Introduction
In the early twentieth century, Ivanow reported the use of the artificial insemination technique (AI) in pig(1,2). However, the commercial application of AI began at the 1980s(3). Its success can be attributed to improvement in the boar:sow ratio, increase of the impact of individual boars in both genetic progress and reproductive efficiency; and limited spread of venereal diseases. Improvement in animal management and quality controls of semen doses and their commercial use have increased the reproductive performance(4). Conventional artificial insemination (CAI) usually employs 2.5 to 4 billion spermatozoa per insemination in a 70 to 100 ml volume of extender, which is deposited through the cervix into the uterus two or three times during the oestrous period(5). Boars used for AI can produce 20 to 40 CAI doses containing 2.5 to 3.0 billion motile sperm in 70 to 100 ml of extender. A reduction in the number of sperm per dose would result in a higher number of doses produced per boar with considerable economic saving, thus new strategies towards lowering the number of spermatozoa per dose in AI are constantly under study(6). Intrauterine insemination (IUI) is an insemination technique that uses a reduced number of sperm per insemination dose respect to CAI(7). However, data reported about the application of this technique show some discrepancy in the number of sperm cells per dose (which is not yet standardized). Moreover, most of the literature comparing treatments does not include groups with similar sperm number per dose, making it difficult to state whether the results are due to sperm number per dose or to the technique itself(4) .
Boar exposure to sows before insemination is considered to induce myometrial contractions which aid sperm transport; however, there is some uncertainty as to whether boar exposure before IUI catheter insertion is detrimental to the catheter insertion and to whether boar exposure has beneficial effects in CAI. To date, there is not enough information to suggest detrimental or beneficial effects for any approach(8). Still other matters of discussion arise when considering the advantages and disadvantages of the application of IUI vs CAI. These are the time consumed to insert the catheters for IUI, which is lower for CAI; backflow due to higher volume in CAI; bleeding at the time of inserting the catheters in IUI; and implementation of fixed-time ovulation induction and insemination.
There is information about the use of IUI technology which shows variations not only among countries, but also within each country(9). In spite of considerable variation among countries and farms, AI can be monitored for success using key measures for quality control and reproductive performance(8). Thus, a study was performed comparing the reproductive parameters: farrowing rate, litter size, live piglets/litter, stillborn and mummified fetuses between CAI and IUI. Furthermore, it has been analyzed the economic impact on the studied farm and the possible impact on the region.
Material and methods
Semen collection
Semen samples were collected from adult fertile boars by the glove-hand method in Medax (Chañar Ladeado, Santa Fe, Argentina). Sperm rich fraction was diluted in Vitasem (Magapor®, Zaragoza, Spain), and conserved at 16 ºC until use for no more than 2 d. Viability was measured through eosin exclusion test and the average for the three boars was 92.6 %. Motility was measured subjectively and the average was 91.26 % motile sperm. Morphology was assessed as previously reported(10) and normal sperm in samples were 89 % for boar B, 91 % for boar C and 93 % for boar A.
Experimental design
The study was conducted at a commercial farm located in Monte Maíz, Córdoba, Argentina (GPS coordinates: -33.206561, -62.600330). Three mature boars, two 415 PIC® (Pig Improvement Company, Pasig City Philippines) (A and B) and one Landrance (C) from Topigs (Topigs Norsvin, Burnsville, USA) were used as semen donors. Boar A showed 91.9 ± 2.13 motile sperm. Boar B showed 91.4 ± 3.2 motile sperm and boar C 90.5 ± 4.0. The inseminations were conducted between February and December of 2015. Five hundred and sixty (560) multiparous housed sows were separated in two groups of 280 sows. The criteria of selection for experimental design were: sows produced by breeding of Large-White female x Landrance boar, age between 190 and 200 d with at least 130 kg and four cycles detected, parity 3.9. A total of 560 inseminations were done. One group was inseminated by conventional artificial insemination (CAI) (280 inseminations) and the other group by intrauterine insemination (IUI) (280 inseminations) using the same boars as donors for each technique. In order to avoid variations on seminal quality due to different factors (individuality of boar, seasonality, physical and sanitary conditions, etc.), distribution of the same ejaculate to practice the inseminations of the two groups was performed. Oestrus detection was performed twice daily by experienced workers. Personnel for insemination procedures were carefully trained and evaluation of return to oestrus before proceeding to new inseminations was done. Sows from the two groups were contemporaneously inseminated by the two techniques. The sows were exposed to the same environment, fed with the same commercial diet and water was provided ad libitum.
Conventional artificial insemination
CAI was performed using spiral catheter (Magapor®, Zaragoza, Spain) and 3 x 109 sperm in 100 ml/dose. All sows were inseminated twice in standing heat in the presence of a boar. CAI was performed with 3x109 spermatozoa in 100 ml.
