Relations between maternal and fetal plasma concentrations of placental lactogen and placental and fetal weights in well-fed ewes

The concentration of ovine placental lactogen (oPL) in maternal plasma varies with litter size and nutritional status, making it difficult to compare these concentrations across studies. In this study, 27 Dorset and Finn-Dorset crossbred ewes with litters of known size and gestational age were used to relate concentrations of oPL in maternal plasma to placental and fetal weights. Fetal oPL concentrations also were correlated to these variables in 12 chronically catheterized singleton fetuses. The concentration of oPL in maternal plasma increased with increasing placental weight across litter sizes ranging from 1 to 3 (r = .716). When expressed per gram of placenta, oPL was greater (P less than .05) in those ewes carrying multiple fetuses. There was no correlation between maternal and fetal oPL in time-matched samples or in average values between individuals for ewes carrying singleton pregnancies. Within the singleton group, placental weight and fetal weight were well correlated (r = .761), as were the concentration of fetal plasma oPL and fetal weight (r = .699). Placental weight plus fetal oPL could explain 81% of the variation seen in fetal weight. These results imply that maternal and fetal oPL release are controlled independently and that fetal oPL affects fetal growth by a mechanism not directly related to placental size.     

Early pregnancy diagnosis by means of ultrasonography as a method of improving reproductive efficiency in goats

Eighteen cyclic Shiba goats were used in this study. Estrus was synchronized with a single injection of 125 microg of a synthetic analogue of prostaglandin F(2)alpha (PGF(2)alpha) after detection of at least one corpus luteum by B-mode ultrasonography. Blood samples were collected from each animal on days 0, 7 and 21 post-mating for progesterone assay. Animals in estrus were either allowed to be mated by fertile bucks twice during estrus (group I; n=12) or not at all (group II; n=6). Ultrasonographic examinations were performed transrectally or transabdominally using a real-time B-mode scanner equipped with a 7.5 or 5 MHz transducer. All animals exhibited estrus 56.0 +/- 2.7 h after injection of PGF2alpha. The results show that the accuracy of the progesterone assay in diagnosing pregnancy on day 21 after mating was 80% for pregnancy and 100% for non-pregnancy, retrospectively. Ultrasonographic examinations showed that gestational sac and embryos heartbeats were detected on days 20.2 +/- 0.6 and 24.3 +/- 0.7 of gestation, respectively. Placentomes were detected on day 35.4 +/- 1.0 of gestation as small nodules (0.7 +/- 0.2 cm in size). At two months pregnancy, skeletal structures like skull, thorax and long bones were clear. Biparietal diameter of the skull and length of long bones could be used as an estimate of gestational age. The accuracy of detection of fetal number using real-time B-mode ultrasonography was 91.7% on day 60 of gestation. In conclusion, progesterone assay at day 21 post-mating (cut-off value, 1 ng/ml) can be used for pregnancy diagnosis in goats. However, B-mode transrectal ultrasonography was more efficient due to detection of embryo and confirmation of its viability by heartbeats. In addition, fetal number and gestational age could be determined only by ultrasonography.     

Determination of gestational age in medium and small size bitches using ultrasonographic fetal measurements

A study was undertaken to estimate gestational age, in terms of days from parturition, in medium and small size dogs by ultrasonographic examination. Serial ultrasonographic examinations were performed in four medium size pregnant bitches throughout two consecutive pregnancies and three small size pregnant bitches throughout one pregnancy, in order to determine the range of variation in the size of selected fetal structures throughout gestation. Formulae were derived to estimate the expected delivery date for both groups of bitches by measuring anatomical fetal structures, so that this method could be applied to a large number of different breeds. The determination of gestational age could be achieved with reasonable precision by selecting fetal structures. Prediction of parturition date was accurate to within one day by ultrasonographic measurement of the diameter of the gestational sac in early pregnancy and the biparietal diameter in late pregnancy in both small size breeds and medium size breeds.     

