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In Section III we apply the conclusions on evolutionary genetics of populations and the deleterious genetic consequences of population size reduction (from Sections I and II) to the genetic management of threatened populations and species.
Taxonomic uncertainties and management units
A critical first step in conserving a species is to gain a clear understanding of its taxonomy. Is the population of interest a unique species? Does it actually consist of multiple cryptic species? Or is it simply another population of a common species? Without this knowledge endangered species may be denied protection, or resources wasted on populations of common species. The use of genetic techniques to assist in resolving taxonomic uncertainties is described in Chapter 16. To do this we must first define what is meant by a species and consider briefly how speciation occurs. Populations within species may be so distinct that crosses suffer reduced reproductive fitness (outbreeding depression). The chapter concludes by considering means for defining management units within species.
Management of wild populations
The genetic management of wild populations is considered in Chapter 17. Typically wild population management is concerned with increasing population sizes and alleviating the effects of population fragmentation. Species with inadequate gene flow among population fragments will suffer insidious processes of inbreeding depression, loss of genetic diversity and eventually population extinctions, unless gene flow is re-established. Sadly, there continues to be only limited activity in this area. Genetic management of fragmented populations represents the greatest unmet genetic challenge in conservation biology.
Meiosis, the antithesis of fertilization, is the unique genetically programmed mode of nuclear division associated with a halving of the chromosome number in sexually reproducing eukaryotes. It thus represents a key cellular and developmental pathway in the life of an organism. In this book, Bernard John presents the first complete, and the most authoritative, review of the events and mechanisms of meiosis including their scheduling, their mechanics and their biochemistry as well as their genetic control and the variations to be found in them in both sexual and subsexual systems. The text is superbly illustrated with 131 figures and 73 tables. Meiosis must be regarded as essential reading for all students, teachers and research workers with an interest in eukaryotic cell biology and genetics.
A significant number of lambs born each year in Australia die within 72 h of birth. Periods of high wind, combined with rain and low temperatures can lead to marked increases in the mortality level. Under these climatic conditions mortality levels may be reduced with the provision of shelter. This study used contact loggers to compare interactions between ewes with twin lambs across two shelter types (Hessian and shrubs), while also comparing ewes with single and twin lambs in a single shelter type (Hessian). The contact loggers record the time of the initial contact (within approximately 4 to 5 m) between collared animals and the duration of each contact. Contact levels between ewes immediately after lambing were only 10% of the initial levels (1 h/day). For single-born lambs, lambs averaged 11 h contact per day with their mother, while for twinborn lambs, each lamb averaged 9.25 h/day with its mother and 14.7 h/day with its sibling. The level of contact between ewes and each of their offspring in the Hessian was 24% lower (P < 0.05) for ewes with twin lambs than with singles. For ewes with twin lambs the level of contact was 17% lower (P < 0.05) in the Hessian shelter compared with shrub shelter. We conclude that shelter type and birth number can affect the level of contact between ewes and their offspring.
Housing conditions for horses impose various levels of confinement, which may compromise welfare. Lying behaviour and activity can be used as welfare indicators for domestic animals and rebound behaviour suggests a build-up of motivation resulting from deprivation. The objective of this study was to determine if activity and lying behaviour of horses are affected by housing conditions and to investigate the occurrence of rebound behaviour after release from confinement. Eight horses were subjected, in pairs, to each of four experimental treatments; paddock (P), fully stabled (FS), partly stabled (PS) and yard (Y). Each horse received 6 days acclimatisation prior to the 24 h recording period. Time spent in lying and activity were electronically recorded using a tilt switch and motion sensor connected to a data logger worn on the horse’s left foreleg. Time spent active during the first 5 min of release from stable to paddock in the PS treatment (days 1 and 5) and at the same time of day in the P treatment was used as a measure of rebound behaviour. Effect of housing conditions on total time spent active was highly significant (FS = 123 s, PS = 158 s, Y = 377 s, P = 779 s, P < 0.001). Housing conditions did not significantly affect total time spent lying (P = 0.646). Horses were significantly more active, compared with baseline paddock behaviour, on release from stabling on both days 1 (P = 0.006) and 5 (P = 0.025) of PS treatment. These results suggest that activity patterns of horses, but not lying behaviour, are affected by the housing conditions tested and that rebound activity occurs in horses after a period of confinement.
