Ram Effect Research Articles

The effect of heterologous seminal plasma from ram, buck or camel on the freezability of ram semen

Here, we compared the effects of ram, buck and dromedary camel seminal plasma mixed with TRIS-egg yolk glycerol extender on the freezing preservation of ram semen. Awassi ram semen samples underwent primary evaluation and were then pooled and diluted with the following diluents: TRIS-egg yolk glycerol mixed with (1) whole ram semen as a control (T); (2) ram sperm after seminal plasma removal (W); or (3) ram, (4) buck or (5) camel seminal plasma (R, B and C, respectively). The diluted semen was frozen using liquid nitrogen vapor. Various sperm parameters were evaluated in the frozen semen. Total motility before and after freezing was significantly higher in R, B and C diluents than in T and W diluents. Progressive motility after freezing was significantly higher in R, B, C and T diluents than in W diluent. Vitality after freezing was significantly higher in B than in W diluent. DNA fragmentation before and after freezing was significantly lower in R, B, C and T diluents than in W diluent. Plasma membrane integrity before and after freezing was significantly higher in R, B and C diluents than in W diluent. Sperm abnormalities before freezing were significantly lower in R, B and C diluents than in W diluent. Malondialdehyde concentration was significantly higher in T and W diluents than other diluents. Reduced glutathione concentration was significantly higher in B diluent than other diluents. Moreover, reduced glutathione concentration was significantly higher in C, R and W diluents than in T diluent. Thus, the addition of ram, buck or camel seminal plasma to TRIS-egg yolk glycerol extender improved the quality of frozen ram semen, while seminal plasma removal adversely affected it. Ram, buck and camel seminal plasma had similar effects, with no significant differences between them on the evaluated parameters of frozen ram semen.

FSI simulation of hydrodynamic ram event using LS-Dyna software

In this study, the effects of hydrodynamic ram on a fuel tank are studied using finite element method. Considered fluid-structure interaction (FSI) problem is solved in an Eulerian-Lagrangian reference frame by using LS-Dyna software. By comparing of the results obtained from the simulations and the experimental data, it can be seen that LS-Dyna software is able to model the different phases of hydrodynamic ram event accurately. Also, comparison of the wall Von Mises stress contours for the fluid-filled tank and the empty tank signifies 30% growth of the maximum Von Mises stress in the wall of the fluid-filled tank compared to the maximum Von Mises stress generated in the wall of the empty tank. In addition, numerical results show that because fluid-filled tank walls are pre-stress due to the fluid shock waves; failure mode of fluid-filled tank is quite different with the failure mode of the empty tank. Finally the effect of variation of parameters such as bullet velocity, tank elastic modulus and fluid density on maximum stress generated on tank was investigated.

Treatments with eCG and courtship behaviour in rams during the breeding and the non-breeding seasons

Equine chorionic gonadotrophin (eCG or PMSG) is a hormone with FSH/LH effect that has been widely used in ewes and cows to induce follicle development. However, the possible positive effects of its administration to males have been rarely studied. ECG stimulates testosterone secretion and increases rams’ ability to stimulate ovulation in anoestrous ewes (the ‘ram effect’), but it is still not known if this effect is at least partially explained by an enhancement of a ram’s sexual behaviour. Thus, the aim was to determine if the administration of eCG induces an increase in testosterone concentration, and thus improves sexual behaviour of Saint Croix rams during both the breeding and the non-breeding seasons. Two doses of 1000 IU of eCG were administered separated by 4 days to 10 rams during the breeding and five rams during the non-breeding seasons, with the same number of animals as untreated controls. Administration of eCG increased testosterone concentration during the breeding (P = 0.008) and the non-breeding (P = 0.0009) seasons. The number of ano-genital sniffings, lateral approaches, as well as total courtship behaviours were greater in treated than untreated rams during the breeding season. Treated rams also tended to mount and mate more during the breeding season. During the non-breeding season, treated rams tended to display more ano-genital sniffs, lateral approaches and total courtship behaviours than untreated rams 6 days after the first dose. Overall, eCG increased testosterone concentrations the breeding and the non-breeding seasons, and was associated with a greater display of sexual behaviours during the former.

