Laparoscopic artificial insemination in sheep

The goal of any AI program is to create improved offspring, and the achievement of this objective will depend on the breeding value of the ram and ewe selected. Laparoscopic AI is being utilized in the sheep industry to extend the use of superior rams, and it offers the producer the opportunity to maximize the reproductive potential of superior sheep. Rapid genetic trait infusion of known superior stud rams into the flock is the primary economic benefit of laparoscopic AI. The success of laparoscopic AI depends on events and factors that interrelate in a complex way. Once the selection and preparation of the ewe have been accomplished, one of the more important steps in the program is the successful synchronization of the ewe to deliver the necessary ova to the site of fertilization at a specific time. One of the best methods of synchronization for laparoscopic AI is the use of a progesterone product for a controlled time period and the administration of PMSG upon its removal. Detecting the onset of estrus is critical, and the addition of sterile (e.g., vasectomized) males is helpful, even essential, to accurately determine when each ewe begins her estrus. The ram effect has been shown to stimulate ovulation and estrus. Ewes must be inseminated within a narrow window of time after the synchronization product is removed. Ewes should be inseminated in the order in which they begin to exhibit signs of behavioral estrus, but age, stage of lactation, duration of behavioral estrus, and breed must be taken into account when this order is established. Fresh-extended semen works well throughout this preferred time frame established for laparoscopic AI, but frozen semen gives best results when used near the end. Advancement in manufacturing technology today removes equipment as a variable factor. It is important, therefore, that the inseminator develop a level of expertise in laparoscopy to ensure maximum fertilization rates. If available, fresh-extended semen is preferred over frozen semen, using at least the minimal number of spermatozoa necessary for fertilization. Evaluation of the post-thaw frozen or fresh semen is necessary to determine motility, morphology, and concentration, all of which help determine the volume of the insemination dose. The minimum necessary for laparoscopic AI in fine-wooled breeds is 20 X 10(6) normal motile spermatozoa; however, the more seasonal and less fertile American sheep need approximately 40 to 50 X 10(6) normal motile sperm to achieve acceptable fertility rates.(ABSTRACT TRUNCATED AT 400 WORDS)     

人工授精技术在辽宁绒山羊改良工作中的重要作用

人工授精技术在辽宁绒山羊产业中的应用，不仅使优秀种用公羊的利用效率明显提高，同时也极大地促进了我国个体的低产绒山羊的改良工作，可提高绒山羊养殖的经济效益，实现科研推广部门和养殖户利益双赢，具有非常大的发展前景。     

Current challenges in sheep artificial insemination: A particular insight

Ovine artificial insemination (OAI) is not commonly performed because of specific problems related to semen application techniques, leading to highly variable results. The ideal methodology (frozen‐thawed semen/vaginal route) is unfeasible under field conditions due to the cervix morphology of the ewe, which prevents the process of intrauterine insemination necessary to obtain acceptable results. Currently, OAI commercial programmes use superficial cervical insemination, CAI (vaginal), with chilled semen (15°C) and intrauterine insemination, LAI (laparoscopic), with frozen‐thawed semen. The ability to improve upon these contrasting techniques may be derived from examining certain poorly studied factors such as insemination time, productive state of females and alternatives of seminal preservation, some of which we reviewed in this work. This interim solution will remain in use until AI by the vaginal route with frozen‐thawed semen is developed, but it poses new challenges in optimizing the freezing of the sperm and adapting the cervical (CAI) and/or transcervical intrauterine AI (TCAI). In this review, we address the current problems and evaluate their methodological (mechanical) and chemical (dilation) alternatives. Currently, TCAI is a methodologically complex technique with poor fertility results, so further studies are needed to improve the logistics of this procedure and the results of its application.     

Fertility after artificial insemination using a soybean-based semen extender in sheep

The present study aimed to compare the fertility of ewes intrauterinally inseminated with frozen-thawed semen using a soybean-based semen extender (AndroMed) with those of ewes intrauterinally inseminated with frozen-thawed semen using a Tris-based extender containing either egg yolk or BSA. Suffolk ewes (n=104) were treated with an intravaginal sponge containing 40 mg fluoroprogesterone acetate (FGA) for 12 days and an intramuscular injection of 500 IU equine chorionic gonadotropin to induce estrus and ovulation during the non-breeding season (July, 2007). Intrauterine insemination was carried out 40-46 h after removal of the FGA sponge (n=90), regardless of the incidence of estrus. The pregnancy rates were not significantly different among the semen extenders containing egg yolk (64.5%) or BSA (58.6%) and AndroMed extender (56.7%). The lambing rates (64.5, 55.2 and 56.7% for the semen extenders containing egg yolk, BSA and AndroMed, respectively) and prolificacy (1.59 to 1.75) were also not significantly different. The present results indicate that an egg yolk-containing semen extender can be replaced with the non-animal derived extender AndroMed, which could be used for intrauterine insemination using frozen-thawed ram semen without reducing fertility.     