Genetics, Health Care and Public Policy is an introduction to the new discipline of public health genetics. It brings together the insights of genetic and molecular science as a means of protecting and improving the health of the population. Its scope is wide and requires an understanding of genetics, epidemiology, public health and the principles of ethics, law and the social sciences. This book sets out the basic principles of public health genetics for a wide audience from those providing health care to those involved in establishing policy. The emphasis throughout the text is on providing an accessible introduction to the field. The content moves from the basic concepts, including definitions and history, through chapters on genetics, genetic technology, epidemiology, genetics in medicine, genetics in health services, ethical, legal and social implications, to the implications for health policy. It provides one-stop, introductory coverage of this rapidly developing and multidisciplinary field.
For many years, the breeding value estimation for Swedish riding horses has been based on results from Riding Horse Quality Tests (RHQTs) of 4-year-olds only. Traits tested are conformation, gaits and jumping ability. An integrated index including competition results is under development to both get as reliable proofs as possible and increases the credibility of the indexes among breeders, trainers and riders. The objectives of this study were to investigate the suitability of competition data for use in genetic evaluations of horses and to examine how well young horse performance agrees with performance later in life. Competition results in dressage and show jumping for almost 40 000 horses from the beginning of the 1960s until 2006 were available. For RHQT data of 14 000 horses judged between 1988 and 2007 were used. Genetic parameters were estimated for accumulated competition results defined for different age groups (4 to 6 years of age, 4 to 9 years of age and lifetime), and for different birth year groups. Genetic correlations were estimated between results at RHQT and competitions with a multi-trait animal model. Heritabilities were higher for show jumping than dressage and increased with increasing age of the horse and amount of information. For dressage, heritabilities increased from 0.11 for the youngest group to 0.16 for lifetime results. For show jumping corresponding values increased from 0.24 to 0.28. Genetic correlations between competition results for the different age groups were highly positive (0.84 to 1.00), as were those between jumping traits at RHQT and competition results in show jumping (0.87 to 0.89). For dressage-related traits as 4-year-old and dressage competition results the estimated genetic correlations were between 0.47 and 0.77. We suggest that lifetime results from competitions should be integrated into the genetic evaluation system. However, genetic parameters showed that traits had changed during the over 35-year period covered due to the development of the sport, which needs to be considered in future genetic evaluations.
In response to environmental threats, numerous indicators have been developed to assess the impact of livestock farming systems on the environment. Some of them, notably those based on management practices have been reported to have low accuracy. This paper reports the results of a study aimed at assessing whether accuracy can be increased at a reasonable cost by mixing individual indicators into models. We focused on proxy indicators representing an alternative to the direct impact measurement on two grassland bird species, the lapwing Vanellus vanellus and the redshank Tringa totanus. Models were developed using stepwise selection procedures or Bayesian model averaging (BMA). Sensitivity, specificity, and probability of correctly ranking fields (area under the curve, AUC) were estimated for each individual indicator or model from observational data measured on 252 grazed plots during 2 years. The cost of implementation of each model was computed as a function of the number and types of input variables. Among all management indicators, 50% had an AUC lower than or equal to 0.50 and thus were not better than a random decision. Independently of the statistical procedure, models combining management indicators were always more accurate than individual indicators for lapwings only. In redshanks, models based either on BMA or some selection procedures were non-informative. Higher accuracy could be reached, for both species, with model mixing management and habitat indicators. However, this increase in accuracy was also associated with an increase in model cost. Models derived by BMA were more expensive and slightly less accurate than those derived with selection procedures. Analysing trade-offs between accuracy and cost of indicators opens promising application perspectives as time consuming and expensive indicators are likely to be of low practical utility.
A total of 24 castrated male Creole were used for digestibility studies on three sugarcane (SC) products: final molasses, SC juice and ground SC. Digestibility of macronutrients were determined in three consecutive experimental trials between 35 and 60 kg BW. The first trial measured the effect of a constant rate of incorporation of those SC products in a control diet (23% on a dry matter (DM) basis) on digestibility of energy and nutrients. The second and the third trials were designed to determine the effects of increasing rates of inclusion of SC juice and ground SC in the control diet on the digestibility of nutrients and energy. The DM content of molasses, SC juice and ground SC were 74.3%, 19.3% and 25.8%, respectively. Free sugar contents were 73.8%, 81.6% and 51.5% of DM for molasses, SC juice and ground SC, respectively. In contrast with molasses and SC juice, NDF content of ground SC was very high (40.3% DM). Energy digestibility coefficients (DC) were 99.0% and 83.6% for SC juice and molasses, respectively. For ground SC, amounts and composition of intakes differed from feed allowance as a consequence of chewing-then-spitting out most of the fibrous contents of ground SC. Expressed as a percentage of energy intake and energy allowance, DC of energy for ground SC were 68.6% and 31.9%, respectively. On an intake basis, digestible energy (DE) and metabolisable energy (ME) values were higher for SC juice (17.3 and 17.2 MJ/kg DM, respectively) than for molasses (13.1 and 12.6 MJ/kg DM, respectively) or ground SC (12.3 and 11.8 MJ/kg DM, respectively). On an allowance basis, the corresponding values for ground SC were only 5.7 and 5.6 MJ/kg DM, respectively. The gradual inclusion rate of SC juice in the diet up to 66% resulted in a linear increase of the DC of the diet organic matter and energy (P < 0.001) by 0.10% per 1% in SC juice DM. On the other hand, the partial substitution of the control diet by ground SC up to 74% resulted in a linear (P < 0.05) reduction of digestibility of nutrients and energy. Each 1% increase of ground SC incorporation rate resulted in a 0.13% and 0.61% linear decrease of DC of the energy, expressed as a percentage of energy intake or energy allowance, respectively. In conclusion, our study provides updated energy values of SC products usable as energy sources for feeding pigs.
