval growth. A number of distinct cell lineages that are clearly specialized at the morphological and functional levels can be discerned in the advanced embryo, and many of these can be traced back to particular sets of early blastomeres. Classical cell lineage and experimental studies (Hörstadius 1939; for review, see Angerer and Davidson 1984) have shown that certain of these lineages appear to be specified, at least in part, in consequence of the maternal components inherited in those regions of egg cytoplasm occupied by their progenitor cells. Specification of others among the early cell lineages clearly depends on inductive interactions that occur between blastomeres during cleavage. For the molecular biologist, as for his predecessors, this rapidly developing and simply constructed embryo offers the advantages of experimental accessibility. Thus, in respect to direct molecular-level analyses of gene activity in the embryo, for both specific genes and overall transcript populations and their protein products, the sea urchin is at present the best known embryonic system (e.g., reviews of Hentschel and Birnstiel 1981; Davidson et al. 1982; Angerer and Davidson 1984).

Four Finnish Landrace X Dorset Horn ewes were each given an intramuscular injection of 15 mg of dexamethazone on day 142 of gestation. Four ewes with the same fetal numbers were used as controls. Administration of the corticosteroid reduced the mean gestation length from 146-5 to 143-3 days and had no effect on the pre-lambing concentrations of Na, Cl, Ca P and Mg in the maternal plasma or on blood pH. There was a slight but significant (P less than 0-05) decrease in plasma K before lambing in the treated ewes. Plasma urea and glucose concentrations were not affected by treatment. There was a significant increase in the plasma concentration of glucose in both groups of ewes immediately after parturition.

Perez Hernandez, Robinson, Aitken and Fraser (1986) showed that the addition of a protected lipid to the diet of lactating ewes increased the fat content of their milk but had little effect on milk yield. The effects on milk composition were reflected in an improvement of approximately 10 per cent in lamb growth rate. In the experiments of Perez Hernandez et al. the response to the lipid supplement was tested using a diet with a high content of undegraded dietary protein. We now report the results of an experiment in which the response of lactating ewes to a ‘protected’ lipid was tested at three levels of protein intake. We also present data from a second experiment carried out to investigate the influence of the ‘protected’ lipid on the fatty acid composition of the ewe's milk.

Daily oral dosing in mid afternoon with 3 mg of the indoleamine, melatonin, from early June onwards is highly effective in advancing the breeding season of both Greyface and Scottish Blackface ewes kept under a natural photoperiod; the mean reaction interval from initial dosing to the onset of ovarian activity in Scottish Blackface ewes being around 65 days compared with 110 days for untreated controls (Robinson et al 1985). Advancing the starting time for the melatonin treatment to mid-March gave a similar reaction interval with behavioural oestrus occurring in late May/early June (Wigzell et al 1986a). Following this reversal of the breeding season by melatonin, continued melatonin treatment in unmated ewes resulted in a period of oestrous cyclicity lasting 4 to 5 months. Thereafter the ewes became refractory to melatonin and returned to anoestrus at a time when untreated controls were commencing ovarian activity (Wigzell et al 1986b). These observations prompted us to investigate the effects of different durations of melatonin treatment on ovarian activity.

Although laparoscopic intrauterine insemination enabled fertilization to occur in lactating ewes induced to ovulate 28 days after parturition, no pregnancies were sustained when the embryos were returned to their respective post-partum uterine environments (McKelvey, Wallace, Robinson & Aitken, 1989). The incidence of inadequate luteal function, as determined by daily progesterone concentrations is high in the early post-partum ewe, yet at least 60% of ewes with an induced oestrus 21 days post-partum exhibit normal luteal function (Wallace, Robinson & Aitken, 1989). This suggests that inadequate luteal function is not the only factor limiting the establishment of pregnancy in the post-partum ewe. Indeed the transfer of good quality embryos into post-partum recipient ewes induced to ovulate 21 days after parturition and exhibiting normal luteal function failed to result in the establishment of pregnancy. This suggests that the involuting uterus of the early post-partum ewe is an inappropriate environment for embryo development (Wallace et al, 1989).

The induction of early breeding in flocks of ewes under natural daylength conditions was made possible following the evolution of a modified progestagen - PMSG treatment (Gordon, 1971). However, lamb production from early bred ewes has invariably been lower than that achieved from ewes bred within the main breeding season. In attempting to elucidate the underlying determinants of the inferior fecundity of the early bred ewe, the present experiment was undertaken to compare the ovulatory and hormonal responses of ewes subjected to progestagen - PMSG treatment at different times of the breeding season.

Previous studies have shown that for Scottish Blackface ewes kept under a natural photoperiod and exposed to the ram the daily administration of the indoleamine melatonin from June onwards advanced the breeding season and appeared to increase ovulation rate and subsequent litter size (Wigzell et al., 1986). In the primate, exposure to melatonin has been shown to stimulate progesterone production by the corpus luteum in an in vivo perfusion system (Webley & Hearn, 1987). Similarly melatonin administered at physiological concentrations stimulated progesterone production by bovine and human granulosa cell cultures (Webley & Luck, 1986).The present experiments were carried out to determine:-(a) whether or not melatonin enhances progesterone production and thereby the establishment of pregnancy and embryo survival in the ewe.(b) whether melatonin acts directly on the corpus luteum or indirectly via increased activity of the hypothalamic GnRH pulse generator.(c) whether or not the presence of the ram in the immediate post-oestrus period alters the endocrine status of the ewe and thereby influences conception.