Patterns of late embryonic and fetal mortality and association with several factors in sheep

Embryonic and fetal mortality reduce lambing rates and litter sizes, thus contributing to economic losses in the sheep industry. In the current study, the timing of late embryonic and fetal loss in ewes and the factors with which these losses were associated were examined. Ewes lambing and lambs born were compared with pregnancy diagnosis and counts of embryos by ultrasonography near d 25, 45, 65, or 85 of gestation. Approximately 19.9% of the ewes experienced late embryonic loss, fetal loss, or both; and 21.2% of the embryos or fetuses were lost from d 25 to term. Potential offspring were lost throughout gestation; 3.7% of embryos from d 25 to 45, 4.3% of fetuses from d 45 to 65, 3.3% from d 65 to 85, and 11.5% from d 85 to parturition; thus, approximately 3 to 4% of the potential offspring were lost for each 20-d period of pregnancy beyond d 25. A greater proportion of ewes lost one (36.7%) rather than all (20.5% single; 3.8% multiple) embryos or fetuses. The patterns of loss were similar in ewes mated during the anestrous season and the transitional period and did not vary with service period within breeding season or method of synchronization of estrus. Late embryonic or fetal losses were not related to the temperature-humidity index. Maternal serum collected near d 25, 45, 65, or 85 of gestation was assayed for concentrations of progesterone, estradiol-17beta , and vascular endothelial growth factor (VEGF). The proportions of embryos or fetuses lost were associated with breed type (P < 0.05), as were concentrations of progesterone (P < 0.01), estradiol (P < 0.05), and VEGF (P < 0.01). The relationships of loss or retention of pregnancy to hormonal variables at the 4 stages studied were limited. Complete and partial losses increased rapidly as maternal progesterone at d 25 decreased below 2 ng/mL (P < 0.05). Survival of fetuses within a litter from d 25 to 65 was greater for ewes with medium concentrations of VEGF near d 25 and from d 65 to parturition was greater for ewes with high concentrations of VEGF near d 45 (P < 0.05). In summary, late embryonic or fetal losses occurred from d 25 throughout gestation and varied with breed type and with concentrations of progesterone in maternal serum on d 25.     

Sonography during the pregnancy of sheep. I. Fetometry for the determination of the stage of gestation and prediction of the time of parturition]

Transrectal and transcutaneous ultrasonography was performed on 187 pregnant Merino ewes to measure the growth of fetal parameters (fetometry) such as the diameters of the eye, braincase and trunk, the width of one rib with its intercostal space and the crown-rump-length (CRL). In the ewes, cross and longitudinal diameters of the intrauterine lumen around the embryo and fetus were determined. Trunk diameter and crown-rump-length of embryos and fetuses were sonographically determined from Day 26 and size of eyes, braincase and ribs were measured from Day 52 to 66 of gestation. Embryonic resp. fetal parameters and uterine diameters showed almost linear growth rate. Relationship between the measured parameters and days of pregnancy is described by regressions and correlation coefficients. Correlation coefficient between gestational stage and the diameter of the trunk was very narrow (r = 0.98) and between gestational stage and the crown-rump-length resp. eye diameter equalled 89% (r = 0.89). These fetal parameters are appropriate to assess gestational age and growth of ovine fetuses. It can be concluded that sonographic fetometry in the ovine can be valuable for the evaluation of fetal development, the estimation of gestational age and the prediction of parturition dates.     

Comparison of the accuracy of two ultrasonographic measurements in predicting the parturition date in the bitch

OBJECTIVES: To compare the accuracy of two ultrasonographic measurements, inner chorionic cavity diameter and biparietal diameter, for the prediction of parturition date in small and medium size bitches. The effects of litter size and fetal sex ratio on the accuracy of the prediction were also investigated. METHODS: Ultrasonographic examinations were performed on pregnant bitches and, depending on the stage of pregnancy, the inner chorionic cavity diameter and biparietal diameter were measured. The mean value of the data of each structure was calculated and the predicted day of parturition was obtained by the application of equations derived from growth curves we previously developed for different size bitches. RESULTS: The parturition term was predicted with similar accuracy during early gestation, by the measurement of inner chorionic cavity diameter, as well as during late gestation, by the measurement of biparietal diameter. Litter size affected only biparietal diameter accuracy, whereas fetal sex ratio did not influence the estimation of the day of parturition. CLINICAL SIGNIFICANCE: Inner chorionic cavity diameter and biparietal diameter were equally reliable parameters in obtaining a reasonably accurate prediction of parturition date at any gestational period at which a bitch is examined.     

