| To study the effects of nutrient levels during pregnancy on body conditions of high-yielding primiparous sows and characteristics of muscle fiber,serum insulin concentrations,and expressions of genes related to muscle developments of offspring.The experiment was based on one-factor-at-a-time(OFAT)experiment.120 8-month-old Landrace-Yorkshire hybrid primary mating sows,weighing over 130 kg in their pregnancy,were selected and divided into three groups according to body condition and body weight.They were treated respectively with low nutrient level(Group LN),standard nutrient level(Group AN)and high nutrient level(Group HN).The sows in each group were fed the same basic diet,and the feeding amount of each sow was calculated according to the nutrition maintenance requirement.During the first 30 days of pregnancy,the nutrient intake was 0.8,1.0 and 1.4 times of the maintenance requirement,while in the middle period(31~90 days),it was increased by 20% on the basis of the previous period,and in the later period(91~112 days),it was increased by 25% on the basis of the middle period.After the delivery,12 sows with more than 13 piglets were selected from each group for the experiment.The experiment showed:(1)The nutrient level during pregnancy significantly affected the growth of sow's weight and backfat during pregnancy.Feeding low nutrition level during pregnancy significantly reduced the weights of primiparous sows before delivery,after delivery,and at weaning(P<0.05),also reduced the backfat before and after delivery(P<0.05),and the sows in LN group lost more backfat than those in AN group(P<0.05).With the increase of nutrient level,the weight loss during lactation tended to increase(P<0.05);the piglet's newborn weight,21-day-old weight,weaning weight and average daily weight gain tended to increase with the increase of nutrient level.The piglet birth weight and average daily weight gain were the highest in HN group,significantly different from those in LN group(P<0.05),but not significantly different from those in AN group(P>0.05).The differences of piglets' 21-day-old-weights and weaned weights were not significant(P>0.05)among groups;the differences in muscle fiber diameter,muscle fiber density,and muscle fiber cross-sectional area of both newborn and weaned piglets were not significant(P>0.05),either.(2)There was no significant difference in the effects of different nutrient levels on the serum insulin concentration in newborn piglets and weaned piglets(P>0.05).The serum insulin concentration in newborn piglets had an increasing trend with the increase in nutrition level,but there was no significant difference among groups(P>0.05),the serum insulin concentration of weaned piglets at 28 th day decreased with the increase of nutrient level,but there was no significant difference among groups(P>0.05);the effects of different nutrient levels on the serum IGF-I concentration of newborn and weaned piglets were not significant(P>0.05),the highest content was in AN group and the lowest content was in HN group;Ig A,Ig G,and Ig M contents in the serum of weaned piglets at 28 th day all showed an upward trend with the increase of the nutrient level.The Ig G content in the HN group was 45.05 ?g / ml higher than that in LN group with the significant difference(P<0.05),while the rest were not significantly different among groups(P>0.05).The protein concentration of longissimus dorsi of newborn piglets and28-day weaned piglets gradually increased with the increase of the nutrition level,but there was no significant difference among groups(P>0.05);the concentration of Ca N in newborn piglets in LN group was significantly lower than that in HN group(P<0.05),and it tended to increase with the increase of nutrition level.There was no significant difference in the concentration of Ca N in weaned piglets among groups(P>0.05);the concentration of CK in the newborn piglets was the highest in AN group,and the content of CK in the newborn piglets in LN group was significantly lower than that in AN group and HN group(P<0.05),and the difference of CK concentration in weaned piglets was not significant(P>0.05).(3)The nutrient levels during pregnancy had no significant effects on the gene expression of IGF-I in the longissimus dorsi of newborn piglets and 28-day weaned piglets(P>0.05),and the gene expression in both newborn piglets and 28-day weaned piglets was highest in AN group;The nutrient levels during pregnancy had no significant effects on the gene expression of MTOR in the longissimus dorsi of newborn piglets and weaned piglets(P>0.05);the nutrient levels during pregnancy significantly affected the gene expression of MRF4 in the longissimus dorsi of newborn piglets and weaned piglets(P>0.05).Among the newborn piglets,those in AN group had the highest gene expression level,which was significantly different from those in LN group and HN group(P<0.05).Among the weaned piglets,those in HN group owed the highest gene expression level,significantly compared with those in LN group and AN group(P<0.05).Results: The nutrient levels during pregnancy affect body conditions of primiparous sows and growth performances of offspring,and appropriate nutrient levels(1.0M in early pregnancy,1.2M in middle pregnancy and 1.5M in late pregnancy)help sows to maintain good body conditions and ensure offspring's normal muscle developments. |
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