Abstract:
Proc. Aust. Soc. Anim. Prod. Vol. 17 REPRODUCTION RESEARCH IN PERSPECTIVE (INVITED REVIEW) R.J. SCARAMUZZI 57 SUMMARY Since recording began early this century the reproductive performance of Although it is not possible to Australian flocks has shown a steady improvement. establish definitive reasons for the improvement, the upsurge in agricultural research which followed the formation of CSIR in 1926 is probably a major factor, especially as most of the improvement in reproduction occurred after 1930. Research has rapidly advanced basic knowledge of reproductive processes in domestic livestock, especially since the introduction of radioimmunoassays for the These advances in knowledge have measurement of hormones in biological tissues. led to . a number of innovations which have wide applicability in animal production. Some improve productivity by providing new treatments, for example the use of either Fecundin or Regulin to increase lambing percentages. Others, enhance such as the 'ram-effect', or the provision of shelter at lambing, management through a better understanding of the constraints imposed by the unique These innovations are described and reviewed in the Australian environment. context of their discovery and their potential value to animal production is assessed. Key words: sheep, reproduction, research policy, melatonin, gonadotrophin releasing hormone, inhibin, progestagens, immunization INTRODUCTION Australia depends heavily on primary industry for its major export earnings. Despite exhortations to the contrary from both sides of politics, this is unlikely to change for some time, because the nation does not possess the population or the educational infrastructure to move our economy rapidly to a Agricultural exports will therefore remain important and technological base. will continue to be influenced by the normal cyclic fluctuations in demand and Given such circumstances, what should our price experienced by most commodities. attitudes be to the continuation of agricultural research, including that into Two alternative,, and in some ways, mutually exclusive animal reproduction? attitudes are: to undertake research towards highly I, efficient, low-cost production systems concentrating on maximum utilization of available resources for extensive production, or towards improving the efficiency of production with anemphasis on increased intensification and sophistication. The advantages of the second alternative, which are a consequence` of the greater control inherent in an intensified system, include a greater control over the quality of the end product and a greater ability to respond rapidly to the demands of the consumer. While this is primarily a political.and economic question, a clear answer is ' important to the future directions of applied research and, to some extent, to the This basic research ultimately responsible for progress i.n. any direction. question should be debated by .profe&ional bodies such as the Australian Society ---7 CSIRO Division of Animal Production, P.O. .Box 239, Blacktown, NSW, 2148, Australia. 58 Proc. Aust. Soc. Anim. prod. VoZ. 17 of Animal Production (ASAP) which should attempt to form a consensus and be in a position to advise government (Lloyd Davies 1988). For the present, these important policy decisions are largely in the hands of funding organizations, which by their very nature are less concerned with the long-term, than the Tertiary short-term needs of animal production (Farnworth 1988; McInnes 1988). institutions, the CSIRO and professional organizations such as the Australian Institute of Agricultural Science (AIAS) and ASAP have an important role to play in thtis process, a role which in recent times has attracted increasing attention (Donald 1988; Radcliffe 1988). In recent years attention has turned to the so-called 'post-farm gate' or Research into consumer preferences and research into marketing and processing. into the most suitable means of promoting agricultural produce has lagged behind production research, and a serious attempt is now being made to redress these shortcomings. However, the very nature of industry funding means that these new areas compete directly with production research for limited funds. These areas (i.e. production research and 'post-farm gate' research) are complementary and they should not have to compete beyond normal healthy competition. Present conditions, the result of uncertain funding, of repeated and essentially superficial re-assessments, of