Normal development of fetuses resulting from Holstein semen processed for sex separation

Semen from two high fertility Holstein bulls with extensive histories in artificial insemination was specially processed for the purpose of sexing and then frozen. The semen was used to inseminate 200 open crossbred beef heifers carefully selected for reproductive soundness from a much larger group. Animals were inseminated alternately with the semen from one of the two bulls and subsequently slaughtered. There were 96 fetuses, ranging in age from 63 to 88 days, which were carefully examined for general appearance, fetal crown-rump length and body weight. There was no effect of sire on fetal size, but the difference between fetal sexes was significant, with the male fetus being appreciably heavier. The regression of fetal length on fetal age was linear and the regression of fetal weight on fetal age was curvilinear. Fetal age accounted for 92% to 96% of the variation in fetal weight and also in crown-rump length.     

In utero characterisation of fetal growth by ultrasound scanning in the rabbit

Fetal development is an important factor influencing the susceptibility of adults to metabolic diseases. In order to study the influence of fetal growth on further development in animal models like the rabbit, methods of measurement of fetal and placental size and viability must be established and validated. In this study, 42 New Zealand does bred naturally (N=12) or transferred with in vivo produced embryos (2, 4 or 6 embryos/doe) have been scanned every 2-3 days with a 7.5 MHz transabdominal probe from Day 7 post-coitum until term to measure fetal and placental growth. Vesicle, placental, fetal length and head size have thus been determined according to number of fetuses and time. In late gestation, the fetuses that were transferred in limited numbers to the uterus of does were significantly larger than their natural breeding counterparts probably due to reduced litter size.     

Development of predictive models for determining fetal age‐at‐length in belugas (Delphinapterus leucas) and their application toward in situ and ex situ population management

For wild belugas (Delphinapterus leucas), gestation length estimates based on fetal size have produced extreme ranges. Ex situ populations thereby provide unique opportunities to define this important life history event. Accordingly, research with ultrasound was conducted on six beluga whales over 11 gestations with known conception dates to serially measure fetal changes in biparietal diameter (BP), thoracic diameter (TD), thoracic circumference (TC), and total length (TL). Incremental polynomial regression analyses were performed on each fetal measurement to develop predictive models for determining age based on fetal size and days from parturition. Gestation length (n = 11) was a mean 467 ± 5.4 d with male calves (478 ± 8.6 d) experiencing a longer gestation (P = 0.04) than females (457 ± 3.9 d). Age at TL was best described using a 2nd order polynomial model, while linear relationships existed for BPD, TD, and TC. Accuracy was improved for predicting age (P = 0.001) or days prior to parturition (P = 0.038) using data from the first vs. the second half of gestation. The results provide accurate models for aging beluga fetuses based on size in both in situ and ex situ populations.     

Factors influencing lamb survival in a high fecundity Booroola Merino x South Australian Merino flock

The effects of year of lambing, age of ewe and litter size on lamb survival and birthweight, and the effects of ewe mating weight and pregnancy wastage (ovulation rate minus litter size) on birthweight were examined in Booroola Merino x South Australian Merino ewes. Year of lambing, litter size and their interaction were significant (P<0.001) sources of variation for lamb survival. When birthweight was included as a linear and quadratic covariate for lamb survival, year of lambing and litter size and their interaction remained as statistically significant sources of variation. Year of lambing, litter size and pregnancy wastage contributed significantly (P<0.05) to variation in birthweight. Ewe liveweight at mating was not an important source of variation (P>0.05). Birthweight was significantly (P<0.05) reduced with an increase in pregnancy wastage. Improvement of birthweight of multiple birth lambs has some potential for increasing lamb survival. Other factors influencing lamb survival (year of lambing, litter size, pregnancy wastage) require further study so that strategies for reducing lamb loss in high fecundity Merino flocks can be developed.     

