Effects Of Energy Levels On The Survival And Development Of Embryos In Yorkshire And Meishan Sows

This experiment was conducted to examine the effects of dietary energy level on fetal survival, secretion of progesterone and expression of relative gene. At the initial day of gestation, a total of 32 pure Large White (LW) gilts were randomly assigned to two different experimental diets contained 3.4 or 3.0 Mcal DE/kg, while same number pure Meishan (MS) gilts were allocated to 3.0 or 2.6 Mcal DE/kg diet groups. All gilts were supplied with 2.0 kg/d of diet from day 0 to 30 and 2.4 kg/d from day 31 to 90 of gestation. After gilts weighing, gilts were slaughtered on days 35,55 and 90 of gestation after deep anaesthetized. The serum, corpus luteum or endometrium tissue were used to investigating the effects of energy level on relative metabolite, hormone concentration and gene expression. The concentration of hormone in serum were conducted by an equilibrium competitive RIA using a commercial Iodine [1251] kit. Progesterone synthesis-related proteins in the corpus luteum and mRNA expression in endometrium tissue were tested by RT-PCR. The results showed:1) In LW gilts, the fetal survival of 3.4 Mcal DE/kg feed LW gilts was higher on day 35 and higher fetal weight and length on day 90 of gestation than that of 3.0 Mcal DE/kg feed gilts (P< 0.05). There was no significant difference about peripheral progesterone concentration between two groups (P> 0.05). However, luteal progesterone concentration was significantly improved (P< 0.05) in 3.4 Mcal DE/kg on day 35 of pregnancy but 3.0 Mcal DE/kg group had higher concentration than 3.4 Mcal DE/kg group on days 55 and 90 of gestation (P= 0.09; P= 0.07). In gilts luteal tissue of 3.0 Mcal DE/kg group, the mRNA expression of gene via scavenger receptor-BI (SRBI), steroidogenic acute regulatory protein (STAR) and 3(3-hydroxysteroid dehydrogenase/A5-A4 isomerase (3(3-HSD) were significant higher than 3.4 Mcal DE/kg group (P< 0.05). In endometrium tissue, uteroferrin (ACP5) and secreted phospoprotein 1 (SPP1) have higher mRNA expression in 3.4 Mcal/kg than 3.0 Mcal/kg treatment group on day 35 of gestation but lower on day 55 of pregnancy (P< 0.05).2) In MS gilts, there were greater fetal survival (P< 0.05) in 2.6 Mcal DE/kg feeding group than 3.0 Meal DE/kg feed group on day 35 of gestation, however, fetal weight in 3.0 Meal DE/kg feed group was higher than 2.6 Meal DE/kg group on days 55 and 90 of gestation (P< 0.05). When investigated luteal progesterone concentration, we found that the levels of luteal progesterone was higher (P< 0.05) in 2.6 Mcal/kg feed group than those in 3.0 Mcal/kg feed group on day 35 of gestation and no difference on days 55 and 90 of pregnancy (P> 0.05). Interestingly, the mRNA expression of luteal tissue did not differ between the two groups of gilts on day 90 of pregnancy (P> 0.05). In endometrium, the gene expression of SPP1 was higher in 2.6 Meal DE/kg feed MS gilts than that in 2.6 Meal DE/kg feed MS gilts on day 35 and mRNA expression of PGR on day 55 of gestation (P< 0.05). There were no differ in others gene which relative to fetal survival in any time of pregnancy (P> 0.05).3) In the same dietary energy level between LW and MS, the uterine length, uterine weight, ovary weight and fetal weight of LW were significant higher than MS (P< 0.05). However, the corpora lutea number, fetal survival and fetal length had no difference between two breeds in three stage of gestation (P> 0.05), The MS gilts had higher serum progesterone concentration and SPP1 expression on days 35,55 and 90 of gestation than LW gilts (P< 0.05).The above results show that:1) In LW gilts, diet with 3.4 Meal DE/kg could improve fetal survival on day 35 but sustainable supply of high energy diet will decrease the progesterone concentration and fetal number on day 90 of gestation.2) Our results revealed the different sensitivity of LW and MS in variational dietary energy intake levels. And diet with 2.6 Mcal DE/kg could increase fetal survival of MS gilts on day 35 of gestation, but 3.0 Meal DE/kg of feeding can increase fetal development on day 90 of gestation.3) In 3.0 Meal DE/kg treatment groups of LW and MS, the fetal survival had no significant different, however, MS had a better inner environment of the uterus than LW gilts.