changing priorities and of a lack of employment opportunities for graduates, are perceived by scientists as a lack of national purpose and cohesion in animal production research. The lack of purpose and cohesion is even more devastating for basic research: it has, led to the often repeated claim that much basic work is esoteric and irrelevant to industry, to a loss of status of basic sciences in the agricultural community and, in recent years, to an alarming fall in the number of young graduates seeking higher The subject of this review paper, recent developments from qualifications. research into reproduction of farm animals that may be of significance to The achievements cover a wide producers, highlights this lack of guidance. Most spectrum of research progressing forward on a broad unto-ordinated front. of the newer developments are more suited to intensified production and, although unplanned, this is the direction in which we seem to be heading. RESEARCH IN RETROSPECT A rational, objective analysis sof the past is invaluable to understanding The keeping of records of reproductive the present, and planning the future. performance is therefore an important part of planning our future research. Records of annual lamb marking percentages have been collected since 1903 in New South 'Wales, but began later in other states (Statistical Handbook of the Sheep and Wool Industry, Bureau of Agricultural Economics,. Canberra (Fourth Edition, 1973); Livestock Statistics in Australia, Australian *Bureau of Statistics, Canberra (1973 to 1981 inclusive); Livestock and Livestock:Products Australia, The Australian Bureau of Statistics, Canberra (1981-82 to 1985-86 inclusive)). ' bene.fits of research are not always easily identified and in the short term aire often imperceptible, .but since. Federation the reproductive performance of Australian flocks has gradually improved, particularly since the 1930s which, significantly,' about the time that government and tertiary organizations is The improvement in commenced organized agricultural research on a' major scale. First, there has- been a reproductive performance is seen in two different ways. steady increase in the lamb marking,percentage over the 80 years for which records The four States presented in Fig. 1 represent the are available (Fig. 1). geographical and exivironmental extremes of the Australian sheep and wool Simp.le regression analysis of the data shows that the lamb marking industries. 1% every four years. ' percentage in' NSW is increasing by approximately Corresponding figures for Tasmania, Western Ausstralia,and Queensland are 3, 6 and The second *feature. is then reduction of the year-to-year 9 years respectively. . Proc. Aust. Soc. Anim. PTod. Vol. 17 60 Proc. Aust. Soc. Anim. PrOd. Vol. 17 Proc. Aust. Soc. Anim. Prod. VoZ. 17 61 variability (expressed as the coefficient of variation within decades) in lamb marking percentages. In New South Wales, for example, the variability in lambing percentages for the decade 1903-1912 was 16% and this. has declined steadily (Fig. 2) to a value of 4% for the decade 1973-82. The pattern of decreasing variability is repeated for the other States (Fig. 2). The patterns in these graphs can be related to the major environmental variables known to influence reproduction (rainfall and drought) but also to some important events in the history of Australian agriculture (Table I>. A period of approximately 60 years (18704930) was required to establish the infrastructure for research, the period from 1930 onwards has seen the accrual of benefits from this research infrastructure. Table 1 The approximate dates of some of the major events in research into sheep production and reproduction Event Year 1870-80 1884 CO 1890 1909 1910 1910-20 1910-20 1916 1926 1926-29 1926-30 1935 1935-50 1945-55 C. 1950 1950 ' 1950-70 1957-60 Departments of Agriculture formed in the various colonies (States) First Australian Agricultulral College established at Roseworthy, SA Establishment of 'Model Farms', later to become Research Stations First Faculty of Veterinary Science (University of Melbourne) First Chair of Agriculture established (University of Sydney) Introduction and widespread use of subterranean clover Wide-scale use of superphosphate on pastures encouraged Formation of a Federal Advisory Council for Science and Industry The Science and Industry Research Act Control of prickly pear infestations Establishment of CSIR Divisions of Animal Nutrition and Health