Effect of grazing system on fetal development in Nellore cattle

Intensive grazing systems for beef females, based on abundant availability of high quality forages and supplementary concentrates, may affect fetal development. The objective of this study was to determine the effect of grazing system on length of gestation, fetal development, and characteristics of the calf at birth. Twenty-four pregnant (bred to Nellore bulls) Nellore females were allocated into two groups. The control group (G1) grazed Brachiaria decumbens (signal grass) in a traditional (extensive) grazing system and the second group (G2) were managed on Panicum maximumcv. Tanzania 1 (Tanzania grass) in an intensive grazing system. Fetal development was evaluated by ultrasonography on days 31, 45, 59, 94, 122, 220, and 255 of gestation. The diameter of the amniotic and allantoic cavities, crown-rump length, circumference, and diameter of the head and ocular orbit were determined. At birth, calves were weighed and height, length, thoracic circumference, and ocular orbit and bi-parietal diameters were measured. There were no differences (P > 0.05) in fetal development. The G1 cows had a longer gestation period (4.5 days; P<0.05) and their calves had greater (P<0.05) weight, height, length, and thoracic circumference at birth. In conclusion, Nellore females raised under intensive pasture management conditions, had significantly shorter gestation and smaller calves at birth than those raised under extensive pasture management conditions. Therefore, adoption of new management practices (e.g. intensive pasture management), should take into consideration animal behavior and productivity.     

Effect of nutrition during pregnancy on fetal growth and survival in Fec(B) Booroola x South Australian Merino ewes

The effect of nutritional manipulation during mid and late pregnancy on fetal growth and survival in high fecundity (Fec(B) Fec(+)) Merino ewes was examined. A total of 4 treatment groups was utilized in each of 3 years (1987, 1988 and 1989); and 2 groups were given low nutrition during mid pregnancy while 2 groups received high nutrition during this period. One group from each of these treatments subsequently received a high protein diet 1 to 2 weeks prior to term. Differential feeding during mid pregnancy resulted in the high and low treatment groups varying by 7.5 and 5.0 kg liveweight at Days 100 and 135 of pregnancy, respectively. Fetal survival was not improved by variation in nutritional intake during mid pregnancy (P>0.05) and neither were placental and fetal growth (P>0.05), as indicated by observations on cotyledon diameter and fetal head width, respectively. However, fetal survival during late pregnancy was reduced by a high level of nutrition during both mid and late pregnancy (P<0.05).     

Effect of equine chorionic gonadotropin on weaning-to-first service interval and litter size of female swine

We evaluated the effect of PMSG on the weaning-to-first service interval, total litter size and born alive litter size in swine. Four doses of PMSG (0, 500, 750 and 1,000 IU) were administered intramuscularly after weaning to sows at 3 different farms, grouped by parities (1, 2 and 3 or higher) and 2 distinct time periods. The associations among main effects and response variables were assessed by analysis of variance. Polynomial orthogonal terms were used to adjust the estimates of weaning-to-first service interval, total litter size and born alive litter size for the interaction effect of parity and PMSG treatment. The weaning-to-first service interval did not differ across periods and farms (P>0.05), although the interval was shorter (P<0.05) for Parity 3+ sows (4.97 d) than for Parity 1 sows (5.29 d), with no other differences in intervals observed across parities (P>0.05). Time period did not influence litter size (P>0.05), but there were differences in litter size across farms (P<0.05). Both litter size traits were lower for Parity 1 sows than for higher parity sows (P<0.05), but there were no differences in litter size between Parity 2 and 3+ sows (P>0.05). Litter size increased with PMSG dose in both Parities 1 and 2 (P<0.05), but not in Parity 3+ (P>0.05). A significant quadratic effect (P<0.05) of PMSG treatment in weaning-to-first service interval was observed for both Parity 1 and 2 sows, with the shortest intervals occurring with the 750 IU dose for Parity 1 sows. Administration of PMSG after weaning was associated with a shortened weaning-to-first service interval in Parity 1 sows and increased litter size in Parity 1 and 2 sows.     