Effects of short-term administration of a glucogenic mixture at mating on feed intake, metabolism, milk yield and reproductive performance of lactating dairy ewes

The effects of the intra-ruminal dosing of a glucogenic mixture including 70% glycerol, 20% propylene glycol and 10% water was studied on thirty late lactation dairy ewes of Sarda breed. The animals were divided in two homogeneous groups receiving by gavage either 200 mL of water (CTR group; body weight 40.9 ± 1.5 kg) or 200 mL of the above mixture (GLY group; body weight 39.4 ± 1.3 kg) twice daily from d 16 to d 19 of the oestrus cycle, synchronised by “ram effect”. The ewes were then mated and their reproductive responses to the synchronised mating evaluated by scanning on d 50 and at lambing. During the treatment, the ewes were housed in an open hut, machine milked twice daily and fed concentrate and hay to meet their nutrient requirements. During the treatment, concentrate intake was markedly reduced in GLY when compared with CTR (P < 0.001), without any effect on ewe body weight or body condition. The administration of the glucogenic mixture increased plasma osmolarity and blood volume as estimated by serum total protein concentration. Moreover, it increased plasma content of glycerol, glucose (P < 0.001) and insulin (P < 0.01) while decreasing plasma level of NEFA (P < 0.001) and urea (P < 0.05). Milk yield (P < 0.01) and milk lactose content (P < 0.001) were decreased by the glucogenic treatment, whereas milk protein and casein contents were increased (P < 0.001). As for reproductive performance, the glucogenic treatment numerically increased ewe’s conception rate, but the difference was not statistically significant. Prolificacy did not change between groups. In conclusion, the administration of a glucogenic mixture to late lactation dairy ewes caused significant changes both in plasma and in milk composition during the treatment. However, reproductive performances were unaffected by the treatment.

Experimental analysis of an attenuation method for Hydrodynamic Ram effects

The Hydrodynamic Ram (HRAM) phenomenon occurs when an object with a high-kinetic energy impacts against a fluid-filled structure, which could induce important damages. An attenuation technique would be of great interest for structures which could be subjected to impact. In this work, honeycomb panels are used to fill the entire space inside the structure in such a way that they are able to alleviate the loading onto it. Experimental tests were carried out varying aluminium honeycomb cells orientation, to determine the configuration that mitigates more efficiently the effects of HRAM comparing the results with a non-protected structure. The experimental tests were analysed using a high speed video camera, strain gauges, residual displacement of the structure walls and the deformation of the honeycomb panels. It is shown that for all the configurations, the honeycomb is able to reduce the plastic deformation of the structure. The honeycomb allows to reduce the cavity expansion in the fluid, which is the most dangerous phenomenon in the studied cases. The best configuration is able to diminish up to 54% the residual expanded volume in the structure walls, and hence considerably attenuating the HRAM effect on the structure.

Follicular size, luteinizing hormone (LH), and progesterone (P4) levels in postpartum Santa Inês ewes subjected to ram effect combined with suckling interruption

The objective was to evaluate the role of ram effect combined with temporary weaning on P4, LH, follicular size and reproductive performance of hair ewes during postpartum. Pluriparous Santa Inês ewes (n = 99) during 15 to 30 days postpartum were selected and isolated from rams for an additional period of 30 days. Before exposure to rams, ewes were allocated to experimental groups, where on SI0, no suckling interruption was performed, and in SI24 and SI48, suckling interruption was performed for 24 and 48 hours, respectively. Mean P4 was according to anestrus condition before the introduction of rams, and it reached cyclicity levels after contact between genders. Ewes displaying a single estrus were more frequent in SI24 than SI48 (P 〈 0.05). The LH pre-ovulatory peaks were detected within 44 hours and 60 hours after introduction of rams, irrespectively of the group. Ovulatory follicles reached a more significant size in SI24 than SI0 and SI48 (P < 0.05). Pregnancy rates differed at first service since SI24 was higher than SI48. Moreover, prolificacy was similar among groups (P 〉 0.05). Ram effect combined with temporary weaning for 24 hours is more efficient for Santa Inês reproduction, since it leads to larger ovulatory follicle size, increased the P4 level and higher pregnancy rate at first service.

