Studies on factors affecting superovulation and embryo transfer in Hungarian merino ewes

The objectives of this study were (a) to assess the ovulatory response and embryo production of Hungarian Merino ewes after superovulation, (b) to investigate the factors influencing the efficiency of embryo transfer (ET) in Hungarian Merino ewes, (c) to compare the results of two ovarian stimulation protocols (PMSG and PMSG + FSH treatment) in Hungarian Merino ewes, and (d) to study how superovulation, laparoscopic insemination and surgical embryo retrieval (ER) affect the subsequent reproduction of Hungarian Merino donor females after an ET programme. There was no significant difference between the ovarian stimulation protocols in the ratio of donor ewes responding to superovulation nor in the average number of corpora lutea. However, the number of transferable embryos recovered per donor ewe was higher in the PMSG + FSH group. The proportion of transferable embryos, unfertilized oocytes and degenerated embryos did not differ between the treatment protocols. The total pregnancy rate was 53.4% (179/335). Neither the developmental stage of the embryo nor the number of transferred embryos affect the implantation of embryos. However, the increased number of transferred embryos positively influenced the pregnancy rate. No difference was found in the pregnancy rate between synchronised and non-synchronised groups of recipients. Thirty-six out of 45 donor ewes (80%) became pregnant within one year after the ET programme, indicating that ovarian stimulation and surgical ER did not affect adversely their reproduction.     

Oxytocin-induced cervical dilation and cervical manipulation in sheep: effects on laparoscopic artificial insemination

The difficulty of cervical penetration severely limits the use of transcervical AI (TAI) in sheep, and trauma from cervical manipulation (CM) may reduce fertility after TAI. We investigated the effects of cervical dilation using exogenous oxytocin (OT) to facilitate TAI and its effects on reproductive variables after laparoscopic AI (LAI). Estrus was synchronized by inserting pessaries impregnated with 6alpha-methyl-17alpha-hydroxyprogesterone acetate (60 mg) for 12 d. In Exp. 1, we determined whether OT and CM before LAI affected the interval from pessary removal to ovulation and fertilization rate. Crossbred ewes (n = 16) were assigned to 1) saline-CM or 2) OT-CM. In Exp. 2, effects of OT and CM on lambing rates were evaluated with white-faced ewes (n = 220) in a 2 x 2 factorial experiment: 1) saline-sham CM; 2) saline-CM; 3) OT-sham CM; and 4) OT-CM. In both studies, eCG (400 IU i.m.) was injected at pessary removal, and LAI was performed 48 to 52 h later. In Exp. 1, ewes received i.v. either 400 USP units of OT or 20 mL of saline at 30 to 60 min before LAI, and CM was administered as for TAI. Beginning 32 h after pessary removal and continuing at 8-h intervals, ovaries were examined with ultrasonography to estimate time of ovulation. Treatment in Exp. 1 did not affect combined ovum/embryo recovery rate (69%), but OT-CM decreased fertilization rate (47 vs 59%; P < 0.05). The OT tended to reduce the interval to ovulation (OT, 59 h vs saline, 66 h; P < 0.06). The OT x CM interaction in Exp. 1 was not significant. For Exp. 2, approximately 25 min before sham CM or CM, 200 USP units of OT or 10 mL of saline was injected i.v. The LAI was performed immediately after sham CM or CM. At 10 to 12 d after AI in Exp. 2, ewes were mated with Suffolk rams. Blood was collected between 24 and 26 d after AI for pregnancy-specific protein B (PSPB) RIA. The PSPB pregnancy and lambing rates were both 62% in saline-sham controls. The CM did not affect pregnancy (69%) or lambing rate (64%). The OT treatment decreased (P < 0.05) PSPB pregnancy (59%) and lambing rates (56%) in OT-sham ewes and pregnancy and lambing rates in CM ewes (both 43%). Neither CM nor OT before LAI affected lambing rates to next estrus, indicating no long-term damage to the cervix or uterus. In summary, CM did not affect fertility after LAI, but OT decreased lambing rate independent of CM. If OT will not be usable for TAI, it may still be a tool for training TAI personnel.     

