Reproduction in Domestic Animals

Low-Dose Insemination in Pigs 349Table 2. Effect of the insertion of the DUI catheter in sowstraditionally inseminated with 3 · 10 9 fresh spermatozoa ⁄ 100 ml ofextender on fertility parameters (from Rodriguez-Vilar et al. 2006)ParameterStandard AI plusDUI catheter insertion(n = 28)Standard AIwithout DUI catheterinsertion (n = 23)Pregnancy rate (%) 89.3 91.3Farrowing rate (%) 85.7 89.3Total piglets born(mean ± SEM)11.0 ± 0.54 11.1 ± 0.53It may be concluded that: (1) the incidence of bleedingafter the DUI procedure is low and similar to thatobserved after standard AI when practiced by suitablytrained personnel and with appropriate DUI cathetersand (2) the insertion of the DUI catheter through thecervix into the uterus does not produce significantdamage to the cervix and ⁄ or uterine wall and does notadversely affect the present and ⁄ or future reproductiveperformance of the sows.Incidence of the unilateral fertilization following DUIwith 150 · 106 spermatozoaThe earliest experiments carried out in our laboratory,comparing DUI with standard AI (3 · 10 9 spermatozoain 80–100 ml), indicated that DUI allows a 20-foldreduction in the number of fresh spermatozoa inseminated,and at least a 16–20-fold reduction in the dosevolume, without affecting farrowing rate or litter size inweaned sows, hormonally induced to ovulate (Martinezet al. 2002). However, preliminary studies using theDUI procedure on weaned, untreated sows under farmconditions indicated that although pregnancy and farrowingrates were not affected, litter sizes after DUI(150 · 10 6 fresh spermatozoa ⁄ 5 ml) could be up to 1.0piglet less (p < 0.01) than after standard AI (3 · 10 9spermatozoa ⁄ 95 ml) (Vazquez et al. 2001; Day et al.2003). More recent data using spontaneously ovulatingweaned sows confirmed these results (Martinez et al.2006).Various experiments have been conducted to determinethe possible factors implicated in such a reductionof prolificacy. In one of them (Martinez et al. 2006), 42weaned sows were inseminated at 12, 24 and 36 h afterthe onset of spontaneous oestrus using one of thefollowing two regimes: (1) DUI (treatment) with150 · 10 6 fresh spermatozoa in 5 ml of BTS extenderor (2) standard cervical AI (control) with 2.85 · 10 9fresh spermatozoa in 95 ml of BTS extender. On day 6,after onset of oestrus, the proximal segment of theindividual uterine horns of the sows were surgicallyflushed under anaesthesia to retrieve ova ⁄ embryos andevaluate the success of fertilization per horn (e.g.occurrence of effective uni- vs bilateral sperm transportrendering uni- or bilateral, complete or partial fertilization).Retrieved embryos were assessed for cleavage andnumber of accessory spermatozoa. Although identicaloverall fertilization rates were achieved in both inseminationgroups, the percentage of sows with partialbilateral fertilization and unilateral fertilization wasmarkedly higher (p < 0.05) in the DUI group (35%)compared with the control (standard AI) group (5%),with a consequent lower (p < 0.001) percentage ofviable early embryos after DUI. The number of spermbound to the zona pellucida (ZP) was higher in embryosfrom control sows than in DUI sows, indicating that thenumber of spermatozoa reaching the sperm reservoirslargely depends on the number of spermatozoa inseminated,as reported in other species (Morton and Glover1974; Nadir et al. 1993).Our results also indicate a high individual variabilityin the number of accessory spermatozoa in the ZP ofembryos from sows inseminated on the same day andwith seminal doses originating from the same ejaculates.This variability was also observed within sow betweenuterine horns, regardless of the AI method used (Fig. 1).In addition, no accessory spermatozoa were found inoocytes retrieved from sows with unilateral fertilization(Fig. 2). This indicates that spermatozoa were not ableto reach the contralateral oviduct in these sows andsuggests that intrinsic characteristics of the sow (i.e.myometrial contractility and ⁄ or local phagocytosis byinvading leucocytes) could be implicated in the incidenceof unilateral fertilizations. It is known that once thesperm dose is deposited deeply into a uterine horn,spermatozoa are able to reach the contralateral oviductand to fertilize a high proportion of oocytes (Martinezet al. 2002; Tummaruk et al. 2007) although spermatozoacan be recovered from only one oviduct via theflushing technique (Tummaruk et al. 2007). It could bespeculated that in some sows, the number of spermatozoareaching the contralateral oviduct might be too lowto establish an efficient sperm population in the reservoirto fertilize the oocytes, and as a consequence, theFig. 1. Individual variations in the number of spermatozoa bound tothe ZP of normal embryos in sows inseminated three times duringoestrus either by deep intrauterine (DUI; 150 · 10 6 spermatozoa⁄ 5 ml) or in contemporaries inseminated cervically (AI;2.85 · 10 9 spermatozoa ⁄ 95 ml). The sows were inseminated on thesame day using doses from the same batch of semen. Each dose ofsemen used for DUI was taken directly from the same bottle used toinseminate the contemporary control sow. *Differences betweenuterine horns of the same sow (p £ 0.002). (a) Differences comparedto the same uterine horn of the contemporary sow (at least p < 0.01).Unilateral fertilization was observed in sow DUI 3. In that sow, allstructures recovered from uterine horn 2 were oocytes with nospermatozoa bound to the ZP and the differences in sperm countbetween her uterine horns or in relation to uterine horn 2 of hercontemporary control AI sow were not analysed (from Martinez et al.2006)Ó 2008 The Authors. Journal compilation Ó 2008 Blackwell Verlag