Formation of the Australian Institute of Agricultural Science Diagnosis and treatment of trace element deficiencies Diagnosis and control of 'acute' clover disease Introduction of Ph.D. degree in Agricultural Science Control of the rabbit plague by myxomatosis Objective measurement and scientifically-based selection Introduction of production levies to fund research and marketing If recognized at all by producers, the improvement in reproductive performance is usually taken for granted as a natural progression, and with little thought for the reasons, Research has almost certainly improved reproductive performance in the face of increased stocking rates, decision-making has become more flexible, and a wide array of management options has emerged. In other words, the industries -have become more efficient and better able to cope with the vagaries of the Australian climate.. In an era of declining margins, improved efficiency is one of the keys to survival. Achievements in reproduction research Reproductive research has produced an impressive list of achievements (Table 2) and it is probable that most,' if not all, livestock producers already take advantage of some of these achievements without even being aware of them. These achievements, some more important' than others, span a period 'of 40 years from R.B. Kelley's first observation that the pattern of reproduction in the Australian Merino was seasonal (Kelley 1937) to the recent release'of Regulin, a commercial form of melatonin, into the Australian market. These events have been associated with the steady increase in the lamb. marking percentage (Fig. I) and the corresponding decline in the variability of lamb marking percentages (Fig. 2). 62 Table 2 Proc. Aust. Soc. 4rzim. Prod. Vd. 17 Some of the major advances in research into sheep reproduction Artificial insemination of ewes demonstrated Definition of seasonality of Australian sheep The benefits of flushing on ovulation rate defined Discovery of the ram effect Definition and control of acute clover disease Control of oestrus using progesterone Out-of-season breeding using progesterone and PMSG Successful embryo transfer in sheep Effect of heat on fetal health and pregnancy 'Sire Sine' mating harness introduced Physiological basis of grazier weather alerts Oestrogenic potency of clover varieties Basis for controlling of pregnancy toxaemia Basis of lamb mortality Intravaginal progestagen sponge introduced Genetic selection increases litter size Successful freezing of ram semen Effect of heat on sperm production Induction of parturition using hormones Successful freezing and thawing of sheep embryos Immunological methods of increasing litter size Benefit shown of shelter belts to reduce lamb losses Real time ultrasound used to detect pregnancy Practical implementation of the ram effect Substitution,of teaser wethers for vasectomised rams Practical intrauterine insemination Glucose test for prevention of pregnancy toxaemia Release of 'Fecundin' to increase twinning rates Basis of practical'fostering of lambs Release of 'Regulin' to increase twinning'rates THE STRUCTURE OF RESEARCH Gunn 1936 Kelly 1937 Underwood and Shier 1941 Underwood et al. 1944 Bennetts et al. 1946 Robinson 1952 Robinson 1954 Hunter et al. 1955 Yeates 1956 Radford et al. 1960 Alexander 1962 Lloyd Davies and Bennett 1962 Reid 1963 Alexander 1964 Robinson 1965 Turner 1969 Mattner'et al. 1969 Salamon and Lightfoot 1970 Braden and Mattner 1970 . Bose 1972 Willadsen et al. 1976' Scaramuzzi 1976 Alexander et al. 1980 Fowler and Wilkins 1980 Oldham 1980 Fulkerson et al. 1981 Killeen and Caffery 1982 Parr and Williams 1982 Scaramuzzi et al. 1983 Alexander et al. 1987 Croker et al. 1987 two Research into reproduction operates within a conceptual framework; Both are vital classes of research, basic and applied, are generally recognised. and need to be nurtured through tertiary education, and supported with sufficient . The resources, if animal production is to continue to benefit from research. opportunities for empirically-derived solutions* from ad hoc research will disappear as problems become more complex and require ' multi-disciplinary research. Research has become more expensive and increasingly subjected to cost-benefit analyses. In other words, we cannot be sure that the approach to research which has served so well over the past 50 years will continue'to do so. Basic research s * This type of research is usually regarded as curiosity-driven, but is increasingly stimulated