The influence of parity and maternal preimmunization on fetal survival in mice

It is known that as parity increases, cell-mediated immunity to paternal antigens increases in mice. The article reports an experiment designed to compare the results of normal parity with artificial immunization simulating maternal sensitization to paternal antigens in mice. Virgin females were immunized at weekly intervals by intraperitoneal injections of 50 mcl of heparinized blood from males with whom they would eventually be mated. The immunized virgins and multiparous females were mated for 4 to 6 weeks after their last injection or litter. The total and live litter size increased with immunization; the total size with natural parity also increased though the live litter size slightly decreased with parity. The mean fetal death rate was relatively the same for both groups. Fetal weight increased with parity but not change was observed in placental weight. Both fetal and placental weight did not change with immunization. There was no increase in the expected number of male fetuses. The increased litter size in the immunized group may be due to increased ovulation rates.     

Growth and development of the Tasmanian devil (Sarcophilus harrisii) at Healesville Sanctuary,Victoria, Australia

A study of the growth and development of the Tasmanian devil (Sarcophilus harrisii) was undertaken on a litter born at Healesville Sanctuary in Healesville, Victoria, Australia. Measurements of crown–rump length, head length, and head width were recorded every week from birth. Body weight was recorded weekly once the joeys were detached from the teat at 142 days of age, until 218 days of age. The growth curves revealed an initial linear increase in crown–rump lengths until approximately 60 days of age, when the gradient increased, while head length and head width showed a largely linear increase with age. The appearances of various morphological characteristics were also recorded. Zoo Biol 22:497–505, 2003. © 2003 Wiley‐Liss, Inc.     

The effect of age on the morphometric sperm traits of domestic pigs (Sus scrofa domestica)

The experiment was conducted using 20 male domestic pigs, which were in 2 (equal-sized) age groups: under 14 months old and over 18 months old. At least 5 ejaculates from each male were taken, and in each ejaculate, morphometric measurements of 50 spermatozoa were made. The measured parameters were head area, head length and width, and flagellum length. For each ejaculate, the basic physical traits and the frequency of occurrence of developmental anomalies of the spermatozoa were examined. It was found that sperm dimensions tended to increase along with the boars' age. Considerable and statistical differences in head area and flagellum length were proved. Spermatozoa collected from older boars (above 18 months of age) had a head area larger by 0.49 microm(2)(P< or = 0.01) and a flagellum longer by 0.67 microm (P< or =0.01) than spermatozoa collected from younger boars (under 14 months of age). The differences in head length and width between the spermatozoa of the tested boars were considerably smaller and were not statistically provable. Significant correlations between the head area of spermatozoa and the head length (r = 0.56, P< or =0.05) and head width (r = 0.36, P< or =0.05) were found. However, the head length was not significantly directly correlated with its width (r = 0.18, P< or =0.05), and flagellum length was negatively correlated with spermatozoan head width (r = -0.71, P< or =0.05). Slight correlations between the morphometric traits of the sperm and the physical traits of the ejaculates (r = -0.11 to 0.16) were found, although in most cases, the correlations were not statistically provable.     

Newborns of Preeclamptic Women Show Evidence of Sex-Specific Disparity in Fetal Growth