Genetic evaluation of calving to first insemination using natural and artificial insemination mating data

Mating and calving records for 51,084 first-parity heifers in Australian Angus herds were used to examine the relationship between probability of calving to first insemination (CFI) in artificial insemination and natural service (NS) mating data. Calving to first insemination was defined as a binary trait for both sources of data. Two Bayesian models were employed: 1) a bivariate threshold model with CFI in AI data regarded as a trait separate from CFI in NS data and 2) a univariate threshold model with CFI regarded as the same trait for both sources of data. Posterior means (SD) of additive variance in the bivariate analysis were similar: 0.049 (0.013) and 0.075 (0.021) for CFI in AI and NS data, respectively, indicating lack of heterogeneity for this parameter. A similar trend was observed for heritability in the bivariate analysis, with posterior means (SD) of 0.025 (0.007) and 0.048 (0.012) for AI and NS data, respectively. The posterior means (SD) of the additive covariance and corresponding genetic correlation between the traits were 0.048 (0.006) and 0.821 (0.138), respectively. Differences were observed between posterior means for herd-year variance: 0.843 vs. 0.280 for AI and NS data, respectively, which may reflect the higher incidence of 100% conception rates within a herd-year class (extreme category problem) in AI data. Parameter estimates under the univariate model were close to the weighted average of the corresponding parameters under the bivariate model. Posterior means (SD) for additive, herd-year, and service sire variance and heritability under the univariate model were 0.063 (0.007), 0.56 (0.029), 0.131 (0.013), and 0.036 (0.007), respectively. These results indicate that, genetically, cows with a higher probability of CFI when mated using AI also have a high probability of CFI when mated via NS. The high correlation between the two traits, along with the lack of heterogeneity for the additive variance, implies that a common additive variance could be used for AI and NS data. A single-trait analysis of CFI with heterogeneous variances for herd-year and service sire could be implemented. The low estimates of heritability indicate that response to selection for probability of calving to first insemination would be expected to be low.     

肉牛品改冷配技术体系中的计算机管理系统

在我国南方很多省份,肉牛主要以散养为主,导致母牛发情后常不能及时冷配,而冷配员却又闲着的现状,从而使母牛配种率低、存栏母牛有下降趋势。针对此情况,研发了肉牛冷配软件(软著登字2009SR11157,软件产品登记测试(2009-12-S2701)),对发情(乏情)预报、发情控制以及冷配员日常工作等方面进行计算机管理。冷配员通过规范地记录日常工作数据,逐步输入计算机,利用软件制定的日常工作计划实施冷配。结果表明:(1)对发情正常但漏配的母牛,通过软件准确预报有效黄体期,实施1次PG同期发情技术,同期发情率高于直肠检查组;(2)对乏情母牛,既实现了不通过直肠检查尽早发现、及时治疗缩短产犊间隔的目的,又获得了较高的受胎率;(3)规范了母牛的繁殖记录、提高了数据利用效率,并促进了牛繁殖数据记录的持续开展。     

Equine artificial insemination

Artificial insemination is an effective technique for improving utilization of the stallion while maintaining normal conception rates in the mare. However, procedures for collection, evaluation, and insemination of semen must be followed carefully to achieve good results. Techniques for preservation of equine semen in the liquid or frozen state could potentially allow for more widespread use of genetically superior stallions. Further acceptance of artificial insemination and the use of cooled or frozen transported semen by breed registries is needed before this will occur. More work is needed to perfect methods of semen preservation, even though semen from some stallions can be cooled or frozen quite successfully at the present time.     

Fertility after different artificial insemination methods using a synthetic semen extender in sheep