by the need to understand a specific industry problem. Basic science is needed It is the platform from which most improvements arise. The need for to understand problems and develop methods. of overcoming them. research of this type in Australia is now greater than ever, because our problems are often unique and it is therefore unlikely that practical solutions could be . Proc. Aust. Soc. Anim. Prod. Vol. 17 63 imported. Even if they could be imported, local expertise would still be needed The nutritional constraint on reproduction imposed to evaluate their usefulness. by our unique environment is a good example. European feeding standards are of little practical value to the improvement of reproduction in a Mediterranean climate, so management options resulting from a sound understanding of basic physiology must be developed locally. Traditionally, progress arises from basic research that is not problem-driven, for example, the use of the ram effect to enhance reproductive performance in spring-mated Merino flocks in Western Australia (Oldham 1980; Pearce and Oldham 1984). Advances in other bio-medical sciences often provide benefits to animal production, for example, the use of real time ultra-sound to diagnose pregnancy and to establish litter size pre-partum (Fowler and Wilkins 1980). Progress can also arise directly from curiosity-driven basic research, for example, the use of the hormone melatonin to improve litter size in Industry and spring-mated ewes (Staples et al. 1986; Poulton et al. 1987a, b). government funding bodies seem to believe that they have no part to play in supporting these types of basic research, at least in the formative stages (Lloyd Davies 1988), and consequently these types of projects may founder at the outset. This is particularly so if the end product of the research is a management option rather than a saleable product. Applied research Co-ordinated problem-driven research is a relatively recent phenomenon, made possible to a large degree by the base of knowledge accumulated through A problem may involve direct production losses curiosity-driven basic research. (e.g. acute clover disease) or may simply reflect a desire to improve a currently The key to this type of accepted standard of productivity (e.g. lamb mortality). research is the need to define the problem with sufficient clarity ,to allow for example, chronic clover well-directed research, programs to be undertaken; disease remains a major source of production loss, but there is no clear definition of this largely hidden problem and no recent progress in overcoming it Reproductive research should aim to achieve a balance such (Adams et al. 1984). that the short-term problems of' the industries' are .addressed without compromising the long-term basic research which is needed to,maintain or increase a competitive The scientists &id their professional 3associations have a role to advantage. play in maintaining this balance 'by countering the legitimate. short-term aims of It would be to our. disadvantageif the level of funding industry funding bodies@'. for basic research wereinadequate by comparison .with otherOECD. countries?, :kRMACOLOGICAL AIDSTO23EPRODUCTION . . 11 > The advent of rddioinimunoassays .in the late;:1960s,:l,which replaced. the . cumbersome and imprec&&ebio-assays.,led to,:a ,goodunderstapding of reproduction in domestic animals .@caramuzzi *et I al . l98X; b Scartiuzzi and. Martin 1984 ; Foxcroft et al. 1.9?5'; ,.: 'rNiswender *.:et 1 al. '.1,98.7) ., I ' Cn.~:r< #of this 'increase\ in research activity -is the: availability. 06 a,numberof kbxaL. compoundsand their **other benefits'synthetic analogues whichcanbe used toman%pulate..reproductionof++ the increased understanding, ..of: reproduction can be. 'seen :in the- steady improvement of managementand increased managerial'flexibility which are reflected: by theimprovement .in l&t@ marking @ercentages@igs l'and 2.). : q l . . 'Melatonin II, ' The pin&l gland+'. located :witbin thy,' 'brain+, and,. %%&ts hormonal. prodtict . ': melatonin are now recognised 'as regulators iof seasonal phenomena (Cardinali 1981).' Reproduction insheep, goats, deer, horFs!.