Intrauterine insemination
IUI was performed according to Hancock(11) using 1.5 x 109 sperm in 50 ml/dose and in the absence of boars, as recommended for better cannula introduction for IUI (foam catheter M. Magapor®, Zaragoza, Spain). Neither bleeding occurrence nor semen backflow were detected. IUI used 1.5x109 spermatozoa in 50 ml doses.
Analyses of the economic impact
Comparison between the economic parameters obtained with each technique was analyzed by the software “Análisis productivo y económico de granjas porcinas”(12) (Productive and economic analysis of porcine farms, APEC). In this computationally modeled analysis, standard catheter cost, labor cost, labor time, price of kilogram of meat and non-productive days (NPD), were the parameters used. NPD were calculated on the base of a sow productive cycle of 136 d (115 gestational days + 21 lactations days). The techniques and processes were approved for ethics by Servicio de Sanidad y Calidad Agroalimentaria (Agroalimentary sanity and quality service, SENASA, Argentina), resolution 63/2011.
Statistical analysis
Statistical analysis was performed using InfoStat (Universidad Nacional de Córdoba, Córdoba, Argentina). Normality test was performed by Shapiro-Wilks and Wilcoxon signed-rank test for non-parametric statistical hypothesis was applied.
Results
Analyses of reproductive parameters
When IUI and CAI were compared using the same boar semen samples, statistical data showed an increase in farrowing rate using IUI respect to CAI. The farrowing rate was 71.44 ± 2.63 for CAI, while for IUI it was 84.80 ± 0.36 (Table 1). The other parameters analyzed, live piglets/litter, stillborn or mummified fetuses showed no statistical differences. However, it is to note that a slight non-significant increase in litter size in IUI respect to CAI (14.61 ± 0.06 vs 13.72 ± 0.52) was observed. Since the same boars were used to perform the inseminations and the inseminations of sows were carried out contemporaneously using the two techniques, Pearson correlation coefficient could be applied to give insight into the observed differences. A statistically positive correlation was found between live piglets/litter and stillborn piglets (r= 1; P= 0.0074), and between stillborn and total number of piglets (r= 1; P= 0.0569) only for CAI (Table 2). The analysis for IUI showed no correlation between the studied parameters.
Analysis of economic impact
The economic impact of using each insemination technique was analyzed, showing an increase on profits using IUI vs CAI in a one-year period, for a farm with 560 sows (Table 3). Based on these data, the potential reproductive performance per sow would be 2.59 farrowing/sow/year, considering 5 d between weaning and further insemination for IUI. This value is above the average for this region of Argentina, which ranges 2.21 to 2.35 farrowing/sow/yr. These results also showed an increase from 2.32 to 2.36 conceptions/sow/yr in favor of IUI. Considering the increase in litter size in 0.89 (14.61 to 13.72) and a mortality percentage of the farm of 6 %, the profit can be calculated as: 0.89 x 2.36 (conceptions/sow/yr) x 280 (sows) = 573.16 – 6% (mortality) = 538.77. Then, 538.77 x 112 kg (weigh of sale per pig) = 60,342 kg. Contemplating a price of U$S 1.09 per kg of pig, there is a calculated benefit of U$S 65,773 using IUI instead of CAI for the studied farm. Taking into account the prize of the catheter for IUI, which is more expensive than CAI, in the computational modeled economic study, there is a net income of U$S 3,428 in favor of IUI. That is, the difference between the net income for IUI and the net income for CAI is U$S 37,008 – U$S 33,580. Contemplating an average of 3,000 pig per farm of a similar size in the region, the profit would be of great benefit for the local economy.
Discussion
Artificial insemination is widely used and there is constant search for new strategies to achieve higher efficiency. Fixed-time AI, use of high genetic merit boars or changing the site of semen deposition are examples of these attempts to improve efficiency. Watson and Behan(7) reported farrowing rates of 91.1, 91.8 and 65.8 % for CAI whereas the IUI technique showed rates of 90.5, 90.5 and 86.9, using 3, 2 and 1 billion spermatozoa in 80 ml, respectively. The mean of the litter sizes with CAI were 12.5, 12.6 and 10.6 and with IUI they were 12.3, 12.3 and 12.1, respectively. They demonstrated that only the 1 billion spermatozoa dose with CAI technique showed a significantly lower farrowing rate and litter size. Rozeboom et al(13), showed that insemination at the beginning of the uterine horn with conventional volumes and spermatozoa numbers (1 billion spermatozoa) produced results similar to insemination in the cervical cavity (4 billion spermatozoa).
