bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Production of Mutations by Chemical Substances
Authors: Auerbach C. , Robson J. M. 
Published: June 2019

Theproduction of mutations by the action of chemical substances on germ cells has often been reported. However, the variability of the spontaneous mutation rate and its dependence not only on environmental conditions and physiological factors, but also on the genotype, make it extremely difficult to assess the value of tests in which only small increases over the spontaneous mutation rate have been found. For this reason, Muller was still able to conclude in 1941 that there was no definite proof that chemical substances could exert an effect on the mutation rate. Since then, Thomas and Chevais (1943) have reported results with sulphonamides which, if they can be confirmed, would indicate a real, though slight, action of these substances on the chromosomes, at least as far as gene mutations are concerned. Stubbe (1940), working on plant material, observed a significant increase in mutation rate with phenol and potassium thiocyanate. It is of interest that Auerbach and Robson (1943) independently observed a similar effect with allyl isothiocyanate in experiments onDrosophila. Even these definite effects are, however, very slight.During the last four years we have been testing a number of chemical substances. Among these a certain group has been found which increases the rate of occurrence of mutations and chromosome rearrangements to a similar extent as that brought about by X-rays and similar physical agencies. The best known representative of this group is mustard gas, and the present report deals only with the effects produced by this substance. Results obtained with other effective substances will be published later.
Somatic Segregation by Microconidial Isolation in Synthesised Heterokaryons ofNeurospora crassa
Authors: Sansome E. R. , Sansome F. W. 
Published: June 2019

Heterokaryosisis the condition in which one cell of a mycelium contains two or more genetically different nuclei. Hansen and Smith (1932), working withBotrytis cinerea, which has multi-nucleate spores, showed that single-spore cultures of this fungus sometimes contained two types of nuclei and that such heterokaryotic types could readily be induced by hyphal fusion between different homokaryotic types. These authors analysed individuals from thirty genera of imperfect fungi and found more than half of them to be heterokaryotic. It seems, therefore, that heterokaryosis is a widespread phenomenon among such fungi.N. crassais a heterothallic fungus with an eight-spored ascus and a pair of well-defined mating-type factors which have been very generally called sex factors. Perithecia are formed only when cultures of the opposite mating types are brought into contact. Both mating types can produce ascogonia, generally conceived to be female organs, and microconidia, sometimes called spermatia (Dodge, 1935), which may correspond to male gametes. Therefore it is doubtful whether the mating-type factors are true sex factors.A non-committal term such as “mating type” or “incompatibility factor” is preferable. However, because of the convenience of the terms associated with sex, such as “unisexual” and “bisexual”, I shall follow previous authors (Dodge, Lindegren, Beadle) in using these terms with reference to the mating-type factors, at the same time emphasising that these factors may not be sex factors in the generally accepted sense of the term.
Recent trends in pig production: the importance of intake
Authors: Riley J. E. 
Published: June 2019

AbstractThe UK pig industry has shown an ability to respond quickly to changing market requirements and improving efficiency of pig meat production. Rapid genetic improvement in breeding stock, particularly in carcass quality and growth traits, together with the adoption of new production strategies, have been the main factors. These changes have had major implications for the way pigs are fed at all stages of the production cycles. Market forces have resulted in a pig population with reduced fat reserves and low appetite. Food intake is a limiting factor at several stages of the production cycle including post weaning, in the case of early-weaned piglets, and the management of young lactating sows. Knowledge of the daily nutrient requirements of the individual animal far exceeds the ability to ensure that those requirements are satisfied by feeding systems in commercial use. Manipulation of food intake to achieve optimum profit is the weakest link in the UK producers' knowledge.
Genetics of food intake in the pig
Authors: Webb A. J. 
Published: June 2019

AbstractThe rôle of voluntary food intake, measured as daily food consumption onad libitumfeeding from 30 to 90 kg live weight, in future selection strategy is reviewed. Intake shows a heritability of 0.3, and genetic correlations of 0.6 with growth rate and –0.4 with leanness. Low genetic correlations between test station and commercial farm performance are reported for growth rate (0.27) and backfat (0.41) which arise either from genotype × feeding level interactions, or from individual feeding at stations. Selection for rate of lean growth appears to lead to a primary increase in rate of protein deposition, whereas selection for efficiency of lean growth appears to lead to a reduction in rate of fat deposition via a decline in intake. Continued reduction in intake may limit further improvement in lean growth rate and sow productivity. As optimum fatness is approached, the selection emphasis is expected to swing towards rate of lean growth to reduce total food used for maintenance. To determine the optimum selection regime, a knowledge is required of the genetic relationship between intake and lean growth rate. Meanwhile, the optimum selection regime may involvead libitumgroup feeding with electronic recording of individual food intake. In the long term, exogenous or endogenous growth promoters could remove the need for selection against backfat, and necessitate a radical genetic increase in intake.
Voluntary food intake of sows and gilts
Authors: Lynch P. B. 
Published: June 2019