For some time now prebiotics have been proposed to improve health by stimulation of beneficial bacteria in the intestine of humans and animals. The current study is aiming to show effects of feeding of either 2% inulin or 2% lactulose in milk replacer on performance and intestinal morphology of male Holstein–Friesian calves. After 20 weeks of feeding inulin led to significantly higher daily weight gains than lactulose while control animals ranged between the experimental feedings. Ingestion of milk replacer was reduced in lactulose treated animals. Additionally differences of villus height in jejunum (P = 0.07) and ileum (P = 0.03) could be found with an increase for lactulose treated animals and a decrease for inulin treated animals. In ileum the density of proliferative epithelial cells tended to be lower in inulin treated and higher in lactulose treated animals (P = 0.08). Both inulin and lactulose tended to decrease the quantity of goblet cells in the tips of ileal villi (P = 0.07). Both prebiotics can affect performance and intestinal morphology of calves and may as such affect animal health. But effects differ between substances.
In order to assess the relative importance of genomic imprinting for the genetic variation of traits economically relevant for pork production, a data set containing 21 209 records from Large White pigs was analysed. A total of 33 traits for growth, carcass composition and meat quality were investigated. All traits were recorded between 1997 and 2006 at a test station in Switzerland and the pedigree included 15 747 ancestors. A model with two genetic effects for each animal was applied: the first corresponds to a paternal and the second to a maternal expression pattern of imprinted genes. The imprinting variance was estimated as the sum of both corresponding genetic variances per animal minus twice the covariance. The null hypothesis of no imprinting was tested by a restricted maximum likelihood ratio test with two degrees of freedom. Genomic imprinting significantly contributed to the genetic variance of 19 traits. The proportion of the total additive genetic variance that could be attributed to genomic imprinting was of the order between 5% and 19%.
Avian embryogenesis can be manipulated by alteration of the temperature during incubation of the brooding egg. Investigations in turkeys showed that a higher temperature during early embryogenesis positively affects the myogenesis accompanied with a higher muscle fibre number (MFN). The aim of this study was to transfer this result to broiler and to investigate if an alteration of the temperature also affects the meat quality after slaughter of the birds. Therefore brooding eggs of the Cobb 500 broiler genetic were either incubated at 37.5°C during the whole incubation period (at normal temperature (NT)), or at 38.5°C during embryonic day (ED) 7 to 10 (at high temperature (HT)). After hatch the chicks were sexed and reared up to an age of 36 days in an experimental stable. Growth and feed conversion properties were determined during this period. After slaughter different meat quality characteristics as well as the muscle microstructure were analysed. The hatch rate and chick weight did not differ between the broiler of the NT and HT group. After 36 days the final body weights and the cumulative feed conversion rates were not different in the NT and HT groups. No differing results were obtained with regard to the slaughter, breast and leg weights of the NT and HT animals. Considering the gender of the animals no differences in the slaughter characteristics could be determined although the carcass and breast weights of the HT cocks were tendentially higher. The muscle fibre areas and MFNs in the breast muscles of the NT and HT cocks did not differ significantly and were in the range of the HT hens. Only the NT hens had significantly larger muscle fibres and less MFN than the other animals. With regard to the meat quality characteristics no clear differences of the pH, electrical conductivity (EC) and colour (L*a*b*) values were found. The L*a*b* values in the investigated breast muscles of all broilers usually increased during ageing. The increase of the incubation temperature had no impact on the hatch, growth, slaughter and meat quality characteristics of the broiler except for the tendentially higher carcass and breast weights of the HT cocks. However, the decrease of the fibre areas in the HT hens is an interesting effect of using a higher incubation temperature, which needs to be considered when implicating further investigations.
