Reproduction in Domestic Animals

Reprod Dom Anim 43 (Suppl. 2), 347–354 (2008); doi: 10.1111/j.1439-0531.2008.01183.xISSN 0936-6768Low-Dose Insemination in Pigs: Problems and PossibilitiesJM Vazquez, J Roca, MA Gil, C Cuello, I Parrilla, I Caballero, JL Vazquez and EA Martı´nezDepartment of Animal Medicine and Surgery, Faculty of Veterinary Medicine, Campus de Espinardo, University of Murcia, Murcia, SpainContentsLow-dose AI procedures are required by the pig industry toefficiently utilize emerging sperm technologies, such ascryopreservation and sex-sorting. Currently, several differentprocedures for inseminating with a low or very low numberof spermatozoa have been described. Deep intrauterineinsemination allows the deposition of the spermatozoa inthe depth of the uterine horn, allowing a significantreduction in the number of spermatozoa inseminated withmaintenance of optimal reproductive performance. Intraoviductallaparoscopic insemination has been recentlyapplied in pigs. This technique has proved to be applicablewith diluted and sex-sorted spermatozoa. This reviewdiscusses several problems encountered during the developmentof deep intrauterine insemination and intra-oviductallaparoscopic insemination of pigs and provides potentialsolutions for the practical application of both the technologies.IntroductionLow-dose insemination techniques are recommended inpigs when the available number of spermatozoa islimited, since standard pig artificial insemination (AI)protocols employ 3 · 10 9 spermatozoa per dose depositedintracervically two or three times during oestrus.Under these standard conditions, one ejaculate can beused to inseminate only a limited number of sows, thusconstraining the efficient use of the boars. The standardAI technique is either unsuitable or inefficient whenapplied to the emerging sperm technologies, such asfrozen-thawed spermatozoa and sperm sexing. For thesereasons, a new procedure has been developed fordepositing spermatozoa deep into the uterine horn(DUI), which allows a reduction of the number ofspermatozoa per dose (Martinez et al. 2001a,b, 2002).When fresh semen is used under field conditions, thesperm dose can be reduced to 150 · 10 6 spermatozoawith acceptable fertility results (Martinez et al. 2002,2006). This practical procedure should offer a greatbenefit for the optimization of the use of fresh semenfrom superior boars or in sanitary contingencies whenthe number of doses to be used is decreased. Currently,the DUI technique has the potential to achieve highfertilityresults using as few as 1–2 · 10 9 total frozenthawedspermatozoa (Roca et al. 2003, 2006). The DUItechnology has the potential to counteract factorslimiting routine application of frozen-thawed spermatozoa,such as the normally high number of spermatozoarequired per dose and the low fertility achieved.The most sought after reproductive technology is preconceptionsex pre-selection. The only accurate andpotentially cost-effective approach for achieving sex preselectioninvolves separating the X- from the Y-chromosomebearing spermatozoa using flow cytometry andsperm sorting (Johnson et al. 2005). However, thenumber of available flow-sorted spermatozoa is toolow for an extended use of the technology in pigproduction, even using DUI methodology (Vazquezet al. 2003, 2005). Laparoscopic insemination into theoviduct (ILI) might be an alternative method, at leastwhen applied under specialized production situations(Vazquez et al. 2006).The following review identifies objections and problems,which appeared during the development of theDUI and ILI procedures, and describes potentialsolutions for practical application of both technologies.Low Dose: Deep Intrauterine InseminationTwo main objections have been raised to the procedureof DUI in sows: (1) putative damage to the cervix andthe uterine wall by the insemination device during itsadvancement along the lumen of the cervical canal andthe uterus and (2) the incidence of the unilateralfertilization when 150 · 10 6 fresh spermatozoa are used.Putative damage of the cervix and uterine wall by the DUIcatheterIt has been suggested that the DUI catheter may causedamage to the cervix and the uterus mucosa during itsinsertion in the sow reproductive tract, potentiallycompromising subsequent fertility. Using a fibre opticendoscope procedure developed in our laboratories fornon-surgical DUI in non-sedated sows (Martinez et al.2001a), slight bleeding of the cervical canal wasobserved in 3 out of 33 sows (9.1%) during the insertionof the endoscope. In addition, during removal of theendoscope from the genital tract, a visible mark on theendometrium of the first uterine curvature was found inseven animals (21.2%). The endometrial damage wasnot accompanied by internal or external bleeding in anysow and did not have a detrimental effect on fertility ofhormonally treated oestrous sows used in that study.Recently, results from Australia indicated that a highproportion of sows (27%) bled during or after DUI andthat 22% of the inseminations resulted in some form ofbleeding from the reproductive tract (Bathgate et al.2007). In that paper, the type of bleeding was dividedsubjectively into three categories: cervical (blood wasseen on the catheter or at anytime during insemination),uterine (blood not noticed during insemination, butbecame evident 12 or more hours after insemination)and both (both types of blood were observed). Theauthors did not find significant differences in non-returnrates, farrowing rates and litter sizes between sows withor without bleeding. The high proportion of sows withÓ 2008 The Authors. Journal compilation Ó 2008 Blackwell Verlag