BackgroundEvidence suggests that in response to in utero insults, male versus female infants have greater disadvantages in pregnancy outcome. In addition, there is a growing body of evidence suggesting that there is a sex-specific fetal response to maternal disease during pregnancy. We considered that a sex-specific relationship may exist between preeclampsia and reduced fetal growth.ObjectiveWe investigated if the relationship between preeclampsia and fetal growth was modified by fetal sex.MethodsWe limited the study population to singleton pregnancies of black and white normotensive and preeeclamptic women enrolled in the Collaborative Perinatal Project (1959–1965). The patients were offspring of 516 preeclamptic and 8801 normotensive women. After adjustment for confounders, interaction terms between preeclamptic status and fetal sex were evaluated to determine if the influence of preeclampsia on fetal growth varied with fetal sex. Separate linear and logistic regression models were then fitted for males and females to report the estimate of the relationship between preeclampsia and fetal growth by fetal sex. The results were stratified by preterm status (<37 vs ≥37 completed weeks of gestation). The mean head and chest circumferences, birthweight, ponderal index, and frequency of small for gestational age were examined. A 2-sided P value of <0.05 was considered statistically significant.ResultsThe results were stratified by preterm status. Male preterm offspring of preeclamptic mothers had greater reductions in chest circumference, head circumference, and birthweight than preterm female offspring of preeclamptic women (P = 0.01, P = 0.02, and P = 0.05, respectively, for interaction). Female versus male preterm offspring exposed to preeclampsia were less susceptible to being small for gestational age (synergy index 0.38; 95% CI, 0.00–0.84). The influence of preeclampsia on the growth of term offspring was more modest, and the influence of sex was opposite that in preterm infants. Compared with term offspring of normotensive women, the reduction in mean ponderal index was greater for female versus term male offspring of preeclamptic women (P = 0.02, interaction).ConclusionFetal growth was more impaired among male versus female preterm infants born to preeclamptic women. Our study underlined the importance of incorporating sex differences in the study of biological mechanisms for immediate- and long-term consequences of suboptimal fetal growth.     

兴安落叶松林生物量、地表枯落物量及土壤有机碳储量随林分生长的变化差异

有关生物量碳随林分生长变化研究较多,而相关土壤有机碳储量随林分生长变化研究较少且结论争议较大。通过对二者随林分生长变化差异的比较,旨在探讨是否可以通过简单林分生长指标来判断土壤有机碳的变化规律。对兴安落叶松人工林分布区内139个样地的生物量与土壤碳动态研究结果表明:(1)林龄是指示生物量碳累积的可靠参数。兴安落叶松个体大小(胸径、树高和单株生物量)随着林龄的增大不断增加,相关性显著(P<0.001),而林分生物量密度随林龄的增大呈线性上升(R²=0.2-0.6,P<0.001)。(2)地表凋落物量与林龄表现显著的二次曲线相关,前37a上升而后开始下降。地表凋落物量与林木大小、生物量密度均相关显著(R²=0.14-0.82,P<0.001),但与树高相关性最高,显示树高变化对于评价地表枯落物生物量可能更有效。(3)林龄、林木大小和林分生物量密度均与土壤不同层碳存在相类似的相关关系。深层土壤有机碳(>40cm)与林龄显著负相关(P<0.05),表层土壤有机碳有增加趋势 (P>0.05),这使得0-40 cm与40-80 cm土壤有机碳储量比值随林龄增加而显著增加(P<0.01);与此类似,林木平均大小也与深层土壤有机碳显著负相关(P<0.05),而表层与深层有机碳储量比值随林木大小(胸径与树高)的增大也呈显著上升趋势(P<0.05);但同时考虑林木个体大小和林分密度的林分生物量密度(地上和地下),并没有发现明显的显著相关关系。这些结果说明,评价土壤有机碳变化的指标中,林龄、树高和胸径可能更优于较为复杂的生物量密度等指标。考虑到深层土壤较表层具有更长期的稳定性,这种表层与深层土壤有机碳比值的增加,意味着土壤碳有向表层积聚而深层减少的趋势,这可能使得土壤有机碳更容易受外界环境变化(如火灾等)的影响。落叶松人工林群落碳储量随林龄增加的变化规律明显,除了占主要部分的生物量碳之外,土壤碳累积值得关注,这一发现对于以固碳增汇为目标的碳汇林建设具有指导意义。     

Maternal age and parity influence ultrasonographic measurements of fetal growth in Dutch Warmblood mares