Conceptus loss in Santa Inês ewes carrying twin pregnancies by natural mating or embryo transfer

Commercial application of reproductive biotechnologies such as multiple ovulation and embryo transfer depends on its overall efficiency. Sheep embryo transfer is gradually gaining wider adoption, but pregnancy rates after embryo transfer remain lower than those derived from natural mating for most breeds. The work was aimed to evaluate embryonic and fetal losses in Santa Inês ewes carrying twin pregnancies by natural mating or embryo transfer. Ewes were subjected to synchronized natural mating by ram effect or used as recipients for embryo transfer. Ewes diagnosed as carrying twin pregnancies at day 25 were used in the experiment (n = 42). Conceptus viability was monitored by ultrasonography on days 30, 35, 40, 45, 50, and 55 after conception. Conceptus loss was similar (P > 0.05) within natural mating 11/42 (26.19%) and embryo transfer 14/42 (33.34%). However, overall embryonic loss (80.0%) was greater (P < 0.05) than fetal loss (20.0%), with no difference within groups The results allow the conclusion that conceptus loss after embryo transfer is similar to natural mating and occurs predominantly during the embryonic stages.

Experimental investigation on dynamic failure of water-filled vessel subjected to projectile impact

In this investigation, a series of experiments are performed to study the deformation and failure of fluid-filled vessel subjected to high speed impact loading. The water-filled vessel with aluminum alloy target panels were impacted by the projectiles at the initial velocities of 100–300 m/s. Three different kinds of projectiles were considered to investigate the influence of nose shape of projectile on the failure modes of the water-filled tank. The high-speed photography was used to record the process of the projectile moving and the formation of cavity in water. The strain histories of target panels were measured by using the strain gauges. The results indicate that the hydrodynamic ram effect in the water-filled tank increased the damage of the target panels. The deformation of panels increased with the projectile nose coefficient (caliber-radius-head, CRH) increasing. The deformation and failure of the rear panel were more serious than those of the front panel. Additionally, the typical failure modes of the panels could be subdivided into three modes. The relationship between the kinetic energy and CRH value of the projectiles and the deformation of the panels was established.

Impact of thyroid status on the response to ram effect in ewes

The role of thyroid hormones on the transition to anestrous has been well established in ewes, but their possible involvement in the induction of reproductive activity remains obscure. The aim of the present study was to investigate the role of thyroid hormones in the induction of the first ovulation in relation to "ram effect" in ewes. Fourty-four ewes of the Greek Zackel mountain type breed were used. The ewes were housed separately from the rams until day 0 (entrance of rams). Blood samples were collected weekly for 4 weeks until 11 weeks after the ram entrance for the determination of thyroxin and progesterone levels. Thirty-five out of 44 ewes (group A) had a silent heat, while the rest 9 ewes (group B) exhibited a delayed estrus. Thyroxin levels rose immediately after ram entrance in animals of group A, but in group Β the increase in thyroid hormone levels was evident only after the first week. The difference in T4 levels between week 0 and 1 for ewes of group A was significantly higher than that observed for animals of group Β (p&lt;005). The pattern of progesterone release was similar between the two groups, but a two week delay in the increase of progesterone concentration was observed in animals of group Β compared to group A. It is concluded that thyroid hormones may act at the beginning of the breeding season to cause a modification in gonadotrophin secretion leading to early ovulation.

The effect of service ram on reproductive performances and birth weight of lambs

The investigation was conducted in population of Mis breed of sheep, divided into three groups. For reproduction had use rams of Ile de France breed. Induction and synchronization of oestrus was done off-season in October. The percentage of lambing sheep, sheep fertility, and number of lambs acquired per father, sex and birth type of lambs were observed. Ram 1 had a highest number of ewes lambed with an excellent percentage of mating success and highest fertility rate of ewes with differences on fertility rate of 17% (between group of ewes in ram 1 and ram 2), 36% (group of ewes in ram 1 and ram 3) and 19% (group of ewes in ram 2 and ram 3).The highest birth weight were on lambs born single from ram 3, born twins from ram1, triplets of ram 3. For the lambs born quadruplets (unfortunately only in rams 1 and 2 with one lamb of each was alive) the lamb of ram 2 was higher in birth weight. The male and female lambs of ram 3 got the highest birth weight while the female lambs of ram 1 acquired the lowest birth weight. The highest average birth weight of lambs was born single, male; born triplets? male from lambs of ram 3 having an average birth weight of 6.36kg and 4.0 kg but got the lowest for lambs born twins on female lambs 3.66 kg. The male lambs of ram 1 got the highest average birth weight on lambs born twins with an average birth weight of 4.38 kg but the lowest on triplets born 3.3kg. Unfortunately only one each of the two ram with lambs born quadruplets alive both male and the higher was that lamb of ram 2 with a birth weight of 3.3 kg. Result showed the influence of ram on number of lambs born and lambs? birth weight. Between subject effects Father* birth type showed a significant effect on birth weight of lambs.

