The aim of this work was to investigate the effects of isoflavone daidzein supplementation to sows diet during late gestation on body weight, morphological and histological characteristics of m. semitendinosus in newborn piglets and slaughter pigs. Also, the influence of litter size on these characteristics in newborn piglets and slaughter pigs, and the influence of gender in slaughter pigs were investigated. The investigation was conducted in two separate experiments. In Experiment 1, sows were fed standard feed which included soy meal. Sows from experimental group were supplemented with 8 mg of synthetic daidzein per kg of feed and day. In Experiment 2, feed of sows did not contain soy, and experimental group of sows was supplemented with 1mg of synthetic daidzein per kg of body weight. The obtained results showed that daidzein supplementation did not influence the increase of body weight and morphological characteristics of m. semitendinosus, neither in newborn piglets nor in slaughter pigs. Treatment of sows with daidzein during late gestation had a minor, but not statistically significant influence on m. semitendinosus structure in newborn piglets, expressed as an increase of total muscle fiber number, number of primary fibers and secondary:primary ratio. Litter size, through its inverse relationship with birth weight, had significant influence on m. semitendinosus structure in newborn piglets. Small littter piglets had significantly higher total number of muscle fibers, number of primary and number of secondary fibers. Daidzein supplementation to sows did not influence muscle fiber type distribution and area of STO, FTO and FTG fibers in progeny at slaughter in Experiment 1. Conversely, in Experiment 2, daidzein supplementation to sows caused significant decrease of FTO percentage (for 3,5%) and increase of FTG percentage (for 5%). Number of nuclei per muscle fiber was not changed in slaughter pigs under daidzein treatment. It was found that number of nuclei per muscle fiber tends to decrease with decrease of muscle fiber cross sectional area. The influence of gender as the only factor, or in interaction with treatment, was detected for body weight, morphological characterisctics of m. semitendinosus, total number of muscle fibers and fiber type distribution in muscle of slaughter pigs. Finally, the results of this PhD thesis point at marginal influence of daidzein supplementation to sows diet during late gestation on postnatal growth and structure of m semitendinosus in the offspring. Further investigations with different concentrations of daidzein, and different timing of their supplementation to sows should be conducted with the aim to obtain better knowledge on influence of this isoflavone on skeletal muscle structure in the offspring. Cilj rada je bio da se ispitaju efekti dodavanja izoflavona daidzeina u hranu suprasnih krmača tokom kasne faze suprasnosti, na porast telesne mase, morfološke i mikroskopske osobine mišića m semitendinosus, kod novorđene prasadi i tovljenika na kraju tova. Takođe, ispitivan je uticaj veličine legla na ove osobine kako kod prasadi tako i kod tovljenika, i uticaj pola kod životinja na kraju tova. Disertacija je sprovedena u dva zasebna eksperimenta. U Eksperimentu 1, krmače su hranjene smešom u koju je bila uključena sojina sačma, a krmače iz ogledne grupe su od 85-og dana suprasnosti dobijale sintetički daidzein u količini 8 mg/kg hraniva. U Eksperimentu 2, krmače su hranjene smešom koja nije sadržala soju, a ogledna grupa je od 85-og dana suprasnosti dobijala u hrani sintetički daidzein u količini 1 mg/kg telesne mase. Dobijeni rezultati su pokazali da nije došlo do statistički značajnog uticaja daidzeina na povećanje postnatalnog porasta telesne mase i morfoloških osobina mišića m. semitendinosus, kako kod novorođene prasadi tako ni kod tovljenika na kraju tova. Tretman krmača daidzeinom, u toku kasne faze suprasnosti, imao je mali ali ne statistički značajan uticaj na strukturu mišića m. semitendinosus, kod novorođene prasadi, izražen kroz povećanje ukupnog broja vlakana, broj primarnih vlakana i odnos sekundarna:primarna vlakna. Veličina legla, kroz inverzan odnos sa masom prasadi pri rođenju, imala je značajan uticaj na strukturu mišića m semitendinosus, kod prasadi. Tako su prasad iz malih legala imala statistički značajno veći ukupan broj mišićnih vlakana kao i broj primarnih i sekundarnih vlakana. Kod tovljenika iz Eksperimenta 1, nije ispoljena značajna promena broja, procentualne zastupljenosti i površine STO, FTO i FTG vlakana, pod uticajem daidzeina. Nasuprot tome, kod tovljenika iz Eksperimenta 2 (krmače hranjene obrocima bez soje), dodavanje daidzeina je dovelo do smanjenja % FTO (za 3,5%) a povećanja % udela FTG vlakana (za 5%). Prosečan broj jedara po jednom mišićnom vlaknu, kod tovljenika, nije bio promenjen pod uticajem daidzeina. Konstatovan je trend smanjenja broja jedara sa smanjenjem površine vlakna. Pol ispitivan kod tovljenika kao jedini faktor, ili u interakciji sa tretmanom, ispoljio je uticaj na telesnu masu, morfološke osobine m. semitendinosus, ukupan broj vlakana i zastupljenost pojedinih tipova vlakana u mišiću. Konačno, rezultati ove doktorske disertacije ukazali su na marginalni uticaj dodavanja daidzeina u hranu krmača tokom kasne faze suprasnosti, na postanatalni rast i strukturu mišića m semitendinosus kod potomaka, i ukazali na potrebu daljih istraživanja u pravcu ispitivanja efekata drugih koncentracija i vremena dodavanja ovog jedinjenja suprasnim krmačama na mišićno tkivo potomstva.