<and poultry, and, probably1 also FYOC. Aust. Soc. Anim. Prod. Vol. 17 in pigs and cattle, is seasonal and dependent on photoperiod. Until the 196Os, the pineal gland of mammals was considered to be little more than a vestigial organ and research in this area was curiosity-driven (Cardinali 1981). Now the potential value of melatonin to animal production is widely acknowledged'and is a direct result of this earlier research. The use of orally administered melatonin to induce oestrus and ovulation in anoestrous ewes was first reported earlier in the decade (Kennaway et al. 1982; Arendt et al. 1983). Melatonin treatment was first seen as a method of out-of-season breeding, an alternative to the now traditional progestagen sponge-PMSG method (Nett and Niswender 1982). It was observed coincidentally that ovulation rates were also increased (Kennaway et al. 1984), and subsequent research has seen the development of commercial technologies to exploit these observations (Hsieh and Chien 1985; Staples et al. 1986; Poulton et al. 1987a). Melatonin administered either as an intra-ruminal soluble glass bolus (Poulton et al. 1987b) or as a subcutaneous pellet will induce ovulation in anoestrous ewes, with the additional benefit of an increase in the twinning rate (Staples et al. 1986). The administration of melatonin interferes with the photoperiodic regulation of the normal seasonal pattern of reproduction, a pattern which restricts the sheep breeding season to the autumn, particularly of British breed sheep and their crosses (Poulton 1988). Melatonin treatment in anoestrus advances the onset of a new breeding season and it appears that the advanced season may also end earlier (Williams et al. 1987)., The practical effect of melatonin treatment is the re-location of the breeding season to a time more suitable to the farmer'. Consequently, it is important that melatonin treatment is synchronized with the desired mating period 'if full benefit is to be derived from treatment. It is possible that melatonin treatment may increase ovulation rate by a direct action on the follicle population of the ovary, or alternatively, that ovulation rate has a seasonal pattern which is photoperiod-dependent (Scaramuzzi and Radford 1983). . Gonadotrophin-releasing hormone Gonadotrophin-releasing hormone (GnR& a IO amino acid peptide, is secreted by the hypothalamus and acts on the pituitary iland to stimulate the release of the gonadotrophins. This substance was first purified and synthesized in 1971 after an intensive ten year research effort' (Arnoss et al. 1971; Matsuo et al. 1971a, b). The first papers reporting its use in farm animals appeared within 12 months (Arimura et al. 1972) and its use to induce fertile oestrus in anoestrous ewes had been demonstrated by 1972 (Reeves et al. 1972; Martin 1984).. Research groups in Australia (Wright et al. 1983) and the United Kingdom (McLeod et al. 1983-J have'been actively developing commercial technologies for the induction of a fertile ovulation in anoestrous ewes. A majoi problem'has been the technique.for administering the hormone: GnRH is not orally active and needs 1nitial;ly it to be administered over a period of several days to be effective. was thought. that GnRR had to be delivered in a pulsatile manner to indtice ovulation `(McLeod? et al, 1982 ), but it-was soon .demonstrated that this was' not necessary, The. two research groups have developed different approaches: the I Australians have opted for a subcutaneous slow release device delivering a prescribed dose of GnRH over a desired period, while the British have chosen to inject a potent long-acting agonist of'GnRH. In either case the treatment needs ' to be combined with progestagen treatment to ensure concomitant oestrus and ovulation. Unlike melatonin, the technology should be effective during seasonal anoestrus, lactational anoestrus, and in pre-pubertal ewes. s This technology could be commercially available within a few `years and would compete directly with PMSG in the out-of-season bree'ding market. Proc. Aust. Soc. Anim. Prod. VoZ. 17 Inhibin 65 In the early 1970s several papers reported the detection of an active principle in rete testis fluid of rams which specifically inhibited the secretion of FSH (de Jong 1979, review). By 1976 a similar active principle had been found in ovarian follicular fluid (de Jong and Sharpe 1976). Inhibin is a potential male contraceptive, and the World Health Organization has co-ordinated an intensive world-wide campaign to isolate and purify inhibin. Any future uses of inhibin in animal production will be a direct benefit of this medical research. Inhibin has now been isolated and characterized (McNeilly et al. 1988, review). It is a glycoprotein, produced by the granulosa cells of the Graafian follicle, the corpora lutea of the ovary (Tsonis et al. 