The Two Populations of Kisspeptin Neurons Are Involved in the Ram-Induced LH Pulsatile Secretion and LH Surge in Anestrous Ewes.

Exposure to a ram during spring stimulates luteinizing hormone (LH) secretion and can induce ovulation in sexually quiescent ewes ("ram effect"). Kisspeptin (Kiss) present in the arcuate nucleus (ARC) and the preoptic area (POA) is a potent stimulators of LH secretion. Our aim was to investigate whether Kiss neurons mediate the increase in LH secretion during the ram effect. With double immunofluorescent detection, we identified Kiss neurons (Kiss IR) activated (Fos IR) by exposure to a ram for 2 hours (M2) or 12 hours (M12) or to ewes for 2 hours (C). The density of cells Kiss + Fos IR and the proportion of Kiss IR cells that were also Fos IR cells were higher in M2 and M12 than in C in ARC (P < 0.002) and POA (P < 0.02). In ARC, these parameters were also higher in M12 than in M2 (P < 0.02 and P < 0.05). Kiss antagonist (P234 10-6M) administered by retrodialysis in POA for 3 hours at the time of introduction of the ram reduced the amplitude of the male-induced increase in LH concentration compared with solvent (P < 0.02). In ARC, P234 had a more limited effect (P < 0.038 1 hour after P234) but pulse frequency increased less than after solvent (P = 0.07). In contrast, Kiss antagonist (P271 10-4M) infused in ARC but not POA 6 to 18 hours after introduction of the ram prevented the LH surge in the ewe (0/6 vs 4/5 and 4/6 in C). These results suggest that both populations of Kiss neurons are involved in the ram-induced pulsatile LH secretion and in the LH surge.

Failure prediction of composite T-joints for hydrodynamic ram test

The wing structure of an aircraft also served as a fuel tank containing fluid. The fuel tank and joint structure are made up of composite structures. Hydrodynamic ram (HRAM) effect occurs when the explosion or high speed object passes through the aircraft wing and high pressure is generated in the fuel tank. High pressure can cause failure in the fuel tank and on joint structure as well as other aircraft wing structures. To ensure the aircraft survivability design, we shall examine the behavior of the joint structures in HRAM effect. In this study, static tensile tests were conducted on four kinds of composite T-joints. The failure behavior of the composite T-joints was examined using strain gauges and high speed camera. The failure stresses and failure pressure of the composite T-joints were calculated by FEA. We also examined the validity of the Finite element modeling by comparing the results of FEA and static tensile tests.

Progesterone concentration and lambing rate of Karakul ewes treated with prostaglandin and GnRH combined with the ram effect during breeding and non-breeding seasons