However, litter size and live piglets/litter were lower in IUI than CAI with those amounts of sperm per dose. Moreover, when 0.5 billion spermatozoa were used for IUI, the farrowing rate decreased approximately 10 % in comparison with the CAI group (78 vs 88.2 %, respectively) and, also, the differences in litter size between both techniques favored CAI (9.4 vs 11.6, respectively). Levis(14) reported similar results. Other work(15) established that the farrowing rate did not differ between CAI using 3.5 x 109 spermatozoa in 100 ml and IUI using 2, 1, or 0.5 x 109 spermatozoa in 50 ml. Peltoniemi et al(16) concluded that uterine insemination did not have a significant effect on live piglets/litter and farrowing rate. The results from those studies do not necessarily reflect the data from similar procedures on other farms. In whole, summarized information about pig reproductive technologies with emphasis in field application suggests that high farrowing rates and litter size are becoming common when using standard AI with only 1.5 billion spermatozoa per insemination(17) .
In the present experimental design, all sows were in the same farm, and were inseminated with the same batches of seminal doses; CAI and IUI were equally distributed in the same day and performed with semen from all the three boars. These controlled parameters make it possible to perform a better comparison between the two techniques. Differences in farrowing rates were found using 3 x 109 spermatozoa in 100 ml for CAI and 1.5 x 109 sperm in 50 ml for IUI, that support the change from CAI to IUI in the studied farm. Moreover, although non-statistically significant, the increase in 0.89 on litter size makes the application of IUI more convenient than CAI. To get higher efficiency, AI must be accomplished reducing the number of spermatozoa, in this work the number of spermatozoa and volume of extender used in each dose were reduced to a half.
IUI with reduction in the number of spermatozoa in a fixed volume has already been analyzed(18); however in such work IUI was not contrasted with CAI. They suggested that 0.5 x 109 spermatozoa in 20 ml are sufficient to perform successful IUI, however in this work tested that volume and, the difficulty of handling a 20 ml dose counteracted the possible improvement. The reduction in sperm and doses volume is highly profitable for artificial insemination centers, as the use of superior boars renders twice the doses for IUI than for CAI, thus this feature must be included in future economic impact analyses.
In addition, in the presented experiments, a boar was present when developing CAI and absent for IUI. The presence of a boar for IUI is not recommended due to difficulty to introduce de cannula. Instead, it is recommended for CAI to help in standing and to induce myometrial contractions which aid sperm transport, but additional labor for boar movement is required(8). Despite the extra aid for sperm transit due to the presence of the boar, farrowing rate did not improve for CAI. This work agrees with the idea of the additional benefit of IUI on the necessity of less boar handling for its application. Since Steverink et al (19), reported that excessive backflow of semen upon CAI has a negative effect on fertilization results when 1 x 109 spermatozoa in 80 ml are used, it was hypothesized that a reduction in volume would improve the efficiency of the technique by reducing the backflow. In this work, no backflow was observed using 50 ml doses, which seems to be an appropriated volume, easy to handle during the procedure. The main obstacle to apply IUI is the complex anatomy of the sow’s genital tract composed by cervical folds and the length and coiled nature of the uterine horns. This obstacle was saved by employing well-trained personnel, who were systematically evaluated throughout the experiment. This may be one of the reasons for the success of IUI in this work. The fact that IUI is time-consuming and requires professional trainers must be included in future economic studies.
To our knowledge, no statistical correlation analysis was made in the precedent works. Interestingly, a statistically positive correlation between live piglets/litter and stillborn was determined in CAI and such correlation was not observed in IUI (Table 2). The Pearson´s correlation coefficient is a measure of the linear correlation between two quantitative variables, so the results presented here may be interpreted as that more services are necessary to obtain more live piglets/litter when using CAI. It is to note that this correlation could be attributed to boar, sow or environmental effects, but results from IUI, which was performed in the same conditions rules out this possibility. With recent data demonstrating the possibility to perform IUI in primiparous sows(20), it seems that the use of fewer boars in AI centers and production of more AI doses with reduced number of sperm, per boar, is an interesting aspect to consider to improve the efficiency in swine production.
Considering that 30 minimal doses could be generated by using one single boar and taking into account health, feed, installations and handling costs, the overall costs could be reduced using IUI instead of CAI. As was demonstrated, the change of CAI to IUI using 1.5 x109 spermatozoa in 50 ml doses would be more profitable.
Conclusions and implications
Using 1.5 x 109 sperm in 50 ml, without the presence of boar and inseminating at heat standing with well-trained personal, IUI had a positive impact on the reproductive performance and on the economic parameters of porcine production.
This article was originally published in Revista Mexicana de Ciencias Pecuarias 2019, vol.10, n.3, pp.583-594. ISSN 2448-6698. http://dx.doi.org/10.22319/rmcp.v10i3.4772. The article is reproduced here with permission from the author.