Relationships between LH and estradiol-17 beta after removal of luteal progesterone in the ewe

Three experiments were conducted to examine the relationship between systemic concentrations of luteinizing hormone (LH) and estradiol-17 beta (E2) after withdrawal of progesterone in cycling ewes. In Exp. 1, ewes were assigned randomly to one of three treatments: laparotomy (C), removal of the luteal ovary (ULO), or ULO plus anesthesia with sodium pentobarbital for 6 h beginning 4 h after surgery. Anesthesia was used in an attempt to block the expected increase in tonic secretion of LH. Patterns of LH and E2 in these three groups did not differ during the 24-h experimental period. In Exp. 2, a longer period of anesthesia was utilized. Forty-eight ewes were assigned at random to one of four treatments: C, ULO, lutectomy or an intrafollicular injection of prostaglandin F2 alpha (PGF2 alpha). One-half of the ewes in each group were anesthetized with sodium pentobarbital from initiation of treatment (0 h) until 10 h after surgery. Sodium pentobarbital did not suppress the increases in LH and E2 after progesterone withdrawal. The regression of concentrations of E2 on concentration of LH was not significant. In Exp. 3, ewes were infused with either saline or dopamine after receiving an im injection of PGF2 alpha. Tonic secretion of LH increased after 4 h in ewes infused with saline, but not in ewes infused with dopamine. Despite the suppression of LH, concentrations of E2 increased in dopamine-treated ewes as in control ewes. Therefore, the initial increase in E2 after a decline of progesterone in cycling ewes is independent of increases in LH.     

Exogenous oxytocin dilates the cervix in ewes.

Cervical anatomy in ewes usually prevents nonsurgical, intrauterine AI and transcervical embryo transfer (ET), which limits their commercial use in sheep. This study was conducted to determine whether oxytocin would dilate the cervix in ewes and permit passage of a stainless steel rod into the uterus. In Exp. 1, at 44 and 52 h after removal of progestogenated pessaries, ewes were injected i.v. with 0 (saline), 200, 400, or 600 USP units of oxytocin. Immediately before and after treatments, stainless steel rods were used to evaluate cervical dilation and determine whether the uterus could be entered. A rod could not be passed through the cervix and into the uterus in any of the saline-treated ewes. All doses of oxytocin given at 44 and 52 h after pessary removal dilated the cervix and permitted easy passage of a rod into the uterus. At both 44 and 52 h, a stainless steel rod was passed into the uterus in 33 of 43 (77%) of the oxytocin-treated ewes. In 93% (40/43) of these ewes, a rod could be passed into the uterus during either the 44-h or during the 52-h attempt. In Exp. 2, on d 9 after pessary removal, ewes were injected i.v. with oxytocin (400 USP units) at 6 or 12 h after i.v. estradiol-17 beta (0, 100, or 200 micrograms). Cervical dilation was evaluated as in Exp. 1. Dose of estradiol x time of oxytocin affected (P less than .01) the proportion of ewes in which a rod could be passed transcervically into the uterus.(ABSTRACT TRUNCATED AT 250 WORDS)     

Technical note: development of a transcervical oocyte recovery procedure for sheep.

An oocyte recovery procedure was developed and evaluated to determine whether a transcervical embryo recovery procedure is feasible with our method, which includes estradiol-17beta (E2) and oxytocin (OT) treatments, for dilating the cervix in ewes. On d 6 of an estrous cycle, oocytes were recovered either transcervically or with a laparotomy procedure. In the laparotomy group, ovulation rate was determined during the procedure and was used to calculate the percentage ofoocytes recovered. The laparotomy procedure was a standard uterine flush, and 12 mL of PBS was used to flush each uterine horn. In the transcervical group, the ovaries in each ewe were evaluated ultrasonically to determine ovulation rate. For transcervical recovery, 100 microg of E2 were injected i.v. on d 5 to increase cervical OT receptors, and 100 USP units of OT were injected i.v. 10 to 12 h later to dilate the cervix. Approximately 25 min after OT, ewes were placed in dorsal recumbency in a Commodore cradle, and a modified Foley catheter was passed through the cervix and into the uterus for injection (80 to 210 mL) and aspiration of PBS. The PBS was aspirated with a vacuum pump. The percentage of PBS recovered was greater (P<.01) at laparotomy than with the transcervical procedure (85.8 vs. 36.2%). Despite that difference, oocyte recovery did not differ significantly between the two groups (67% for laparotomy vs. 50% for transcervical; [oocytes recovered/number of corpora lutea] x 100), and there was no evidence that the transcervical procedure damaged the oocytes; the zona pellucida remained intact around all of the oocytes. In conclusion, a procedure that includes E2-OT-induced cervical dilation, passage of a modified Foley catheter into the uterus, and incremental infusion and aspiration of media through the catheter can be used to recover oocytes transcervically from ewes. This procedure may make transcervical embryo recovery feasible for sheep.     