Ultrasound during mid‐gestation: Agreement with physical foetal and placental measurements and use in predicting gestational age in sheep

To determine the effects of poor maternal nutrition and litter size on foetal growth during mid‐gestation, pregnant ewes (n = 82) were fed 100%, 60% or 140% of NRC TDN beginning at day 30.2 ± 0.2 of gestation. Transabdominal ultrasound was performed weekly between day 46.0 ± 0.4 and 86.0 ± 0.7 to monitor foetal heart width (HW), umbilical diameter (UMB), rib width (RW) and placentome outer (OD) and inner diameter (ID). Data were analysed with repeated‐measures using the mixed procedure for effects of maternal diet, litter size and gestation, and equations predictive of gestational age were generated using the regression procedure. To determine the agreement of ultrasound measurement and actual size, ewes (n = 20–21) were euthanized at day 45 or 90 to obtain corresponding postmortem measurements for Bland–Altman analysis. The HW, UMB and placentome OD and ID increased with gestation (p < .0001) but were unaffected by maternal diet or litter size (p ≥ .12). Ultrasound underestimated postmortem measurements of HW (14.8%), UMB (7.3%), placentome OD (4.5%) and ID (37.3%) at day 90 of gestation. Ultrasound underestimated RW at day 45 (7.7%) but overestimated RW (23.8%) at day 90, indicating inconsistent bias when reporting RW by ultrasound. Combining the HW, UMB, RW and placentome OD generated the strongest equation predictive of gestational age (R² = .91). These findings indicate that during mid‐gestation, maternal diet or litter size did not affect HW, UMB or placentome diameters and these factors can be used to estimate gestational age.     

PREGNANCY DIAGNOSIS WITH ULTRASOUND IN THE DOMESTIC CAT

Ultrasonographic examinations of seven pregnant cats with known breeding dates were made on successive days to establish the identifiable characteristics of pregnancy. Subsequent serial examinations were made to sonographically characterize normal feline prenatal development before 30 gestational days. An enlarged uterus, gestational sacs, and fetal poles were recognized as the features of early feline pregnancy and were first seen at 4, 11, and 15 days, respectively. Cardiac activity was detected earliest on gestational day 16, and recognizable feline fetal morphology appeared at day 26. Fetal membranes became apparent at as early as 21 days of gestation. Generalized fetal movements were first noted at day 28. Live and dead fetuses were compared in utero and marked differences were noted, with dead fetuses rapidly losing previously recognizable morphology. Determination of litter size in each cat could not be done accurately by ultrasound examination. It was concluded that the diagnosis and accurate dating of early pregnancy in the domestic feline may be accomplished with serial ultrasound evaluation.     

Maternal low-dose porcine somatotropin treatment in late gestation increases progeny weight at birth and weaning in sows but not in gilts

Birth weight positively predicts postnatal growth and performance in pigs and can be increased by sustained maternal porcine ST (pST) treatment from d 25 to 100 of pregnancy (term ～115 d). The objective of this study was to test whether a shorter period of maternal pST treatment in late pregnancy (d 75 to 100) could also increase birth and weaning weights of progeny under commercial conditions. Gilts (parity 0) and sows (parities 2 and 3) were not injected (controls) or injected daily with pST (gilts: 2.5 mg?d(-1), sows: 4.0 mg?d(-1), both ～13 to 14 μg?kg(-1)?d(-1)) from d 75 to 100 of pregnancy. Litter size and BW were recorded at birth and weaning, and dams were followed through the subsequent mating and pregnancy. Maternal pST injections from d 75 to 100 increased litter average progeny weight at birth (+96 g, P = 0.034) and weaning (+430 g, P = 0.038) in sows, but had no effect on progeny weight in gilts (each P > 0.5). Maternal pST treatment did not affect numbers of live-born piglets and increased numbers of stillborn piglets in sows only (+0.4 pigs/litter, P = 0.034). Maternal pST treatment did not affect subsequent reproduction of dams. Together with our previous data, these results suggest that sustained increases in maternal pST are required to increase fetal and postnatal growth in gilt progeny, but that increasing maternal pST in late pregnancy may only be an effective strategy to increase fetal and possibly postnatal growth in sow progeny.     