Ultrasonographic examination of the equine fetus in mid-late gestation is usually performed only if there are concerns about fetal or maternal health. Even then it is difficult to determine whether development is ‘normal’ for gestational age because the reference values include considerable error margins. This study examined maternal factors that influence fetal growth with the aim of producing more precise late gestation fetal growth curves for Dutch Warmblood horses. Fetal development was monitored at 2-week intervals from day 100 of gestation until term in 32 mares ranging from 4 to 18 years in age; seven of the mares were primiparous. Transrectal and/or transabdominal ultrasonographic measurement of the fetal eye orbit, cranium, aorta, heart rate and of the combined thickness of uterus and placenta (CTUP) were performed using a portable ultrasound machine equipped with 6 MHz linear and 3.5 MHz curved array probes.During days 100–250 of gestation, the CTUP was thicker in primiparous than multiparous mares (p < 0.05). After day 220 the maximum cross-sectional area, but not diameter, of both the eye orbit and cranium were also greater in primiparous than multiparous mares (p < 0.05). Fetal aorta diameter was not influenced by parity but was affected by maternal age, being smaller in mares ≥15 years of age than younger animals (p < 0.05). Only biparietal cross-sectional surface area and aorta diameter increased linearly throughout late gestation. However, even allowing for the effects of parity and maternal age, the late gestational variation in fetal size is such that serial measurements may be required to definitively identify abnormal development.     

Effect of birth litter size, birth parity number, growth rate, backfat thickness and age at first mating of gilts on their reproductive performance as sows

The present study was performed to evaluate retrospectively the influence of birth litter size, birth parity number, performance test parameters (growth rate from birth to 100kg body weight and backfat thickness at 100kg body weight) and age at first mating (AFM) of gilts on their reproductive performance as sows. Traits analysed included remating rate in gilts (RRG), litter size, weaning-to-first-service interval (WSI), remating rate in sows and farrowing rate (FR). Data were collected from 11 Swedish Landrace (L) and 8 Swedish Yorkshire (Y) nucleus herds and included 20712 farrowing records from sow parities 1-5. Sows that farrowed for the first time during 1993-1997, having complete records of performance test and AFM, were followed up to investigate their subsequent reproductive performance until their last farrowing in 1999. Analysis of variance and multiple regression were applied to continuous data. Logistic regression was applied to categorical data. The analyses were based on the same animals and the records were split into six groups of females, i.e. gilts, primiparous sows, and sows in parities 2-5, respectively. Each additional piglet in the litter in which the gilt was born was associated with an increase of her own litter size of between 0.07 and 0.1 piglets per litter (P<0.001). Gilts born from sow parity 1 had a longer WSI as primiparous sows compared with gilts born from sow parity 4 (0.3 days; P<0.05) or parity 5 (0.4 days; P<0.01). Gilts with a higher growth rate of up to 100kg body weight had a larger litter size (all parities 1-5; P<0.05), shorter WSI (all parities 1-5; P<0.05) and higher FR (parities 2 and 5; P<0.05) than gilts with a lower growth rate. Gilts with a high backfat thickness at 100kg body weight had a shorter WSI as primiparous sows (P<0.001) compared with low backfat gilts, and 0.1 piglets per litter more as second parity sows (P<0.01). A 10 day increase in AFM resulted in an increase in litter size of about 0.1 piglet for primiparous sows (P<0.001) and a decrease (P<0.05) for sow parities 4 and 5.     

Influence of induced delayed parturition on fetal survival in pigs

Pregnancy was prolonged as long as 23 days in gilts receiving daily oral 6-methyl-17 acetoxy-progesterone (MAP) at a level of 0.27–0.41 mg/kg body weight. These levels of progestin did not effect fetal welfare if administered throughout gestation and did not interfere with normal parturition and live litter size if treatment was terminated at the calculated term date which corresponded with the day of milk let-down. The initiation of milk let-down was not effected by treatment. Severe fetal death occurred in all gilts delivering young naturally during prolonged pregnancy and in gilts whose litters were delivered surgically 12 days or more after milk let-down. Mean live litter size was normal in gilts whose young were delivered surgically within 11 days of milk let-down. Fetal death at 12 days or more of prolonged pregnancy was attributed to placental insufficiency. The reproductive parameters studied were unaffected by the addition of 0.001 to 0.013 mg/kg body weight of diethylstilbestrol (DES) to the progestin treatment or the use of this agent alone.     