The present study aimed to investigate the fertility of ewes artificially inseminated with three different methods using a synthetic semen extender, AndroMed. The three methods of artificial insemination (AI) were cervical AI with fresh-diluted or frozen-diluted semen at observed estrus, and an intrauterine AI with frozen-thawed semen. A total of 80 ewes were treated with a controlled internal drug release (CIDR) containing 0.3 g progesterone per device for 12 days. In Experiment 1 (26 Suffolk ewes), superovulation was induced with 20 mg follicle-stimulating hormone and 250 IU equine chorionic gonadotropin (eCG) two days and one day before CIDR removal, respectively, during the non-breeding season. In Experiment 2 (54 Suffolk and Suffolk crossbred ewes), an intramuscular injection of 500 IU eCG was administered one day before CIDR removal to synchronize estrus and ovulation during the breeding season. In Experiment 1, fresh-diluted or frozen-thawed semen was deposited into the cervical orifice after estrus detection, and an intrauterine AI with frozen-thawed semen was performed by laparoscopy at a fixed-time basis without estrus detection. Embryos were recovered by uterine flushing 6 days after AI, and the rates of recovered, fertilized (cleaved) ova and embryos at the morula or blastocyst stage were compared among the three AI methods. In Experiment 2, the pregnancy rates after the three AI methods were compared. In Experiment 1, the rates of recovered ova were not significantly different among the three AI methods (52.5-56.7%). The rate of fertilized ova (81.0%) by laparoscopic AI with frozen-thawed semen was significantly higher compared with cervical AI of fresh-diluted (25.5%) or frozen-thawed (3.5%) semen, but the rate of embryos at the morula or blastocyst stage (17.6%) was significantly lower than that of the cervical AI with fresh-diluted semen (69.2%). The rates of ewes yielding fertilized ova were not significantly different among the three groups (44.4, 11.1 and 62.5% for cervical AI with fresh-diluted and frozen-thawed semen and intrauterine AI with frozen-thawed semen). In Experiment 2, the pregnancy rate of ewes intrauterinally inseminated with frozen-thawed semen (72.2%) was significantly higher than those of ewes inseminated cervically with fresh-diluted (5.5%) or frozen-thawed (0.0%) semen. The present results showed that acceptable fertilization and pregnancy rates could be obtained by an intrauterine AI with frozen-thawed semen using a synthetic semen extender (AndroMed), but not sufficient by the cervical AI with either fresh or frozen semen.     

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.     

Influence of PMSG and time of artificial insemination on fertility of progestogen-treated sheep in confinement

The need for pregnant mates' serum gonadotropin (PMSG) in breeding confined sheep by artificial insemination (AI) at progestogen-synchronized estrus was assessed in 152 adult crossbred ewes brought into season by a controlled light regimen. One-half of the ewes received 500 IU PMSG after intravaginal progestogen treatment; all ewes were inseminated either 54, 57 or 60 h after sponge removal or at 54 and again at 60 h. Based on progesterone determinations 18 d after AI, conception rates with single insemination 54, 57, or 60 h and double insemination at 54 and 60 h were 76, 72, 47 and 72%, respectively, among ewes receiving PMSG, compared to 17, 22, 47 and 43%, respectively, among ewes not give PMSG (P less than .01) Lambing rates were higher (P less than .01) with PMSG (67, 67, 37 and 61%) than without PMSG (11, 11, 26 and 33%). While there was only a small increase (.06 less than P less than .05) in litter size with PMSG, fecundity decreased (P less than .01) from 1.4 to .3 when PMSG was not used. These data indicate that, even with controlled lighting to induce estrous activity, additional stimulation of ovulation by PMSG at progestogen-synchronized estrus is necessary for normal fertility when confined sheep are bred by AI.     

青海农区藏羊同期发情及适时授精技术试验研究

对219只农区藏羊进行同期发情试验,其结果表明,采用CIDR+PMSG法处理后,农区藏羊72h内的同期发情率达到82%,情期受胎率达到80.00%;采用PG+PG法处理,农区藏羊的72h内农区绵羊的同期发情率达到62.50%,情期受胎率达到60.42%,而对照组中72h内农区绵羊的同期发情率仅为37.04%,情期受胎率仅为37.03%,卡方检验结果表明,与对照组相比,CIDR+PMSG组和PG+PG组与对照组的同期发情率及情期受胎率相比,差异显著(P<0.05)。     

浅谈绵羊人工授精技术

绵羊人工授精是指利用器械以人工方法采集公羊的精液，经检查、稀释、保存等特定方法处理后，用器械输入到发情母羊生殖道的特定部位，使其妊娠的一种家畜繁殖技术。人工授精在当前仍然是先进的繁殖技术之一，在绵羊的杂交改良、新品种育成方面发挥着重要作用。     

积极推广人工授精,加速牛的杂交改良进程

今年自治区九届人民代表大会强调实施良种工程 ,要加快发展草食动物 ,切实抓好一批奶牛示范基地建设 ,努力把我区水产畜牧业发展为大的优势产业。加强品种改良进程 ,2 0 0 2年要发展改良型奶水牛 2万头。自治区政府孙瑜副主席在今年 2月 2 3日召开的全区水产畜牧工作会议上强调品种改良 ,要搞人工授精。自治区水产畜牧局陈荣贵局长提出今年全区牛改1 6万头的任务。可见牛的品种改良已真正纳入了政府工作日程 ,形势喜人 ,形势逼人。1　大力开展牛品种改良时机已经成熟1 .1　牛肉、牛奶市场上供不应求随着人民生活水平的提高 ,从吃得饱发展到…     