The combination of ram effect with two injections of PGF2α 10-days apart and the same protocol plus an additional injection of GnRH prior to the first injection of PGF2α were examined in Karakul ewes during breeding and non-breeding seasons, respectively. Plasma progesterone (P4) concentrations (to detect the presence of active corpus luteum), twin lambing, litter size and synchronization of lambing were evaluated. In each study 70 ewes (2–4 years old) were divided to a treatment (n = 40) and a control (n = 30) group. During the breeding season, on days −10 and 0 before ram release, the treatment group was injected intramuscularly with PGF2α (D-Cloprostenol; 0.15 mg). During the non-breeding season, on day −15 before ram release the treatment group was injected with GnRH (buserelin; 4.2 μg) intramuscularly followed by two injections of PGF2α on days −10 and 0. In both studies, the rams were released into the ewe flock after the second prostaglandin injection (day 0). Blood samples of ewes were collected on days −10, 0, 20 and 70 of the study in breeding season and on days −15, −10, 0, 20 and 70 during non-breeding season. The treatment group had higher P4 concentrations compared to the control ewes on day 0 in the breeding season (5.80 ± 0.61 vs. 5.0 ± 0.93 ng/mL) and day −10 in the non-breeding season (3.50 ± 0.33 vs. 2.70 ± 0.35 ng/mL) though the differences were not significant (P > 0.05). Based on plasma P4 concentrations (>1 ng/mL) on day 70, in the breeding season all control ewes (100%) and 91.9% of the treatment ewes were detected to have active corpus luteum (P = 0.09). An almost inverse result (90% vs. 97.5%; P = 0.2) was detected in the non-breeding season. The lambing rate was higher (P = 0.03) in the treatment group compared to the control ewes during the non-breeding season (90% vs. 70%), but tended to be lower (P = 0.07) in the breeding season (73% vs. 90%). Twin lambing rate was higher in the treatment group compared to the control ewes in the breeding (40.7% vs. 0.0%; P < 0.05) and non-breeding (22.2% vs. 0.0%; P < 0.05) seasons. The litter size of the control and treated ewes were 1.0 ± 0.0 vs. 1.40 ± 0.10 in the breeding and 1.0 ± 0.0 vs. 1.22 ± 0.10 in the non-breeding season (P < 0.05). No effect was observed regard to synchronization of the treated ewes. In the breeding season two injections of PGF2α ten days apart combined with ram effect, may lower the lambing rate, but may enhance twin pregnancies and litter size in Karakul ewes. In the non-breeding season, however, the GnRH-PGF2α treatment plus ram effect may enhance the lambing rate, twin pregnancies and litter size.

Feed supplementation improves estrus response and increases fertility of sheep induced to breed out of season.

To test the efficacy on reproductive performance of nutritional supplementation in an out-of-season mating system, 66 adult prolific Barbarine ewes were selected and induced to breed using "ram effect". The ewes were allocated to two homogeneous groups; each ewe received on a daily basis 700g of hay and 500g of barley grains starting 3weeks before or 1week after rams' introduction in group 1 and group 2, respectively. Supplementation ended 1month after rams' introduction and mating lasted 60days. Final live weight 30days after introduction of rams was higher (P < 0.05) for ewes in group1 (39.45 vs. 36.72kg). Seven days after introduction of rams, ewes in group 1 recorded higher plasma glucose levels than females in group 2 (4.12 and 3.9S.E.M. 0.05mmoll-1). Proportions of ewes which displayed estrus between days 16 and 26 were 48 and 38% in group 1 and group 2, respectively (P < 0.05), and those which had a normal induced cycle (16-17days) were 25 and 11% in group 1 and group 2, respectively (P < 0.05). Fertilities were higher (P < 0.05) for ewes in group 1 than in group 2 (91.17 vs. 75.75% and 97.1 vs. 81.8% for fertility at induced estrus and total fertility, respectively). It is concluded that a timed supplementation starting 3weeks before introduction of rams is effective in yielding high reproductive performance for the prolific strain of the Barbarine breed.

The "Ram Effect": A "Non-Classical" Mechanism for Inducing LH Surges in Sheep.

During spring sheep do not normally ovulate but exposure to a ram can induce ovulation. In some ewes an LH surge is induced immediately after exposure to a ram thus raising questions about the control of this precocious LH surge. Our first aim was to determine the plasma concentrations of oestradiol (E2) E2 in anoestrous ewes before and after the “ram effect” in ewes that had a “precocious” LH surge (starting within 6 hours), a “normal” surge (between 6 and 28h) and “late» surge (not detected by 56h). In another experiment we tested if a small increase in circulating E2 could induce an LH surge in anoestrus ewes. The concentration of E2 significantly was not different at the time of ram introduction among ewes with the three types of LH surge. “Precocious” LH surges were not preceded by a large increase in E2 unlike “normal” surges and small elevations of circulating E2 alone were unable to induce LH surges. These results show that the “precocious” LH surge was not the result of E2 positive feedback. Our second aim was to test if noradrenaline (NA) is involved in the LH response to the “ram effect”. Using double labelling for Fos and tyrosine hydroxylase (TH) we showed that exposure of anoestrous ewes to a ram induced a higher density of cells positive for both in the A1 nucleus and the Locus Coeruleus complex compared to unstimulated controls. Finally, the administration by retrodialysis into the preoptic area, of NA increased the proportion of ewes with an LH response to ram odor whereas treatment with the α1 antagonist Prazosin decreased the LH pulse frequency and amplitude induced by a sexually active ram. Collectively these results suggest that in anoestrous ewes NA is involved in ram-induced LH secretion as observed in other induced ovulators.