AbstractThe lactating sow requires 5 to 7 kg food daily if it is to maintain body weight and condition in lactation but even on ad libitum intake sows fail to achieve the required food consumption and so lose both weight and tissue. The problem is most acute in primiparous sows and low lactation food intake is recognized as a major factor in post-weaning anoestrus and impaired reproductive performance. Studies of sows from the Moorepark herd are reported. Older animals, those with high suckling load and thin animals all tend to eat more with maximum daily intake occurring at 4 to 5 weeks of lactation. Although intake reduces at high environmental temperatures, this has been alleviated by wet feeding, offering a high energy-density diet or a high-protein diet. Other factors observed to influence voluntary food intake are breed, lighting pattern, dietary calcium and phosphorus levels.
Meat quality, carcass composition and intake
Authors: Wood J. D. 
Published: June 2019

AbstractIn pigs, variation in appetite under ad libitum feeding conditions is often associated with variation in carcass composition and meat quality. Breeds, strains and pigs types possessing high appetites are frequently fatter and have better meat quality (e.g. lower PSE incidence and more juicy meat) than those possessing low appetites, although for different physiological reasons. These conclusions are based on published reports of performance, carcass and meat characteristics in the following pig types: carriers of the halothane gene, Pietrain and Duroc breeds, animals selected for low backfat thickness and entire males. Selection schemes which reduce carcass fatness yet increase appetite are preferable to those which depress appetite so far as meat quality is concerned.
Production of transgenic pigs and possible application to pig breeding
Authors: Brem Gottfried , Brenig Bertram , Müller Mathias , Kräußlich Horst , Winnacker Ernst-Ludwig 
Published: June 2019

ABSTRACTThe generation of transgenic pigs is an entirely new way of breeding. In contrast to classical breeding techniques the objects of manipulation in this case are individual genes rather than the entire genome of an organism. In pigs DNA-microinjection into the pronuclei of zygotes is the only available technique of transferring genetic material developed so far. The process involves collection, manipulation, microinjection, cultivation, and transfer of early embryos and also molecular-biological techniques allowing cloning of gene constructs, preparation of suitable injection solutions, and techniques allowing detection of integrated and expressed transgenes in transgenic animals. Gene transfer in pigs usually yields less than 1% transgenic piglets per injected zygote. Our own experiments have shown that simultaneous transfer of untreated control embryos increases yields from 0.5% to 1%.Gene transfer in pigs can be employed in particular to increase growth performance and carcass composition by using genes encoding hormones of the growth hormone cascade (GHRH, GH, IGF-I). So far, the effects already known from experiments in mice have not been reproduced in pigs.We are currently investigating whether the transfer of the influenza resistance gene Mx+of mice will yield disease-resistant pigs.Breeding with transgenic animals must take into account that approximately 30% of the primary transgenic animals will be mosaics which will not pass on the transgene to their offspring. Unwanted side effects may also occur during gene transfer. Most important examples are instability of integrated transgenes and variability of gene expression over many generations.In about 5% of all primary transgenic animals integration of the transgene can be assumed to lead to the generation of insertion mutations. Animals carrying these mutations should not be used for breeding. Furthermore severe health problems may be caused by uncontrolled over-expression of the transgene.Much more work will be necessary in future before we will be able to employ gene transfer techniques in practical breeding programmes.
The application of gene technology to the improvement of fish
Authors: Maclean Norman , Penman David 
Published: June 2019

AbstractBecause fish lay large numbers of eggs, in which both fertilisation and development is external, they are rather suitable organisms for transgenic induction. To date fish of many different species have been used in such work - rainbow trout, atlantic salmon, channel cat fish, tilapia, medaka, zebrafish, goldfish, carp and loach. Normally the induction of transgenics has involved injection of multiple copies of the chosen novel gene into the egg cytoplasm soon after fertilisation, followed by assays for subsequent gene integration, expression and transmission to progeny.Genes which have been utilised for transgenic induction in fish include somatotrophin (growth hormone) of both mammalian and piscine origin, metallothionein, 'antifreeze' protein, and crytallin coding sequences. A number of laboratories have demonstrated by Southern blotting of restricted DNA fragments that genomic incorporation has been achieved, although in others there appears to be a continuing problem of long term persistance of extrachromosomal DNA material. Expression of the injected sequences tends to be at a low level and in some cases not to be detectable. This is probably due to the inefficiency of mammalian gene promoters in fish cells and will hopefully be overcome by the use of genes of piscine origin. Germ line integration and transmission to progeny of the novel sequence has been established in a few laboratories.Transgenic fish may also offer some potential as expression systems for valuable pharmaceutical products. Problems of containment and planned release of transgenic fish are also briefly discussed.
Cellular growth - the key to animal growth
Authors: Goddard C. 
Published: June 2019