Incidence of splayleg pigs in Nebraska litter size selection lines

Genetic parameters for the splayleg (SL) condition were estimated from 37,673 records of pigs from six lines derived from a Large White-Land-race base population. Random selection for 22 generations was practiced in Lines C1 and C2. Line C2 was derived from C1 at Generation 8. Selection lines were as follows: 1) Line I, selected 11 generations for an index of ovulation rate and embryonic survival followed by 11 generations of selection for litter size; 2) Line IOL, derived from Line I at Generation 8 and which underwent eight generations of two-stage selection for ovulation rate and number of fully formed pigs per litter followed by four generations of litter size selection; 3) Line COL, derived from Line C1 at Generation 8 and selected eight generations in two stages for ovulation rate and number of fully formed pigs followed by four generations of litter size selection; and 4) Line T, selected 12 generations for increased testis size. From logistic models, it was found that boars were 224% more likely to have SL than gilts (P < 0.01). Decreases in birth weight, dam age at puberty, dam nipple number, and dam embryonic survival, and increases in dam litter size and inbreeding increased the odds of SL (P < 0.05). Direct and maternal heritabilities of SL were 0.07 and 0.16, respectively, and the correlation between direct and maternal effects was -0.24. Correlations between direct genetic effects for SL and number born alive, nipple number, birth weight, age at puberty, and embryonic survival were -0.19, -0.36, 0.23, -0.19, and -0.32, respectively. Except for the correlation of 0.32 between maternal effects for SL and direct effects for number of live pigs, correlations of SL maternal genetic effects with direct genetic effects of other traits were less than 0.11. Annual direct genetic trends (%) for SL in I, IOL, COL, T, C1, and C2 were -0.003 +/- 0.003, 0.121 +/- 0.012, -0.273 +/-0.009, 0.243 +/-0.014, -0.274 +/-0.004, and 0.086 +/-0.008, respectively; annual maternal genetic trends (%) were 0.106 +/-0.004, 0.508 +/-0.019, 0.383 +/-0.015, 0.527 +/-0.024, 0.188 +/-0.005, and 0.113 +/-0.012, respectively. Annual genetic maternal trend in Line I after Generation 12 was 0.339 +/-0.014. Maternal breeding value for SL is expected to increase as a correlated response to selection for increased litter size and increased size of testes.     

Altered muscle development and expression of the insulin-like growth factor system in growth retarded fetal pigs

We have used a porcine model of spontaneous differential fetal growth to investigate the effects of fetal size on muscle development. We hypothesized that altered muscle development may occur in small fetuses as a consequence of modified expression of selected genes of the insulin-like growth factor system. We examined the development of the Longissimus muscle (m. Longissimus) in small fetuses and their average sized littermates. We collected small for gestational age fetuses and their average sized sibling on days 45, 65 and 100 of gestation (term is 113-116 days). Small fetuses had significantly lower body weight at all three stages of gestation (p<0.05) and significantly reduced secondary to primary muscle fibre ratio in m. Longissimus on day 100 (p<0.05) compared to their littermates. On day 65, the expression of insulin-like growth factor receptor 1 and insulin-like growth factor binding protein 3 were significantly higher (p<0.05) in m. Longissimus of the small fetuses compared with their average sized littermates. On day 100, the expression of insulin-like growth factor receptor 1 remained significantly higher (p=0.001), in addition to significantly higher levels of insulin-like growth factor receptor 2 and insulin-like growth factor binding protein 5 in the small fetuses (p<0.05). No difference in levels of myogenin was observed between the small and average sized littermates. In conclusion, we demonstrate that reduced fetal muscle development is associated with an increased expression of several genes of the insulin-like growth factor system in small fetuses in mid to late gestation.     