Lifespan of corpora lutea induced in estrous-synchronized cycling and anestrous ewes

The effect of pretreatment with flurogestone acetate (FA) on the lifespan of corpora lutea induced with pregnant mare serum gonadotropin (PMS) was examined in cycling and anestrous ewes. Cycling ewes received one of three treatments: 750 IU PMS 2 d before expected estrus (P), FA-impregnated vaginal sponges for 16 d (F), and FA sponges for 16 d and 750 IU PMS 2 d before sponge removal (FP). A fourth group served as controls (C). When compared with d 12 means within treatment, plasma progesterone means were lower (P less than .05) on d 16 in control ewes, on d 15 in P and F ewes, and on d 14 in FP ewes. Only 44% of ewes receiving FA treatment alone exhibited estrus (P less than .05) compared with 100% of untreated ewes. The FP treatment increased ovulation rate compared with controls (P less than .01). The decrease in luteal lifespan observed in cycling ewes suggests a possibility of asynchrony between the uterus and embryo, which could result in failure of an embryo to prevent luteal regression, thus resulting in reduced fertility. None of the seasonally anestrous ewes that received PMS alone and only 55% of those treated with FA sponges for 8 d before PMS injection exhibited estrus. Ewes pretreated with FA exhibited higher plasma progesterone concentrations on d 10 through 16 after PMS injection. There were no differences in luteal lifespan as measured by peripheral plasma progesterone patterns. Although FA treatment did not alter luteal lifespan in anestrous ewes, the increased plasma progesterone concentrations observed with FA treatment suggest that progestogen pretreatment may be essential for optimal luteal function.     

Effect of excess degradable intake protein on early embryonic development, ovarian steroids, and blood urea nitrogen on days 2, 3, 4, and 5 of the estrous cycle in mature ewes

Two trials were conducted to determine whether feeding excess degradable intake protein (DIP) during a synchronized estrous cycle and the first 5 d after breeding alters early embryonic development, ovarian steroids, or BUN concentrations in ewes. Ewes were group-fed in Trial 1 (T1) and individually fed in Trial 2 (T2) either 100 (control; T1, n = 15; T2, n = 12) or 200% (high-protein; T1, n = 16; T2, n = 12) of the NRC protein recommendation for maintenance during a synchronized estrous cycle until surgery in the next cycle. Ampullae (AMP), isthmi (IST), and uterine horns (UT) of high-protein and control ewes were removed on d 2 (T1), 3 (T2), 4 (T1), or 5 (T2) after breeding. In T1, jugular blood samples were taken once daily starting on d 2 of the synchronized cycle, and in T2 on d 2, 9, 15, 16, and 17, and in both trials from estrus (d 0) to the day of surgery. Ampullae, IST, and UT flushings were examined microscopically for the presence of embryos, embryo condition, and embryo cell number. There was no trial x treatment interaction (P > or = 0.10), so data for both trials were pooled. Concentrations of BUN were higher (P < 0.05) in high-protein-fed ewes than in control ewes during the synchronized cycle and the first 5 d of the next cycle. Progesterone concentrations of the synchronized cycle did not differ (P > 0.10) between treatments. During the first 5 d of the next cycle, estradiol-17beta concentrations were lower (P = 0.06) in high-protein-fed than in control ewes. Progesterone increased (P < 0.05) to higher concentrations by d 5 in high-protein-fed ewes than in control ewes. More (P < 0.05) embryos were found in AMP of high-protein-fed ewes than in AMP of control ewes on d 4. Fewer (P = 0.05) embryos were found in UT of high-protein-fed ewes than in UT of control ewes on d 4. More embryos were found in UT of high-protein-fed ewes than in UT of control ewes on d 5. Fewer (P = 0.05) embryos were found in IST of high-protein ewes than in the IST of control ewes on d 5. Embryos of high-protein-fed ewes had more (P < 0.05) cells than embryos from control fed ewes on d 5. Feeding ewes excess DIP protein during an estrous cycle and the first 5 d after breeding initially impeded embryo transport; thereafter, embryo transport and development through the oviduct was accelerated.     

Gonadotropin concentrations, follicular development, and luteal function in pituitary stalk-transfected ewes treated with bovine follicular fluid.

