This means that the larger the litter, the less space for placental attachment, which can lead to smaller piglets. In this time range, the initial placental expansion begins. The expansion is rather quick and occurs between Day Around day 30, which is in the middle of the expansion phase, sows can be checked for pregnancy via ultrasound.
When using an ultrasound machine, fluid filled sacs indicate that a litter is developing properly. In group gestation housing systems, if sows were not housed together immediately after breeding, it is best to wait until after confirmed pregnancy to group sows together. By this time, placental attachment is considered sufficient to survive fighting that might occur between sows.
During this time noticeable organ development begins. Bones begin calcifying at Day Sometimes, for a variety of reasons, individual fetal pigs will stop developing and die in the uterus.
Fetal pigs that die during this time of gestation can lead to the presence of mummies at farrowing. A mummy is a fetus that died after calcification of bone has occurred, and therefore, cannot be reabsorbed. Rather, it decomposes and mummifies in its placenta. For a pig producer, a litter that has many mummified fetuses found at farrowing can be a sign of trauma to the sow or developing offspring during the earlier stages of gestation. Trauma can include rough handling, poor nutrition, environmental stressors, or disease stress.
Final placental expansion begins at Day This is the in-utero hallmark of late gestation, however late gestation is observed on the outside of the sow by visible mammary tissue expansion. At this time, colostrum and milk production is beginning in addition to continued fetal growth. This is to help increase the amount of nutrients for sows for the final growth periods of both fetal and mammary tissues. Bump feeding has been shown to increase birth weights; however, it can be expensive and has not been seen to have any effect on final market weight of the piglets.
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Popular corded compound microscopes and cordless microscopes for elementary to advanced use. The reproductive performance of sows is presented in Table 2. The body composition and organ ratios of sows are shown in Table 3. In addition, no significant differences in crude fat concentration were observed at day 45 of gestation.
The amino acid AA composition of fetal pigs is shown in Table 5. The FA composition of fetal pigs is shown in Table 6. The present study aimed to determine the changes in the nutrient composition of fetuses according to BW and gestation period using Huanjiang mini-pig models. LBW fetuses exhibited lower amounts of crude fat and several FAs at mid-gestation and late-gestation, which may in turn affect adaptability, growth, and development.
During gestation, sows undergo dramatic changes and must acquire enough nutrition to maintain their own health and development and that of their fetuses. An improper supply of nutrition will negatively affect the health of sows as well as fetal growth and development [ 23 ].
In the present study, uterus weight, litter weight, and average individual fetal weights increased as gestation progressed, mainly due to continuous growth and development of the fetuses. However, no significant difference in fetus number was observed between days 45, 75, and of gestation. Maximal fetal growth occurs during the third trimester of pregnancy, during which sows must increase their nutrient intake to meet the demands of the growing fetuses [ 25 ]. In the present study, the BW gain and carcass weight of sows increased as gestation progressed, due to the continued growth of the mother and her conceptuses, and previous studies have indicated that maternal fluid expansion throughout pregnancy contributes to such increases [ 26 ].
We also observed that body fat percentage tended to increase as gestation progressed, which is beneficial to fetal growth. The percentage of muscle and the ratio of liver, lung, and stomach to BW decreased as gestation progressed, due to the rapid increase in the size of the conceptuses. Fetal growth and development is influenced by several factors including genetics, epigenetics, maternal maturity, maternal nutrition during gestation, uterine capacity, placental efficiency, litter size, day of gestation, and other environmental factors [ 8 , 27 , 28 ].
Our findings indicate that the BW of fetal pigs undergoes dynamic changes as gestation progresses, suggesting that nutrients are progressively accumulated in fetal pigs. At day of gestation, the BW of HBW fetuses was significantly higher than that of LBW fetuses in the present study, while no significant difference in BW was observed at days 45 and 75 of gestation, suggesting that the within-litter variation of fetal BW becomes more apparent during the late stage of gestation, in accordance with the findings of previous studies [ 23 , 30 ].