笼养种鸡人工授精技术经验总结

我厂饲养种鸡 1 0万套左右 ,自 1 996年以来 ,大部分种鸡逐渐改为笼养 ,采用人工授精。经过探索与努力 ,培养了一批技术熟练的工人 ,使种鸡的人工授精率平均达到 94%以上。根据本厂的生产实践 ,现将种鸡人工授精技术总结如下 :1　技术人员的管理和培训首先应挑选责任心强 ,有一定专业技术 ,最好是职业中学毕业的 ,身体健壮的饲养员 ,经技术培训后用作种鸡人工授精的技术员。其次是制订出一整套奖罚分明的管理制度和措施 ,把受精率与报酬挂钩 ,充分调动他们的劳动积极性。只有如此 ,才能确保种鸡高的受精率。2　种公鸡的选择2 .1　笼养种公鸡…     

A bioeconomic approach to derive economic values for pasture-based sheep genetic improvement programs

Economic values for a range of different maternal and carcass sheep performance traits were derived for hill sheep in the United Kingdom. A bioeconomic model that includes estimates of available energy supply and herbage intake for sheep from hill and mountain pastures, together with that from improved grassland, has provided a base from which to define the economic limitations to genetic improvement in harsh environments. The degree to which different farm systems can accommodate changes in animal performance as a result of genetic improvement was explored. Results showed that genetic improvement in harsh environments is likely to be of greater benefit to farms with fewer constraints to improvements in production, such as better quality pasture or a higher ratio of improved grassland to hill pasture. For farm types in the harshest locations, the economic value of improving litter size was only positive within defined production limits. Increasing litter size beyond these limits resulted in diminishing marginal returns because the costs of additional inputs outweighed the benefits of extra returns. Results also showed that relative improvements in maternal characteristics are at least as economically important as improvements in lamb carcass quality. The effects of variation in market prices on economic values for the major costs and returns of the sheep enterprises showed that, in general, economic values are robust. The methodology described could be adapted and applied to other extensive sheep systems worldwide.     

Stochastic simulation of Manchega sheep breed selection scheme. Impact of artificial insemination, progeny testing system and nucleus size on genetic progress and inbreeding

Manchega is a local Spanish sheep breed located in the region of Castilla la Mancha, Actually there are 0.8 million of milked ewes. The selection scheme of Manchega breed (ESROM) started in 1988, involving a selection nucleus composed by 103,887 ewes distributed in 106 flocks. Results obtained from the ESROM has been moderate in comparison with other similar European schemes. By this and other reasons, to develop a specific tool to study the ESROM system seems to be necessary.

The objectives of this work were to develop a genetic simulation model based on the ESROM real system and to study the effects on genetic progress and inbreeding level achieved from different rates of AI used, the progeny test system and the selection nucleus size.

An additive infinitesimal model was assumed for the trait 120 days Total Milk Yield (TMY). Five alternatives selection criteria (two per each group of animals to be selected), differentiated on their selection intensities, were associated to the selection of lambs for future artificial insemination rams, natural mating rams and ewes. All selection decisions were based on periodical genetic evaluations (BLUP), using an animal model with repeated measures. 60 specific cases were studied, each one with 20 replicates.

An average true genetic progress per year ranging from 1.04% to 2.10% in AI rams and 0.59% to 2.11% in ewes were observed. Results of phenotypic progress varied from 0.44% to 1.83% per year. True inbreeding levels of ewes at year 17 were between 0.218% and 1.879%.

The model used had the expected behavior. In general, the studied selection scheme had its better results (maximum genetic progress), when AI rate was equal or greater than 50%, a greater number of new rams were tested per year (75 and 44) and a selection nucleus size equal or greater than 9000 ewes (30 flocks). Selection intensity of natural mating rams had a great impact on the genetic progress, especially when the use of AI was low. The greater the nucleus size, the higher the genetic progress, but an operative scheme from around 9000 initial ewes could be established.

Results observed demonstrate the existence of some critical areas, which could be verified on the real system in order to improve their effectiveness. In this framework, the ESROM could develop two complementary strategies: to improve the selection system of Natural Mating Rams (selecting only sons of AI rams) and/or to increase the levels of AI until 50%.