ABSTRACTThere is an increasing possibility that animal performance may be manipulated by new techniques incorporated into efficient breeding programmes. In order to fully exploit these techniques to increase the efficiency of growth, gene products involved in the control of growth, development and also reproduction must be identified. Correct expression or manipulation of these genes to provide optimum effect on a trait requires complete knowledge of their biological action. The transgenic approach has provided some success using growth hormone and growth hormone releasing hormone to increase growth in mice. Further possibilities exist, since recent work suggests that peptide growth factors such as the insulin-like growth factors, fibroblast growth factor and transforming growth factor-β may be primary regulators of normal growth. This brief overview introduces some of these peptide growth factors, provides basic information on them and offers them for discussion as potential targets for manipulation.
1.2 Computers and Their Potential: Software
Authors: Geisler Pamela A. , France J. 
Published: June 2019

At the present time, with the high reliability and performance of computer hardware, computer systems applied in any field must be judged more by the quality of the software provided. Thus it is highly relevant in an investigation of the use of computers in a field such as animal production, to concentrate on aspects of the software.Software provides the computer with the ability to obey instructions and to do as the user wishes. However, before arriving at these ‘machine instructions’ a number of steps have to be covered. First, it is essential to design the software — that is, to establish the requirements to be achieved on the computer. This design stage is followed by the implementation phase, in which the requirements as stated in English are transformed into such instructions as the machine can read and obey. The final phase is testing, in which it must be determined whether the requirements have been met, and to modify the design and iterate until the performance is satisfactory.Software in general can be divided into three classes — systems, utility and applications software. The systems software drives the machine and its associated peripherals such as a VDU and printer. The systems software also includes a file system for organization of the data on the relevant storage media (floppy disks, cartridges, magnetic tape). Also considered part of the systems software are the assembler, interpreters and compilers for high level languages such as BASIC and FORTRAN and for programming aids such as DEBUGGERS. Systems software is normally supplied with the computer and needs to be evaluated along with the hardware by any prospective purchaser of a computer system.
3.4 Lactation Curves
Authors: Wood P. D. P. 
Published: June 2019

An algebraic description of the lactation curve is a useful component of any model of the day-to-day production of lactating animals. Observation and common sense suggest that such a function should rise to a peak early in lactation and decline thereafter but simpler models have been used. Ostergaard (1979), for example, used a linear model to study strategies for concentrate feeding to obtain optimum feeding levels in high yielding dairy cows. His model waswhere y (t) was the yield in week t and a and b were the usual linear regression coefficients. The error term is omitted here and elsewhere for clarity. Gaines (1927) used the decay functionwhere A and k are the constants fitted to log y (t).These models, one linear, the other exponential, peak in Week 1 and require only two parameters. In this paper, more sophisticated functions are described and compared.A lactation curve is assumed to contain two components, one of which is the intrinsic biological drive to produce milk and the other is an environmental constraint upon it. The algebra may be justified by biological argument according to the skill and the leanings of the modeller.
Neonatal survival: an overview
Authors: Varley M. A. 
Published: June 2019

AbstractMortality in neonates has always represented significant economic wastage and slow progress has been made in the understanding of the factors influencing the probability of survival or death. There is also increasing pressure in the animal agriculture sphere to pursue improved welfare and in the situation where neonatal deaths are a high proportion of the liveborn offspring, then this becomes not only an economic concern but also a welfare issue. This paper highlights principal problems within the neonatal area in order to introduce the ensuing text dealing with specific technical challenges.The magnitude of loss for different species including humans is given and the factors affecting mortalities are discussed. The major components include: human factors, pathogenic agents, immunological factors, temperature and thermoregulation, nutrition, behaviour and physical factors.Although single factors are often ascribed as the cause of death, the reality is that there are usually multifactorial components involved which interact and contribute to the final mortality of the individual.The approach to the practical management of neonates varies widely between the different animal industries and the techniques deployed depend on relative economic values. In human health care every available resource is used to ensure very high survival rates because of the incalculable value of each individual delivered. With farm animals the use of resources is at a much lower level and survival rates are lower. It ought to be possible in animal agriculture to adopt some of the methods used in the medical profession to assess high risk situations and to divert resources appropriately.
Immune development in the gastrointestinal tract of the pig
Authors: Stokes C. R. , Vega-Lopez M. A. , Bailey M. , Telemo E. , Miller B. G. 
Published: June 2019