Expression and possible role of 20alpha-hydroxysteroid dehydrogenase in the placenta of the goat

20Alpha-hydroxysteroid dehydrogenase (20alpha-HSD) catalyzes the conversion of progesterone to its inactive form 20alpha-dihydroprogesterone (20alpha-OHP). 20Alpha-HSD is expressed in the murine placenta, suggesting a role, yet unidentified, played by this enzyme during the course of pregnancy. To elucidate the possible roles of 20alpha-HSD during pregnancy, 20alpha-HSD gene expression in the placenta was examined by Northern blot analysis, and progestin (progesterone and 20alpha-OHP) concentrations in the maternal and fetal sera and the amniotic fluid were measured by radioimmunoassay in pregnant Shiba goats. The expression of 20alpha-HSD mRNA was observed in the placenta and the intercaruncular part of the uterus during mid to late pregnancy. Analysis by in situ hybridization revealed that 20alpha-HSD mRNA was mainly localized in the endometrial epithelium of the caruncle side of the placenta. Considerable enzyme activity of 20alpha-HSD was also detected in the cytosolic fraction of the placenta and intercaruncular part of the uterus. Although concentrations of progesterone and 20alpha-OHP in the maternal serum showed similar profiles, progesterone levels in the fetal serum stayed extremely low throughout the pregnancy. The 20alpha-OHP concentration in the fetal serum was always higher than that in the maternal serum. In the amniotic fluid, the concentrations of both progesterone and 20alpha-OHP remained at very low levels throughout the pregnancy. These results support the notion that 20alpha-HSD protects the fetus from the cytotoxic effects of progesterone, and thereby maintains the normal development of the fetus.     

草食家畜母体营养对子代生命健康影响的研究进展

母体营养对胎儿基因表达的调节作用逐渐成为围产期生命营养科学研究的热点。妊娠期作为发育可塑性的关键窗口,甲基供体对胎儿发育的相关代谢基因起到修饰作用,表观遗传学可能涉及其中的分子机制。动物研究表明,母体营养供给不足或过剩都会限制胎儿的生长。结合国内外研究报道,探讨了草食家畜妊娠期母胎的营养需求、激素在稳态调节中发挥的作用以及妊娠期能量需求对妊娠健康的重要意义,概括了妊娠期草食动物营养在表观遗传学方面的研究进展,探讨了表观遗传相关技术在草食家畜育种中的应用,以期为制定草食动物妊娠期最佳营养策略、提高胚胎质量、培养高质量后代提供参考。     

Relationship between litter birth weight and litter size in six breeds of sheep

Metabolizable energy requirements of the ewe increase during pregnancy due to increases in fetal and maternal metabolism. Fetal metabolism is related to total weight of the fetuses. Fetal number is a primary contributor to fetal weight. Litter birth weight represents the culminated fetal growth of the litter and can be used to estimate the effect of fetal metabolism on energy requirements of the ewe. We hypothesized that litter weight in sheep would increase at a decreasing rate with increasing litter size. Birth weights of lambs born to yearling (11 to 15 mo) and mature ewes (> 34 mo) were collected on litters born to Dorset, Rambouillet, Suffolk, Finnsheep, Romanov, and Composite III ewes mated to produce straightbred lambs. Litter birth weight expressed as a function of litter size increased at a decreasing rate and the quadratic term differed from zero for mature Rambouillet, Suffolk, Finnsheep, Romanov, and Composite III litters (P < 0.042). The quadratic coefficient differed among breeds. In yearlings, litter weight increased at a decreasing rate for Suffolk ewes (P = 0.002). The quadratic term for the relationship between litter weight and litter size did not differ from zero for Finnsheep (P = 0.39) or Romanov litters (P = 0.07). The hypothesis that litter weight increases at a decreasing rate with increased litter size is supported by experimental results.     