Two experiments, each arranged as a 2 x 2 factorial, were conducted in ewes to examine direct effects of bovine follicular fluid (bFF) on follicular development and luteal function and to further characterize follicular development and luteal function after pituitary stalk transection (SS). In Exp. 1, ewes were sham-operated or SS on d 6 of an estrous cycle and received 5 ml of saline or bFF three times daily on d 5 through 11 of the same cycle. In Exp. 2, all ewes were SS on d 6 of an estrous cycle and treated with saline or bFF three times daily on d 5 through 11 and with ovine FSH (60 micrograms; NIADDK-oFSH-16) or saline (1.2 ml) from d 7 to 11. In Exp. 2, ewes were ovariectomized on d 11 to assess effects of treatments on follicular development and luteal function. In both experiments, concentrations (ng/ml) of FSH on d 7 were suppressed (P less than or equal to .005) by bFF compared with saline (.50 +/- .17 vs 1.63 +/- .15) and remained suppressed (P less than or equal to .005) through d 11 (.46 +/- .12 vs 1.54 +/- .12). Replacement therapy (oFSH) restored concentrations of FSH. Concentrations of LH were not affected by bFF but were elevated (P less than or equal to .05) 1 d after SS (d 7; .88 +/- .09 vs .56 +/- .09) and remained elevated (P less than or equal to .05; 1.31 +/- .20 vs .65 +/- .11) from d 6 through 11. Concentrations of progesterone were unaffected by SS.(ABSTRACT TRUNCATED AT 250 WORDS)     

季节对杜泊羊体内胚胎生产与移植效果的影响

为了研究季节对杜泊羊体内胚胎生产效率及胚胎移植妊娠率的影响,于2016年选取内蒙古赛诺草原羊业有限公司种羊场经产纯种杜泊母羊作为供体,采用同期发情、超数排卵及腹腔镜人工输精等方法对供体羊进行处理后,利用手术冲胚的方法获得纯种杜泊羊胚胎,同时对受体羊进行同期发情处理和胚胎移植。经统计分析,2016年全年该公司共有放栓供体4 241只,超排处理4 180只,配种供体4 131只,冲胚供体3 987只,供体可用率为94.01%;冲出胚胎总数为23 516枚,可用胚胎18 002枚,胚胎可利用率为76.55%,平均每只供体能获得可用胚胎4.52枚。供体在10月、11月、12月冲胚所获得的平均冲胚数和平均可用胚数明显高于4月、5月、6月(P<0.05),其中10月的平均冲胚数和平均可用胚数最高(P<0.01),分别为7.04枚和5.62枚。将获得的部分胚胎用于胚胎移植,移植单胚怀孕受体数为4 446只,妊娠率为53.67%;移植双胚怀孕受体数805只,妊娠率65.02%。此外,受体在1月、3月、6月、12月受胎率较其他月份高(P<0.05)。该研究可为杜泊种羊超数排卵、胚胎移植和肉羊的产业化生产提供一定的数据参考。     

Co-culture of ovine ova with oviductal cells in medium 199

Three experiments were conducted to test the suitability of medium 199 supplemented with 10% fetal calf serum (M199FCS) as a medium for co-culture of one-cell sheep ova with sheep oviductal cells. In Exp. 1, ova were co-cultured for 5 d in 5 ml of M199FCS or in Ham's F10 medium supplemented with 10% fetal calf serum (F10FCS). Co-culture did not increase the number of cleavages at the end of 5 d of culture, but M199FCS supported more cleavages than did F10FCS (P = .016). In Exp. 2, ova were cultured for 1 to 3 d in M199FCS alone or on oviductal, uterine or kidney cell monolayers from ewes 2 d postestrus and transferred to recipients from which they were recovered at 8 d postestrus. Co-culture with oviductal cells improved (P less than .001) the cleavage index of recovered embryos compared with culture in medium alone or co-culture with other cell types. In Exp. 3, monolayers of oviductal cells from ewes 2 d postestrus and from luteal-phase ewes were cultured as in Exp. 2. No difference was observed between the two sources of oviductal cells for their ability to support in vitro development of one-cell sheep eggs for 1 or 2 d. These studies suggest that M199FCS may be a good medium to use in an oviductal cell co-culture system for one-cell sheep ova. Results further suggest that specific secretions of oviductal cells may be important for early embryo development in vivo.     

