So far in this course we have dealt entirely with the evolution of characters that are controlled by simple Mendelian inheritance at a single locus. There are notes on the course website about gametic disequilibrium and how allele frequencies change at two loci simultaneously, but we didn’t discuss them. In every example we’ve considered we’ve imagined that we could understand something about evolution by examining the evolution of a single gene. That’s the domain of classical population genetics. For the next few weeks we’re going to be exploring a field that’s actually older than classical population genetics, although the approach we’ll be taking to it involves the use of population genetic machinery. If you know a little about the history of evolutionary biology, you may know that after the rediscovery of Mendel’s work in 1900 there was a heated debate between the “biometricians” (e.g., Galton and Pearson) and the “Mendelians” (e.g., de Vries, Correns, Bateson, and Morgan). Biometricians asserted that the really important variation in evolution didn’t follow Mendelian rules. Height, weight, skin color, and similar traits seemed to

Human biochemical genetics

Selection signatures in livestock genome: A review of concepts, approaches and applications

The aim is to give an overview of available literature data on the role of feed processing on gut health and function with specific focus on particle size and hydrothermal processing. In addition, influence of feed processing on efficacy of exogenous feed enzymes will be discussed. The current feed processing technologies are such that ingredient choices and diet form are refined to improve feed intake and nutrient utilization efficiency. Finer feed particle size enables optimal nutrient utilization and enhances animal performance due to increased surface area allowing better contact with digestive enzymes. Moreover, adequate diminution of feed ingredients is beneficial to feed manufacturing processes such as mixing and hydrothermal treatments including pelleting, extrusion, and expansion. However, emerging trends in consumer and regulatory demands for restriction or cessation of animal production practices such as use of antimicrobial growth promoters are challenging current approaches to feed processing. There is limit as to the fineness of the particle size, as very fine particles negatively affect gut health due to higher incidences of stomach ulceration in pigs and gizzard dysfunction in poultry. Coarse particle size increases stomach and hindgut acidification which may be beneficial in controlling proliferation of enteric pathogens such as salmonella and E. coli. Optimal particle size could be designed in the grinding process using roller or hammer mill. However, since most commercial pigs and poultry diets are subjected to hydrothermal processes, additional reduction of feed particle size is inevitable. The need to achieve high physical quality and to reduce potential levels of feed-borne pathogens such as Salmonella has led to the application of relatively high conditioning temperatures during conventional hydrothermal processes, a practice that does not favor high nutrient utilization and stability of heat sensitive feed additives such as feed enzymes. Therefore, with evolving pig and poultry production practices, the regimens for feed processing will no longer be appreciated only in terms of optimizing nutrients utilization, but also in terms of impact on feed hygienic status, efficacy of feed additives, animal health, and food safety.

/pdf/role-of-feed-processing-on-gut-health-and-function-in-pigs-3jyf6qbgtj.pdf

Role of Feed Processing on Gut Health and Function in Pigs and Poultry: Conundrum of Optimal Particle Size and Hydrothermal Regimens.

Twenty percent of the world domestic animal breeds are classified as being “at risk” of extinction. Seventy percent of the mammalian breeds, for which no risk status data are available, are found in the developing world. This is a serious constraint to effective prioritization and planning of sustainable breed conservation measures, including sustainable breeding strategies. The objectives of this thesis were to develop improved approaches to characterization of sheep resources, and sustainable conservation-based sheep breeding strategies under smallholder traditional systems, taking Ethiopia as a case study. Analysis of microsatellite variation showed that geographic isolation is the primary cause of genetic differentiation among Ethiopian sheep breeds. However, there is a strong indication of adaptive divergence in morphological characters. Using a combination of microsatellite analysis and morphological divergence, we propose a classification of Ethiopian sheep into six breed groups and nine breeds. The objective of characterizing animal genetic resources is to facilitate decisions on prioritization in conservation of these resources. Our results show that a maximum-utility-strategy combining threat status, contributions to farmer livelihoods and to genetic diversity of livestock breeds should be adopted to prioritize them for conservation purposes. Such an approach balances the trade-offs between conserving breeds as insurance against future uncertainties and for current sustainable utilization. Selective breeding within indigenous livestock breeds is an option for conserving livestock breeds. Our results indicate that selective breeding can lead to significant genetic improvement under low-input systems and marginal environments. Assessment of farmers’ selective breeding objectives showed that adaptive traits are more important than or as important as production traits, indicating that sustainable animal breeding strategies require a broad definition of breeding objectives that emphasize maintaining adaptation to local circumstances and biodiversity, in addition to profitability. It is concluded that the most rational and sustainable way to conserve livestock genetic resources is to improve their competitiveness through sustainable breed improvement programs (i.e. conservation through use). To this end, community- or village-based selective breeding schemes with full participation of farmers appear to be the best option to start with.