The field dependent–independent cognitive style and role of simultaneous and successive processes
Educators and researchers have long recognized the unique differences among individuals and the effects these differences can have on learning. Concern for these differences led to research on the cognitive variables or cognitive styles that individuals possess (Tamaoka, 1985). Green (1985) defines cognitive style as consistencies in the ways in which people perceive, think, respond to others, and react to their environment. He contends that cognitive styles are bipolar, value neutral, consistent across domains, and stable over time. With nearly 5,000 references in the literature, field dependence/independence has received the most attention by researchers of all the cognitive styles (Chinien & Boutin, 1993; Harold, 1996; Kent-Davis & Cochran, 1989).
The Field Dependent–Independent cognitive style was hypothesized by Herman Witkin (e.g., Witkin, 1950; Witkin & Goodenough, 1981) and refers to the extent to which a person is dependent vs. independent in organization of the surrounding perceptual field. Measures of cognitive style provide a more extensive and more functional characterization of the child than could be derived from IQ tests alone (Messick, 1984).
A principal measure of field dependence–independence is the Embedded Figures Test (e.g., Children's Embedded Figures Test by Karp & Konstadt, 1971; The Diagnostic Embedded Figures Test by Aalders & Pennings, 1981), in which children locate a previously seen simple figure within a larger, complex figure (pattern). Bowd (1976) stated that embedded figures tests are the most widely used measures designed to assess field dependence–independence in children.
Down syndrome (DS), or trisomy 21, is divided according to three etiological subcategories: (1) standard trisomy, (2) mosaicism, and (3) translocation. In 97% of all cases (the standard trisomy 21 subcategory), the genetic error takes place in the ovula or the spermatozoid before syngamy or during the first cell division. All the living cells of the embryo receive three chromosome 21s. In 1% of all cases (Hamerton et al., 1965; 2% according to Richards, 1969; the mosaicism subcatregory), the genetic error takes place during the second or the third cell division. In those cases, the embryo develops with a mosaic of normal cells containing the regular number of 46 chromosomes and cells with three chromosome 21s. In the remaining 2% (1%, according to Richards) of all cases (the translocation subcategory), the additional chromosomic material is not a triplicate of chromosome 21 but a part or the totality of another chromosome (often chromosome 14 or 22). In about 66% of the translocation cases, the genetic error takes place during the formation of the ovula or the spermatozoid, or during the first division of the embryo cell. In 34% of the cases, one of the parents, although phenotypically normal in all respects, carries the translocation in his/her genotype.
Miniature pigs have been recognized as valuable experimental animals in medical research. However, porcine models related to gene knockout of human diseases are not widely available. The objective of this study was to establish Mx1-Cre pigs using somatic cell nuclear transfer. In this study, we created transgenic pigs using somatic cell nuclear transfer (SCNT). Transfer of 210, 230, 250 and 215 zygotes to four surrogates produced 10 piglets. The Cre recombinase expression in transgenic pigs was studied using reverse transcriptase (RT)-PCR and immunohistochemistry. Mx1-Cre swine were shown to harbor the Cre gene in their genomic DNA using the PCR. In conclusion, Mx1-Cre transgenic piglets were successfully produced by SCNT. These transgenic swine, in conjunction with inducible systems for controlling Cre expression and function, are likely to have a profound impact on the study of human diseases.
Williams syndrome (WS) is a genetically based neurodevelopmental disorder, which is caused by a microdeletion of chromosome 7, more specifically, at the region of chromosome 7q11.23 (Doll & Grzeschik, 2001; Ewart et al., 1993; Korenberg et al., 2000). Due to its uneven cognitive profile, WS has recently been the focus of scientific research in the field of developmental cognitive neuroscience (Clahsen & Almazan, 1998; Clahsen & Temple, 2003; Jordan et al., 2002; Thomas et al., 2001). Impaired visuo-spatial cognition, planning, and problem solving co-occur with relatively spared abilities in the domain of language, social cognition, and face processing (Bellugi et al., 1988; Karmiloff-Smith, 1998; Karmiloff-Smith et al., 1997; Mervis et al., 2000; Tager-Flusberg et al., 2003; Tager-Flusberg & Sullivan, 2000).
There is much controversy surrounding the status and development of the relatively spared cognitive abilities in WS, especially language. More specifically, some researchers argue that language development in WS (and other developmental disorders) reflects the abnormal development of the entire cognitive system (Karmiloff-Smith, 1998; Thomas et al., 2001; Thomas & Karmiloff-Smith, 2002). Consequently, the developmental pattern in WS is expected to be qualitatively different from typical development. If this is the case, then there should not be selective preservation of cognitive abilities in WS while the rest of the system develops abnormally. In other words, there should be no evidence for “residual normality” in WS (Thomas & Karmiloff-Smith, 2002).