Effect of progesterone supplementation on pregnancy and embryo survival in ewes

Two hundred eighteen ewes were used in experiments 1) to develop a progesterone supplementation regimen capable of sustaining serum concentrations of progesterone at about 2.0 ng/ml for a period of 50 d (Exp. 1) and 2) to determine the effects of progesterone supplementation (d 6 to 50 after mating) on pregnancy and embryo survival rates in mated ewes (Exp. 2). In ovariectomized ewes in Exp. 1, s.c. administration of four cylindrical (9.5 x 60 mm) silastic implants, containing 20% (1.1 g) progesterone by weight, sustained mean serum concentrations of progesterone of 1.9 +/- .07 ng/ml compared with 1.03 +/- .05 ng/ml in ewes bearing two implants. In Exp. 2 each ewe (n = 159) was mated to two fertile rams at a spontaneous estrus (d 0) during mid-breeding season. Mean ovulation rate, determined on a subgroup of 46 ewes, was 1.45 +/- .05. On d 6, ewes were assigned randomly to control (two implants containing no progesterone) or progesterone-treated (four implants similar to those used in Exp. 1) groups. From d 7 to 50 after mating, progesterone concentrations in serum were greater (P less than .001) in progesterone-treated (four implants similar to those used in Exp. 1) groups. From d 7 to 50 after mating, progesterone concentrations in serum were greater (P less than .001) in progesterone-treated (3.50 +/- .06) than in control (2.65 +/- .05) ewes. Pregnancy rates (86% and 83%) and calculated embryo survival rates (77% and 78%) were similar (P greater than .05) for the control and progesterone-treated groups, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ovsynch plus CIDR protocol for timed embryo transfer in suckled postpartum Japanese Black beef cows

We compared synchronization and pregnancy rates, and the increase in blood progesterone concentrations during luteal development, between (1) Ovsynch plus an intravaginal controlled internal drug release (CIDR) device protocol followed by timed embryo transfer (timed ET), and (2) a conventional estrus synchronization method using PGF(2 alpha) and ET in suckled postpartum Japanese Black beef cows. Cows in the PGF group (n=18) received a PGF(2 alpha) analogue when a CL was first palpated per rectum at 10-d intervals after 1 to 2 month postpartum. Cows (n=11), which showed estrus (Day 0) within 5 d of the PGF(2 alpha), and had a CL on Day 7, received ET. Cows in the Ovsynch+CIDR group (n=19) underwent the Ovsynch protocol plus a CIDR for 7 d (GnRH analogue and CIDR on Day-9, PGF(2alpha) analogue with CIDR removal on Day-2, and GnRH analogue on Day 0), with ET on Day 7. The ovulation synchronization (100%) and embryo transfer (100%) rates in the Ovsynch+CIDR group were greater (P<0.01) than the estrus synchronization (66.7%) and the embryo transfer (61.1%) rates in the PGF group. The postpartum interval at ET in the Ovsynch+CIDR group (62.5 +/- 2.5 d) was shorter (P<0.01) than in the PGF group (74.9 +/- 3.9 d). The pregnancy rate in the Ovsynch+CIDR group (57.9%) did not differ significantly from that in the PGF group (50.0%). Plasma progesterone concentrations were not significantly different in the two groups on Days 0, 1, 2, 5, 7, 14 and 21. In summary, higher synchronization and transfer rates, and shorter postpartum interval to ET, can be achieved with timed ET following the Ovsynch plus CIDR protocol than after estrus with the single PGF(2 alpha) treatment followed by ET in suckled postpartum recipient beef cows. Pregnancy rates were similar. Also, the increase in blood progesterone concentrations during luteal development following ovulation synchronized by the Ovsynch plus CIDR protocol was similar to that after estrus induced by the PGF(2 alpha) treatment.     

Effects of feed restriction on reproductive and metabolic hormones in ewes

The goal of this study was to determine the effects of short-term feed withdrawal on reproductive and metabolic hormones during the luteal phase of the estrous cycle in mature ewes. Mature ewes observed in estrus were assigned randomly to control and fasted groups (n = 10 per group Trials 1 and 2). For Trials 1 and 2, control ewes had ad libitum access to feed, whereas fasted ewes were not fed from d 7 through 11 of their estrous cycle; on d 12, all ewes were treated with 10 mg of PGF2alpha, and fasted ewes were gvien ad libitum access to feed. For Trial 1, blood samples were collected daily through fasting and at 2-h intervals following PGF2alpha for 72 h. Serum concentrations of insulin (P < or = 0.002) and IGF-I (P < or = 0.01), but not GH (P > or = 0.60), were decreased during fasting compared with fed ewes. Serum concentrations of 29 (P = 0.02) and 34 kDa (P = 0.04) IGFBP were greater in fasted ewes at 96 h after initiation of fasting than in control ewes. Two control and four fasted ewes in Trial 1 did not exhibit a preovulatory surge release of LH by 72 h. Therefore, Trial 2 was conducted so that the timing of the LH surge could be predicted following the collection of blood samples at 2-h intervals for 112 h and then at 6-h intervals until 178 h following PGF2alpha administration and realimentation. The magnitude of the preovulatory LH surge in Trial 2 was decreased (P = 0.009) and delayed (P = 0.04), and serum concentrations of estradiol were diminished (P < or = 0.03) 12 h before the LH surge in fasted ewes. Ovulation rates were not influenced (P > or = 0.32) by fasting in Trials 1 and 2. Serum concentrations of progesterone in both Trials 1 and 2 were, however, greater (P < 0.001) in fasted than in control ewes. A third trial with ovariectomized ewes was conducted to determine whether the increased serum concentrations of progesterone observed in fasted ewes during Trials 1 and 2 were ovarian-derived. Ovariectomized ewes were implanted with progesterone-containing intravaginal implants and allotted to control (n = 5) or fasted (n = 5) treatment groups and fed as described for Trials 1 and 2. Similar to intact ewes, serum concentrations of progesterone were approximately twofold greater (P < 0.001) in fasted than in control implanted ovariectomized ewes. In summary, feed withdrawal for 5 d during the luteal phase of the estrous cycle increased serum concentrations of progesterone and evoked endocrine changes that could perturb the subsequent estrous cycle.     

