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

Nutrient requirements of dairy cattle , Nutrient requirements of dairy cattle , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Nutrient requirements of dairy cattle

Biology of dairy cows during the transition period : the final frontier?

Reproductive loss in high-producing dairy cattle: where will it end?

https://www.webpages.uidaho.edu/ruminant_nutrition/Reading%20materials%20411/dietary%20factors%20affecting%20feed%20intake-Allen2000.pdf

Effects of Diet on Short-Term Regulation of Feed Intake by Lactating Dairy Cattle

Influence of supplemental fats on reproductive tissues and performance of lactating cows.

Fats in the diet can influence reproduction positively by altering both ovarian follicle and corpus luteum function via improved energy status and by increasing precursors for the synthesis of reproductive hormones such as steroids and prostaglandins. Dietary fatty acids of the n-3 family reduce ovarian and endometrial synthesis of prostaglandin F 2α, decrease ovulation rate in rats and delay parturition in sheep and humans. Polyunsaturated fatty acids such as linoleic, linolenic, eicosapentaenoic and docosahexaenoic acids may inhibit prostaglandin F 2α synthesis through mechanisms such as decreased availability of its precursor arachidonic acid, an increased competition by these fatty acids with arachidonic acid for binding to prostaglandin H synthase, and inhibition of prostaglandin H synthase synthesis and activity. It is not known whether polyunsaturated fatty acids regulate expression of candidate genes such as phospholipase A 2 and prostaglandin H synthase via activation of nuclear transcription factors such as peroxisome proliferator-activated receptors. Manipulation of the fatty acid profile of the diet can be used potentially to amplify suppression of uterine synthesis of prostaglandin F 2α during early pregnancy in cattle, which may contribute to a reduction in embryonic mortality. Feeding fats and targeting of fatty acids to reproductive tissues may be a potential strategy to integrate nutrition and reproductive management to improve animal productivity.

/pdf/effects-of-dietary-fatty-acids-on-reproduction-in-ruminants-xojnvlxj69.pdf

Effects of dietary fatty acids on reproduction in ruminants

Relationship between ovarian activity and energy status during the early postpartum period of high producing dairy cows.

Energy balance and size and number of ovarian follicles detected by ultrasonography in early postpartum dairy cows.

Contents

Cattle are fed moderate amounts of long chain fatty acids (FA) with the objective to enhance lactation and growth; however, recent interest on lipid feeding to cows has focused on reproduction, immunity and health. Increasing the caloric density of the ration by fat feeding has generally improved measures of cow reproduction, but when milk yield and body weight losses were increased by fat supplementation, positive effects on reproduction were not always observed. Feeding fat has influenced reproduction by altering the size of the dominant follicle, hastening the interval to first postpartum ovulation in beef cows, increasing progesterone concentrations during the luteal phase of the oestrous cycle, modulating uterine prostaglandin (PG) synthesis, and improving oocyte and embryo quality and developmental competence. Some of these effects were altered by the type of FA fed. The polyunsaturated FA of the n-6 and n-3 families seem to have the most remarkable effects on reproductive responses of cattle, but it is not completely clear whether these effects are mediated only by them or by other potential intermediates produced during rumen biohydrogenation. Generally, feeding fat sources rich in n-6 FA during late gestation and early lactation enhanced follicle growth, uterine PG secretion, embryo quality and pregnancy in cows. Similarly, feeding n-3 FA during lactation suppressed uterine PG release, and improved embryo quality and maintenance of pregnancy. Future research ought to focus on methods to improve the delivery of specific FA and adequately powered studies should be designed to critically evaluate their effects on establishment and maintenance of pregnancy in cattle.

C.R. Staples

Papers

Influence of supplemental fats on reproductive tissues and performance of lactating cows.

Effects of dietary fatty acids on reproduction in ruminants

Relationship between ovarian activity and energy status during the early postpartum period of high producing dairy cows.

Energy balance and size and number of ovarian follicles detected by ultrasonography in early postpartum dairy cows.

Long chain fatty acids of diet as factors influencing reproduction in cattle.