AbstractThe epitheliochorial placenta of the pig does not allow the passage of immunoglobulin to the foetus and thus the young piglet is born without passive immune protection. During the first 36 h of life there is a massive transmission of macromolecules across the intestine, virtually all that are present in the gut may be effectively endocytosed and transmitted into the blood stream. The postnatal transmission of antibody from colostrum during this period provides the young animal with a spectrum of serum antibodies indistinguishable from that of its mother. It is established that evenin uterothe piglet is capable of mounting some response to antigenic challenge. Despite this, the ability of the young animal to respond may be influenced profoundly by the absorption of macromolecules (antibodies and antigens in colostrum and in sow's milk as well as antigens in the farrowing house) during the first hours after birth. These effects range from passive protection from infectious agents during the neonatal period to determining the precise nature of the immune response to antigens during later periods (e.g. at weaning).At birth all cellular components of the immune system are represented but during the first few weeks of life dramatic changes occur in the number and distribution of these cells. Our histological studies have shown that shortly after birth the predominant T lymphocytes in the small intestine are T2+, T4−and T8−; whilst in other organs there are large numbers of conventional T4+and T8+cells. By 1 week of age there is a dramatic increase in the numbers of T4+cells, whilst T8+cells remain low, and only start to increase by week 7. Thus, changes in lymphocyte populations are occurring concurrent with increasing exposure to environmental antigens. The functional capacity of these cells also changes during this period and this process may be particularly affected by early weaning.During the neonatal period an animal is presented with a vast array of antigenic material for the first time. How and when these antigens are presented may profoundly influence the capacity of the immune system to respond to them.
Thermoregulation in piglets: environmental and metabolic consequences
Authors: Close W. H. 
Published: June 2019

AbstractAt birth the neonate switches from a dependent to a totally independent extra-uterine environment. It must begin to regulate its own body temperature to survive. This paper considers thermoregulation in the newborn piglet and those factors which influence survival.The first few days are important for the development of thermoregulation. Metabolic heat production and rectal temperature both increase and the development of adequate thermal insulation helps to withstand the effects of a cold environment. The body reserves play an important rôle and are needed to ensure that the piglet survives within the first hours of life. It is the glycogen and fat reserves that are readily utilized as major energy substrates for heat production within the first 12 to 24 h; the contribution from protein is minimal. However, not all reserves are available for mobilization. Attempts to improve the body reserves of piglets have been unsuccessful but the quality and composition of colostrum, especially its fat content, can be manipulated by maternal nutrition. Coldness impairs the development of thermostability and induces hypothermia. This diminishes the vigour of the piglet and reduces colostrum intake and hence immunoglobulins. The incidence of disease, especially scouring, may therefore be increased. The maintenance of an adequate environment also ensures a good immunological status. The development of housing, husbandry and management practices must take these various phenomena into account.
Postnatal intestinal development
Authors: Kelly D. , Begbie R. , King T. P. 
Published: June 2019

AbstractEarly postnatal intestinal development involves the preparation of the intestinal epithelium for extrauterine life when maternal secretions provide the sole nutrient source. A further shift in the digestive capability of the epithelium occurs later in development with the introduction of complex solid foods. Ontogenesis involves extensive epithelial cell proliferation and cytodifferentiation including changes in the expression of enzymes, receptors and transport systems and is regulated through the interaction of endogenous and exogenous factors. The mucosal epithelium plays a key rôle in the reception and transmisson of these trophic signals. In particular, the interplay between dietary constituents and microvillar membranes exerts profound influence on intestinal development and adaptation during the postnatal period.
Calf rearing practice at the National Agricultural Centre Beef and Calf Unit
Authors: Spedding A. 
Published: June 2019

AbstractA system of high-care calf rearing which was developed and demonstrated at the National Agricultural Centre Beef and Calf Unit is described. The unit reared around 600 calves per year which were purchased at 2 to 3 weeks of age, reared and then transferred to one of several finishing systems on the unit. The system depends on good calf nutrition, airy buildings which were rested regularly, careful disinfection of equipment and buildings and a programme of health management.The calves were purchased mostly in batches of about 40 from a farmers' co-operative and reared on milk replacer which was restricted and given twice daily to force a discipline for inspection of calves. They were also fed through teats which gave more efficient food conversion than buckets. They were penned in pairs because it had been found they were less stressed in pairs than penned singly. Detail of management and health routines are described. Target live-weight gains on the system were 0.5kg per day up to weaning and 1.0 kg per day thereafter. For simplicity the commercial names of foods, drugs and vaccines are given.