Sodium chlorate reduces the presence of Escherichia coli in feces of lambs and ewes managed in shed-lambing systems

Our objective was to establish doses of orally administered NaClO(3) that reduced the presence of generic Escherichia coli in intestines of ewes and neonatal lambs managed in a shed-lambing system. Neonatal lambs (n = 32; age = 7.1 ± 1.2 d; BW = 6.8 ± 1.0 kg) and yearling ewes (n = 44; BW = 74.8 ± 5.6 kg) were used in 2 experiments. In both experiments, lambs and ewes were randomly assigned to 1 of 4 groups, and groups were randomly assigned to 1 of 4 treatments. In Exp. 1, neonatal lambs were given single, aqueous, oral doses of saline (control; NaCl, 30 mg·kg of BW(-1)) or 30, 60, or 90 mg of NaClO(3)·kg(-1) of BW. At 25.9 ± 1.3 h after treatment, lambs were euthanized, and intestinal contents were collected aseptically. In Exp. 2, ewes were given single, aqueous, oral doses of saline (NaCl, 150 mg·kg of BW(-1)) or 150, 300, or 450 mg of NaClO(3)·kg(-1) of BW. At 24.0 ± 0.8 h after treatment, fecal samples were collected aseptically from the rectum of each ewe. For both experiments, generic E. coli were enumerated from intestinal contents and feces within 4 to 12 h after collection. In Exp. 1, the effect (P = 0.08) of NaClO(3) on the presence of generic E. coli in colon contents was dose-dependent. This effect was linear (P < 0.01) and negative, which indicated that as NaClO(3) dose increased, generic E. coli that could be isolated from colon contents decreased. Specifically, lambs dosed with 60 and 90 mg of NaClO(3)·kg(-1) of BW had fewer E. coli cfu·g(-1) of content than control lambs (P < 0.06). Lambs dosed with 90 mg of NaClO(3)·kg(-1) of BW had fewer E. coli cfu·g(-1) of content than lambs dosed with 30 mg of NaClO(3)·kg(-1) of BW (P = 0.09). Sodium chlorate dose did not influence (P = 0.58) the presence of generic E. coli in contents collected from the cecum. In Exp. 2, the effect (P < 0.0001) of NaClO(3) on the presence of E. coli in fecal contents from ewes was dose-dependent. This effect was quadratic (P < 0.0001) and negative; ewes dosed with 150, 300, and 450 mg of NaClO(3)·kg(-1) of BW had fewer E. coli cfu·g(-1) of feces than control ewes. No differences in E. coli cfu·g(-1) of feces were detected between NaClO(3) treatments (P = 0.88 to 0.97). Based on these results, a single oral dose of at least 60 and 150 mg of NaClO(3)·kg(-1) of BW in neonatal lambs and yearling ewes, respectively, significantly decreased the presence of generic E. coli in contents from the lower intestine.     

受体绵羊人工授精后移植胚胎的试验

试验通过使用人工授精后绵羊作为受体进行胚胎移植,以寻找一种更加有效的方法提高绵羊胚胎移植的经济效益。试验中使用FSH对10只无角道赛特绵羊进行超数排卵处理,同时对60只受体小尾寒羊进行同期发情。供体羊在发情配种后4.5～5.0d从子宫角收集胚胎。同时,将胚胎移植到同期发情并进行人工授精的受体羊子宫内。总共有57枚可用胚移植给44只受体小尾寒羊,32只怀孕到分娩,共产下羔羊51只(无角道赛特羔28只,道赛特与小尾寒羊杂种羔23只)。此外,经人工授精但未进行手术移植的7只小尾寒羊产下15只杂种羔羊。移胚植受体妊娠率72.7%(32/44),移胚受体繁殖率118%(51/44),受体利用率88.3%(53/60)。移胚受体总妊娠率和受体利用率均显著高于常规ET组(P<0.01)。与常规胚胎移植相比,受体羊人工授精后移植胚胎不仅提高了无角道赛特母羊的繁殖率,而且提高了受体羊的利用率。     