1988) and the sertoli cells of the testis (de Jong 1979). The molecule comprises about 200 amino acid residues arranged into two chains, or sub-units, designate-d alpha and beta. The principal function of inhibin seems to be the feedback regulation of FSH levels, but it may also act directly on the ovary. This is still uncertain. The long-term treatment of males with inhibin could be expected to suppress FSH, leading to an impairment of spermatogenesis and rendering treated subjects infertile. Immunity to inhibin, on the other hand, will lead to increased levels of FSH and, in the female, to increased ovulation rate (Forage et al. 1987). Because inhibin is a protein it is not orally active, but it can be administered The by subcutaneous injection or it can be adsorbed from mucosal surfaces. development of synthetic or genetically-engineered long-acting analogues of inhibin would simplify the problem of administration. The evaluation of potential benefits of inhibin therapy for animal production could then commence in earnest. Irmnunity to inhibin was induced by genetically fusing the alpha chain of bovine inhibin to an unrelated peptide (bacterial B galactosidase), producing a hybrid molecule fusion protein which was used to immunize ewes. . When administered to ewes this immunogen stimulated the production of antibodies to inhibin and led to an increase in the ovulation rate (Forage et al. 1987). Further evaluation of this technology, as a method of increasing twinning rates in sheep and cattle, can be expected over the coming few years. Growth factors and other peptides The use of'growth factors and other peptides to alter ovarian function and ovulation rate is a. new and potentially profitable area of research (Cahill 1984; The identification and study of regulatory substances, Cahill et al. 1985). undoubtedly present, in follicular fluid of Graafian follicles, may openthe way It for the control,of follicle development, ovulation rate and superovulation. .without the accompanying =Y also be possible to induce superovulation hypersecretion of oestrogen which is 'extremely harmful to ;gamete transport and. The control of the Graafian follicle is one of the fertilization (Moore 1982). keys to prolificacy and fertility (Scaramuzzi et al. 1988). 1, . 'Opiates and neurotransmitters hold .the~ key to understanding and eve,ntual . control of the .~'pul~ar'~~ the neural network in the hypothalamus tihich regulates the pulsatile release of GnRH into the pituitary portal circulation s and The consequently determines the pulsatile pattern of LH secretion (Martin 1984). control of the pulsar is the key. ,to overcoming the seasonal; post-partum, .pre-pubertal anoestrous states that can' severely limit production. Immunization`against The development of radioimmunoassays 'hormones in the 1960s increased'interest in 66 Proc. Aust. Soc. Anim. Prod. Vol. 17 antibodies to hormones and, virtually as a by-product of this, curiosity in the physiological responses of animals used to produce antibodies (Nieschlag and Wickings 1978). The observation that steroid immunity increased ovulation rate (Scaramuzzi 1976) therefore arose from curiosity-driven basic research. Auto-immunity is a technique which allows the action of a selected hormone to be prevented in the immune animal; the hormone-binding antibodies block the normal biological action(s) of the hormone. The subject has been extensively reviewed in two recent books (Crighton 1984; Talwar 1985). Sheep immunized against androstenedione (Scaramuzzi et al. 1977), testosterone (Martensz 1977), oestrone (Martensz 1977) or oestradiol (Scaramuzzi 1976) under appropriate conditions can have elevated ovulation rates. The mechanism of the response to oestrogen-immunity appears to be an increased level of FSH (Scaramuzzi 1984), while in the.androgen-immune ewe the mechanism probably involves a direct action on the ovary. Recent experiments have shown that hypophysectomized ewes immunized against androstenedione still have elevated ovulation rates when induced to ovulate using exogenous gonadotrophins (Philipon et al. 1988). Fecundin is a commercial product with the immunogen comprising androstenedione-human serum albumin conjugate in an adjuvant of 5% DEAE dextran. Immunization with Fecundin leads to the formation of antibodies against the androstenedione. The normal action(s) of androstenedione are inhibited and this leads to an increase in ovulation rate and to an increased lambing percentage. Extensive testing of Fecundin