Pregnancy‐Associated Glycoprotein Secretion in North Moroccan Goats

The plasma profile of pregnancy‐associated glycoprotein (PAG) and its relationship with fetal number were studied in 14 North Moroccan goats using a semi‐heterologous radioimmunoassay (RIA). Peripheral blood was collected every day during the first month of pregnancy, afterward the blood samples were collected trice a week. The PAG were first detected at day 20 of pregnancy, their levels increase to week 8 of gestation then decrease slightly until parturition. Statistical differences between goats carrying one or two foetuses are observed from week 5 of pregnancy until parturition. Factorial Discriminant Analysis provides mathematical models for the discrimination between the litter size using the PAG level and the week of pregnancy. Using only one blood sample per week, high sensitivity, specificity and overall accuracy (74%, 88% and 81%) were obtained using these models. It is concluded that the PAG RIA is an effective tool for early diagnosis of pregnancy and for discrimination between the litter sizes in North Moroccan goats.     

Cellular Remodelling by Apoptosis During Porcine Placentation

The mechanisms that regulate the apoptosis are essential to the normal development and maintenance of homoeostasis and play an important role in placental development in mammals. During porcine pregnancy, there must be a proper cellular remodelling to achieve a normal gestational development. Knowledge of pig physiology during pregnancy will explore options to increase the productivity of this species of high economical value. The purpose of this work was to study the cell morphology and apoptosis of porcine placentas from early, mid and late pregnancy. For that purpose, high‐resolution light microscopy and transmission electron microscopy were performed to the study of cell morphology. TUNEL, the apoptosis index (IAp) and the expression of c‐FLIP through immunohistochemistry technique were used to the study of apoptosis. High‐resolution light microscopy and transmission electron microscopy confirmed the presence of placental cells with ultrastructural apoptotic features. Apoptotic nuclei were detected by TUNEL in different placental structures and phagocytes containing apoptotic bodies. The IAp in villi was 9.34% at early, 0.82% at mid and 23.85% at late pregnancy. Statistically significant differences were found between periods (p < 0.05). In previous studies, we determined a differential induction of the apoptotic routes in the placental villi in agreement with the gestational period. A co‐expression of receptors and mitochondrial proteins in placental connective tissue was detected, but the immunolocalization of c‐FLIP would indicate an endogenous inhibition of the extrinsic pathway. In conclusion, in swine there exists differential activation of inducing apoptotic pathways in different placental structures according to the gestational period.     

Die Ultrastruktur der Meerschweinchen-Subplazenta

The significance of the subplacenta, a special organ present only in hystricomorphous rodents, is generally not known. In the present study of the ultrastructure of this organ the subplacentas of 35 conventional, domestic, genetically undefined guinea pigs during the 19th to the 65th day of their pregnancy were used. The subplacentas were fixed by immersionand studied histologically on semi-thin sections and by transmission electronmicroscopy. The findings clarify the development and regression of the maternal blood lacunae. Hereby wasshown that the subplacenta in none of its developmental stages was supplied simultaneouslyby maternal and fetal blood. The function of the subplacenta is seen in the preparation of anot yet identified but ultrastructurally visible secretion.     

Maternal selenium supplementation and timing of nutrient restriction in pregnant sheep: Impacts on nutrient availability to the fetus

To determine the effects of maternal Se intake and plane of nutrition during mid or late gestation or both on AA concentrations and metabolite concentrations in the dam and fetus, pregnant ewe lambs (n = 64) were assigned to 1 of 8 treatments arranged in a 2 × 2 × 2 factorial array: Se level [initiated at breeding; adequate (ASe; 3.05 μg/kg of BW) or high (HSe; 70.4 μg/kg of BW)] and nutritional level [100% (control; CON) or 60% (restricted; RES) of NRC recommendations] fed at different times of gestation [d 50 to 90 (mid) or d 91 to 132 (late)]. A blood sample was obtained from each ewe and fetus on d 132 of gestation and used to measure circulating concentrations of glucose, NEFA, blood urea N, and AA. The late RES ewes and their fetuses had less (P ≤ 0.03) circulating glucose compared with late CON ewes and fetuses at d 132; however, no effect (P ≥ 0.14) of diet on the fetal:maternal glucose concentration ratio was observed. Late RES ewes had a smaller (P = 0.01) fetal:maternal NEFA ratio compared with late CON ewes. Ewes fed ASe had a greater (P = 0.01) fetal:maternal blood urea N ratio compared with HSe ewes. Fetal:maternal ratios of total circulating AA, total essential AA, and total nonessential AA were each affected (P ≤ 0.03) by the combination of Se treatment and late gestation nutritional level.     