Doppler ultrasonographic assessment of maternal and fetal blood flow in abnormal canine pregnancy

The aim of this study was to describe the changes of uterine artery, umbilical artery and fetal abdominal aorta, renal and internal carotid arteries blood flow in abnormal canine pregnancy. Twenty-two, Brucella-negative pregnant bitches were retrospectively classified into abnormal (which had either interrupted their pregnancy between days 52 and 60 or had perinatal death >60% of the litter; n=11) and normal (which had delivered healthy puppies at term; n=11). In all the animals, color and pulsed-wave Doppler examinations of uterine artery were conducted every 10 days from Day 20 to 50 from estimated luteinizing hormone peak. Doppler ultrasonography was also conducted in the fetuses to assess umbilical artery, abdominal aorta, renal and internal carotid arteries from Day 40 to 60 of gestation. Throughout the study, resistance index (RI) of uterine, umbilical and fetal renal arteries decreased up to -15% compared to -36% (P<0.01), -11% compared to -23% (P<0.05) and 2% compared to -13% (P<0.05), respectively in the abnormal and normal bitches. Fetal abdominal aorta and internal carotid did not differ between groups (P>0.05). It is concluded that in dogs, uterine artery, umbilical artery and fetal renal artery RI differ between normal and abnormal gestation being useful for the prediction of adverse obstetric outcome.     

Frozen-sectioning yields similar results as traditional methods for fetal cephalic examination in the rat

BACKGROUND: An integral component of developmental toxicity studies is the evaluation of fetal anatomy, which consists of external, visceral, and skeletal examinations. The visceral examination includes an assessment of the fetal head which, in the rat, is typically completed after chemical fixation. Because chemical fixation requires approximately 7 days, a comprehensive visceral examination, including the head, of the fetal rodent cannot be completed at the time of cesarean section. An alternative method to chemical fixation was desired, whereby one could complete an overall visceral examination at the time of cesarean section. In addition, the method would also have to present fetal cranial structures in a manner consistent with that derived after chemical fixation. METHODS: Pregnant Sprague-Dawley rats were administered either 6-aminonicotinamide (6AN), 6 or 12 mg/kg on gestation day 13, or all-trans retinoic acid (RA) 5 or 25 mg/kg on gestation days 9 and 10, untreated dams served as a control group. On gestation day 20, fetuses were sacrificed and removed via cesarean section and one-half of the fetuses from each litter were placed in Bouin's solution (chemical fixation) and the remaining fetuses maintained under refrigeration until just before frozen tissue preparation (freeze fixation). Sectioning of the fetal head was similarly conducted after either chemical or frozen-fixation. Fetal cranial findings observed after chemical fixation were compared to those observed after frozen-fixation in the untreated control and 6AN and RA-treated groups. RESULTS: The incidence and severity of the cranial findings, including effects on the eye, brain, and palate, were similarly observed, regardless of fixation method. CONCLUSIONS: A frozen sectioning method for evaluation of the fetal head, yielding results comparable to those derived after chemical fixation, is described. This procedure provides a viable alternative to chemical fixation, and allows the teratologist to complete a comprehensive fetal visceral examination at the time of cesarean section.     

Growth characteristics of the fetal ligament of the head of femur: significance in congenital hip disease.

Measurement of the length and width of the ligament of the head of femur (ligamentum teres) in 140 normal human fetuses between 12 weeks and term provides limits for growth changes in this structure. These observations provide no morphological evidence of a significant difference between males and females, or between the right and left sides, to explain the female and left hip preponderance reported in congenital hip disease. The ligament is shown to be variable in length, width, and shape, and it is not a distinctly linear structure through linearity may increase with age. Tests of femoral head mobility support the opinion that this ligament must play a role in fetal and neonatal hip joint stability. Weak correlation only was demonstrated between the ligament variables and acetabular depth, which suggests that ligament shape and socket shape are not closely related. Comparison of measurements from normal and 12 dysplastic or subluxated joints provides no evidence to support previous observations that this structure is unusually long in abnormal hip joints which are not frankly dislocated.     