Electrostatic analyzer measurements of ionospheric thermal ion populations

AbstractWe define the observational parameter regime necessary for observing low‐altitude ionospheric origins of high‐latitude ion upflow/outflow. We present measurement challenges and identify a new analysis technique which mitigates these impediments. To probe the initiation of auroral ion upflow, it is necessary to examine the thermal ion population at 200–350 km, where typical thermal energies are tenths of eV. Interpretation of the thermal ion distribution function measurement requires removal of payload sheath and ram effects. We use a 3‐D Maxwellian model to quantify how observed ionospheric parameters such as density, temperature, and flows affect in situ measurements of the thermal ion distribution function. We define the viable acceptance window of a typical top hat electrostatic analyzer in this regime and show that the instrument's energy resolution prohibits it from directly observing the shape of the particle spectra. To extract detailed information about measured particle population, we define two intermediate parameters from the measured distribution function, then use a Maxwellian model to replicate possible measured parameters for comparison to the data. Liouville's theorem and the thin‐sheath approximation allow us to couple the measured and modeled intermediate parameters such that measurements inside the sheath provide information about plasma outside the sheath. We apply this technique to sounding rocket data to show that careful windowing of the data and Maxwellian models allows for extraction of the best choice of geophysical parameters. More widespread use of this analysis technique will help our community expand its observational database of the seed regions of ionospheric outflows.

Effects of service ram on litter size in Romanov sheep

The objective of the present study was to examine and quantify the effects of factors acting during the mating period (service ram, mating group) on subsequent litter size in the highly prolific Romanov breed of sheep and to propose models for the potential inclusion of this effect in mixed model equations for breeding value estimation. A dataset of 4412 lambings of purebred Romanov sheep in a performance test program from 1998 to 2013 was used in analyses. The basic model fitted to litter size was a single-trait repeatability animal model with fixed effect of ewe age and random effects of contemporary groups of ewes during lambing, direct additive genetic effect of ewe, permanent environmental effect of ewe and random residual. Eight modifications of the basic model examined various combinations of mating effects, contemporary group of ewes during mating (harem), and additive genetic and permanent environmental effect of service ram. When the service ram effect was analyzed without inclusion of the population relationship matrix in the model, the proportion of variance attributable to service ram was 0.081. When the relationship matrix was included in the analysis, however, service ram heritability estimates varied from 0.046 to 0.10, depending upon whether raḿs permanent environmental effect, a harem effect or both were included in model. Models containing the additive genetic effect of service ram had slightly lower proportions of residual variance than models lacking this effect. Including effects of mating (service sire, harem, and/or raḿs permanent environmental effect) in the model favourably decreased deviance information criterion. Means of estimated BVs by year of birth increased across the 22 years from about 0.45–0.60 lambs per litter for female fertility and from 0.55 to 0.59 lambs per litter for BV male contribution on litter size, with only small differences among models. Results from present study demonstrate that service rams in Romanov sheep have a clearly detectable influence on litter size of their mates. Genetic parameter estimates indicate that direct selection on the service ram effect could increase litter size and achieve genetic gain through ram selection.

Reproductive response of mature and nulliparous yearling ewes to the ram effect during the non-breeding season

Sudden introduction of rams to ewes that remained isolated from males during the non-breeding season induces ovulation and thus out-of-season breeding. The aim of this study was to compare the reproductive response of mature and nulliparous yearling ewes to the ram effect during the non-breeding season. The experiment was performed during October–November (mid non-breeding season) with 122 Merilin ewes 56 were mature multiparous (group ME) and 66 nulliparous, 1year old ewe lambs (group HE) that previously remained isolated from males. All ewes were pretreated with intravaginal sponges for 6days before the introduction of the rams. More ME than HE ewes ovulated (87.5 vs 66.7%, P<0.01), and come into oestrus (66.1 vs 30.3%, P<0.0001), and the ovulation rate was also greater in ME than HE (1.27±0.05 vs 1.10±0.04, P<0.05). The pregnancy rate in the first oestrus period was also greater in ME than in HE ewes (39.3 vs 16.7%, P<0.01). Overall, yearling ewes can respond to the ram effect ovulating and becoming pregnant during the non-breeding season. However, the reproductive response was lower compared with that of mature ewes.