Such findings also indicate that fetal growth retardation occurs principally during the late gestational stage [ 23 , 31 ]. The nutrient composition of fetal pigs reflects nutritional deposition in the maternal uterus. In the present study, we observed that DM and crude fat concentrations in fetuses increased as gestation progressed, regardless of fetal BW. These findings are consistent with those of previous studies in which DM, CP, and crude fat concentrations increased exponentially in fetal pigs as gestation progressed [ 15 , 29 ].
McPherson et al. At days 75 and of gestation, crude fat concentration in HBW fetuses was significantly higher than that of LBW fetuses, suggesting that distinctions in crude fat concentration occur among fetal pigs of different BWs during mid-gestation and late-gestation, and that HBW fetuses can accumulate more fat than LBW fetuses. Fat concentration is related to energy storage in the body; therefore, our findings suggest that HBW fetuses conserve more energy and are more capable of adapting to the postnatal environment than LBW fetuses.
AAs have extremely different biochemical properties and functions, playing a prominent role not only as building blocks for proteins but also as substrates for the synthesis of a range of physiologically important molecules of immense biological importance [ 32 — 34 ]. Furthermore, AAs are known to exert various effects on body composition, blood flow, metabolic regulation, growth, and development [ 9 ]. Several studies have indicated that the concentrations of AAs vary remarkably in fetal fluid during pregnancy [ 35 — 37 ].
Suryawan et al. Thus, the availability of these AAs may become limited, requiring an increase in dietary intake to satisfy the growth and development of fetuses that occur during mid-gestation and late-gestation.
In the present study, we observed increases in Arg, Gly, and Tyr concentrations as gestation progressed, indicating that the demand for these AAs progressively increases throughout gestation. An insufficient supply of Arg is likely to limit the growth and development of fetal pigs during mid-gestation and late-gestation.
Dietary supplementation with Arg during these periods may increase the birth weights of piglets and decrease variation in piglet birth weights [ 40 , 41 ]. Notably, it has been reported that ovine fetuses have a high metabolic demand for Gly during late-gestation [ 42 ]. Additional studies have indicated that Tyr concentration increases during mid-gestation and late-gestation, and that Tyr is crucial for proper pigmentation of the skin, hair, and eyes [ 43 ].
Taken together, these findings demonstrate that fetuses need more Arg, Gly, and Tyr during mid-gestation and late-gestation to satisfy their developmental needs. Therefore, additional supplementation of these AAs during these periods may improve fetal growth and development. However, this result conflicts with previous reports, which indicated that transportation of AAs is decreased in IUGR fetal pigs [ 44 , 45 ]. This may be because the transportation of AAs does not occur distinctly at day 45 or 75 of gestation.
FAs have remarkable metabolic and regulatory versatility in animals [ 36 ]. Fetal accretion of PUFA during the third trimester coincides with a period of substantial growth and continued organ development [ 50 ].
This enables the storage of energy for fetal growth and development. Previous studies have indicated that this occurs due to growth of the liver during early-gestation [ 29 ]. A previous study has also reported that levels of maternal lipids affect the FA composition of fetal tissue [ 51 ]. Moreover, McNeil et al. Maternal body composition changes as gestation progresses. The most marked differences occur primarily during mid-gestation and late-gestation.
LBW fetuses exhibit decreased amounts of crude fat and several FAs including C, C, C, and Cn6c during mid-gestation and late-gestation, which may in turn affect the adaptability, growth, and development of the fetus. These findings may provide a theoretical basis for developing nutritional interventions that target fetuses with low birth weight in animals.
Additional studies are needed to demonstrate the underlying mechanisms through which these effects occur during gestation. We thank the staff and postgraduate students of Laboratory of Animal Nutritional Physiology and Metabolic Process for collecting samples and technicians from Key Laboratory of Agro-ecological Processes in Subtropical Region for providing technical assistance. Browse Subject Areas? Click through the PLOS taxonomy to find articles in your field. Abstract Low birth weight may negatively affect energy storage and nutrient metabolism, and impair fetal growth and development.
Dissection is a hands-on, investigatory kind of activity for students. Historically, dissection has been the principle tool of investigation for anatomists 2. Dissection impresses on students the normal variation that is present in the natural world. No two fetal pigs, even though they are perfectly normal, will look exactly the same.
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