| This thesis studied in effects of dietary zinc, selenium and vitamin E content on growth and reproductive performance in breeding pigs, and it is arranged in three parts: part I, i.e chapter I, is a review of literatures; part II including chapters II-IV, deals with the experimental work in female breeding pigs, a L9 (34) orthogonal test design was used; part III including chapters V-VII, deals with the experimental work in boars, a 5x5 orthogonal latin square test design was used.The objective of the study in chapter II was to investigate the effects of dietary zinc ( three levels, i.e 45, 85, 125 mg.kg-1 diet), selenium (three levels, i.e 0.10, 0.25, 0.40 mg.kg1 diet ] and vitamin E ( three levels, i.e 15 s 30 s 45 lU.kg-1 diet ) content on relative parameters in prepubertal gilts. The results indicated that when theprepubertal gilts were fed a diet containing 85 mg.kg-1 of zinc, 0.25 mg.kg"1 of selenium and 45 IU.kg-1 of vitamin E : (1) the age of first estrus was the earliest, i.e. 187.4+6.6 days, 185.9+8.4days, 189.1 + 7.3days [P<0.05 ), respectively. (2) estrogen and progesterone concentration in serum were the highest ( P<0.05). (3) total protein content in serum maintained the highest level ( P<0.10) and urea concentration n serum maintained the lowest level ( P<0.10) which might mean that higher protein efficiency to body. (4) GSH-Px activity in serum was highest ( P<0.05or P<0.10) An conclusion, the appropriate content of dietary zinc, selenium and vitamin E is 85 mg.kg-1, 0.25 mg.kg-1, and 45 lU.kg-1 respectively for crossbred prepubertal gilts (Danish landrace x Yorksire).The objective of the study in chapter III was to investigate the effects of dietary zinc (three levels, i.e 45, 85, 125 mg.kg-1 diet), selenium (three levels, i.e 0.10s 0.25s 40 mg.kg1 diet) and vitamin E (three levels, i.e 15s 30s 45 lU.kg-1 diet) content on reproductive performance and relative parameters in primiparous gilts. The results indicated that when the dietary zinc, selenium and vitamin E content were 125 mg.kg-1, 0.40 mg.kg-1, 45 lU.kg-1 , respectively (1) litter sizes were the largest in gilts ( P<0.10): 9.9+ 1.1 piglets/litter, 9.9 + 1.4 piglets/litter, 10.0+ 1.2 piglets/litter, respectively; the gestation and the interval from post-weaning to estrus were the shortest ( P<0.10 ). (2) primiparous gilts show better reproductiveperformance when estrogen concentration in serum maintained relative high level during pregnancy, and when progesterone concentration in serum maintained relative high level during the early part of pregnancy and relative low level during the late part of pregnancy. (3) total protein content in serum maintained high level and urea concentration in serum maintained low level which might mean that higher protein efficiency to maternal body and fetus. (4) GSH-Px activity in serum was lower during the late part of pregnancy than that during the early part of pregnancy, which means that more peroxides may produce during the late part of pregnancy. In conclusion, the appropriate content of dietary zinc, selenium and vitamin E is 125 mg.kg-1, 0.40 mg.kg-1, and 45 lU.kg-1 , respectively for crossbred primiparous gilts ( Danish landrace x Yorksire).The objective of the study in chapter IV was to investigate the effects of dietary zinc (three levels, i.e 45, 85, 125 mg.kg-1 diet), selenium (three levels, i.e 0.10, 0.25, 40 mg.kg-1 diet )and vitamin Efthree levels, i.e 15, 30, 45 lU.kg-1 diet) content on reproductive performance and serum reproductive hormones and serum nutritive-biochemical parameters in sows. The results indicated that when the dietary zinc, selenium and vitamin E content were 85 mg.kg-1, 0.40 mg.kg-1, 45 lU.kg-1, respectively (1) litter sizes were the largest ( P<0.10 ): 10.3 +1.0, 10.2 +1.2, 10.3 +1.0 piglets/litter,respectively, and the interval from post-weaning to estrus were the shortest ( P<0.05). (2) sows show better reproductive performance as primiparous gilts when estrogen concentration in serum maintained relative high level during pregnancy, a...
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