Welcome to the next lecture in Leaning Unit 3 where you will learn about the importance of nutrients in animal life I am Dr Peter Ferket and this lecture is about nutrition and reproduction In learning unit 2 you learned some basic concepts of nutrients including protein energy vitamins and minerals In this lecture we will discuss how these nutrients function to support reproductive performance and the health of their young 1 Ask any expecting mother and she will tell you her doctor recommends her to take her prenatal vitamin and mineral supplement every day and eat a balanced diet Indeed nutrition plays important roles in reproductive success Nutrition is important in both male and female fertility The growth of the fetus and placental tissues have a high priority for nutrients especially those relating to energy and protein requirements The ultimate role of all organisms is the successful completion of reproduction otherwise the propagation of the species will not continue and they would eventually become endangered or extinct On an evolutionary basis animals developed physiological mechanisms that inform them metabolically as to whether undertaking reproduction at a particular time will be successful As illustrated in this figure for example it would NOT be an evolutionarily sound strategy for wild ungulates in northern regions to give birth in mid winter So through the fall testosterone levels in males increase to peak during the October rut when estrous cycles begin through to early winter so calving can occur during spring when the weather warms up Reproductivity also can depend on the availability of important nutrients such as energy and phosphorus in available foodstuffs A developing dry season would result in reduced feed availability and thus reduced availability of energy providing nutrients Reduced energy intake could provide a cue to alter hormonal status to inhibit reproduction In general low energy intakes and poor body condition will tend to impair reproduction Nutrients that are involved in energy metabolism such as enzyme cofactors will impair reproduction For example phosphorus has a role in phosphorylation of sugars in carbohydrate metabolism Dietary phosphorus deficiency thus provides a cue that energy metabolism is impaired if deficient Phosphorus deficiency of livestock is relatively common in various parts of the world where soil contents of the mineral are low including along the eastern seaboard of the USA parts of the mid west and northern plains Spain and the middle east India and China In these areas dietary phosphorus deficiency may risk reproductive health of grazing animals There are a few fat soluble vitamins that affect reproduction Vitamin E is often called the fertility vitamin or anti sterility factor This designation was an accident of history In the early days of vitamin research what had been called fat soluble vitamin A was fractionated into what we now know as vitamin A and vitamin D Rats fed with these two vitamins along with all other nutrients known at that time did not reproduce normally Supplementation of the rats with various foods restored fertility Wheat germ oil was especially effective The active component was i s o l a t ed a nd na med vitamin E When the chemical structure was elucidated it was named tocopherol from the Greek words for childbirth and to bear However d e s p i t e t h i s e a r l y a s s o c i a t i o n w i t h reproduction vitamin E functions primarily as an I t s a n t i o x i d a n t reproductive effects are actually due to the maintenance of tissue structural integrity by 6 antioxidant activity 6 Vitamin A deficiency continues to be a serious problem in the world This is a map of the world reported by the World Health Organization that identify vitamin A deficiency problems that are critical in red severe subclinical in orange moderately subclinical in yellow mild subclinical in brown and under control in green No data is available about vitamin A deficiency in the blue areas Vitamin A deficiency is common in developing countries but rarely seen in developed countries likely because developing countries consume more meat and animal products In contrast most people in developing countries are vegetarians and they don t consume much green leafy vegetables or yellow fruits and vegetables Moreover several factors reduce the bioconversion efficiency of carotenoid rich foods in developing countries such as low fat intake intestinal roundworms recurrent diarrhea tropical entropathy and other factors that affect the absorptive function of the intestinal epithelium and intestinal transit time 7 Vitamin A exists in natural products in many different forms It exist as preformed retinoids which are stored in animal tissues and as provitamin A carotinoids which are synthesized as pigments by many plants and are found in green orange and yellow plant tissues All trans retinol A is the reference form of highest biological activity One microgram of all trans retinol is equal to one retinol equivalent and 1 USP unit or IU is equal to 0 3 micrograms of all trans retinol Aldehyde forms of the vitamin can exist as all trans retinal B or 11 cis retinal D The acid forms can exist as all trans retinoic acid C or 13 cis retinoic acid E All trans retinyl palmitate as well as other fatty acid esters of retinol is the most prevalent form of Vitamin A in milk meat and eggs All trans retinoyl beta glucuronide G is an endogenously active water soluble metabolite of retinol Trimethyl methoxyphenol H is an analogue of all trans retinoic acid Finally beta carotene I is provitamin A as it can be theoretically bioconverted to two moles of retinol 8 Vitamin A has critical roles in the reproductive performance of males and females and it has significant impact on the developing fetus or embryo In males vitamin A is required for steroidogenesis especially the synthesis of testosterone the predominate male hormone Vitamin A is also necessary for spermatogenesis In females vitamin A is required for steroidogenesis especially the synthesis of estrogen and progesterone Vitamin A is also is necessary for the formation of normal uterine epithelial tissue and maintaining the uterine environment during gestation Vitamin A is required for embryo development as it regulates cell differentiation and proliferation A deficiency in Vitamin A results in weak dead or malformed offspring Excessive dietary intake of vitamin A called hypervitaminosis A can also