胎次与产仔数对广东小耳花猪初生仔猪均匀度的影响

初生仔猪均匀度常用窝初生个体均重的标准偏差及变异系数表示,是反映母猪孕期繁殖效率的重要指标之一。为了研究不同胎次及产仔数对初生仔猪均匀度的影响,研究对1011窝广东小耳花猪的历史分娩数据进行分析。结果表明:窝初生个体均重为0.67 kg,窝初生个体均重的标准偏差为0.13 kg,窝初生个体均重的变异系数为19%;窝初生个体均重与窝初生个体均重标准偏差的相关系数是0.296,呈极显著正相关(P约0.01);窝初生个体均重变异系数与总产仔数的相关系数是0.028,与产活仔数的相关系数为0.024,均呈现弱正相关。研究建议在地方猪开发利用中,合理调整群体胎龄结构,改善饲养管理方式,合理调整孕期母猪营养水平,进一步提高群体初生仔猪均匀度。     

Long-term, but not short-term, treatment with somatotropin during pregnancy in underfed pigs increases the body size of progeny at birth

Treatment of pigs with porcine ST (pST) in early to mid-pregnancy increases body weight and length of their fetuses by mid-pregnancy, but this increased weight may not persist to birth. We investigated the effects of short- (25 d) and long-term (75 d) treatment with pST, and interactions between long-term pST treatment and crude protein content of diet, in restricted-fed gilts. In both experiments, Large White x Landrace gilts were bred at first estrus to Large White x Duroc boars and allowed to farrow naturally. In the first experiment, gilts were fed 1.8 kg/d of a diet containing 13.5 MJ DE/kg of DM and 15.05% CP (as-fed basis) throughout pregnancy, and were injected daily with 0, 2, or 4 mg pST from d 25 to 50 of pregnancy. Maternal treatment with pST from d 25 to 50 of pregnancy did not affect the number of piglets born per litter or progeny size at birth. In the second experiment, gilts were injected daily with 0 or 2 mg of pST and fed 2.2 kg/d of a diet containing 14.5 MJ DE/kg and either (as-fed basis) 16.6% (0.81% lysine) or 22.2% CP (1.16% lysine) from d 25 to 100 of pregnancy. All gilts were then fed 3.0 kg/d of the lower protein diet from d 100 of pregnancy to farrowing. Treatment with 2 mg pST/d from d 25 to 100 of pregnancy increased live weight of all gilts during the treatment period (P = 0.016), but the change in maternal live weight from d 25 to 100 of pregnancy was only increased (P = 0.001) by pST in gilts fed the higher protein diet. Live weight of gilts 1 d after farrowing was increased by pST treatment (P = 0.007), but was not altered by protein content of diet during pregnancy. In gilts fed the lower protein diet, but not in those fed the higher protein diet, pST treatment decreased maternal backfat depth during treatment (P < 0.020) and 1 d after farrowing (P = 0.002). Treatment with pST during pregnancy did not affect the number of piglets born per litter but independently increased body weight by 11.6% (P < 0.001) and length by 3.4% (P = 0.005) of progeny at birth and decreased (P < 0.01) the negative effect of litter size on body weight at birth. We conclude that in feed-restricted gilts, fetal weight gains in response to 25 d of pST treatment before mid-pregnancy are not maintained to term but that treatment with pST during most of pregnancy increases progeny size at birth and reduces maternal constraint of fetal growth.