An association analysis of sow parity,live-weight and back-fat depth as indicators of sow productivity

Understanding how critical sow live-weight and back-fat depth during gestation are in ensuring optimum sow productivity is important. The objective of this study was to quantify the association between sow parity, live-weight and back-fat depth during gestation with subsequent sow reproductive performance. Records of 1058 sows and 13 827 piglets from 10 trials on two research farms between the years 2005 and 2015 were analysed. Sows ranged from parity 1 to 6 with the number of sows per parity distributed as follows: 232, 277, 180, 131, 132 and 106, respectively. Variables that were analysed included total born (TB), born alive (BA), piglet birth weight (BtWT), pre-weaning mortality (PWM), piglet wean weight (WnWT), number of piglets weaned (Wn), wean to service interval (WSI), piglets born alive in subsequent farrowing and sow lactation feed intake. Calculated variables included the within-litter CV in birth weight (LtV), pre-weaning growth rate per litter (PWG), total litter gain (TLG), lactation efficiency and litter size reared after cross-fostering. Data were analysed using linear mixed models accounting for covariance among records. Third and fourth parity sows had more (P<0.05) TB, BA and heavier BtWT compared with gilts and parity 6 sow contemporaries. Parities 2 and 3 sows weaned more (P<0.05) piglets than older sows. These piglets had heavier (P<0.05) birth weights than those from gilt litters. LtV and PWM were greater (P<0.01) in litters born to parity 5 sows than those born to younger sows. Sow live-weight and back-fat depth at service, days 25 and 50 of gestation were not associated with TB, BA, BtWT, LtV, PWG, WnWT or lactation efficiency (P>0.05). Heavier sow live-weight throughout gestation was associated with an increase in PWM (P<0.01) and reduced Wn and lactation feed intake (P<0.05). Deeper back-fat in late gestation was associated with fewer (P<0.05) BA but heavier (P<0.05) BtWT, whereas deeper back-fat depth throughout gestation was associated with reduced (P<0.01) lactation feed intake. Sow back-fat depth was not associated with LtV, PWG, TLG, WSI or piglets born alive in subsequent farrowing (P>0.05). In conclusion, this study showed that sow parity, live-weight and back-fat depth can be used as indicators of reproductive performance. In addition, this study also provides validation for future development of a benchmarking tool to monitor and improve the productivity of modern sow herd.     

Polymorphism of FecB Gene in Nine Sheep Breeds or Strains and Its Effects on Litter Size, Lamb Growth and Development

Nine sheep breeds or strains, including 615 individuals were screened with forced PCR RFLP method for the FecB gene to study the polymorphism and its effects on litter size, body weight and body size. Results showed that the polymorphism frequencies of FecB gene were significantly imbalanced in these breeds or strains. The Hu sheep were all homozygous carriers of FecB gene(BB). In the Chinese Merino prolific meat strain, the genotype frequencies of BB, B+ and ++ were 51%, 30% and 19%, respectively, whereas all the other flocks had only the wild-type (++) genotype. Results within the Chinese Merino prolific meat strain showed that the mean litter size of ewes with genotype BB and B+ were 2.8 (±0.74) and 2.3 (±0.63) (P<0.05). whereas ++ genotype ewes had a litter size of only 1.2 (±0.68) (P<0.01). At day 90 after birth, the body weights of BB/B+ genotype lambs were higher than that of ++ genotype lambs (18.6±3.70 kg. 18.0±3.71 kg vs 15.6±2.22 kg, P<0.05). In addition, the heart girth and chest width of BB/B+ genotype lambs were significantly longer than those of the ++ lambs (P<0.05). No significant differences were observed in either body weight or body size at day 120. Litter size at first lambing from Hu at Natural Source Conservative Region was found to be significantly higher than that from the other two regions sampled (P<0.05). In addition to the additive effect on litter size, these findings showed for the first time that the FecB gene had a positive effect on early postnatal body growth.