under widely varying conditions has demonstrated that it can produce about 25 extra lambs per 100 ewes mated (Scaramuzzi et al. 1983; Geldard et al. 1984a, b) although its, effectiveness may bereduced insome circumstances (Scaramuzzi et al. 1983). Immunity to reproductive hormones, other than the steroids, may also have practical value in manipulating reproduction. Immunization against inhibin has already been discussed above. Immunization against GnRH leads to a rapid fall in circulating levels of LH and subsequently to gonadal atrophy (Schanbacher 1984; Fraser 1985), This effect, often referred to as immunocastration, may'provide an inexpensive alternative to surgical castration (Fraser 1985). Immunity to the luteolytic hormone prostaglandin F2 c1 (Scaramuzzi and Baird 1976; Chang et al. 1987) and to oxytocin (Sheldrick et al. 1980) both lead to a lengthening of the oestrous cycle and form the basis of vaccines to induce anoestrus. Immunity to .FSH in the male leads, to. sterility without diminution in testosterone production and libido, so it is'seen as an ideal male contraceptive (Moudgal et al. 1985). It may also be of value to the ram trade to the middle eastern countries where there is a strong consumerpreference for intact males. . Progestagens The discovery, by M.C. Chang (Pincus anddchang; 1953), -that progesterone could prevent ovulation in rabbits, stimulated the sea'rch for orally-active progestagens which- could be used as contraceptives. The development of the progestagen 'sponge subsequently was a direct benefit of this bio-medical research. Were it not for this stimulus, the 'progestagen'sponge' would not have been developed. ' The progestagen sponge, developed in 1965 (Robinson 1965, 1967)'and us&d virtually unchanged sinc,e that time, has spawned a number of competitors which have attempted to address some of its shortcomings (Welch 1983). The progestagen sponge made the .widespread ixse of oestrus synchronization and of out-of-season. breeding .a prdctical possibility. The one major drawback is the lowered . fertility at the first oestrus following sponge removal. Fertility is reduced by approximately 10% compared to that in unsynchronized ewes (Robinson 1967). The Proc. Aust. Soc. Anim. Bad. Vol. 17 63 various substitutes for the sponge have claimed to overcome this, and other lesser problems, with varying degrees of success (Evans 1988), but at their present prices they are unlikely to replace the sponge as the most cost-effective method. MANAGEMENT AIDS TO REPRODUCTION It could be argued that the Australian environment is not conducive to gives intensive animal production and that low-cost extensive production Australian producers an advantage in world markets. Research which leads to increasing intensification of the industry will reduce Australian competitiveness in two ways: by increasing costs and by improving the productivity of overseas competitors. On the other hand, the ability to produce reliably and to market a defined and uniform end product is essential for success in the consumer-conscious world of today; products meeting the exacting demands of today's consumers are more readily produced under the controlled conditions typical of intensive production. Within this context, we can classify management aids into two broad categories, namely, low and high technology options. Low technology options generally improve decision-making and managerial flexibility and lead to improved productivity without necessarily increasing costs and intensifying production. High technology options usually increase production efficiency through increased inputs and intensification of production. Low technology The close relationship between good nutrition and Manipulating nutrition reproduction has been recognised for centuries (Scaramuzzi 1986, review) but despite a plethora of descriptive data, there is still no lucid account of how Some authors improved nutrition increases twinning rate in ewes (Martin 1984). have speculated that qualitative and quantitative changes in the supply of amino acids to the reproductive tissues bring about an increase in ovulation rate (Scaramuzzi 1986). Such a change in the amino acid supply can be brought about directly by increased protein in the diet, or indirectly as a protein-sparing Not all authors agree with effect of diets high in energy (Nettle et al. 1985). this point of view, and it has also been suggested that the supply of energy can The supply of amino directly stimulate ovulation r