/pdf/sheep-resources-of-ethiopia-genetic-diversity-and-breeding-2u2h5nfa9p.pdf

Sheep resources of Ethiopia : genetic diversity and breeding strategy

The importance of small ruminants to the dairy industry has increased in recent years, especially in developing countries, where it has a high economic and social impact. Interestingly and despite the fact that the mammary gland is the specialised milk production organ, very few authors studied the modifications occurring in the mammary gland through the lactation period in production animals, particularly in the small ruminants, sheep (Ovis aries) and goat (Capra hircus). Nevertheless, understanding the different mammary gland patterns throughout lactation is essential to improve dairy production. In addition, associating these patterns with different milking frequencies, lactation number or different diets is also of high importance, directly affecting the dairy industry. The mammary gland is commonly composed of parenchyma and stroma, which includes the ductal system, with individual proportions of each changing during the different periods and yields in a lactation cycle. Indeed, during late gestation, as well as during early to mid-lactation, mammary gland expansion occurs, with an increase in the number of epithelial cells and lumen area, which leads to increment of the parenchyma tissue, as well as a reduction of stroma, corresponding macroscopically to the increase in mammary gland volume. Throughout late lactation, the mammary gland volume decreases owing to the regression of the secretory structure. In general, common mammary gland patterns have been shown for both goats and sheep throughout the several lactation stages, although the number of studies is limited. The main objective of this manuscript is to review the colostrogenesis and lactogenesis processes as well as to highlight the mammary gland morphological patterns underlying milk production during the lactation cycle for small ruminants, and to describe potential differences between goats and sheep, hence contributing to a better description of mammary gland development during lactation for these two poorly studied species.

/pdf/the-mammary-gland-in-small-ruminants-major-morphological-and-3hl7htvx3y.pdf

The mammary gland in small ruminants: major morphological and functional events underlying milk production – a review

Breeding objectives for beef cattle used in different production systems

Pedigree analysis of the endangered Old Kladruber horse population

Economic values for health and feed efficiency traits of dual-purpose cattle in marginal areas

Economic values of 15 production and functional traits for Slovakian Pied cattle were calculated under different marketing strategies. The traits were as follows: birth weight of calves, daily gain of calves in fat- tening, mature weight of cows, weight of calves at 120, 210 (weaning weight) and 365 days (yearling weight) of age, dressing percentage, mean class for fleshiness and fat covering, conception rate of heifers and cows, losses of calves at calving and from 48 hours to weaning, lifetime of cows and mean class for calving performance. A pure- bred cow-calf pasture system producing its own female and male replacement was assumed for all strategies. The following marketing strategies for surplus weaned female and male calves were taken into account: (A) export of all surplus calves, (B) intensive fattening of all surplus calves, (C) rearing and selling of all surplus non-pregnant (1) or pregnant (2) breeding heifers and fattening or export of surplus male calves. All calculations were carried out with the computer program Ecoweight. The relative economic importance of traits was calculated multiplying the economic values by the genetic standard deviations of the traits. The lifetime of cows was the most important trait when applying export or fattening of all calves or when selling pregnant breeding heifers, whereas the yearling weight was even more important for the strategy with selling non-pregnant heifers. The second most important trait was weaning weight in strategy A, yearling weight in strategy B and lifetime of cows in marketing strategy C. Carcass conformation traits had the lowest economic importance in all calculations.

/pdf/economic-values-of-traits-for-slovakian-pied-cattle-under-5bntfzlyry.pdf

Economic values of traits for Slovakian Pied cattle under different marketing strategies

Economic values of 14 production and functional traits for two Slovak dairy sheep breeds (Improved Valachian and Tsigai) were calculated. Semi-extensive production systems with one lambing per year were simulated using a bio-economic deterministic computer model. The marginal economic value of a trait was defined as the partial derivative of the profit function with respect to that trait. The relative economic value expressed the percentage proportion of standardized economic value (marginal economic value×genetic standard deviation) of a trait in the sum of the absolute values of the standardized economic values over all traits. Milk yield was of highest relative importance (26% and 32% in Improved Valachian and Tsigai) followed by productive lifetime and conception rate of ewes (16% and 15% in Improved Valachian and Tsigai, in both traits). Conception rate of female lambs and litter size had nearly the same relative economic importance in both breeds (9% to 11%). Survival rate of lambs at lambing and till weaning reached slightly lower economic values (4% to 7%). The economic importance of all remaining traits was less than 4%. (Key Words : Dairy Sheep, Economic Weights, Milk Production, Functional Traits, Improved Valachian, Tsigai)

Economic Values for Dairy Sheep Breeds in Slovakia

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