The effect of permanent or temporary contact with the lamb and contact with males on the lambing to first ovulation interval in Saint Croix sheep

The effect of suckling and presence of the lamb, or ram, on the lambing to first ovulation interval in Saint Croix sheep was determined. Ten days after lambing 50 ewes and their lambs were assigned to three different suckling treatments: continuous suckling (CS), restricted suckling (RS), restricted lamb presence (RP). Ewes from each treatment were allocated to groups that had contact with a ram (TR) or remained isolated from rams (IR). Therefore, overall, there were six groups with 2 factors: CS-IR (n=7) CS-TR (n=7); RS-IR (n=11); RS-TR (n=11); RP-IR (n=7), and RP-TR (n=7). The presence of the ram (P=0.01) and restricted suckling (P=0.05) reduced the interval from lambing to first ovulation, while no interaction was found (P>0.05) between these two factors. An effect of treatment and its interaction influenced significantly the number of vocalizations and growth rate in lambs. At the day of weaning RP vocalized more than RS (P<0.01), which in turn vocalized more than CS (P<0.01), followed by a general decline to pre-weaning levels 48h later. Lambs in RP had greater growth rate during first 3 d after weaning compared with RS (P<0.05), which displayed greater growth rate that CS (P<0.05). In addition, an effect of treatment (P=0.05) was found in cortisol concentration. Our results indicate that Saint Croix ewes respond to the ram effect in early postpartum, shortening the resumption of postpartum ovarian activity. When this technique is combined with restricted suckling, additional benefits are achieved for lambs with reduced weaning stress.

수압램 시험을 위한 복합재 T-Joint의 파손 압력 예측

항공기 날개 구조물은 유체를 포함한 연료탱크로 사용되며, 연료탱크와 날개구조물을 연결하는 체결부는 복합재 구조물을 사용한다. 항공기 날개 구조물에 고속의 물체가 관통 또는 폭발하게 되면 수압램 현상이 발생하며, 수압램 현상에 의해 연료탱크에 높은 압력이 생성된다. 이러한 높은 앞력은 날개구조물 뿐만 아니라 연료탱크와 체결부의 파손을 야기하기 때문에 전투용 항공기의 기체 생존성 확보를 위해서는 수압램 효과에 대한 체결부의 거동을 확인해야 한다. 본 연구에서는 수압램 검증 시험에 앞서 항공기의 복합재 날개 외피와 스파 체결부를 모사한 4종류의 복합재 T-Joint에 정적 인장 시험을 수행하여 시편의 파손 거동을 스트레인 게이지와 초고속 카메라를 통해 확인하였다. 스트레인 게이지를 통해 얻은 변형률을 기준으로 동일한 형상과 하중 조건을 갖는 유한요소해석 모델링의 해석 결과를 비교하여 모델링의 타당성을 확인하였으며, 정적 하중에서 복합재 T-Joint의 파손응력을 확인하였다. 유한요소해석을 통해 향후 진행될 수압램 시험에서 각 시편이 파손되는 압력을 예측하였다. Aircraft wing structure is used as a fuel tank containing the fluid. Fuel tank and joint parts are consists of composite structure. Hydrodynamic Ram(HRAM) effect occurs when the high speed object pass through the aircraft wing or explosion and the high pressure are generated in the fuel tank by HRAM effect. High pressure can cause failure of the fuel tank and the joint parts as well as the aircraft wing structure. To ensure the aircraft survivability design, we shall examine the behavior of the joint parts in HRAM effect. In this study, static tensile tests were conducted on four kind of the composite T-Joints. The failure behavior of the composite T-joint was examined by strain gauges and high speed camera. We examine the validity of the Finite Element Modeling by comparing the results of FEA and static tensile tests. The failure stresses and failure pressure of the composite T-Joint were calculated by FEA.