Asynchronous Embryo Transfer in Sheep:Lack of Survival in Progestinized Recipient Ewes

Synchronization of development between the embryo and uterus is required for successful pregnancy establishment.Transfer of early embryos requires synchrony with the recipient uterus of 2 days or less in sheep,because asynchrony of 3 days or more results in failure of pregnancy recognition signaling for maintenance of corpus luteum (CL) and progesterone (P4) production and/or uterine support of the embryo.The objective was to determine if P4 treatment of recipient ewes would obviate the need for pregnancy recognition signaling and maintain a uterine environment conducive to embryo survival after asynchronous transfer,thereby establishing a universal recipient.Embryos (morulae/blastocysts) were recovered on day 6 from super-ovulated donor ewes.Recipient ewes received 25 mg P4 daily from day 6 post-estrus until 60 days after embryo transfer.Embryos were transferred into recipients on day 6,9,12,18,or 30 post-estrus.The pregnancy rate on day 22 post-transfer was 60% for synchronous transfers to day 6 ewes,44% and 22% for asynchronous transfers to day 9 and 12 ewes,and 0% for asynchronous transfers to day 18 and 30 ewes.On day 39 post-transfer,pregnancy rates remained 60% for day 6 ewes,33% for day 9 ewes,and 0% for day 12,18,and 30 ewes.The P4 treatment did extend the window of uterine receptivity to early embryos in ewes by one day,but did not create a universal recipient.Available results support the idea that a window of uterine receptivity to the conceptus exists in sheep that is independent of pregnancy recognition signaling.     

Influence of the embryo on intrauterine migration in sheep.

Mechanisms of intrauterine migration were examined in 55 ewes. In the first experiment, corpora lutea were removed from unilaterally ovariectomized ewes on d 4 (d 0 = estrus) and pregnancy was maintained by giving exogenous progesterone. In Exp. 2, the reproductive tract was altered surgically such that embryos initially entered the uterine horn contralateral to the site of ovulation. In Exp. 3, ewes received beads of silastic polydimethylsiloxane that released either cholesterol or estradiol-17 beta in an attempt to mimic embryonic synthesis of estradiol. In the fourth experiment, unilaterally ovariectomized ewes were superovulated and spacing of embryos within the uterus was then examined. In all experiments, ewes were slaughtered on d 15 and recovery of embryos or beads from each uterine horn indicated that migration had occurred. All ewes in Exp. 1 and 2 that had two conceptuses experienced embryonic migration. Beads impregnated with estradiol migrated farther (P less than .01) than cholesterol-containing beads (27.6 +/- 4.3 vs 12.5 +/- 1.6 cm, respectively). In Exp. 4, only one conceptus had migrated into the contralateral horn in all ewes. These results demonstrated that 1) embryonic migration was not affected by local vs systemic exposure to progesterone, 2) embryos migrated into the unoccupied horn, regardless of the initial horn of entry, 3) estradiol may stimulate embryonic migration, and 4) conceptuses were not equally distributed between horns.     

Effects of maternal selenium supply and plane of nutrition during gestation on passive transfer of immunity and health in neonatal lambs

To investigate the influence of maternal Se supply and plane of nutrition on lamb morbidity, mortality, and passive transfer of IgG, pregnant ewe lambs were used in 2 experiments with 2 × 3 factorial treatment arrangements. Supplementation of Se began at breeding and was either adequate Se (ASe, 9.5 μg/kg of BW) or high Se (HSe, 81.8 μg/kg of BW) in Exp. 1 or ASe (11.5 μg/kg of BW) or HSe (77.0 μg/kg of BW) in Exp. 2. On d 50 or 40 of gestation for Exp. 1 or 2, respectively, ewes were assigned randomly to 1 of 3 nutritional planes: 60% (RES), 100% (control, CON), or 140% (HI) of NRC requirements. This resulted in the following treatments: ASe-RES, ASe-CON, ASe-HI, HSe-RES, HSe-CON, and HSe-HI. Upon parturition, lambs were separated from their dams and serum samples obtained. Lambs were fed artificial colostrum for the first 20 h and then placed on milk replacer and grain pellets until completion of the study (Exp. 1, 57 d; Exp. 2, 21 d). Twenty-four hours after parturition, lamb serum samples were collected for IgG analysis. All lambs were reared similarly and morbidity and mortality assessed. Main effects were considered significant when P ≤ 0.05. In Exp. 1, there was a Se × plane of nutrition interaction (P ≤ 0.01) for lamb morbidity from birth to weaning and for 24-h IgG concentration. Lambs from ASe-RES and HSe-HI ewes were treated more frequently (P < 0.01) for respiratory and gastrointestinal disease, and lambs from HSe-HI ewes had the smallest (P < 0.01) 24-h serum IgG concentration. In Exp. 1, lambs from HI ewes also had the greatest (P < 0.01) mortality rates from birth to weaning compared with lambs from CON and RES ewes. In Exp. 2, there was an effect (P < 0.01) of maternal plane of nutrition with lambs from RES ewes having increased 24-h IgG compared with lambs from CON and HI ewes. There was no effect of maternal Se supplementation on lamb 24-h IgG in Exp. 2; however, there was a Se × plane of nutrition interaction (P < 0.01) for morbidity. From birth to 21 d of age, lambs from ASe-CON ewes had fewer (P < 0.01) treatment days compared with lambs from any of the other treatment groups. There also tended (P = 0.08) to be an effect of maternal Se supplementation on lamb mortality with increased mortality observed in lambs from HSe ewes. Results from the studies show a restricted maternal plane of nutrition can increase lamb serum IgG concentration. Selenium results were not consistent between the 2 experiments and may be due to differences in maternal Se.     

The influence of pregnancy and source of supplemental protein on intake, digestive kinetics and amino acid absorption by ewes

Three experiments were conducted with ewes to determine the effects of pregnancy and(or) supplemental protein source on amino acid absorption and digestive criteria. In Exp. 1, four mated and five nonmated ewes fitted with abomasal and ileal cannulas were offered 272 g of cracked corn/d and ad libitum alfalfa hay (22% CP). Mated ewes absorbed greater quantities (P less than .10) and percentages (P less than .05) of amino acids presented to the abomasum than did nonmated ewes between d 121 and 124 of gestation. In Exp. 2, three nonmated ewes were used in a latin square design experiment to compare amino acid absorption when timothy hay (6% CP; 67% NDF) was offered alone or with supplements of corn plus either alfalfa hay (ALF) or soybean meal (SBM). Supplementation increased total, essential and nonessential amino acid flow to the abomasum and amino acid disappearance. In Exp. 3, 12 mated and 12 nonmated ewes were assigned to treatments in a 2 x 2 factorial arrangement to compare the effects of production status (gestation followed by lactation vs nonmated) and supplemented protein source (ALF vs SBM) on voluntary intake and digestive criteria. Ewes were pulse-dosed with Yb-marked NDF from hay on d 124 and 137 of gestation and d 26 of lactation. During lactation (d 7 to 28), dietary DM intakes were greater (P less than .05) by ewes consuming ALF compared with SBM and by lactating ewes compared with nonmated ewes. Flow rates were greater (P less than .05) from mated ewes throughout the experiment. It appears that pregnant ewes met their increased nutrient demands by increasing flow rates and by more efficient apparent absorption of amino acids.     

Maintenance of the corpus luteum of early pregnancy in the ewe. IV. Changes in luteal sensitivity to prostaglandin F2 alpha throughout early pregnancy

Two experiments were conducted to examine the temporal aspects of luteal resistance to the luteolytic effect of prostaglandin (PG) F2 alpha during early pregnancy. In Exp. 1, 14 pregnant and 12 nonpregnant ewes were treated with PGF2 alpha either on d 10 or 13 post-estrus. Jugular venous blood samples were collected at -30 min, 0, 6, 12, 18, 24, 30 and 36 h post-injection for quantification of progesterone. The difference (delta P) between pre-treatment and post-treatment concentrations of progesterone was calculated for each ewe. There was a significant interaction between pregnancy status and day of treatment on delta P (P less than .05). Pregnant and nonpregnant ewes treated on d 10 showed a large delta P. A large delta P also was observed in nonpregnant ewes treated on d 13 post-estrus. However, delta P in pregnant ewes treated on d 13 was smaller than in the other three groups (P less than .05). The temporal patterns of concentrations of progesterone in serum were different among treatment groups (P less than .05). A suppression in the concentration of progesterone was observed by 24 h post-injection in all four treatment groups. Progesterone returned to pre-treatment levels only in pregnant ewes treated on d 13. In Exp. 2, 47 pregnant ewes were treated with PGF2 alpha on d 10, 13, 16, 19, 22, 26 or 30 postestrus. Blood samples were collected and data were analyzed as described for Exp. 1.(ABSTRACT TRUNCATED AT 250 WORDS)